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no.49 J

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Geology

NEW SERIES, NO. 49

Large Archaeohyracids (Typotheria,
Notoungulata) from Central Chile and
Patagonia, Including a Revision of
Archaeotypotherium

Darin A. Croft
Mariano Bond
John J. Flynn
Marcelo Reguero
Andre R. Wyss

I

GO
CM

November 26, 2003
Publication 1527

PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY

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UMiVERSirr OF iLLINOIS

LIBRARY
AT URBANA-CHAMPAIGN

GEOLOGY

FIELDIANA

Geology

NEW SERIES, NO. 49

Large Archaeohyracids (Typotheria,
Notoungulata) from Central Chile and
Patagonia, Including a Revision of
Archaeotypotherium

Darin A. Croft
Mariano Bond
John J. Flynn
Marcelo Reguero
Andre R. Wyss

Contributors ' affiliations are listed on page v.

Accepted May 2, 2003
Published November 26, 2003
Publication 1527

PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY

© 2003 Field Museum of Natural History

ISSN 0096-2651

PRINTED IN THE UNITED STATES OF AMERICA

^.^

GEOLOGY LIBRARY

ijrc^t^ UO V

Table of Contents

Abstract 1

Introduction 1

Taxonomic Notes 3

Abbreviations 3

Tooth Wear AND Dental Measurements .... 5

Systematic Paleontology 8

A rchaeotypotherium propheticus 9

Archaeotypotherium tinguiriricaense 14

A rchaeotypotherium patter soni 22

Pseudhyrax eutrachytheroides 25

Pseudhyrax strangulatus 30

Pseudhyrax sp. indet 30

Phylogenetic Relationships 31

Conclusions 35

Acknowledgments 36

Literature Cited 36

1 1 . Casts of skull and deciduous dentition
of A. tinguiriricanese, SGOPV 2900

and SGOPV 3080 18

12. Casts of specimens of A. pattersoni:
right maxilla (holotype), SGOPV 2918,

and right mandible, SGOPV 2917 23

13. Bivariate plots of lower molars of
Pseudhyrax 25

14. Mandibles from Tinguiririca Fauna re-
ferred to Pseudhyrax 26

15. Pseudhyrax cf. P. eutrachytheroides,
SGOPV 2877 27

16. Pseudhyrax eutrachytheroides speci-
mens from the Mustersan of Chubut,
Argentina: occlusal views 28

17. Pseudhyrax sp. indet.: left mandibular
fragment, SGOPV 2901 30

18. Strict consensus tree representing the
phylogenetic relationships among ar-
chaeohyracids 33

List of Illustrations

List of Tables

1 . Holotype of Archaeohyrax patagoni-

CM5, MACN A52-617 2

2. Bivariate plots of upper and lower first
molars of specimens of Archaeohyrax

sp. nov 7

3. Bivariate plots of upper and lower
third molars of specimens of Archaeo-
hyrax sp. nov 7

4. Holotype of Archaeotypotherium pro-
pheticus, MLP 52-XI-4-168a, occlusal
view 9

5. Casts of species synonymized under A.
propheticus 10

6. Specimens included in hypodigm of A.
propheticus 11

7. Cast of holotype of Archaeotypother-
ium tinguiriricaense, SGOPV 2823 15

8. Cast of A. tinguiriricaense: palate, oc-
clusal view, SGOPV 2851 16

9. Lower dentition of A. tinguiriricaense,
SGOPV 3067 and SGOPV 3052 16

10. Cast of A. tinguiriricaense: mandibles,

SGOPV 3034 17

1. Measurements of teeth of Archaeohy-
rax sp. nov. from the Deseadan SAL-
MA deposits at Salla, Bolivia 4

2. Measurements of molar row lengths for
specimens of Archaeohyrax sp. nov.
from the Deseadan SALMA of Salla,
Bolivia, and Pseudhyrax species from
the Mustersan SALMA of Chubut, Ar-
gentina 8

3. Dental measurements of A rc/iaeofy-
potherium propheticus specimens 12

4. Dental measurements of Archaeoty-
potherium tinguiriricaense specimens .... 19

5. Dental measurements of Archaeoty-
potherium pattersoni specimens 24

6. Dental measurements of Pseudhyrax
specimens 28

7. Identification of archaeohyracid speci-
mens 29

8. Matrix of characters used in phyloge-
netic analysis of archaeohyracid rela-
tionships 32

9. Currently recognized hyracid species .... 32

ui

Contributors

Darin A. Croft

Department of Organismal Biology

and Anatomy
The University of Chicago
1027 East 57th Street
Chicago, Illinois 60637
U.S.A.

Mariano Bond

Departamento Cientifico de Paleontologia

de Vertebrados
Museo de La Plata
Paseo del Bosque s/n
1900 La Plata
Argentina

John J. Flynn

Department of Geology

Field Museum of Natural History

1400 South Lake Shore Drive

Chicago, Illinois 60605-2496

U.S.A.

Marcelo Reguero

Departamento Cientifico de Paleontologia

de Vertebrados
Museo de La Plata
Paseo del Bosque s/n
1900 La Plata
Argentina

Andre R. Wyss

Department of Geological Sciences
University of California, Santa Barbara
Santa Barbara, California 93106
U.S.A.

Large Archaeohyracids (Typotheria, Notoungulata)
from Central Chile and Patagonia, Including a
Revision of Archaeotypotherium

Darin A. Croft
Marcelo Reguero

Mariano Bond
Andre R. Wyss

John J. Flynn

Abstract

The Tinguiririca Fauna of the Andean Main Range of central Chile is remarkable for its
abundant and diverse archaeohyracids. This study recognizes four relatively large-bodied spe-
cies from the Tinguiririca Fauna, two of which are new. Together with two previously described
small-bodied forms, the total of six species makes the archaeohyracid assemblage from Tin-
guiririca the most diverse known, representing the co-occurrence of at least 40% of all ar-
chaeohyracid species in a single fauna. The two new archaeohyracids are referred to Archaeo-
typotherium {A. tinguiriricaense and A. pattersoni), for which a revised diagnosis also is pre-
sented. The revision synonymizes the Argentine taxa Archaeohyrax propheticus, Archaeoty-
potherium transitum, and Archaeohyrax {''''Bryanpattersonia") nesodontoides under
Archaeotypotherium propheticus (new combination). Four specimens from central Chile, in-
cluding three mandibular fragments and one partial upper dental series, are referred to the two
existing species of Pseudhyrax. The upper dental series is one of the best examples known for
the taxon, and is referred to Pseudhyrax cf. P. eutrachytheroides. Based on a metric study of
Pseudhyrax specimens from Argentina, one of the Chilean mandibles is referred to Pseudhyrax
eutrachytheroides, one to Pseudhyrax strangulatus, and a third to Pseudhyrax sp. indet. Anal-
ysis of a large sample of Archaeohyrax specimens from Salla, Bolivia, provides the basis for
interpreting wear-related metric variation in archaeohyracid tooth dimensions. It demonstrates
that most cheek teeth decrease in length and increase in width through increasing wear, although
upper and lower third molars are exceptions. Owing to the dramatic metric and morphologic
differences between worn and unworn archaeohyracid teeth, care should be taken when inter-
preting the systematic significance of metric differences among specimens of different wear
states. A preliminary phylogenetic analysis suggests that taxa traditionally included in the
Archaeohyracidae do not form a monophyletic group exclusive of Hegetotheriidae and that a
comprehensive review of the names associated with major clades of typothere notoungulates
is needed.

Introduction

Despite the rich Cenozoic record of South
American fossil mammals, significant gaps punc-
tuate the sequence of South American Land Mam-
mal "Ages" (SALMAs; Flynn & Swisher, 1995).
Until recently, faunas between the well-known
Mustersan (late Eocene) and Deseadan (mid- to
late Oligocene) SALMAs were not known or rec-

ognized as such (Wyss et al., 1990, 1994). In
1988, a small prospecting team from our research
group (see Novacek, 2(X)2) discovered the first
specimens of a diverse fossil assemblage in cen-
tral Chile, later known as the Tinguiririca Fauna
(Novacek et al., 1989; Wyss et al., 1990, 1994,
1996; Flynn & Wyss, 1990, 1999; Charrier et al.,

1990, 1996; Wyss & Flynn, 1991; Flynn et al.,

1991, 2003; Wyss, Flynn, et al., 1992; Wyss, Nor-

FIELDIANA: GEOLOGY, N.S., NO. 49, NOVEMBER 26, 2003, PP. 1-38

Fig. 1. MACN A52-617, holotype oi Archaeohyrax patagonicus, left side of skull, viewed as right (adapted from
Ameghino, 1897). Scale bar ^^ 1 cm.

ell, et al., 1992; Wyss, Flynn, et al., 1993; Wyss,
Norell, et al., 1993). Subsequent studies have re-
vealed that the Tinguiririca Fauna helps fill this
long and important late Eocene-early Oligocene
gap in the SALMA sequence and provides im-
portant evidence regarding the response of South
American mammal faunas to the worldwide cool-
ing event and environmental transformation
known as the Eocene-Oligocene Transition (Flynn
& Wyss, 1998; Flynn et al., in press). Addition-
ally, it has clarified the interpretation of several
other faunas from Argentina that were previously
regarded as Mustersan in age or mixtures of sep-
arate Casamayoran, Mustersan, and Deseadan
faunas (Wyss et al., 1994; Bond et al., 1996;
Bond, Lopez, et al., 1997; Bond, Reguero, et al.,
1997; Reguero, 1998; Hitz et al., 2000; Flynn et
al., 2003; Reguero et al., 2003).

We have presented robust evidence elsewhere
that the Tinguiririca Fauna from Chile represents
a new SALMA (e.g., Wyss et al., 1990, 1994;
Wyss, Flynn, et al., 1993). This biochronologic
interval was informally referred to as New SAL-
MA ("Tinguirirican") in the SALMA chronology
of Flynn and Swisher (1995) and is named and
defined formally as a new SALMA, the Tingui-
rirican, in Flynn et al. (2003). The stratotype se-
quence for this SALMA assemblage is a compos-
ite section representing the basal Abanico
(=Coya-Machali) Formation near Termas del Fla-
co, in the upper Rio Tinguiririca valley, Chile
(Charrier et al., 1996; Flynn et al., 2003), with
correlative assemblages in Argentina, including
those from the "Astraponoteen plus superieur"
("APS") of the Gran Barranca, Chubut (see Bond
et al., 1996; Bond, Reguero, et al., 1997; Reguero,
1998; Kay et al., 1999; Hitz et al., 2000). Levels
in the stratotype producing the Tinguiririca Fauna
have yielded high-precision '"'Ar/''^Ar radioisoto-
pic dates, as have underlying nonfossiliferous
beds, indicating that the fauna is at least 31.5 Ma
in age, spanning a range potentially as large as

31.5-37.5 Ma or more (spanning the Eocene-Ol-
igocene transition). Various lines of evidence sug-
gest that it might be only of very short duration
(possibly less than 2 m.y. and entirely earliest Ol-
igocene, —31-33 Ma; Flynn et al., in press.). Ho-
rizons unconformably bracketing the correlative
Tinguirirican "APS" faunas in the Gran Barranca
of Argentina have yielded radioisotopic dates and
paleomagnetic stratigraphies, including a K-Ar
date of 28.8 ± 0.9 Ma (Marshall et al., 1986)
above and 36-38.5 Ma below (Kay et al., 1999;
see also Flynn & Swisher, 1995 and Flynn et al.,
2003).

The abundance and diversity of its archaeohy-
racid assemblage are among the most distinctive
features of the Tinguiririca Fauna (Wyss, Norell,
et al., 1993; Wyss et al., 1994; Croft, 1998, 2000;
Reguero et al., 2003; Flynn et al., 2003). At least
six archaeohyracid species occur at Tinguiririca
(40% of all currently recognized archaeohyracid
species), the greatest diversity of archaeohyracids
known from a single fauna. These six taxa include
two new species of Protarchaeohyrax (Reguero
et al., 2003), two new species of Archaeotypo-
therium (present study), and two previously de-
scribed species of Pseudhyrax (Simpson, 1967).
Based on the new material from the Tinguiririca
Fauna and detailed comparative studies of Argen-
tine specimens, revised diagnoses of both Ar-
chaeotypotherium and Pseudhyrax are presented
here.

The Archaeohyracidae was named by Ameghi-
no in 1897 and placed in the Hyracoidea, an oth-
erwise Old World group. He based Archaeohyrax,
and his taxonomic placement of the group, on the
type specimen of Archaeohyrax patagonicus
(MACN A52-617), an excellent skull and man-
dibles from the Deseadan SALMA of Chubut, Ar-
gentina (Fig. 1). Although Ameghino believed the
Archaeohyracidae to be allied with hyraxes, most
other early workers (e.g., Sinclair, 1909; Loomis,
1914) recognized that archaeohyracids (and other

FIELDIANA: GEOLOGY

typotheres) were members of the endemic South
American group Notoungulata. George Gaylord
Simpson's views on the taxonomic position of the
Archaeohyracidae changed during the course of
his studies. In his landmark classification of mam-
mals (Simpson, 1945), he placed the Archaeohy-
racidae in the Toxodontia (contra Sinclair, 1909),
but later allied them with the hegetotheriids in the
Hegetotheria (Simpson, 1967). Although some
studies have suggested that hegetotheriids are
more closely related to mesotheriids than to
archaeohyracids (Wyss, Norell, et al., 1993; Croft,
1998), most recent phylogenetic studies have sup-
ported the close relationship between archaeohyr-
acids and hegetotheriids (Cifelli, 1993; Hitz,
1995; Reguero, 1998; Croft, 2000).

For many years MACN A52-617 (the holotype
of Archaeohyrax patagonicus; Fig. 1) was the
only archaeohyracid skull known. Until this study,
it remained the only one figured and described.'
As exemplified by MACN A52-617, taxa cur-
rently included within the Archaeohyracidae are
characterized by a complete (3/3, 1/1, 4/4, 3/3)
and essentially closed dentition (lacking signifi-
cant diastemata), with enlarged and procumbent
first incisors and an evenly graded cheek tooth
series. The skull is low and broad across the orbits
and occiput but narrow across the snout. Archaeo-
hyracids are small- to medium-sized mammals;
the maximum length of the skull of MACN A52-
617 is approximately 15 cm, and Tinguirirican ar-
chaeohyracids are estimated to have had body
masses between 250 g and 4 kg (Croft, 2000;
Rynn et al., 2003). No postcranial bones definite-
ly attributable to the family Archaeohyracidae
have yet been described, although currently un-
prepared specimens are present in the Tinguiririca
Fauna.

Until recently, archaeohyracids have been the
subject of very few studies. This has been due
primarily to the scarcity of archaeohyracid mate-
rial, even in many well-sampled faunas. The dis-
covery of the Tinguiririca Fauna has renewed in-
terest in this group of notoungulates (Wyss, No-
rell, et al., 1993; Wyss et al., 1994; Reguero,
1993, 1998; Croft, 1998, 2000; Reguero «fe Lopez,
1999; Reguero et al., 2003), as has continued col-
lecting in the archaeohyracid-rich Deseadan Salla
Beds of Bolivia (MacFadden et al., 1985; Shock-
ey, 1997; Reguero & Cifelli, 1997). The present

' Other skulls are known from both the Tinguiririca
Fauna (Tinguirirican SALMA) and Salla, Bolivia (De-
seadan SALMA).

study strives to clarify some of the taxonomy and
nomenclature of the Archaeohyracidae as a basis
for future comprehensive studies on the phylog-
eny, biogeography, biochronology, and paleobi-
ology of the group.

Taxonomic Notes

Most recent phylogenetic analyses suggest that
the Archaeohyracidae (as that name is currently
employed) represents a paraphyletic assemblage
of taxa closely related to hegetotheriids (Cifelli,
1993; Hitz, 1995; Croft, 1998, 2000; Reguero,
1999; see also the phylogenetic analysis below).
However, the relationships among archaeohyra-
cids and hegetotheriids have yet to be rigorously
tested. Because the term Archaeohyracidae is fa-
miliar to South American paleomammalogists,
and because no one has proposed a phylogenetic
definition and/or alternative name for the least in-
clusive clade encompassing these taxa, we use the
terms Archaeohyracidae and archaeohyracids in
their traditional sense for the purposes of this pub-
lication.

Taxonomic names that are potentially invalid
due to synonymy (e.g., "Archaeohyrax concen-
tricus'') are indicated through the use of quotation
marks.

Abbreviations

AMNH, American Museum of Natural History,
New York; MLP, Museo de La Plata, Argentina;
SGOPV, vertebrate paleontology collections, Mu-
seo Nacional de Historia Natural, Santiago;
MACN, Museo Argentino de Ciencias Naturales,
"Bernardino Rivadavia," Buenos Aires; APS,
"Astraponoteen plus superieur"; CV, coefficient
of variation; FA, first occurrence; HI, hypsodonty
index (height of unworn tooth/length of tooth); K,
potassium; Ar, argon; Ma, megannum; m.y., mil-
lions of years; mm, millimeter; cm, centimeter; g,
gram; kg, kilogram; SALMA, South American
Land Mammal "Age." Upper tooth loci are in-
dicated by uppercase letters (e.g., II, P2, Ml) and
lower tooth loci by lowercase letters (e.g., il, p2,
ml); deciduous teeth are indicated by a "d/D"
preceding the tooth position.

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FIELDIANA: GEOLOGY

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Tooth Wear and Dental
Measurements

The early attainment of hypsodonty (the pres-
ence of high-crowned teeth) is one of the most
distinctive features of the Archaeohyracidae. In-
deed, archaeohyracids are among the — if not
the — earUest notoungulates to exhibit this feature,
although the Casamayoran Eohyrax is certainly
much less hypsodont than later archaeohyracids.
Associated with increased hypsodonty is an in-
creasingly dramatic difference in size and shape
of the occlusal surface between unworn and
heavily worn teeth within a given species; rela-
tively low-crowned archaeohyracids (e.g., Eohy-
rax) demonstrate this phenomenon only to a mi-
nor extent, but extremely hypsodont taxa (e.g.,
Archaeohyrax) display significant differences be-
tween newly erupted and heavily worn teeth. Such
wear-related changes make it difficult to accurate-
ly describe and diagnose archaeohyracid taxa in
the absence of a large sample that includes spec-
imens in varying stages of wear. Unfortunately,
archaeohyracids are rare in most faunas, making
such extensive collections uncommon. A conspic-
uous exception is the Deseadan-aged fauna from
Salla, Bolivia. In contrast to Deseadan faunas
from Patagonia, archaeohyracids are among the
most common taxa at Salla (MacFadden et al.,
1985; Reguero & Cifelli, 1985), thus permitting
studies requiring large sample sizes. Although ar-
chaeohyracid specimens are numerous in the Tin-
guiririca Fauna, the extremely hard matrix has
greatly limited the number of specimens that have
been prepared and thus are presently available for
study. Each of the Tinguirirican taxa described be-
low is represented by only a small number of
specimens, and consequently it has not been pos-
sible to document wear-related metric and mor-
phologic variation directly. Instead, we apply an
estimate of the expected range of variation with
wear for individuals within a single species, based
on an analysis of the extensive material from Bo-
livia.

To estimate the amount of dental variation ex-
pected within a single Tinguirirican archaeohyra-
cid species, metric changes were investigated us-
ing a large sample (71 mandibular and 34 max-
illary fragments) of Archaeohyrax sp. nov. (Re-
guero & Cifelli, 1997) from Salla, Bolivia. Each
tooth was measured to the nearest 0.1 mm using
digital calipers and was assigned to one of three
wear stages: little wear (central fossa not yet iso-
lated), moderate wear (central fossa completely

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

isolated), or heavy wear (central fossa absent; fea-
tureless occlusal surface). Although division of
tooth wear into a greater number of stages would
have been desirable, the morphology of the teeth
was such that this could not have been done in an
objective way without a more detailed study of
the dentition of this undescribed species (currently
underway by one of us [M.R.] and R. Cifelli).
Moreover, these three categories can be general-
ized to other archaeohyracids without having to
worry about differences in hypsodonty and rela-
tive depth of accessory fossettes/fossettids (which
could potentially be used to further subdivide
wear stages). In addition to individual tooth
lengths, molar row lengths were recorded for the
Salla Archaeohyrax specimens, as well as for a
complementary but smaller sample of Pseudhyrax
specimens from Chubut, Argentina.^ Upper tooth
lengths were measured parallel to, and widths per-
pendicular to, the ectoloph. Lower tooth lengths
were measured parallel to, and widths perpendic-
ular to, the long axis of the tooth. It should be
noted that since each tooth is scored for wear in-
dividually, some mandibular fragments include
teeth of all three wear states. Graphical and sta-
tistical procedures were performed using Micro-
soft Excel 4.0 or StatView 4.1 for the Macintosh
computer.

Table 1 lists univariate statistics for all the mo-
lars and the last two premolars. The coefficient of
variation (CV) was calculated as CV = 100 X
(standard deviation/mean), following Gingerich
(1974). Values for the entire sample, along with
wear stage, are given by tooth position.

Several generalizations can be drawn from the
data. Disregarding wear, the coefficients of vari-
ation for each tooth position are very high for a
single population from a single locality. In most
cases, CVs decrease when each wear category is
considered separately. Therefore, when compar-
ing metric values from different specimens to de-
termine their taxonomic affinity, it is important to
compare specimens displaying similar wear. Even
when comparing similarly worn teeth, however,
significant variation persists. A tooth 20% larger
or smaller than the mean is not unusual, and two
teeth may vary by as much as 40% in their di-
mensions (although the large variation in Ar-
chaeohyrax sp. nov. may result in part from pool-
ing specimens from different stratigraphic levels

within the Salla beds^). This has important impli-
cations for the use of these sorts of metric values
alone to distinguish archaeohyracid species (see
recommendations below).

The data also demonstrate that as teeth undergo
wear, they generally become shorter (mesiodistal-
ly) and wider (buccolingually). The relationship
between tooth wear and tooth shape is most easily
seen in bivariate plots of tooth length and width
for upper and lower first molars (Fig. 2). The Ml-
2 and ml -2 become shorter and broader with in-
creasing wear. Accordingly, in comparing speci-
mens of unequal wear, if the longer one is more
worn, it is more likely that these differences re-
flect taxonomic rather than individual (species or
ontogenetic) variation; the reverse is true when
the longer tooth is less worn, since it can be in-
ferred that it would shorten with additional wear.
Upper and lower third molars do not follow this
trend (Fig. 3); upper third molars increase in
length with wear, and whereas the plot for lower
third molars suggests a similar trend may exist,
the large amount of overlap among wear catego-
ries precludes useful differentiation.

Finally, molar row lengths (M/ml-3) tend to
be less variable than individual tooth lengths (Ta-
ble 2). Archaeohyrax specimens from Salla and
specimens of Pseudhyrax from Chubut both have
small molar row length CVs (<10), with nearly
all specimens (28 out of 30 Archaeohyrax speci-
mens, all Pseudhyrax specimens) varying within
10% of the mean. Two factors might contribute to
this lower variability. One possibility is that mea-
suring tooth-row lengths tends to "average out"
wear-related size differences between teeth. Spec-
imens with the molars in different wear stages
(due to different eruption times) are common,
while specimens having either all unworn or en-
tirely heavily worn molars are rare. Thus, com-
parisons between the extremes of the wear spec-
trum are much less common for molar rows than
for individual teeth. Also, as noted previously, be-
cause third molars tend to lengthen with wear, this
may offset some of the shortening associated with
wear in the more anterior molars. Regardless of
the precise cause, this study documents that molar
row lengths are less variable than individual tooth
lengths and should be used whenever possible in
taxonomic studies. This is especially true for more
hypsodont archaeohyracids, as suggested by the

~ Individual tooth lengths were also recorded for the
Pseudhyrax specimens but are not included in the pre-
sent study due to the small sample size.

^ Testing for the effects of stratigraphic level on size
was precluded by the lack of stratigraphic data for the
majority of specimens measured.

FIELDIANA: GEOLOGY

E
E,

♦-»

•D

/.a-

• •

M1 WEAR

■ Little

7.0-

A Moderate

.

/• ^

• Heavy

6.5-

:

•

6.0-

• A

5.5-

Ja^

■

•

■

5.0-

•

■

4.5-

• 1 • > 1

1 1 • • 1 1 1 1 • 1 1 1 • • 1 1

1 • > 1 I 1 > 1

5.0 6.0 7.0 8.0 9.0 10.0 11.0

Length (mm)

o.u-

•
•

ml WEAR

■ Little

• •

A Moderate

b.5-

• •

• •

• Heavy

• •

A

5.0-

•

n

A

A

i^

A

4.5-

•

•^♦^-

A

■ ■

•

A

A

■

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4.0-

•

■
■

■
■

I 1 1 1 1 1 ) 1 1 1 1

■ III

I 1 1 1 1 1 I 1

1 ( 1 1 I 1 1 I I 1

5.0 6.0

7.0

8.0

Length (mm)

Fig. 2. Bivariate plots of upper and lower first molars, sorted by wear, from specimens of Archaeohyrax sp. nov.
(Reguero & Cifelli, 1997) from the Deseadan SALMA deposits at Salla, Bolivia.

smaller CV for Pseudhyrax molar rows as com-
pared to Archaeohyrax lower molar rows. Pseud-
hyrax, with lower CVs, is moderately high-
crowned, whereas Archaeohyrax sp. nov., with its
much higher CVs, represents maximum hypso-
donty for the Archaeohyracidae (and therefore
probably exhibits maximum variation in metric
values with wear).

Based on the above observations, we recom-
mend that (in the absence of other corroborating
morphologic distinctions), whenever possible,
only tooth rows of similar wear be compared

when attempting to distinguish between morpho-
logically similar archaeohyracids (or other no-
toungulates with hypsodont, but rooted, cheek
teeth) using size alone. Where such comparisons
of linear tooth-row measures are possible, the
larger taxon should exceed the smaller by at least
10%. If only individual molars are available for
comparison, then the larger should exceed the
smaller by at least 30%. If only isolated first or
second molars of different wear states are avail-
able for comparison, then the larger should exceed
the smaller by 50% if it is the less worn, and by

7.5 -

7.0^

6.5-

g" 6.0

■B 5.5-
■g

5.0-

4.5

4.0

M3 WEAR

■ Little

A Moderate

• Heavy

A

A

' I ' I ' I ' I ' I ' I ' I I I ' I ' I ' I

8.0 9.0 10.0 11.0 12.0 13.0

Length (mm)

4.5

4.3-

4.1-

3.9-

3.7-

3.5-

3.3

m3 WEAR

■ Little

A Moderate!

• Heavy J ^

A ^
I A«

• • •

• • •■A

■••

8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0

Length (mm)

Fig. 3. Bivariate plots of upper and lower third molars, sorted by wear, from specimens oi Archaeohyrax sp. nov.
(Reguero & Cifelli, 1997) from the Deseadan SALMA deposits at Salla, Bolivia.

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

Table 2. Measurements of molar row lengths for specimens of Archaeohyrax sp. nov. (Salla, Bolivia; Deseadan
SALMA) and Pseudhyrax species (Chubut, Argentina; Mustersan SALMA). Measurements are made to the nearest
0.1 mm. Coefficient of variation (CV) = 100 X (standard deviation/mean).

Salla Archaeohyrax

Ml-3 (n = 11)

ml-3 (n = 19)

Chubut
Pseudhyrax

ml-3 (n = 5)

Mean ± SD

Range

Range (% of mean)

CV

25.0 ± 1.3
22.3-26.8
89%- 108%
5.1

26.0 ± 1.8
23.2-29.7
89%- 114%
6.9

30.8 ± 0.8
30.0-31.8
97%-103%
2.6

15% if it is the more worn; this should be reversed
for isolated M3s (i.e., the difference should be
greater if the larger specimen is the more worn,
less if it is the less worn). Individual lower third
molars of different wear states should differ by at
least 30%.

Systematic Paleontology

Mammalia Linnaeus, 1758
Notoungulata Roth, 1903
Typotheria Zittel, 1892
Hegetotheria Simpson, 1945
Archaeohyracidae Ameghino, 1897

Archaeotypotherium Roth, 1903

Archaeohyrax Ameghino, 1897 (partim): 435.
Archaeohyrax Ameghino, 1901 (partim): 361-

362.
Eomorphippus Ameghino, 1901 (partim): 373.
Bryanpattersonia Simpson, 1967 (partim): 115.

Type Species — Archaeotypotherium transitum
Roth, 1903, here regarded as a junior synonym of
Archaeotypotherium propheticus (Ameghino,
1897).

Comments — Archaeotypotherium transitum
was recognized by Roth (1903) on the basis of a
maxillary fragment from Canadon Blanco, in
Chubut, Argentina. (For a discussion of this enig-
matic locality, see Wyss et al., 1994; Flynn et al.,
2003.) Although this taxon was ignored by most
subsequent authors, we recognize it here as dis-
tinct from all other described archaeohyracids,
consistent with Roth's view. Moreover, we con-
sider the various specimens/species previously al-

located to Archaeohyrax, Eomorphippus,'^ and
Bryanpattersonia as more properly included in
Archaeotypotherium. These specimens/species all
appear to be conspecific, and the name Archaeo-
typotherium propheticus has chronologic priority.
Given the temporal congruence of the specimens
referred to Archaeotypotherium (Wyss et al.,
1994; Flynn et al., 2003; see also Reguero, 1993,
1998; Bond et al., 1996; Kay et al., 1999; Hitz et
al., 2000), this synonymy is not surprising.

Included Species — The type, Archaeotypo-
therium tinguiriricaense (new species, below),
and Archaeotypotherium pattersoni (new species,
below).

Diagnosis — A member of the Hegetotheria that
differs from Hegetotheriidae in the absence of
hypselodont (ever-growing) cheek teeth, absence
of hypselodont II, absence of straight lingual face
on lower molars, presence of fossettes/fossettids
at some stages of wear in upper and lower molars,
and presence of significant change in cheek tooth
occlusal shape with wear. Differs from Archaeo-
hyrax in its lower-crowned cheek teeth (newly
erupted teeth are rooted in Archaeotypotherium,
unrooted in Archaeohyrax; HI = 1.75-2.25 in Ar-
chaeotypotherium, HI > 2.5 in Archaeohyrax),
relatively larger II, less triangular upper molars,
more elongate central fossae on upper and lower
molars, larger lower premolars, more persistent
accessory fossettes/fossettids on upper and lower
molars, M3 without posterior lobe formed by me-
tastyle, m3 proportionately shorter, and labial sul-
cus on m3 talonid less pronounced. Differs from
Protarchaeohyrax by more persistent accessory
fossettes/fossettids on upper and lower molars,
absence of lingual sulcus on uppers molars, M3
without posterior lobe formed by metastyle, and

" Roth misidentified several specimens of Archaeoty-
potherium as Eurystomus stehlini, a junior synonym of
Eomorphippus obscurus (Simpson, 1967).

FIELDIANA: GEOLOGY

Fig. 4. MACN A52-618, holotype of Archaeotypotherium propheticus, mandibular symphysis and portion of
right horizontal ramus with right il-2, c, p2-4 and left i2-3, c, pi, occlusal view (from Ameghino, 1897). Scale
bar = 1 cm.

much larger size. Differs from Pseudhyrax by
higher-crowned cheek teeth (HI = 1.3-1.6 in
Pseudhyrax), relatively larger 1 1 , less pronounced
paracone and parastyle ridges on upper molars,
larger lower premolars, and proportionately lon-
ger talonids on lower molars. Differs from the
new archaeohyracid taxon from Antofagasta de
La Sierra (Lopez, 1997; Reguero «fe Lopez, 1999)
by its much larger size, higher-crowned cheek
teeth (HI of Antofagasta form similar to that of
Pseudhyrax), longer molar talonids, and more per-
sistent talonid fossettids. Differs from Eohyrax by
much higher-crowned cheek teeth (HI < 1.25 in
Eohyrax) and much larger size.

Age and Distribution — Earliest Oligocene
Tinguirirican SALMA (Flynn et al., 2003) of Pa-
tagonia and east-central Chile: Abanico (=Coya-
Machali) Formation, Chile; Cailadon Blanco, pre-
sumably the Sarmiento Formation, Chubut, Ar-
gentina (Roth, 1903); "Astraponoteen plus super-
ieur" (APS) horizon of the Sarmiento Formation
at the Gran Barranca south of Lake Colhue Huapi,
Chubut, Argentina. Horizons bearing the Chilean
Tinguiririca Fauna have yielded two high-preci-
sion '*°Ar/^^Ar dates near 31.5 Ma (the range of
the means and associated errors spanning —31-32
Ma), and they are underlain by a basalt unit whose
upper part also was dated at about 3 1 .5 ± 1 .0 Ma.
Available radioisotopic dates from horizons
bracketing Tinguirirican "APS" levels in the
Gran Barranca of Argentina (Kay et al., 1999) are
generally congruent with the geochronologic in-
formation from Chile.

Archaeotypotherium propheticus (Ameghino,
1897), new combination

(Figures 4-6)

Archaeohyrax propheticus Ameghino, 1897: 435.
Archaeohyrax nesodontoides Ameghino, 1901:

361; Simpson, 1967: 113.
Archaeohyrax concentricus Ameghino, 1901:

361-362.
Eomorphippus rutilatus Ameghino, 1901: 373.
Archaeotypotherium transitum Roth, 1903: 22-

23.
Bryanpattersonia sp. Simpson, 1967: 115.

Holotype of Archaeohyrax propheticus —
MACN A52-618, mandibular symphysis and por-
tion of right horizontal ramus with right il-2, c,
p2-4 and left 12-3, c, pi (Fig. 4).

Lectotype of Archaeohyrax nesodontoides —
MACN 10905a, a right ml measuring 12.2 by 6.3
mm (Fig. 5A).

Paralectotypes of Archaeohyrax nesodonto-
ides — MACN 10905 (9 isolated lower cheek teeth
[catalogued b to j] and 7 isolated upper cheek
teeth [catalogued k to q]; selected specimens il-
lustrated in Fig. 5A).

Lectotype of Archaeohyrax concentricus —
MACN A52-625, incomplete facial region of
skull with left I1-M2 and right I1-M3 (Fig. 5B).

Paralectotype of Archaeohyrax concentri-
cus— MAC^ A52-629, left p4.

Lectotype of Eomorphippus rutilatus —
MACN 10915, right upper molar.

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

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FIELDIANA: GEOLOGY

Fig. 6. Specimens included in hypodigm of Ar-
chaeotypotherium propheticus. A. MACN A52-630,
right M2 and right m3. B. MACN A52-628, partial right
mandible with ml-3. Scale bar = 1 cm.

HOLOTYPE OF ArCHAEOTYPOTHERIUM TRANSI-

TUM—MLP 12- 1524a, left maxilla bearing Ml-3
(M3 partially erupted; Fig. 5C).

Hypodigm — Holotype of A. propheticus; all
specimens included in junior synonyms above;
MACN A52-630, right M2 and right m3 (Fig. 7);
MACN A52-628, partial right mandible with ml

(Fig. 6B); AMNH 28943, neariy unworn isolated
left M3; AMNH 28955, damaged left P2-M3;
MLP 89-XII-21-1 (Roth's Nos. 1414), left Ml,
left ml, and right ml; MLP 69-III-31-2, right
upper molar; MLP 12-1516, left mandible with
ml-3.

Localities — Only one of the type specimens of
"Archaeohyrax concentricus" (MACN A52-625)
is accompanied by a locality label. This label
reads "Coluapi Pyrotherium,'' indicating a ?De-
seadan SALMA locality — precisely which one is
uncertain — near or at the south end of Gran Bar-
ranca, Chubut. Similarly, only a single specimen
assigned to ''Archaeohyrax nesodontoides"
(MACN A- 10911, perhaps part of the hypodigm
for that taxon) has geographic provenience data.
The accompanying label reads: "Colhuapi Noto-
stylops (parte sup.)," the "parte sup." indicating
a level in the Gran Barranca distinct from that
where Casamayoran SALMA fossil vertebrates
were collected. It appears to cortespond to the
portion of profile M of Simpson that Bond et al.
(1996) cortelated with the "Astraponoteen le plus
superieur" of Ameghino (1901). It is not improb-
able, then, that all of the specimens referted to
"Archaeohyrax nesodontoides^' come from the
Gran Bartanca. Ameghino's placement of "A. ne-
sodontoides'" {Archaeotypotherium propheticus of
this study) and "A. sulcidens'' {Protarchaeohyrax
gracilis of Reguero et al., in press) in the "Capas
con Astraponotus" (Mustersan SALMA; Amegh-
ino 1901, 1902) appears to be incortect, taking
into account the recent stratigraphic data collected
from the Gran Bartanca by M. Bond and one of
the authors (M.R.) and, more recently, by joint
Argentine-U.S. teams led by R. Kay. Moreover,
at typical Mustersan localities (La Gran Hondon-
ada, Cerro del Humo, and Laguna del Mate),
Pseudhyrax is the only archaeohyracid present.

The type of Archaeotypotherium " transituni'''
(MLP 12- 1524a) and MLP 12-1516 come from
Cafiad6n Blanco, Chubut. The former has a label
that reads "T.i.C.B.", indicating "Terciario infe-
rior de Cafiadon Blanco" ("Formacion terciaria
inferior, Cafiadon Blanco [Territorio del Chu-

FiG. 5. Epoxy casts of species synonymized under Archaeotypotherium propheticus. A. MACN 10905, selected
syntypes of Archaeohyrax nesodontoides including (from left to right) right ml (lectotype, MACN 10905a); left ml
or m2 with little wear (paralectotype, MACN 10905g or 10905h); right P4 (paralectotype, MACN 10905p). B. MACN
A52-625, lectotype of Archaeohyrax concentricus, incomplete facial region of skull with left I1-M2 and right II-
M3. C. MLP 12- 1524a, holotype of Archaeotypotherium transitum, left maxilla with Ml-3 (M3 partially erupted).
Scale bar = 1 cm.

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

11

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FIELDIANA: GEOLOGY

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but]"). MLP 69-III-31-2 comes from "Campo de
Velazquez, Paso de Indios, Chubut." MLP 89-
XII-29-1 was collected by Santiago Roth in 1898
and comes from Laguna Sega or Seca, found by
Roth situated close to the road between Paso de
Indios and Choiquenilahue, near Laguna Palacios,
Chubut. AMNH 28955 was collected by Justino
Hernandez in 1934 from Locality IV of Rincon-
ada de los Lopez, just northeast of Tapera de Lo-
pez, Chubut (Simpson, field notes on file at
AMNH; Marshall et al., 1986). MACN 1 454 1
comes from "Chubut km 163," Gran Barranca,
Chubut.

Age and Distribution — Earliest Oligocene
Tinguirirican SALMA (Flynn et al., 2003) of Pa-
tagonia (see above).

Diagnosis — As for Archaeotypotherium. Dif-
fers from A. tinguiriricaense (new taxon, below)
in larger size, more persistent fossettes on upper
molars, and presence of trigonid and talonid fos-
settids on lower molars. Differs from A. pattersoni
(new taxon, below) in more persistent fossettes on
upper molars, presence of trigonid and talonid
fossettids, and larger and less quadrangular pre-
molars.

Description — Ameghino (1897) distinguished
Archaeohyrax propheticus from Archaeohyrax
patagonicus by the presence of pi and the rela-
tively larger premolars in A. propheticus. The for-
mer character was based on a mistaken observa-
tion by Ameghino (pi is present in both A. pro-
pheticus and A. patagonicus), but the latter char-
acter, and a variety of others outlined in this study,
clearly illustrate the distinctiveness of A. prophe-
ticus and A. patagonicus, consistent with Ameghi-
no's recognition of the two taxa as distinct. Mea-
surements for the upper and lower dentitions of
this taxon are presented in Table 3.

Upper Dentition — The upper incisors and ca-
nine of Archaeotypotherium propheticus resemble
those of Archaeohyrax, but all are lower-crowned
(Fig. 5B). The combination of the relatively low-
crowned 1 1 , clearly the major cropping tooth, with
the relatively much higher-crowned posterior pre-
molars and molars is a curious feature of this tax-
on; it is implanted obliquely as in Archaeohyrax,
hegetotheriids, and mesotheriids. 12 is slightly
longer in A. propheticus than in Archaeohyrax, its
anterior portion projecting forward well beyond
the root and curving inward a little. II, 12, 13, and
C are offset from each other by short diastemata.

The first premolar differs from that of Archaeo-
hyrax in its more convex external face and by the
presence of a shallow anterolingual notch. The es-

CROFT ET AL.: LARGE ARCHAEOHYR ACIDS FROM CHILE AND PATAGONIA

13

sential characters of the remaining upper cheek
teeth have been given in the diagnosis of Ar-
chaeotypotherium. Detachment of the facial por-
tion of the right maxilla of MACN A52-625 re-
veals a progressive, steplike increase in the
heights of the premolar crowns, and very clearly
shows that Archaeotypotherium is less hypsodont
than Archaeohyrax. The cheek teeth are at an ear-
lier stage of wear than in the type of A. patago-
nicus, yet they are notably lower-crowned. On
P2-4 the anteroexternal fossette is more persistent
than the posteroexternal fossette, whereas on the
molars the reverse is the case. The internal fos-
sette is elongate, and is bifid anteriorly, in P3-
M2.

The incomplete M3 of MACN A52-625, the
least worn of the available teeth, reveals a few
details of crown pattern (Fig. 5B). A shallow
notch still persists between the protocone and the
slender lingual extremity of the hypocone. The
metaloph appears to have been directly transverse
in orientation. There is a very small posterior cin-
gulum, interrupted labially and joined lingually to
the tip of the hypocone. The posteroexternal fos-
sette is a long slit that curves posteriorly toward
the midline, the lingual portion being very shal-
low. The internal fossette is a mere slit labial to
the protocone. Between this fossette and the pos-
teroexternal one is a wide, abraded area. To judge
from an unworn Ml of the Mustersan-aged
Pseudhyrax eutrachytheroides, this area, when
newly erupted, consisted of a posterior crista
joined to a bulbous cusp or crochet attached to
the metaloph.

Lower Dentition — The lower incisors, canines,
and pi -3 are known only from the type of A.
propheticus, a very mature individual in which
the dentition is deeply worn (Fig. 4). The teeth at
this stage show no appreciable differences in
structure from those oi Archaeohyrax. A compar-
ison of a p4 oi Archaeotypotherium (MACN A52-
629) and a mandible of Archaeohyrax patagoni-
cus (MACN A52-624) at similar stages of wear
demonstrates that the talonid fossettid and the lin-
gual groove in the trigonid are more persistent in
Archaeotypotherium than in Archaeohyrax, and
that the lingual groove posterior to the entoconid
is less persistent. They also demonstrate that the
lingual groove between the trigonid and talonid is
less persistent than the one posterior to the ento-
conid in Archaeotypotherium, whereas in Ar-
chaeohyrax the reverse is the case. The greater
persistence of the trigonid and talonid fossettids
in the lower molars of Archaeotypotherium is

convincingly shown by MACN A52-628 and
A52-630 (Fig. 6), both old individuals in which
the roots are either formed (ml -2) or forming
(m3). A talonid fossettid persists on m2 in both
specimens, a trigonid fossettid on m3 of A52-630,
and both fossettids on m3 of A52-628.

The facial region and the mandible show no
important differences from Archaeohyrax, al-
though the muzzle of A. propheticus is slightly
broader than in A. patagonicus.

Archaeotypotherium tinguiriricaense sp. nov.

(Figures 7-11)

HoLOTYPE— SGOPV 2823, rostrum with left
and right C1-M2 (canines barely erupted; Fig. 7).

Hypodigm — Holotype of A. tinguiriricaense;
SGOPV 2851, palate with highly worn left 11-3,
left and right P2-M3 (Fig. 8); SGOPV 2853, right
maxilla with transversely crushed C1-M2 (P3
with damaged ectoloph); SGOPV 2900, slightly
distorted skull with crushed dentition (left and
right II, right P2-M3, left P2-3, Ml-2; Fig.
1 1 A); SGOPV 2909, left maxillary fragment with
?Ml-2; SGOPV 3043, partial left and right man-
dibles (fused) with left il-3, pl-m3 and right il-
p3 (Fig. 10); SGOPV 3052, partial left mandible
with p3-m3 (Fig. 9B); SGOPV 3060, left ?M1;
SGOPV 3067, skull and mandible with mildly
worn dentitions, partially prepared (Fig. 9A, man-
dible only); SGOPV 3080, palate with left and
right PI, dP2-4, Ml (Fig. IIB); SGOPV 3260,
partial right mandible with ml-3; SGOPV 3261,
partial left mandible with p4-m2.

Type Locality — Locality C-89-21b, purple-
brown volcaniclastic sediment of the Abanico
Formation (Charrier et al., 1996; Flynn et al.,
2003); 34°59'S, 70°26'W, approximately 1 km
north of pass identified by its elevation, 2738 m
(Anonymous, 1985), known locally as Portezuelo
El Fierro (Charrier et al., 1996), south of the Rio
Tinguiririca, northeast of Cerro Alto del Padre,
and about 3 km south of Termas del Flaco, Chile.

Age and Distribution — Earliest Oligocene
Tinguirirican SALMA (Flynn et al., 2003) of east-
central Chile (see above).

Diagnosis — As for Archaeotypotherium. Dif-
fers from A. propheticus in its smaller size
(approx. 20% smaller), less persistent fossettes on
upper molars, and absence of trigonid and talonid
fossettids on lower molars. Differs from A. pat-
tersoni (new species, below) in smaller size
(approx. 20% smaller), shallower mandible, and

14

FIELDIANA: GEOLOGY

Fig. 7. Epoxy cast of SGOPV 2823, holotype of Archaeotypothehum tinguiriricaense, palate with left and right
C1-M2 (canines barely erupted), in right lateral view (above) and occlusal view (middle and below). Specimen
illustrates relatively unworn dental morphology of Archaeotypotherium tinguiriricaense. Scale bar = 2 cm.

proportionately smaller and more triangular pre-
molars.

Etymology — In reference to the Rio Tinguirir-
ica and the Tinguiririca Fauna of Chile, the type
locality and fauna for the species.

common archaeohyracid in the Tinguiririca Fau-
na; numerous specimens are referable to it, in-
cluding two skulls (only the second and third pub-
lished for an archaeohyracid), a palate bearing a
deciduous dentition, and several other upper and

Description — A. tinguiriricaense is the most lower dentitions. It is slightly larger than the com-

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

15

Fig. 8. Epoxy cast of SGOPV 2851, palate with left 11-3, left and right P2-M3, in occlusal view. Specimen
illustrates heavily worn upper dental morphology of Archaeotypotherium tinguiriricaense. Scale bar = 2 cm.

Fig. 9. Lower dentition of Archaeotypotherium tinguiriricaense. A. Portion of SGOPV 3067, little worn left
mandible showing p2-m2, occlusal view. B. Epoxy cast of SGOPV 3052, partial left mandible with p3-m3, occlusal
view. Scale bars - 1 cm.

16

FIELDIANA: GEOLOGY

Fig. 10. Epoxy cast of SGOPV 3043, partial left and right mandibles (fused) of Archaeotypotherium tinguiriri-
caense with left il-3, pl-m3, and right il-p3. A. Left lateral view (shown as right lateral). B. Occlusal view. Scale

bar - 1 cm.

mon Archaeohyrax sp. nov. from the younger fau-
na at Salla, Bolivia (Deseadan SALMA) but much
less hypsodont. Dental measurements are present-
ed in Table 4. A rostrum with upper dentition
(SGOPV 2823) is designated the holotype for this
new taxon because it preserves many diagnostic
features, and archaeohyracid taxa typically are
most easily distinguished on the basis of the upper
dentition. A skull was not designated the holotype
because in one (SGOPV 2900), the teeth are
crushed, and in the other (SGOPV 3067), some
adult teeth are unerupted and deciduous teeth are
present.

Upper Dentition — In the current state of prep-

aration, the relatively unworn upper dentition is
best represented by the holotype specimen
SGOPV 2823 (Fig. 7), a rostrum with both left
and right C1-M2. No incisors are preserved. The
upper canines are visible within their alveoli and
are in the process of erupting. M3, if present, is
completely unerupted. The lateral surface of the
maxilla is present on the left side of the rostrum,
but is not preserved on the right.

The canine is small and bladelike (approxi-
mately 2.8 mm in length) and appears to be sep-
arated from PI by a small diastema. The posterior
edge of PI abuts the anterior edge of P2. It is a
simple tooth, consisting primarily of a single.

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

17

Fig. 1 1. Epoxy casts of skull and deciduous dentition of Archaeotypotherium tinguiriricaense. A. SGOPV 2900,
slightly distorted skull with crushed teeth (left and right II, right P2-M3, left P2-3, Ml -2) in right lateral view
(above) and occlusal view (below). B. SGOPV 3080, palate with left and right PI, dP2-4, and Ml in occlusal view.
Scale bar = 2 cm.

rounded cusp occupying nearly the entire anterior
half of the tooth. A small, sloping shelf is located
distolingual to this main cusp.

The other premolars (P2-P4) more closely re-

semble the molars in shape and complexity. An
anterolabially projecting parastyle is present on all
premolars, but the parastyle does not extend as far
apically as does the adjacent paracone. Strong la-

FIELDIANA: GEOLOGY

Table 4. Measurements to the nearest 0.1 mm for specimens of Archaeotypotherium tinguiriricaense. Specimens
are arranged in order of increasing wear, as determined by various morphologic indicators (e.g., presence or absence
of fossettes, height of cheek teeth). Measurements in parentheses are estimated.

Upper dentition

Wear

PI

P2

P3

P4

Ml

M2

M3

Specimen

L

W

L W

L W

L W

L W

L W

L W

SGOPV 2823
SGOPV 2853
SGPOV 30601
SGPOV 2909
SGOPV 2851

Light

Light

Moderate

Moderate

Heavy

4.9 3.9

6.4 —

5.5 4.6

7.5 5.2
(6.4) —

4.2 6.5

7.2 6.0
7.1 —

5.0 7.5

10.0 6.6

9.0 —

9.1 7.6

8.2 8.4

6.3 9.6

(10.6) (6.6)
10.3 —

9.6 8.2
8.5 8.3

(11.2) —
13.1 7.5

Lower dentition

Wear

Pl

p2

p3

p4

ml

ml

m3

Specimen

L

w

L W

L W

L W

L W

L W

L W

SGOPV 3261
SGOPV 3067
SGOPV 3043
SGOPV 3052

Light
Light
Heavy
heavy

5.C

1 2.3

6.6 2.5

5.9 3.5
6.0 3.6

7.0 4.1
6.8 3.2
6.6 3.8
6.5 4.1

9.3 4.7
8.8 4.5
8.2 4.7
8.1 5.1

10.4 3.8

10.2 3.8

8.9 4.7

9.6 5.3

15.0 4.9
(14.4) 4.7

bial ridges demarcate both the parastyle and para-
cone; the two are separated by an asymmetric
concavity that is steeper at the anterior face of the
paracone ridge than it is on the posterior face of
the parastylar ridge. Differentiation of the para-
cone and metacone increases distally in the tooth
row. A posterior cingulum is present on all pre-
molars at a height about halfway between the al-
veolar margin and the occlusal surface of the me-
taloph. No differentiation of the protocone or the
hypocone is evident along the lingual face of the
premolars. Each premolar roughly resembles a
right triangle, with the ectoloph forming the long
leg and a convex, anterolingual protoloph forming
the hypotenuse.

The second upper premolar exhibits a simple
occlusal morphology. Lingual to the paracone
there is a very weakly developed first crista. Pos-
terior to this is a second crista, which is united
with a well-developed crochet. Two spaces are
thus isolated: an internal fossa and a postero-ex-
temal fossette. The internal fossa is oriented
slightly obliquely to the long axis of the tooth. Its
anterior end is expanded between the protoloph
and the second crista, and the incipient first crista
can be seen projecting into the fossa from the ec-
toloph. The lingual face of the tooth is smoothly
convex, gently grading into the posterior cingu-
lum.

The third and fourth upper premolars are sim-
ilar in size, shape, and morphology, but P4 is
more worn. Of the cheek teeth, these show the

greatest development of the labial groove between
the parastylar and paracone ridges. The cristae
and crochet are better developed on the occlusal
surfaces, and an antecrochet projects into the an-
terior end of the internal fossa and contacts the
first crista, isolating an anterior external fossette
with wear. This crochet closely parallels the pro-
toloph along a portion of the lingual side of the
crown, nearly pinching out the middle portion of
the internal fossa. With wear, this creates a con-
stricted internal fossa that is slightly expanded
both anteriorly and lingually. The crochet contacts
the short second crista, isolating a posterior ex-
ternal fossette that is larger than the anterior ex-
ternal fossette. In a little-worn tooth, the internal
fossa can be seen to extend laterally to the ecto-
loph, situated between the two cristae opposite the
paracone and metacone. This portion of the inter-
nal fossa disappears with wear, and the two cristae
become confluent; there is no median external
fossette. A posterior cingulum is present on both
teeth, positioned well below the occlusal surface
of the metaloph.

The first upper molar is the most heavily worn
cheek tooth, but still is relatively unworn. Its an-
terior portion resembles the posterior premolars,
but due to wear the posterior cingulum is joined
with, and forms the distal portion of, the occlusal
surface. Additionally, the protocone and hypo-
cone (the latter not being evident in the premo-
lars) are differentiated and separated at their bases
by a short internal cingulum. At this slightly worn

CROFT ET AL.: LARGE ARCH AEOHYR ACIDS FROM CHILE AND PATAGONIA

19

stage, the internal cingulum is slightly below the
occlusal surface of the lingual portion of the
tooth. The presence of a hypocone and the distal
lengthening of the tooth create a more trapezoidal
tooth shape in which the labial and lingual sides
form roughly parallel edges and the segment
along the distal edge of the tooth is perpendicular
to both.

Five fossae/fossettes are present on the occlusal
surface of Ml. Most anterior is a small fossette
resulting from the joining of the antecrochet with
the first crista (i.e., the anterior portion of the con-
joined first and second cristae). Posterior to this,
situated approximately halfway along the labial
edge of the tooth, is the posterior external fossette.
Between these two fossettes, but located more lin-
gually, is a small anterolingual fossette formed by
the "pinching off" of the internal fossa by the
well-developed crochet; it is not a true external
fossette, as the first and second cristae become
confluent with wear, preventing the fossette from
reaching the ectoloph. The posterior portion of the
internal fossa is situated lingually, just lateral to
the small internal cingulum. The internal fossa is
connected to the anterolingual fossette by the
elongate remnant of the internal fossa. Finally, a
mediolaterally elongate posterior fossette is pre-
sent between the posterior cingulum and the me-
taloph.

The second upper molar is partially erupted;
only the anterior half of the tooth has undergone
any wear and the posteriormost portion of the
tooth is nearly flush with the surface of the palate.
Two cingula are clearly demonstrated in this
tooth: a small, somewhat papillate posterior cin-
gulum and a slightly shorter, gently rounded, and
more robust internal cingulum. The hypocone
arises from between these two structures and is
the lowest of the cusps. Its apex is flat and is
already confluent with the rest of the metaloph.
The metastyle lies opposite the hypocone, along
the labial margin of the tooth. It is significantly
larger than the hypocone and has a distinct, point-
ed apex. It is confluent with the rest of the ecto-
loph, but only near its base. The second crista is
well developed and is nearly as high as the worn
anterior portion of the tooth. The crochet, how-
ever, is not nearly as tall, but extends anteriorly
from the metaloph to contact the second crista. As
on Ml, an anterior external fossette is present
along the lingual margin of the ectoloph, just an-
terior to the combined first and second cristae.
Two bands of enamel extend lingually from the
fossette, suggesting a possible connection of the

fossette with the internal fossa before wear had
taken place.

Although the incisors are not present in
SGOPV 2823, they are at least partially preserved
in SGOPV 3067 (the remaining teeth are unpre-
pared), and SGOPV 2851 (Fig. 8), a specimen
with highly worn teeth. In SGOPV 3067, the left
first incisor is recently erupted and displays little
or no wear. It appears to be much less robust than
in Archaeohyrax, but, owing to the unprepared
lingual surface of the tooth, this is uncertain. The
occlusal edge of the tooth is approximately 6.5
mm in length. II is about twice as large as 12, and
12 is slightly larger than 13. 13 is in the process
of erupting, and 12 may be broken away from its
root, precluding a more detailed description of
their morphology. In SGOPV 285 1 , all teeth have
undergone significant wear and all three incisors
have been worn nearly to their roots. They are
separated by small diastemata (each approximate-
ly 1 mm long) and all have less than 2 mm of
enamel present labially.

Measurements of upper cheek teeth for speci-
mens of Archaeotypotherium tinguiriricaense are
listed in Table 4. It should be noted that the mea-
surements of teeth of different specimens vary in
the orderly fashion predicted from the aforemen-
tioned studies of changes with wear in other ar-
chaeohyracid taxa.

Lower Dentition — The relatively unworn lower
dentition of Archaeotypotherium tinguiriricaense
is best exemplified by SGOPV 3067 (Fig. 9A).
Both mandibles are preserved, but the posterior
portion of the right mandible remains unprepared.
The two mandibles are joined at a completely
fused symphysis that is approximately 21 mm in
length; in lateral view, the symphysis is oriented
at an angle of about 30° below the level of the
mandibular tooth row.

The lower incisors are small and procumbent,
their size increasing from mesial to distal. The
first two incisors are very small and are the only
teeth of the mandible exhibiting significant wear.
The third incisor exhibits no wear and is much
larger than the first two. Because SGOPV 3067
represents a young individual of A. tinguiriri-
caense (most teeth are unworn and m3 is unerupt-
ed), comparisons with specimens of older individ-
uals of this taxon (e.g., SGOPV 3043, described
below) suggest that the first two incisors in
SGOPV 3067 are deciduous. The identification of
the third incisor is ambiguous; it may be either a
late-erupting deciduous tooth or an early-erupting
permanent tooth. Based on its similar size and

20

FIELDIANA: GEOLOGY

structure to i3 in other specimens, we favor the
latter alternative, pending additional specimens
that might suggest otherwise. Tooth replacement
in notoungulates has yet to be thoroughly inves-
tigated, and the presence of 13 in this specimen
would suggest that the third incisor may not have
a deciduous precursor in archaeohyracids.^

In SGOPV 3067, the greatest occlusal dimen-
sion is perpendicular to the sagittal plane in dil,
45° to this plane in di2, and nearly parallel to this
plane in 13. A slight differentiation of two cusps
is present on the lingual surface of 13, dividing
the tip of the lingual face into a large, rounded
posterior cusp and a smaller anterior cuspule. This
division is even more pronounced on the canines;
the two cusps show greater separation and are
more similar in size than they are in 13. The right
canine has recently erupted, but on the left side
the tip of the already fully erupted tooth is par-
tially broken off.

The teeth of the premolar series grade from ca-
niniform to molariform. The first premolar is ca-
niniform, consisting of a simple pointed crest. The
second premolar is significantly longer than pi
and shows a differentiated trigonid and talonid.
The trigonid of p2 consists of a single sigmoid
crest with its highest point located at the meta-
conid. The short segment of the trigonid crest pos-
terior to the metaconid hooks around the lingual
side of the talonid, which is low, narrow, and c-
shaped. The highest point of the talonid is at its
posterior end, where a cuspule lies just medial to
the most anteriorly projecting part of p3. The third
premolar is similar in morphology to p2, but both
the trigonid and talonid are expanded buccolin-
gually. The metaconid and its posterior crest are
still the highest points on the occlusal surface, but
the trigonid has expanded to form a small basin
instead of merely a crest. Lingual expansion of
the paraconid, which is much better developed
than on p2 (best seen in lingual view), creates this
basin. A similar expansion of the entoconid oc-
curs in the talonid, creating a talonid basin. The
structure of p4 is very similar to that of p3, except
the talonid is proportionately longer In both p3
and p4 a very slight vertical groove is present on
the posterolingual portion of the talonid, separat-
ing the entoconid from the hypoconulid. This

5 Sinclair (1909) noted that Pl/pl do not have decid-
uous precursors in Santacrucian SALMA interatheriids,
so the lack of deciduous precursors for some teeth is not
unprecedented in notoungulates.

structure is much more evident in the molars, es-
pecially with increasing wear.

The molars of SGOPV 3067 have undergone
little wear and there is still much relief between
the metaconid, with its posterior crest, and the re-
mainder of the occlusal surface. The ml trigonid
is a long, thin structure with two grooves on its
internal face. The first of these grooves is located
anteromedially on the trigonid, dividing the para-
conid from the metaconid. The second groove is
located on the lingual side of the posterior meta-
conid crest; it divides the crest into two unequal
portions, the more posterior one being about twice
as long as the anterior On m2, the paraconid is
enlarged lingually, creating a trigonid basin much
larger than on ml (though the larger basin may
be due, in part, to increased wear). The more an-
terior of the lingual trigonid grooves is essentially
absent in m2, but a small protuberance is still ev-
ident on the anteromedial side of the trigonid, just
anterior to the more posterior groove. As on the
premolars, a lingual groove is present on the ml
talonid, creating a bifid posterolingual talonid
face. The internal talonid groove is short in ml,
extending perhaps a quarter of the distance from
the occlusal surface to the alveolus. On m2, how-
ever, the groove is much deeper and extends be-
low the level of the alveolus. The m3 is unerupt-
ed.

The morphology of a heavily worn lower den-
tition is shown by SGOPV 3043 (Fig. 10) and
3052 (Fig. 9B). SGOPV 3052 is slightly more
worn, but other than small wear-related differenc-
es, the two specimens are almost identical in size
and morphology (Table 4).

SGOPV 3043 includes the anterior portion of
the right mandible (with il-p3) and a complete
left mandible and associated dentition. The first
incisor on each side is small, peglike, and oriented
at approximately 45° to the long axis of the man-
dible (in lateral view). In occlusal view, the sur-
face of il is nearly perpendicular to the sagittal
plane, whereas 12 is nearly parallel to it. Both il
and 12 are larger and more robust than their de-
ciduous counterparts in SGOPV 3067. The third
incisor and the canine possess a high anterior por-
tion and low posterior portion, similar to the con-
figuration of the trigonid and talonid in many gen-
eralized mammal lower molars. The size of each
tooth increases progressively from il-c. In both
SGOPV 3043 and 3067, the unusual spoutlike na-
ture of the symphysis is evident, appearing
"pinched in" on both sides. A mental foramen is

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

21

present within the lateral depressions on the sym-
physis, almost directly beneath the canine.

The premolars are all heavily worn, and the pi
occlusal surface level is approximately equal in
height to that of the posterior portion of the ca-
nine. No occlusal morphology is retained on pi
or p2, while on p3-p4 and ml only a single fossa
is present separating the trigonid from the talonid.
Enamel height on the labial surface of p3 is ap-
proximately 4.2 mm. Both the m2-3 talonid and
trigonid are slightly damaged, but most of the
morphology remains discernible. In both SGOPV
3043 and 3052 the hypoconulid is directed pos-
teriorly. Although not evident in SGOPV 3043,
SGOPV 3052 appears to demonstrate that on m3,
in addition to the fossa between the trigonid and
talonid, a fossettid forms between the hypoconid
and hypoconulid.

Discussion — Owing to the large number of
well-preserved specimens of this taxon from the
Tinguiririca Fauna, A. tinguiriricaense will likely
prove to be one of the best-known archaeohyra-
cids. Since many of these specimens have yet to
be fully prepared from the exceptionally hard vol-
caniclastic matrix, however, a complete descrip-
tion of the skull and preserved/available parts of
the appendicular skeleton is not yet possible.
These specimens will be thoroughly described
when preparation has been completed. Of note,
however, is the well-preserved basicranium of
SGOPV 2900, which illustrates two characters
Patterson (1936, unpublished manuscript) recog-
nized as linking Archaeohyrax and hegetotheriids:
the absence of a hamular process on the pterygoid
and an anteriorly located carotid foramen (see
phylogenetic analysis below).

A. tinguiriricaense includes both of the speci-
mens (SGOPV 2823 and SGOPV 2900) previous-
ly referred to "archaeohyracid new taxon A" and
one of the specimens (SGOPV 285 1 ) referred to
"archaeohyracid new taxon D" in Wyss et al.,
1994 (see discussion below).

Archaeotypotherium pattersoni

(Figure 12)

HOLOTYPE— SGOPV 2918 (Fig. 12 A), right
maxilla with P2-M3, labial portions of teeth in-
completely preserved.

Hypodigm — Holotype of A. pattersoni; SGOPV
2917 (Fig. 12B), right mandible with p2-m3
(likely from the same individual as SGOPV
2918).

Type Locality — Locality C-89-37, otherwise
as for A. tinguiriricaense.

Age and Distribution — Earliest Oligocene
Tinguirirican SALMA (Flynn et al., 2003) of east-
central Chile (see above).

Diagnosis — As for Archaeotypotherium. Dif-
fers from Archaeotypotherium propheticus in less
persistent fossettes on upper molars, smaller and
more quadrangular upper premolars, and absence
of trigonid and talonid. Differs from A. tinguirir-
icaense in larger size (approx. 20% larger), pro-
portionately larger premolars, deeper mandible,
and thicker labial enamel on upper molars.

Etymology — After Bryan "Pat" Patterson, in
honor of his extensive contributions to South
American paleontology in general and archaeo-
hyracids in particular.^

Description — A maxilla with upper dentition is
designated the holotype for A. pattersoni because
it preserves many diagnostic features, and ar-
chaeohyracid taxa typically are most readily dis-
tinguished using characters of the upper dentition.
A well-preserved mandible with moderately worn
p3-m3 (SGOPV 2917; Fig. 12B) probably rep-
resents the lower dentition of A. pattersoni. This
specimen matches the holotype maxilla very well
in size, degree of hypsodonty, and state of wear.
The two specimens were found near each other in
the field and exhibit similar preservation, and it is
quite possible that they represent the same indi-
vidual.

Upper Dentition — Specimen SGOPV 2918
(Fig. 12 A) consists of a right maxilla with mod-
erately worn P2-M3; most of the teeth have in-
completely preserved labial surfaces. A very
small portion of PI is also present within its al-
veolus. The specimen is quite high-crowned, with
a level of hypsodonty comparable to, or perhaps
slightly exceeding, that of A. tinguiriricaense. Be-
cause the teeth have undergone moderate wear,
little occlusal morphology is evident, except the
central fossa. Because the first and second upper
molars are broken labially, we are unable to dis-
cern the pattern of external fossettes (if present).
However, as M3 exhibits no external fossettes and

* Most of Patterson's research on archaeohyracids ex-
ists only in the form of an unpublished manuscript.
Simpson (1967) alluded to this work-in-progress and
chose to honor Patterson's research by erecting a new
taxon, Bryanpattersonia. Because the present publica-
tion formally invalidates the name Bryanpattersonia
(based on the principle of priority), it is especially ap-
propriate that one of the new species in this group be
named for Pat in its place.

22

FIELDIANA: GEOLOGY

Fig. 12. Epoxy casts of specimens of Archaeotypotherium pattersoni. A. SGOPV 2918 (holotype), right maxilla
with P2-M3, slightly damaged labially, occlusal view. B. SGOPV 2917, right mandible with p2-m3 (likely same
individual as SGOPV 2918), occlusal view. Scale bar = 1 cm.

is the least worn of the molars, it is likely that
these fossettes (if indeed present in more anterior
molars) disappeared early in wear. The premolars
all are trapezoidal in outline, as are M2 and M3.
Well-defined parastyle and paracone grooves are
present on all cheek teeth and are the only pro-
nounced features of the labial surface. Dental
measurements are presented in Table 5.

Lower Dentition — A single fossettid is located
between the trigonid and the talonid on p4-m2,
resulting from an isolated fragment of the internal

groove; this has not yet been isolated through
wear in m3. The lingual sides of the teeth are
nearly flat, although a short groove is present on
the posterointernal corner of the talonid, separat-
ing the entoconid from the hypoconulid; it has
been obliterated by wear in ml but is still present
as a wide sulcus in m3.

The mandibular ramus is substantially deeper
than in A. tinguiriricaense (SGOPV 3043, 3067).
In A. pattersoni the mandible is 18.6 mm deep
just anterior to m 1 and perpendicular to the lower

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

23

Table 5. Measurements to the nearest 0.1 mm for specimens oi Archaeotypotherium pattersoni. Measurements
in parentheses are estimated.

Upper dentition

P2

P3

P4

Ml

M2

Lower dentition

p2

p3

p4

ml

in2

M3

Specimen

Wear

L

W

L

W

L

W

L

w

L

W

L

W

SGOPV 2918

Moderate

(5.7)

(6.3)

(6.5)

7.2

8.5

8.1

10.1

—

10.3

(9.1)

12.5

6.9

m3

Specimen

Wear

L

W

L

W

L

W

L

W

L

w

L

W

SGOPV 2917

Moderate

—

—

8.4

5.2

8.3

6.0

8.8

6.4

11.0

5.9

12.2

5.0

edge of the mandible, whereas in A. tinguiriri-
caense (SGOPV 3043) it measures only 15.7 mm.
Posterior to m3, the mandibular depth is just over
28 mm in A. pattersoni, whereas it is about 24
mm in A. tinguiriricaense.

Discussion — Wyss et al. (1994) tentatively at-
tributed SGOPV 2918 and the highly worn
SGOPV 2851 (Fig. 8) to "archaeohyracid new
taxon D" based on a number of shared character-
istics. These included: (1) the two specimens are
within 30% of each other in size; (2) the mor-
phology of SGOPV 2851 could plausibly be de-
rived from SGOPV 2918 through significant
wear; (3) the concave form and the texture of the
molar bases are similar in both specimens; (4) the
general cheek tooth outlines are similar in both
specimens.

Two of the characteristics listed above as sup-
porting the assignment of SGOPV 2918 and 2851
to the same taxon do not distinguish these speci-
mens from A. tinguiriricaense: SGOPV 2851 can
also plausibly be derived from specimens of A.
tinguiriricaense through wear (No. 2 above) and
the general cheek-tooth outlines are comparable
(No. 4 above). The primary characteristic that dis-
tinguishes A. tinguiriricaense and A. pattersoni is
size, the latter being significantly larger and the
former comparing much more favorably with
SGOPV 2851. This is especially apparent when
the state of wear of each specimen is taken into
account. Additionally, the labial surfaces of the
teeth of SGOPV 2918 have been exposed to their
bases, permitting basal lengths (presumably sim-
ilar to lengths after much wear) to be compared
directly. In SGOPV 2851, the bases of P2-M3
measure 41.2 mm, whereas the corresponding
length in SGOPV 2918 is approximately 51 mm,
a difference of 20%. Although this would not nor-
mally be considered a significant difference when

comparing individual tooth values between ar-
chaeohyracid specimens, it is considerable for a
tooth-row length. Unfortunately, no upper teeth of
A. tinguiriricaense have been exposed to their ba-
ses, precluding a comparable measurement in that
taxon. As Table 4 illustrates, the tooth measure-
ments of SGOPV 2851 are what would be ex-
pected for a specimen of A. tinguiriricaense with
heavily worn teeth.

The lack of comparable specimens of A. tin-
guiriricaense again does not allow for a proper
comparison of features of the tooth bases (i.e.,
concave nature and similar texture. No. 3 listed
above). The variation in these characters within
the species (and within individuals) is not known,
but it is interesting to note that the right M3 of
SGOPV 285 1 is much more concave than the left
M3 of the same specimen. Additionally, there are
differences in the morphology of SGOPV 2851
and SGOPV 2918, including a much more gently
tapering shape to the edge of the enamel in
SGOPV 285 1 , although this also could be a var-
iable character. In light of the metric similarities
between SGOPV 2851 and A. tinguiriricaense and
the lack of discrete morphologic differences, it
seems more likely that SGOPV 285 1 represents a
specimen of A. tinguiriricaense with heavily worn
teeth, rather than A. pattersoni. Thus, we here re-
fer to A. pattersoni two of the three specimens,
SGOPV 2918 and SGOPV 2917, previously attri-
buted to "Archaeohyracid new taxon D" (Wyss
et al., 1994).

Pseudhyrax Ameghino, 1901

(Figures 13-17)

Type Species — Pseudhyrax eutrachytheroides
Ameghino, 1901.

24

FIELDIANA: GEOLOGY

Included Species — The type species, Pseudhy-
rax strangulatus (Ameghino, 1901), and the in-
determinate material described here.

Diagnosis — Simpson (1967, p. 109) diagnosed
Pseudhyrax as "Closely similar to Eohyrax and
probably intergrading with that genus, but more
progressive, more hypsodont, lower molars tend-
ing to develop a second closed talonid fossette
and a closed trigonid fossette." As emended here,
Pseudhyrax is a member of the Hegetotheria that
differs from Hegetotheriidae in absence of hyp-
selodont (ever-growing) cheek teeth, absence of
hypselodont 1 1 , absence of straight lingual face on
lower molars, presence of fossettes/fossettids at
some stages of wear in upper and lower molars,
and presence of significant change in cheek tooth
shape with wear. Differs from Archaeotypother-
ium, Protarchaeohyrax, Archaeohyrax and the
new archaeohyracid taxon from Antofagasta de
La Sierra (Lopez, 1997; Reguero & Lopez, 1999)
by lower degree of hypsodonty, greater persis-
tence of accessory fossettes with wear, presence
of internal sulcus on endoloph, more pronounced
ectoloph ridges, and more quadrangular cheek
teeth. Larger than Protarchaeohyrax and the new
archaeohyracid taxon from Antofagasta de La Si-
erra (Lopez, 1997; Reguero & Lopez, 1999). Pro-
toloph less transverse than the new archaeohyra-
cid taxon from Antofagasta de La Sierra (Lopez,
1997; Reguero & Lopez, 1999).

Age and Distribution — Latest Eocene Muster-
san of Patagonia and earliest Oligocene Tinguirir-
ican SALMA (Flynn et al., in press) of Patagonia
and east-central Chile (see above).

Comments — Simpson (1967) recognized two
species of Pseudhyrax: P. eutrachytheroides and
P. strangulatus. These two are differentiated by
size only, and Simpson (1967), while still recog-
nizing the specific status of P. strangulatus, ex-
pressed doubt as to whether its smaller size was
due to taxonomic distinction or merely intraspe-
cific variation.

In order to examine size variation within the
Argentine sample of Pseudhyrax, molar lengths
and widths from a large number of specimens (N
= 23) were recorded and examined on a bivariate
plot (Fig. 13). This plot reveals the following
points. First, a gap in the size distribution appears
to be present, and is most pronounced for m3.
This distribution suggests that Pseudhyrax speci-
mens with m3 longer than 11.5 mm and wider
than 5.0 mm should be referred to P. eutrachy-
theroides, while those with m3 shorter than 9.2
mm and narrower than 5.0 mm should be referred

:5 1.8-
■g

"c 1.7

;

■ ■

: •

•

■

▲

;

• •

nm

\

V-".

•

•

: ■

. ^

A

A
A

A^

ml

m2 m3

.

A ^

P. eutnchyttteroides

■ A

■

P strangulatus

■ A

■

1 ■ ■ ■ 1 1 T 1

r I I t I 1 •

Tinguifirica Pseudfiyrax

D A

1 r I r t I 1 T I 1 r T

■T F T I

1.9 2.0 2.1 22 2.3 2.4 2.5 2.6 2.7 2.8

In(Length)

Fig. 13. Bivariate plot of lower molars of Pseud-
hyrax from the Mustersan of Chubut, Argentina. Tin-
guiririca specimen 1 represents SGOPV 2985 (P. eu-
trachytheroides) and Tinguiririca specimen 2 represents
SGOPV 2887 (P. strangulatus).

to P. strangulatus. Second, based on this plot, one
large specimen identified as P. strangulatus (MLP
67-11-27-272) is probably referable to P. eutrach-
ytheroides. Finally, the uneven ratio of P. eu-
trachytheroides to P. strangulatus specimens
(approx. 10:1) suggests that this size difference is
not due to sexual dimorphism, and more likely
represents taxonomic distinction.

Pseudhyrax eutrachytheroides Ameghino, 1901

(Figures 14-16)

HoLOTYPE — M ACN A- 1 1 662, maxillary frag-
ment with dP2-4, Ml (Simpson, 1967).

Referred Specimens— SGOPV 2985, right
mandibular fragment with partial m2, m3 (Fig.
14B); SGOPV 2877 (tentatively), left and right II
and left P3-M3 (Fig. 15).

Type Locality — Unknown.

Age and Distribution — As for Pseudhyrax.

Diagnosis — Differs from P. strangulatus in its
larger size.

Comments— SGOPV 2985, a right mandibular
fragment with partial m2, m3, compares well with
moderately worn specimens of Pseudhyrax from
Argentina. Based on its size and indistinguishable
morphology, SGOPV 2985 is referred to P. eu-
trachytheroides (see Fig. 13 and Table 6).

No upper teeth attributable to Pseudhyrax
have been previously recorded from the Tingui-
ririca assemblage. Wyss et al. (1994) noted the
possibility that, given the conservative nature of

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

25

Fig. 14. Mandibles from the Tinguiririca Fauna referred to Pseudhyrax. A, Epoxy cast of SGOPV 2887, Pseud-
hyrax strangulatus, right partial mandible with m2-3. B, SGOPV 2985, Pseudhyrax eutrachytheroides, right man-
dibular fragment with partial m2, m3, photo of epoxy cast (left) and illustration (right). Scale bar - 5 mm.

archaeohyracid lower dentitions, one or both of
the Tinguiririca Fauna lower dentition specimens
identified as Pseudhyrax might instead pertain to
another archaeohyracid species from Tinguiriri-
ca, better known from upper teeth. The other
possibihty, endorsed here, is that some (or at
least one) of the well-known upper dentitions
from Tinguiririca is/are actually referable to
Pseudhyrax (viz., SGOPV 2877, "archaeohy-
racid new taxon B" of Wyss et al., 1994; Table
7).

SGOPV 2877 is a well-preserved upper dental
series, including left and right II and left P3-M3
(Fig. 15; Table 6). Although a small fragment of
P2 is preserved, the morphologies of the posterior
incisors, canine, and anteriormost premolar (if
they were present) are unknown. No bone of the
palate or maxilla is present, so the presence of
teeth cannot be discerned from alveoli. The cheek
teeth are relatively low-crowned (at least as com-
pared with other contemporaneous archaeohyra-
cids), similar to that exhibited by Pseudhyrax. The

teeth are moderately worn, except for M3, which
is only slightly worn.

The two incisors are enlarged and spatulate.
They curve posteriorly and are obliquely implant-
ed, meeting at the tips. A strong enamel face is
present on the anterior face of each tooth, but
enamel appears to be absent from the back, thus
creating a long, self-sharpening edge.

The premolars in SGOPV 2877 show a rela-
tively high degree of molarization. In lateral view,
the metacone, paracone, and parastyle ridges are
easily distinguishable, the latter two being conflu-
ent at the base of the tooth. In occlusal view, the
ridges of the paracone and parastyle are more pro-
nounced than that on the metacone, but no par-
astylar "spur" is present. Each premolar is sub-
quadrangular and longer than wide; the lingual
and labial sides are essentially parallel, and the
anterior and posterior faces are nearly so. The
only feature on the tooth distinguishing the two
internal cusps is a slight sulcus on the lingual
face. Both premolars are worn and have nearly

26

FIELDIANA: GEOLOGY

B

Fig. 15. SGOPV 2877, Pseudhyrax cf. P. eutrachytheroides, left and right II, left P3-M3. A. Occlusal view. B.
Reconstruction of SGOPV 2877 with M3 in life position. Scale bar = 1 cm.

featureless occlusal surfaces, save for an elongate
central fossa oriented anterolabially.

The first two molars also display moderate
wear. As in the premolars, the amount of wear on
each tooth increases posterolingually, resulting in
the anterolabial comer of each tooth being the
highest part of the crown. The ectoloph is at least
half again as high as the endoloph in these teeth,
and the front edge of each tooth is higher than the
posterior edge of the tooth directly in front of it.
The molars possess a better-developed parastylar
spur than do the premolars, but this structure
overlaps little, if any, with the proximate anterior
tooth. Enamel is absent along the labial portion of
the anterior and posterior faces of Ml -2, permit-
ting a confluence of the dentine of the occlusal
surfaces just medial to the ectoloph.

Both Ml and M2 retain a central fossa that is
confluent with the median external fossette. In M 1
this fossa is concave anteromedially. The central
fossa is larger in M2, owing to the lesser amount
of wear. Additionally, whereas the external fos-
sette is a small circular structure abutting the cen-
tral fossa in Ml, in M2 it is located further labi-
ally and is joined to the central fossa by a long,
thin isthmus. Only M2 retains a posterior external
fossette. Due to the high angle of wear along the
internal face of the ectoloph, the posterior external

fossette appears as an elongate structure, roughly
parallel to the median external fossette and its
isthmus.

The third molar is separated from M2 by a siz-
able gap (5 mm), presumably the result of post-
mortem dislocation. As expected with the eruption
pattern, M3 shows the least amount of wear and
preserves the greatest occlusal detail among the
molars; the lesser degree of wear is especially ev-
ident in the shape of the tooth (subtriangular), the
high protocone (it is flush with the occlusal sur-
face in worn teeth), and the shape of the ectoloph
in lateral aspect (the ectoloph is tapered at both
the base and the occlusal surface in M3, whereas
it only tapers at the base in worn teeth like Ml-
2). It possesses a pronounced metastylar ridge that
becomes more prominent toward the base of the
tooth.

As in M2, a more posteriorly located external
fossette is evident on M3, in addition to the cen-
tral fossa and associated median external fossette.
This posterior external fossette has less occlusal
exposure than does the corresponding fossette in
M2 (owing to a less oblique angle of wear) and
it appears as an oval structure that is approxi-
mately the same size as the posterior end of the
central fossa. Other very small, isolated enamel
lakes (microfossettes) are located on the surface

CROFT ET AL.: LARGE ARCH AEOHYR ACIDS FROM CHILE AND PATAGONIA

27

Fig. 16. Occlusal views of P. eutrachytheroides
specimens from the Mustersan of Chubut, Argentina. A.
MLP 61-IV-9-1, slightly worn left maxilla with P1-M3
from Laguna del Mate, shown as right. B. MLP 67-11-
27-359, heavily worn palate with left and right II -Ml,
right M2 and partial M3 from La Gran Hondonada.
Scale bar = 1 cm.

of M3. Two microfossettes form a transversely
oriented pair in the anteroexternal region of the
tooth; two others form an obliquely oriented pair
in the posteroexternal region of the tooth; and a
single microfossette is located posteriorly and in-
ternal to the posterior external fossette.

SGOPV 2877 has been described as one of the
more unusual typotheres known from the Tingui-
ririca Fauna, and was designated "archaeohyracid
new taxon B" by Wyss et al. (1994) and as Ty-
potheria incertae sedis by Croft (2000). However,
further comparisons among a wider series of spec-
imens and a better understanding of wear-related
change in archaeohyracid teeth suggest that the
atypical morphology of SGOPV 2877 may result
from unusual preservation (e.g., the lack of bone
and the absence of some teeth), a relative scarcity
of appropriate comparative material, and unusual
wear-related shape changes in the teeth relative to
other taxa.

SGOPV 2877 can be excluded from all other
typotheres except the Archaeohyracidae based on
the following characteristics: differs from Cam-
panorcidae in presence of more hypsodont teeth,
presence of more deeply rooted 1 1 , absence of un-
dulating ectoloph on upper molars; differs from
Archaeopithecidae in presence of spatulate first
incisors, premolars with enlarged hypocone, ab-
sence of lingual sulcus on upper molars, more
pronounced parastyle ridge on molars, and large
size; differs from Oldfieldthomasiidae in more
hypsodont cheek teeth and enlarged incisors; dif-
fers from Notopithecinae in large size and lack of
bilobed incisors; lacks hypsodont, bilobed upper
cheek teeth of Interatheriinae; lacks hypsodont,
trilobed upper cheek teeth of Mesotheriidae; and

Table 6. Measurements to the nearest 0.1 mm for specimens of Pseudhyrax (P. eutrachytheroides: SGOPV 2985
and tentatively SGOPV 2877; P. strangulatus: SGOPV 2887; Pseudhyrax sp. indet.: SGOPV 2901). Measurements
in parentheses are estimated.

Upper dentition

P2

P3

P4

Ml

M2

M3

Specimen

Wear

L

W

L

W

L

W

L

W

L

W

L

W

SGOPV 2877

Moderate

—

—

5.8

7.2

7.0

7.6

7.6

8.6

9.8

7.9

10.3

6.8

Lower dentition

p2 p3 p4 ml m2 m3

Specimen Wear LWLWLWLW LW L W

SGOPV 2985 Moderate ______ _ _ _ 6.8 12.7 5.8

SGOPV 2887 Moderate ______ _ _ 8.1 5.3 (8.2) 4.5

SGOPV 2901 Moderate — — — _ _ _ (7.2) (65) (8.1) (7.3) (10.0) (5.3)

28

FIELDIANA: GEOLOGY

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lacks hypselodont, simplified upper cheek teeth of
Hegetotheriidae.

Among the Archaeohyracidae, the following
characters suggest affinities with Pseudhyrax:
hypsodonty greater than that exhibited by Eohy-
rax, but less than that in Archaeotypotherium,
Protarchaeohyrax, and Archaeohyrax; upper
cheek teeth with prominent paracone and para-
style ridges on molar ectolophs; accessory fos-
settes present on molars even after moderate wear;
presence of elongate central fossa, oriented anter-
olabially; and presence of a slight sulcus on en-
doloph dividing protocone and hypocone.

The total absence of the maxillary bones (and
associated alveoli) does not permit the presence
or absence of I2-P1 to be ascertained. Although
it has been speculated that a significant diastema
could have been present (Wyss et al., 1994; Croft,
2000), the presence of a closed dentition is equal-
ly plausible. Nothing in the morphology of the
preserved dentition precludes referral to Pseudhy-
rax.

In overall form, SGOPV 2877 is most similar
to MLP 61-IV-9-1 (Fig. 16A), a Pseudhyrax left
maxilla from Laguna del Mate (reference) with all
premolars and molars preserved. If such a speci-
men were to undergo further wear, one would ex-
pect the prominence of the external fossettes to
decrease and the teeth to become shorter (antero-
posteriorly), wider, and more quadrangular. Such
a hypothetical specimen would likely be very sim-
ilar to SGOPV 2877. Unfortunately, few Pseudhy-
rax specimens containing the upper cheek tooth
series are known, and so a direct comparison be-
tween SGOPV 2877 and a Pseudhyrax specimen
of comparable wear state is not possible. MLP 67-
11-27-359 (Fig. 16B) represents a Pseudhyrax pal-
ate with most of the teeth preserved, but it has
undergone even more wear than SGOPV 2877. A
comparison of tooth outlines in MLP 61-IV-9-1,
SGOPV 2877, and MLP 67-11-27-359 suggests
that these specimens may represent a reasonable
wear series for Pseudhyrax.

If the upper dentition of SGOPV 2877 does
represent Pseudhyrax, it solves the "problem" of
the lack of good candidates for the lower dentition
of SGOPV 2877 (see further discussion below);
there do exist good candidates, they just were
never recognized as such. Similarly, the recogni-
tion of SGOPV 2877 as Pseudhyrax also provides
an explanation of why no upper remains referable
to Pseudhyrax had been found previously within
the extensive archaeohyracid collections from the
Tinguiririca Fauna. Again, at least one example

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

29

Fig. 17. SGOPV 2901, Pseudhyrax sp. indet., left
mandibular fragment with partial ml-m3 in oblique la-
bial view (left) and occlusal view (right). Scale bar = 1
cm.

would have been present, but was unrecognized.
As P. eutrachytheroides is the better known of the
two species of Pseudhyrax, and because SGOPV
2877 is similar in size and morphology to Argen-
tine specimens referred to P. eutrachytheroides,
SGOPV 2877 is tentatively referred to that taxon.

Pseudhyrax strangulatus (Ameghino, 1901)

(Figure 14 A)

HoLOTYPE — MACN 10774, partial right man-
dible with p4-m2.

Referred Specimen — SGOPV 2887, right man-
dibular fragment with m2-3 (Fig. 14A).

Type Locality — Unknown.

Age and Distribution — As for Pseudhyrax.

Diagnosis — Differs from P. eutrachytheroides
in its smaller size.

Comments — SGOPV 2887, a right mandibular
fragment with m2-3, is morphologically similar
to relatively unworn specimens of Pseudhyrax
from Argentina. Based on its size, SGOPV 2887
is referred to P. strangulatus (see Fig. 13 and Ta-
ble 6).

Pseudhyrax sp. indet.

(Figure 17)

Referred Specimen— SGOPV 2901, left man-
dibular fragment with partial ml-m3 (Fig. 17),
from the Tinguirirican-aged Tinguiririca Fauna of
Chile (see above for age discussion).

Comments — SGOPV 2901 is a peculiar speci-
men. As noted by Wyss et al. (1994: 18), it re-

sembles specimens of Pseudhyrax, but the "bi-
zarre anteroposteriorly shortened talonid on m2"
and "its posteroexternal termination which forms
a tight, nearly 90° corner" make this taxon "un-
mistakably distinct from any archaeohyracid
known." A similar shortening of the talonid is
described in the new archaeohyracid taxon from
Antofagasta de La Sierra (Lopez, 1997; Reguero
& Lopez, 1999), an archaeohyracid allied to
Pseudhyrax (Reguero & Lopez, 1999, in prep.)
from probable Mustersan-aged strata from north-
west Argentina (Lopez, 1997). However, the de-
gree to which the m2 talonid is compressed and
the abrupt angle of the posteroexternal corner of
SGOPV 2901 make the specimen distinct from
any other notoungulate currently known.

Wyss et al. (1994) referred SGOPV 2901 to
"archaeohyracid new taxon C" and suggested,
based on size and morphology, that it might rep-
resent a portion of the lower dentition of what
they called "archaeohyracid new taxon B"
(SGOPV 2877, discussed above). The plausibility
of SGOPV 2877 and SGOPV 2901 representing
the same taxon was also supported by Croft
(2000). If the conclusions reached above regard-
ing the taxonomic affinities of SGOPV 2877 are
correct (viz., that SGOPV 2877 is referable to
Pseudhyrax eutrachytheroides), the potential for
the referral of SGOPV 2901 to that taxon warrants
consideration.

Indeed, certain attributes of SGOPV 2901 sup-
port the interpretation that the very unusual fea-
tures of this specimen may be the result of incom-
plete preservation and post-mortem deformation,
rather than peculiar attributes of a new taxon.
First, although the lingual portions of the talonids
of both ml and m2 are preserved, only the talonid
of m2 exhibits the unusual, 90° posteroexternal
termination. In other notoungulates, the morphol-
ogies of the talonids on m 1 and m2 are generally
very similar to each other. This suggests that one
of the two talonids in SGOPV 2901 may have
been deformed, probably the talonid of m2. Sec-
ond, a slight ridge is present on the lateral surface
of the mandible in SGOPV 2901, oriented nearly
perpendicular to the long axis of the mandible.
The ridge terminates at the base of the talonid of
m2 and looks as if it might have resulted from a
small anteroposterior compression fold in that
portion of the mandible. If this deformation took
place plastically, it might have altered the typical
rounded talonid morphology (exhibited by ml)
into the peculiar, sharply angled morphology ex-
hibited by m2. Third, the talonid of ml presents

30

FIELDIANA: GEOLOGY

a small fossettid directly posterior to the central
fossa, a condition characteristic of Pseudhyrax; no
other characters of ml, the trigonid of m2, or m3
preclude assignment to that taxon. Finally, the di-
mensions of at least m3 suggest that SGOPV 2901
falls within the range exhibited by Argentine and
Tinguirirican Pseudhyrax material (Fig. 13; Ta-
ble 6).

Taking into consideration these observations,
there is a reasonable possibility that SGOPV 2901
represents Pseudhyrax eutrachytheroides. How-
ever, if the unusual structure of the talonid is not
due to deformation, the specimen surely repre-
sents a new archaeohyracid, perhaps allied to the
new archaeohyracid taxon from Antofagasta de
La Sierra (Lopez, 1997; Reguero & Lopez, 1999).
Given the abundance of poorly founded and/or
synonymous names that already exist for so many
notoungulates, we refrain from proposing a new
taxon based on SGOPV 2901, at least until ad-
ditional specimens come to light that further clar-
ify the specimen's affinities. SGOPV 2901 is
therefore provisionally referred to Pseudhyrax sp.
indet.

Phylogenetic Relationships

To determine the phylogenetic relationships of
the new Tinguirirican archaeohyracids, a prelim-
inary analysis of the five currently recognized ar-
chaeohyracid "genera" was undertaken. Two
well-known basal typotheres were chosen as out-
groups, Oldfieldthomasia (Oldfieldthomasiidae)
and Acropithecus (Archaeopithecidae). A repre-
sentative hegetotheriid (Hegetotherium) was also
included in the analysis, since many recent phy-
logenetic analyses have suggested that hegetoth-
eriids are nested within the series of taxa tradi-
tionally included with the Archaeohyracidae (Ci-
felli, 1993; Hitz, 1995; Croft, 1998; Reguero,
1999; Croft, 2000). The eight taxa were scored
for 22 craniodental characters, most modified
from the more detailed analyses in Croft (2000).
The complete list of characters follows. Charac-
ters with multiple derived character states are or-
dered unless designated by an asterisk. The char-
acter-taxon matrix is presented in Table 8.

1. Height of cheek tooth crowns: brachydont,
HI < 1.0 (0); moderately hypsodont, 1.0 <
HI < 1.75 (1); very hypsodont, HI > 1.75
(2); rootless, HI undefined (3).

2. Cementum: absent (0); present (1).

3. Relative size of II: mesiodistal length <
50% premaxilla length (0); mesiodistal
length ^ 50% premaxilla length (1).

4. Enamel on 1 1 : present on anterior and pos-
terior faces (0); present only on anterior face

(1).

5. 12: present (0); significantly reduced (peg-
like and < 50% size of M 1 ) or absent ( 1 ).

6. Upper dentition: closed (0); with diastemata
separating anterior teeth (1).

7. Upper molars: with lingual sulcus (0); with-
out lingual sulcus (1).

8. Accessory fossettes on upper molars after
isolation of central fossa: present (0); absent

(1).
9.* Shape of lingual notch separating upper mo-
lar protocone and hypocone; broad-based,
"u-shaped" (0); sharp-based, "v-shaped"
(1); no notch present (2).

10. M3: without posterior lobe (0); with poste-
rior lobe formed by metastyle (1).

11. Lower incisors: implanted subvertically (0);
markedly procumbent (1).

12. Relative size of p3 and p4: smaller than an-
terior molars (0); similar in size to anterior
molars (1).

13. Lower molar central trigonid fossettid: ab-
sent (0); present (1).

14. Lower molar lingual fossettid between tri-
gonid and talonid: absent (0); present (1).

15. Lingual side of lower molars: with sulcus
(0); flat after advanced wear (1); present as
salient, straight wall (2).

16. Lower molar shape: varies little with wear
(0); develops lingual talonid extension with
heavy wear (1).

17.* Shape of lingual notch separating m3 ento-
conid and hypoconulid: narrow and deep
(0); wide and shallow (1); notch absent (2).

18. Small fossettid between m3 entoconid and
hypoconulid: absent (0); present (1).

19. Labial surface of m3 talonid: relatively
smooth (0); with sulcus between hypoconid
and hypoconulid (1); with pronounced notch

(2).

20. Carotid foramen: located posterior to audi-
tory bulla (0); shifted anteriorly, medial to
auditory bulla (0).

2 1 . Vertical septum in auditory bulla: absent (0);
present (1).

22. Hamular process of pterygoid: present (0);
absent (1).

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

31

Table 8. Matrix of characters used in phylogenetic analysis of archaeohyacid relationships.

1

1

1

1

1

1

1

1

1

1

2

2

2

1

2

3

4

5

6

7

8

9

1

2

3

4

5

6

7

8

9

1

2

Oldfieldthomasia

Acropithecus

1

7

1

2

Eohyrax

1

1

7

7

7

7

Pseudhyrax

1

7

1

7

7

1

1

1

7

7

7

Archaeotypotherium

2

1

1

1

1

1

1

1

I

1

7

1

Protarchaeohyrax

2

7

7

7

7

1

1

1

1

1

1

1

7

7

7

Archaeohyrax

2

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

Hegetotherium

3

1

1

1

1

1

1

1

2

1

1

2

2

1

1

1

The data matrix, analyzed using the exhaustive
search option in PAUP 3.1.1, resulted in four
equally most parsimonious trees of 36 steps each.
The strict consensus of these four trees is pre-
sented in Figure 18. Consistent with previous
analyses, Hegetotherium nests within a clade that
would traditionally be termed the Archaeohyra-
cidae, suggesting that Archaeohyracidae (in its
classical sense) is paraphyletic. Specifically, He-
getotherium and two archaeohyracids {Protar-
chaeohyrax and Archaeohyrax) are united in an
unresolved polytomy based on shared, derived
features of the upper dentition: No. 8(1): acces-
sory fossettes on upper molars absent after iso-
lation of central fossa; No. 10(1): M3 with pos-
terior lobe formed by metastyle; No. 9(1): lingual
notch between protocone and hypocone "v-
shaped" ("u-shaped" is ancestral condition; no

notch is present in Hegetotherium). The identity
of the closest relative of Hegetotherium is uncer-
tain, an ambiguity arising from the relatively large
amount of missing data for Protarchaeohyrax;
pending the recovery of material permitting the
scoring of these missing characters, either Ar-
chaeohyrax or Protarchaeohyrax is the likeliest
proximal outgroup to Hegetotheriidae. Of partic-
ular utility would be recovering of specimens pre-
serving the anterior dentition of Protarchaeohy-
rax. The temporally later occurrence of Archaeo-
hyrax (Table 9) and the presence of at least one
synapomorphy shared by Archaeohyrax and He-
getotherium to the exclusion of Protarchaeohyrax
(No. 2(1): cementum present), predict that future
analyses will find support for an exclusive closest
relationship between Archaeohyrax and Hegeto-
theriidae. (In the present analysis, no synapomor-

Table 9. Currently recognized archaeohyracid species.

Taxon

SALMA

Region

Reference

FORMALLY NAMED TAXA

Eohyrax rusticus Casamayoran

Eohyrax isotemnoides Casamayoran

Eohyrax praerusticus Casamayoran

Pseudhyrax strangulatus Mustersan

Tinguirirican

Pseudhyrax eutrachytheroides Mustersan

Tinguirirican

Protarchaeohyrax gracilis Tinguirirican

Protarchaeohyrax intermedium Tinguirirican

Protarchaeohyrax minor Tinguirirican

Archaeotypotherium propheticus Tinguirirican

Archaeotypotherium tinguiriricaense Tinguirirican

Archaeotypotherium pattersoni Tinguirirican

Archaeohyrax patagonicus Deseadan

INFORMAL TAXA

Gen. et sp. nov. Mustersan

Protarchaeohyrax sp. nov. Deseadan

Archaeohyrax sp. nov. Deseadan

Patagonia

Patagonia

Patagonia

Patagonia

Central Chile

Patagonia

Central Chile

Patagonia; central Chile

Central Chile

Patagonia

Patagonia

Central Chile

Central Chile

Patagonia

Catamarca, Argentina

Uruguay

Bolivia

Bolivia

Simpson, 1967
Simpson, 1967
Simpson, 1967
Simpson, 1967
Present study
Simpson, 1967
Present study
Reguero et al., 2003
Reguero et al., 2003
Reguero et al., 2003
Present study
Present study
Present study
[Ameghino, 1897]

Reguero & Lopez, 1999
Reguero et al., 1995
Reguero & Cifelli, 1997
Reguero & Cifelli, 1997

32

FIELD! AN A: GEOLOGY

Oldfieldthomasia

Acropithecus

Eohyrax

Pseudhyrax

Archaeotypotherium

Protarchaeohyrax

Archaeohyrax

Hegetotherium

Fig. 18. Strict consensus tree representing the phy-
logenetic relationships among archaeohyracids. The out-
groups for the analysis are Oldfieldthomasia (Oldfield-
thomasiidae) and Acropithecus (Archaeopithecidae).
Consistency Index (CI) = 0.78; Rescaled Consistency
Index (RCI) = 0.59; Retention Index (RI) = 0.76;
Length = 36 steps.

phies uniting Protarchaeohyrax and Hegetother-
ium to the exclusion of Archaeohyrax were iden-
tified.)

The taxa forming the focus of the present study,
Archaeotypotherium and Pseudhyrax, represent
successive outgroups to the Protarchaeohyrax-
Archaeohyrax-Hegetotherium triad. Five synapo-
morphies Hnk Archaeotypotherium with these
three taxa, making it the most robustly supported
clade in the analysis: No. 1(2—3): HI of cheek
teeth > 1.75; No. 6(1): upper dentition with dia-
stemata separating anterior teeth; No. 7(1): upper
molars without lingual sulcus (reversed in Protar-
chaeohyrax); No. 15(1 ~2): lingual side of lower
molars flat; No. 17(1): wide and shallow lingual
notch separating m3 entoconid and hypoconulid
(the notch is absent in Hegetotherium). The three
basicranial characters (Nos. 20-22) and two in-
cisor characters (3 and 1 1 ) represent derived
states shared by at least these taxa (and possibly
more basal archaeohyracids as well, although the
lack of skulls and anterior dentitions for those ear-
lier diverging taxa precludes more definitive iden-
tification of the node[s] to which these synapo-
morphies pertain).

Three synapomorphies diagnose Pseudhyrax
and later diverging archaeohyracids (plus Hege-
totherium) to the exclusion of Eohyrax (the ear-
liest diverging archaeohyracid): No. 13(1) pres-
ence of lower molar central trigonid fossettid (lost
in Hegetotherium); No. 18(1): presence of small
fossettid between m3 entoconid and hypoconulid
(either lost in Protarchaeohyrax and Hegetother-

ium [ACCTRAN optimization] or independently
derived in Pseudhyrax, Archaeotypotherium, and
Archaeohyrax [DELTRAN optimization]); No.
19(1): labial surface of m3 talonid with sulcus be-
tween hypoconid and hypoconulid (lost in Prot-
archaeohyrax).

Eohyrax is located at the base of the tree in a
polytomy with the two outgroup taxa and the
clade of remaining ingroup taxa. Although this
topology does not indicate that Eohyrax and other
archaeohyracids share a most recent common an-
cestor (MRCA) exclusive of the outgroups, the
presence of a single derived character in Eohyrax
and all archaeohyracids for which the character
could be coded [No. 4(1): lack of enamel on the
posterior face of II] suggests more detailed anal-
yses will find greater support grouping Eohyrax
and other archaeohyracids. Based on their distri-
bution, the derived character states present in Ac-
ropithecus appear to have been acquired indepen-
dently in some archaeohyracids and/or Hegeto-
therium.

A notable feature of this analysis is the strong
congruence between the branching order of the
cladogram and the relative stratigraphic positions
of the taxa (cf. Fig. 18 and Table 9); in no instance
does the proximal outgroup to a clade have a first
appearance later than any of the ingroup taxa.
Since many of the derived character states in this
analysis are likely correlated with the consump-
tion of more abrasive vegetation (e.g., higher HI
values, simplified occlusal surfaces in the cheek
teeth, increased emphasis on the anterior dentition
and cheek teeth), the tight correlation between
cladogenesis and morphologic evolution suggests
that dietary selection strongly influenced archaeo-
hyracid evolution. The most robustly supported
clade in the analysis {Archaeotypotherium, Pro-
tarchaeohyrax, Archaeohyrax, Hegetotherium) re-
cords its first appearance in the earliest Oligocene
Tinguirirican SALMA (Flynn et al., 2(X)3); this
implies an initial divergence approximately coin-
cident with, and possibly causally related to, the
Eocene-Oligocene climatic deterioration (see be-
low). From a phylogenetic perspective, most (if
not all) of the characters conventionally used to
diagnose hegetotheriids (enlarged and hypselo-
dont II, hypselodont cheek teeth, complete lack
of dental fossettes and fossettids; Cifelli, 1993;
Reguero, 1998; Croft, 2(X)0) can be interpreted as
elaborations of derived character states already
present in the later diverging archaeohyracids. It
is therefore not surprising that Archaeohyracidae

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONIA

33

(in the classical sense of that name) is now shown
to be paraphyletic.

From the perspective of phylogenetic taxonomy
(de Quieroz & Gauthier, 1990), however, whereby
names are defined by linking them to specified
clades, names refer to monophyletic groups (by
definition). Thus, if one were to fashion a phylo-
genetic definition for the least inclusive clade in-
cluding Eohyrax and Archaeohyrax (e.g., Ar-
chaeohyracidae = MRCA of those two taxa plus
all its descendants), Archaeohyracidae would re-
fer to a clade happening to have as one of its
members a group (viz., Hegetotheriidae) of
"equivalent" taxonomic rank (at least as far as
traditional taxonomic suffixes are concerned).
Whether or not this "clash of suffixes" is viewed
as significant, the present phylogenetic analysis
points to the need for a comprehensive review of
the names associated with major clades of typo-
there notoungulates.

Based on the topology obtained in this analysis,
the species classically referred to as archaeohy-
racids and hegetotheriids (with the possible ex-
ception of Eohyrax) share an exclusive common
ancestry, and thus form an evolutionary entity
worthy of naming. A phylogenetic definition of a
name for this clade can be fashioned any number
of ways, each with pros and cons. For example,
in naming this clade, the clade itself might be de-
scribed (in the definition statement) with reference
to the MRCA of its earliest diverging member
{Eohyrax) and some other constituent (e.g., Ar-
chaeohyrax, Hegetotherium), plus all of its de-
scendants. Which taxon is specified in the second
position of this definition statement is relatively
unimportant, as any number of options would en-
compass all species presently termed archaeohyr-
acids or hegetotheriids and would exclude other
notoungulates.

One potential disadvantage of phrasing a defi-
nition in such a node-based fashion is that it
would not accommodate the discovery of earlier
diverging members of the clade. A stem-based def-
inition (sensu de Queiroz & Gauthier, 1990), how-
ever, would overcome this problem. Mesotheri-
idae has been advocated as the proximal outgroup
to archaeohyracids plus hegetotheriids (e.g., Ci-
felli, 1993; Croft, 2000), but the interrelationships
of typotheres have yet to be thoroughly examined.
Pending a comprehensive examination of the phy-
logenetic relationships among typotheres, a stem-
based definition for archaeohyracids plus hege-
totheriids could be formulated as all typotheres
more closely related to Archaeohyrax (or Hege-

totherium) than to Mesotherium, Interatherium,
Acropithecus, or Oldfieldthomasia.

Perhaps the more difficult question is which
names to attach to the major subclades of typoth-
eres about whose existence we are confident. The
names most commonly associated with the groups
discussed herein are the "family" names Ar-
chaeohyracidae and Hegetotheriidae. If conserv-
ing both of these long-used names is considered
desirable, Archaeohyracidae could be defined
such that it refers to all taxa previously referred
to both of these "families" collectively. As noted
above, however, having Hegetotheriidae nested
within another clade bearing a name with the
same suffix (Archaeohyracidae) could potentially
cause confusion. This problem might be circum-
vented by amending Hegetotheriidae to Hegetoth-
eriinae (and changing the included groups Hege-
totheriinae and Pachyrukhinae to Hegetotherini
and Pachyrukhini, respectively), but this tactic
would not preserve the two "family" names (the
original intention of such a scheme) and would
likely cause more confusion than clarification. Al-
ternatively, the name Hegetotheriidae could be de-
fined such that it applies to hegetotheriids plus the
taxa traditionally termed archaeohyracids, but
again, this arrangement would fail to preserve the
two "family" names. In either case, these names
would dramatically differ from their traditional
conceptions.

Rather than employ a traditional "family"
name to refer to the clade including both archaeo-
hyracids and hegetotheres, an alternative would
be to redefine a name traditionally used to encom-
pass a similar group. One obvious choice would
be Simpson's Hegetotheria (Simpson, 1945). This
suborder of Notoungulata originally included only
the Hegetotheriidae, but was later modified to also
include the Archaeohyracidae (Simpson, 1967). It
would thus seem reasonable to tie either a node-
based or a stem-based definition to this name to
encompass both hegetotheriids and archaeohyra-
cids, concordant with Simpson's conception of the
group. Another option would be Hegetotheroidea,
proposed by Romer (1966) as including both ar-
chaeohyracids and hegetotheriids. Since Romer's
recognition of the association between archaeo-
hyracids and hegetotheriids was proposed a year
prior to Simpson's revision of Hegetotheria, use
of the name Hegetotheroidea would be an appro-
priate tribute. Similar (but novel) names based on
the earliest diverging members of the group (e.g.,
Archaeohyracia, Archaeohyracoidea) or a combi-

34

FIELDIANA: GEOLOGY

nation of the members (e.g., Archaeohegetotheria,
Hegetoarchaeohyracoidea) could also be used.

Some combination of these higher-level and/or
traditional "family" names could be used if there
were sufficient justification to attach names to
multiple components of the preferred phylogeny.
The precise phrasing of such definitions may be
tailored to insure nomenclatural stability in the
face of potential future changes in topology.

None of the potential combinations of defini-
tions and names discussed above is ideal; each
represents a compromise. As the present phylo-
genetic study is not a comprehensive examination
of relationships among archaeohyracids and he-
getotheriids, we do not propose new definitions of
names at this time. We raise these issues to illus-
trate potential options for doing so, since we our-
selves have grappled with the question of how
best to refer to the clades in question. We defer
the naming of clades to a more comprehensive
cladistic analysis.

Conclusions

One of the most striking aspects of the Tingui-
ririca Fauna of Chile is its high diversity of ar-
chaeohyracids. In the preliminary description of
the fauna, Wyss et al. (1994) argued that no fewer
than five and perhaps as many as nine archaeo-
hyracid taxa might be represented. The present
study (combined with the findings of Reguero et
al., 2(X)3) recognizes at least six archaeohyracid
taxa from the Tinguiririca Fauna, and notes the
possibility of a seventh. The revised identifica-
tions of archaeohyracid specimens considered in
Wyss et al. (1994) are listed in Table 7.

This remarkably high diversity represents the
peak for the Archaeohyracidae. Besides Tinguirir-
ica, no single fauna is known to have had more
than three contemporaneous archaeohyracid spe-
cies, and among South American Land Mammal
Ages, the Tinguirirican records the occurrence of
eight of the 15 currently recognized species, al-
most triple that of any other SALMA (no others
have more than three species. Table 9; see also
Flynn et al., 2(X)3, Table 2). With increasingly
precise age constraints for middle Cenozoic South
American fossil localities (Flynn & Swisher,
1995; Madden et al., 1997; Kay et al., 1999;
Flynn et al., 2003), it has become apparent that
the archaeohyracid radiation that resulted in this
peak diversity during the Tinguirirican SALMA

took place over a relatively short period of time —
the entire stratigraphic range of the group may be
as little as 15 million years, depending on the age
of the beginning of the Casamayoran SALMA
(wherein the first archaeohyracids are recorded).
With the exception of the Archaeopithecidae (a
small group of basal notoungulates known exclu-
sively from the Casamayoran) and Campanorci-
dae (a monotypic family, also from the Casama-
yoran), this is likely the shortest range of any of
the 14 traditional notoungulate "families."

Although the reason for such a rapid diversifi-
cation of archaeohyracids is unknown, its tem-
poral proximity to the Eocene/Oligocene bound-
ary suggests the group might have been "pre-
adapted" to exploit, or at least were able to re-
spond extremely rapidly to, the changing habitats
associated with the Eocene-Oligocene transition
and early Oligocene "climatic deterioration"
(Wolfe, 1971; Prothero & Berggren, 1992; Proth-
ero, 1994). Alternatively, these changes may have
led to greater habitat fragmentation and increased
isolation of archaeohyracid populations, with al-
lochthony yielding higher levels of speciation and
cladogenesis. Current evidence suggests that the
global events that marked the Eocene-Oligocene
transition also resulted in cooler, drier climates
and more open habitats in South America (e.g.,
MacFadden, 1985; Pascual & Ortiz Jaureguizar,
1990; Wyss et al., 1993, 1994, 1996; Pascual et
al., 1996; Flynn & Wyss, 1998, 1999; Kay et al.,
1999; Croft, 2001; Flynn et al., 2003). As modem
mammalian herbivores that graze in open habitats
tend to exhibit high levels of hypsodonty (Janis
1984, 1988, 1990, 1995), the environmental
changes associated with the Eocene-Oligocene
transition would likely have favored more hyp-
sodont herbivores. Indeed, most clades of early
Oligocene Tinguirirican notoungulates exhibit
sharply increased hypsodonty as compared with
their late Eocene Mustersan relatives (e.g., inter-
atheriids, archaeohyracids, notohippids), suggest-
ing across-clade responses to these changing hab-
itats (Flynn et al., 2003). Since archaeohyracids
were among the first hypsodont members of the
Notoungulata (as illustrated by the late Eocene
Casamayoran Eohyrax; Simpson, 1967), the
group might have diversified so rapidly during the
Tinguirirican as a result of already having initi-
ated hypsodonty and thus being "better posi-
tioned" to quickly respond evolutionarily to the
dramatically changing climate and habitats. This
advantage seems to have been short-lived, how-
ever, as archaeohyracids are last known from the

CROFT ET AL.: LARGE ARCHAEOHYRACIDS FROM CHILE AND PATAGONL\

35

mostly late Oligocene Deseadan SALMA. Filling
a niche that presumably was similar to that of the
hypsodont archaeohyracids, other small notoun-
gulates with hypselodont (ever-growing) cheek
teeth (e.g., hegetotheriids, interatheriids, mesoth-
eriids) diversified during the late Oligocene (De-
seadan SALMA) and into the early Miocene.
Nevertheless, Tinguirirican SALMA assemblages
document a short, previously unrecognized burst
of exceptional evolutionary success for Archaeo-
hyracidae, the first notoungulate "family" domi-
nated by hypsodont species.

Acknowledgments

This publication was critically reviewed and
improved by the insightful comments of Guiller-
mo Lopez, Bruce Shockey, and an anonymous re-
viewer. We thank Daniel Frassinetti and the Mu-
seo Nacional de Historia Natural (Santiago), and
the Consejo de Monumentos Naturales de Chile,
for their long-term support of our Andean work.
Reynaldo Charrier freely shared his geological ex-
pertise in the area. He, along with Gabriel Car-
rasco and numerous others, provided invaluable
assistance in the field. Barry Albright, Jose Bon-
aparte, Bruce MacFadden, and Rosendo Pascual
allowed access to specimens under their care.
Richard Cifelli graciously provided access to Bry-
an Patterson's unpublished manuscript on Desea-
dan archaeohyracids. Mark Widhalm (FMNH) ex-
ecuted many of the photographs, and Marlene
Donnelly created the line drawings. This work
would not have been possible without the skill
and dedication of Andrew Lehman, Robert Ma-
sek, William Simpson, and the late Steve Mc-
CarroU, who prepared the exceptionally challeng-
ing material. Work was supported by NSF grants
DEB-9020213, 9317943, and 9318126 (J.J.F and
A.R.W); a John Simon Guggenheim Memorial
Foundation fellowship (J.J.F); and the Hinds Fund
and NSF Biodiversity Training Grant (GRT-
9355032) from the University of Chicago, and the
Paleobiological Fund (D.A.C.).

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