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Patagonian Eocene Archaeopithecidae Ameghino, 1897 (Notoungulata):
systematic revision, phylogeny and biostratigraphy
Bárbara Vera
Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-Mendoza, Ruiz Leal s/n, 5500 Mendoza,
Argentina, 〈bvera@mendoza-conicet.gob.ar〉
Abstract.—The Archaeopithecidae is a very poorly known group of native ungulates from the Eocene of Patagonia
(Argentina), whose alpha taxonomy has remained obscure since Ameghino’s times. It is traditionally considered as a
family representative of the Casamayoran (middle Eocene) South American Land Mammal Age, and is thought to be
morphologically close to the notopithecids. After studying >200 specimens from several institutions, including all
the type specimens, a taxonomic overestimation is established. Out of the six species considered originally as
archaeopithecids, Archaeopithecus rogeri Ameghino, 1897 is here recognized as the only valid name and species;
subsequent synonymies are proposed and previous taxonomic hypotheses discarded. This exhaustive revision has
permitted improving the knowledge of A.rogeri and, for the first time, it has revealed many craniodental characters,
which allow amending its diagnosis and differentiating this taxon from other Eocene notoungulates. Archaeopithecus
rogeri is a small-sized taxon characterized by its complete and rooted dentition, which is relatively higher than that
of other contemporaneous short-crowned notoungulates and shows ontogenetic variation in size and morphology.
The body mass range of A.rogeri (1.4–2.5 kg) is comparable to those of notopithecids and some small hegetotheriids.
The phylogenetic analysis shows A.rogeri is not directly related to any family within Notoungulata, appearing into
a polytomy, as a basal taxon of typotherians. The biochronological range of A.rogeri is adjusted to Vacan
(middle Eocene) through Barrancan subages (late middle Eocene); older (Riochican, late early Eocene) and younger
(Mustersan, late Eocene) records remain to be confirmed.
Introduction
The archaeopithecids are a group of small native ungulates,
typically representative of the Casamayoran South American
Land Mammal Age (SALMA; Ameghino, 1906; Simpson,
1945, 1967b; Marshall et al., 1983; Cifelli, 1985) and known
presently only from Chubut Province, Patagonia (Argentina).
However, there are a few older (Riochican SALMA) and
younger (Mustersan SALMA) records, yet to be confirmed, that
could modify first and last appearances (see below). Little is
known about this group—its systematic background is compli-
cated, being frequently related in the literature and collections
to notopithecids, which is another Patagonian group of Eocene
notoungulates that recently has been revised (Vera, 2013b,
2016). This emphasizes the difficulty in differentiating archae-
opithecids from notopithecids based on dental morphology,
as well as from other taxa such as Oldfieldthomasiidae or
Henricosborniidae, or an “oldfieldthomasiid-archaeopithecid-
notopithecine complex”as Simpson (1967b, p. 63) expressed.
The concept of family Archaeopithecidae was created
by Ameghino (1897) based on the genus and species
Archaeopithecus rogeri, including also the monotypic genus
Pachypithecus and its species P.macrognathus Ameghino,
1897. According to Ameghino, Archaeopithecidae shared some
features with primates, such as brachydont dentition and a
primate-like jaw, which he cited as a reason to consider this
family in the Prosimiae, just as did with the family Notopithe-
cidae Ameghino, 1897.
Later, Ameghino (1901) described the species
Archaeopithecus alternans and A.rigidus, the genus Ultra-
pithecus with two species (U.rutilans and U.rusticulus), and
the species Guilielmoscottia plicifera, and placed them
within Archaeopithecidae. In a subsequent work, Ameghino
(1903) described the genus Acropithecus and its type species
A.tersus, and placed it in the family Notopithecidae. Con-
currently, he transferred to Acropithecus the species Adpithecus
plenus Ameghino, 1902, previously described within notopithe-
cids. Thus, the genus Acropithecus sensu Ameghino, 1902,
comprised two species: A.tersus and A.plenus.According
to one of his last contributions, Ameghino (1906) listed
among the ‘Notostylopense fauna’(Casamayoran SALMA) both
Archaeopithecus and Acropithecus, and placed them in the
Archaeopithecidae and Notopithecidae, respectively.
Schlosser (1923) transferred Guilielmoscottia to Noto-
pithecidae, which was accepted by Roth (1927), Simpson (1936,
1945, 1967b), and Scott (1937); however, Ultrapithecus was
considered to be a member of the Oldfieldthomasiidae and
Pachypithecus a nomen dubium by Simpson (1967b, p. 246).
Scott (1937) regarded Archaeopithecus as a member of the
Notopithecidae, but provided no justification.
Simpson (1967b, p. 64) argued that Ameghino’s original
definitions for Notopithecidae and Archaeopithecidae were not
Journal of Paleontology, page 1 of 24
Copyright © 2017, The Paleontological Society
0022-3360/15/0088-0906
doi: 10.1017/jpa.2017.53
1
substantive, and stated that Notopithecus Ameghino, 1897
(type genus of the family Notopithecidae) and Archaeopithecus
(type genus of the family Archaeopithecidae) could not be
distinguished based on Ameghino’sdefinitions for the two
groups. Despite this, Simpson stated that Archaeopithecus was
closer to Acropithecus and should be in the same family,
but separated from Notopithecus, therefore he transferred
Acropithecus to Archaeopithecidae.
According to Simpson (1967b), Archaeopithecus is similar
to Acropithecus, and their generic differences rely on the
anterior upper premolars. Simpson (1967b) argued that in
Archaeopithecus the premolars, and most notably P1–2, are
more transverse and symmetrical, the ectoloph columns are less
pronounced, and P1 is markedly wider than long. In
Acropithecus, P1 is longer than wide and P2 is less transverse
than in Archaeopithecus, the P1–2 are asymmetrically trian-
gular, and the ectoloph columns are strong (see below).
Simpson (1967b) had hundreds of specimens of Archae-
opithecidae available for study as a result of the Scarritt
Patagonian Expeditions (1930–1933 and 1933–1934), includ-
ing the better-preserved specimen. Strikingly, he neither figured
any of them nor provided any descriptions, in contrast to what
he did for notopithecids (Simpson, 1967b, figs. 22–28). Many of
these specimens still lack a catalogue number, and remain
labeled only with a field number in some cases, which may
explain why Simpson did not include them in his systematic
work.
From the most complete specimen, AMNH FM 28782
(partial skull and associated mandible), Simpson (1967b) incor-
porated substantial systematic changes into the family Archae-
opithecidae, with the following nomenclatural actions: (1) he
transferred Archaeopithecus rigidus to the genus Acropithecus,
establishing the combination Acropithecus rigidus (Ameghino,
1901) and assigning AMNH FM 28782 to A.rigidus;(2)he
considered Archaeopithecus alternans and Acropithecus tersus
synonymous names of Acropithecus rigidus; and 3) he transferred
Notopithecus fossulatus Ameghino, 1897 to the genus Archae-
opithecus, establishing (with some doubt) the combination ?A.
fossulatus. In summary, after Simpson (1967b), the family
Archaeopithecidae comprised the genus Archaeopithecus with
two species, A.rogeri (type species) and ?A.fossulatus
(Ameghino, 1897), and the genus Acropithecus with a single
species, A.rigidus. Under this late name Acropithecus rigidus,
Simpson (1967b) placed most of the specimens recovered by the
Scarritt Patagonian Expeditions at Cañadón Vaca, Chubut
Province (Argentina), which belong to the AMNH collection.
Since Simpson’s work (1967b), the members of this group
have not been subjected to systematic revision or other detailed
studies, and Acropithecus rigidus is practically the only species
considered in subsequent studies including Archaeopithecidae
(Cifelli, 1985, 1993; Hitz et al., 2006; Reguero and Prevosti,
2010; Reguero et al., 2010; Billet, 2011; Elissamburu, 2012;
Vera, 2016), most likely because the specimens of Acropithecus
are represented by much more complete material that the type of
Archaeopithecus.
From a phylogenetic point of view, the family Archae-
opithecidae was regarded as a member of suborder Typotheria
(Simpson, 1931, 1967b; Scott, 1937; Mones, 1986; Cifelli,
1993; Billet, 2011), but Simpson (1945) placed it into suborder
Toxodontia as it shared numerous notoungulate characters with
Archaeohyracidae and Oldfieldthomasiidae. Later, the analysis
by Reguero and Prevosti (2010) places Archaeopithecidae close
to Oldfieldthomasiidae, both excluded from Typotheria and,
thus, in partial agreement with Simpson’s (1945) criterion.
Then, in Billet’s (2011) analysis, Acropithecus forms part of a
large basal bush branching out into the oldfieldthomasiids
Oldfieldthomasia,Colbertia and Ultrapithecus; the genus
Campanorco; the Interatheriidae; and a clade uniting the
Archaeohyracidae, Mesotheriidae and Hegetotheriidae. More
recently, a revision of the subfamily Notopithecinae (sensu
Simpson, 1945, 1967b) yields novel taxonomic modifications
for this group (Vera, 2012a, 2012b, 2013a, 2013b; Vera and
Cerdeño, 2014), including the Archaeopithecidae. For the latter,
Vera (2013b) hypothesizes an overestimation in the number of
species and preliminarily proposes two monospecific genera.
Finally, Vera (2016) considers Acropithecus rigidus as the
sister taxon of Typotheria sensu Reguero and Prevosti (2010),
which includes the notopithecid clade, but she disagrees with
the hypothesis of these authors grouping A.rigidus with
Oldfieldthomasia; in the minority of topologies (Vera, 2016,
fig. 2B), Acropithecus rigidus is nested into the notopithecid
clade as the sister taxon of Guilielmoscottia plicifera and
Transpithecus obtentus. Based on morphological characters,
Vera’s (2016) analysis was the first to suggest a possible link
between archaeopithecids and notopithecids from a phyloge-
netic point of view.
In this paper, the type material and many other specimens
of archaeopithecids from several institutions are subjected to an
exhaustive revision in order to determine the alpha taxonomy
and provide robust diagnoses. This work sheds light on the
systematic of the group and enables and concrete discussions of
biostratigraphic issues, geographic distribution and phyloge-
netic relationships with respect to other groups. In addition, the
large sample of archaeopithecid specimens allows for a body
mass estimation and for inferring ecological attributes.
Materials and methods
Descriptions and comparisons are based on personal observa-
tions of ~215 catalogued specimens of archaeopithecid from
several institutions (see below), including the type material of
the Ameghino collection, and the Scarritt Pocket and Egidio
Feruglio collections. These specimens come from different
localities of Chubut Province, Argentina (Fig. 1) and they are
detailed below.
To facilitate the description and comparison, each speci-
men forming part of a lot is indicated with a letter accompanying
the catalog number, particularly for the type specimens from the
Ameghino collection. The term Casamayoran SALMA is used
in the traditional sense to include the Vacan and Barrancan
subages.
The mesiodistal and labiolingual diameters for each tooth
were taken at occlusal level with a digital caliper to the nearest
0.1 mm. Each specimen was assigned to one of three wear stages
(based on upper and lower cheek molars features): little wear,
moderate wear and heavy wear (see Description). It should be
noted that this procedure became subjective and difficult when
assigning a particular wear stage to an isolated teeth, which
2Journal of Paleontology
occurs with some specimens considered in the present study
(see below). In addition, upper teeth are much more numerous
than lower dentition, particularly P4, M1 and M2. Descriptive
statistics (mean, maximum, minimum, standard deviation,
coefficient variation) were used to describe all upper and lower
cheek teeth (Tables 1–2) and for each wear category separately
(Supplemental Data 3). Eight specimens with complete P4–M1
tooth rows representing the three wear stages were chosen to
evaluate metric changes throughout ontogeny. Graphical and
statistical procedures were performed using Microsoft Excel
2010 and InfoStat (Di Rienzo et al., 2016).
A phylogenetic analysis was performed based on a modified
version of Vera’s (2016) matrix. It consists of 29 terminal taxa and
87 morphological characters (0–57, upper and lower dentition;
58–70, skull and mandible; and 71–86, postcranium). The polar-
ization of the characters was based on out-group comparison cri-
teria using the notoungulate Simpsonotus praecursor Pascual,
Vucetich, and Fernández (1978). With respect to Vera (2016),
some characters previously unknown for archeopithecids are
coded differently in the present study (see below) and Archae-
ohyrax patagonicus was included as representative of Archae-
ohyracidae. When no information was known for a taxon,
characters were scored as missing data; when a character was not
present, it was scored as non-applicable. All characters are treated
as unordered. They are referred to in brackets with the character
state in superscript. Maximum parsimony under equal weights
was assumed. The computer program TNT 1.1 (Goloboff et al.,
2008) was used to conduct heuristic searches with the Tree
Bisection Reconnection swapping algorithm (TBR), using 1000
random addition sequences and saving 100 trees. Subsequent
searches were repeated from previously obtained trees (trees from
RAM), in order to save all the most parsimonious topologies.
Branch support was estimated by absolute and relative Bremer
support–BS–(Bremer, 1990) and Symmetric Resampling
(Goloboff et al., 2003). The characters and states, and the data
matrix used in this analysis are explained in Supplemental Data 1
and Supplemental Data 2, respectively.
Body masses were estimated for archaeopithecids and
notopithecids using Vera’s (2013b) dataset and applying the
equations from Janis (1990) and Scarano et al.’s (2011) based on
dental measurements. Three variables were selected from Janis
(1990), lengths of first lower molar (FLML), second upper
molar (SUML) and lower molar row (LMRL). In turn, four
variables were applied on the Scarano et al.’s (2011) models,
lengths of first, second, and third lower molars (FLML, SLML,
TLML), and length of second upper molar (SUML). In parti-
cular for Notopithecus, body mass was also inferred from
astragalar parameters selected from Tsubamoto (2014), which
are based on the transverse width of the tibial trochlea (Li1),
proximodistal length of the lateral trochlear ridge of the tibial
trochlea (Li2), proximodistal length of the astragalus (Li5), and
dorsoventral thickness of the medial part of the astragalus (Li9).
Figure 1. Localities mentioned in the text, from which most of the studied specimens of Archaeopithecus rogeri derive. (1) Cerro Solo, (2) Lomas Blancas,
(3) Las Cascadas, (4) Campo Muriette, (5) El Pajarito, (6) Oeste Río Chico, (7) Cabeza Blanca, (8) Cañadón Vaca, (9) Cañadón Hondo, (10) Bajo Palangana,
(11) Pico Salamanca, (12) Bahía Solano, (13) Cañadón Blanco, (14) Colhué Huapi (and vicinity).
Vera—Eocene archeopithecids from Patagonia 3
Table 1. Dimensions (mm) of upper dentition of Archaeopithecus rogeri.MD=mesiodistal diameter; LL =labiolingual diameter; SW =stage of wear: 1,
little; 2, middle; 3, heavy (see text for details); CV (coefficient of variation) =100 × (SD/mean). Approximate values in parentheses. Dashes represent not
measured dimensions (broken tooth or alveolus).
P1 P2 P3 P4 M1 M2 M3
Specimen SW MD LL MD LL MD LL MD LL MD LL MD LL MD LL
AMNH FM 15902c 2 4.0 -
AMNH FM 28534 2 4.2 6.5 4.5 -
AMNH FM 28782 3 - - 4.6 5.5 4.5 6.8 4.7 7.0 4.3 7.5 4.9 7.9
AMNH FM 28824 1 (5.7)
AMNH FM 28827 3 4.2 6.4 4.1 6.9 5.1 7.0
AMNH FM 28841 2 4.0 6.0 4.0 6.3
AMNH FM 28868 2 3.6 - 3.7 5.8 4.0 6.1 - -
AMNH FM 28871 2 4.3 6.3 4.6 4.8
AMNH FM 28884c 3 3.9 4.5 4.1 5.8
AMNH FM 28884b 3 4.9 6.1
AMNH FM 28886 2 4.7 5.9
AMNH FM 28895 3 4.0 - (4.1) -
AMNH FM 144692 3 4.8 - 5.1 - 4.9 6.3
AMNH FM 144695 3 3.9 6.3 3.4 6.4
AMNH FM 144696 2 4.3 5.7
MACN-A 10813a 2 3.9 6.7 (4.6) - 4.4 6.3 - -
MACN-A 10813b 1 4.3 6.1 4.2 6.3 4.8 -
MACN-A 10813c 1 3.6 5.2 4.6 4.9 4.8 6.0
MACN-A 10813d 2 3.9 - 4.8 - 4.5 6.4
MACN-A 10813e 1 3.6 4.2 4.2 5.0 4.0 5.5
MACN-A 10813f 1 4.4 6.6
MACN-A 10813g 2 - 5.6 5.0 6.4
MACN-A 10813h 2 4.5 6.3
MACN-A 10813i 1 4.6 6.2
MACN-A 10815 2 - 6.3 5.6 6.9 4.9 6.1
MACN-A 10816 2 3.6 4.1 3.8 5.6 4.3 6.0 4.9 6.4 3.8 6.5 4.4 7.0
MACN-A 10831 1 5.1 6.0
MACN-A 10833c 4.7 7.0
MACN-A 10850a 3 4.8 6.0
MACN-A 10850b 3 4.6 6.4
MACN-A 10850c 1 4.3 6.1
MACN-A 10851a 3 (3.4) - 4.8 7.5 (3.4) -
MACN-Pv 11237 2 3.7 - 4.6 7.0
MACN-Pv 12842 2 (4.4) - (4.9) - (4.9) -
MGP 31362 3 3.9 6.3 (4.6) 6.6 - 6.0
MGP 31595 1 4.2 5.7
MGP 31600 1 4.0 6.1
MGP 31606 3 4.0 6.0
MGP 31658 2 4.1 5.9
MGP 31729 1 3.7 5.8
MGP 31753 2 3.7 5.4
MGP 31769 2 3.7 5.1
MGP 31777 2 3.7 5.3
MLP 34-V-22-7 2 4.3 6.0
MLP 61-VIII-3-148 3 3.5 (4.0) 3.8 5.2 4.1 (6.0) 4.5 6.2 (4.3) (6.0)
MLP 61-VIII-3-176 1 3.8 5.6 4.6 5.8 4.8 6.6
MLP 61-VIII-3-177 2 4.2 6.0 (4.4) 6.3 (4.5) (7.0)
MLP 61-VIII-3-427 1 4.5 5.0
MLP 61-VIII-3-430 2 4.9 6.2
MLP 66-V-9-16 1 5.0 6.8 4.9 7.2
MLP 66-V-10-4 2 4.9 6.9
MLP 75-II-3-19 1 4.9 6.9
MLP 79-I-17-10 2 3.8 5.0 4.4 6.0 - -
MLP 79-I-17-20 1 4.1 5.7 - - 5.3 6.6
MLP 79-I-17-36 2 4.0 5.6
MLP 79-I-17-37 2 4.3 5.9
MLP 79-I-17-41 1 4.9 5.4
MLP 79-I-17-48 2 3.7 5.6
MLP 79-I-17-50 2 4.1 5.4 4.7 6.0 - 6.8
MLP 93-XI-22-3f 3 4.7 6.5
MLP 93-XI-22-3g 2 5.2 6.9
MMdP-M 727 2 3.0 2.3 4.2 5.3 4.1 6.4 4.5 (6.8) 4.2 6.6 4.9 (7.6) (4.4) (6.8)
MNHN-CAS 739 2 4.1 5.8 4.0 6.6 - - 4.6 7.2
MNHN-CAS 751 2 4.1 6.4
MPEF-PV 1570a 3 4.4 6.4
MPEF-PV 1570b 2 4.8 5.9
MPEF-PV 1570c 2 5.2 6.2
MPEF-PV 1570d 1 4.2 5.7
MPEF-PV 1580b 2 (4.6) - (4.1) -
MPEF-PV 1580c 3 3.3 5.6
PVL 210 1 5.0 7.8
PVL 242 2 4.3 5.8
Number 3 3 8 7 18 17 30 28 29 25 26 20 16 15
Range 3.0–3.6 2.3–4.1 3.5–4.6 4.0–6.0 3.7–4.5 5.1–6.8 3.3–5.0 5.0–7.0 3.4–5.2 4.9–7.5 4.3–5.7 6.0–7.9 4.1–5.1 4.8–6.8
Mean 3.4 3.5 4.0 5.1 4.0 5.9 4.3 6.2 4.2 6.2 4.9 6.9 4.6 5.9
SD 0.3 1.0 0.4 0.7 0.2 0.5 0.4 0.5 0.4 0.5 0.3 0.5 0.3 0.5
4Journal of Paleontology
Mean values for each model and taxon, as well as the average
total, are listed in Table 3. Additionally, the obtained values are
compared with those previously inferred for archaeopithecids
and notopithecines (Elissamburu, 2012; Vera, 2013b) and for
other similar-sized notoungulates (Scarano et al., 2011; Cassini
et al., 2012a, 2012b; Elissamburu, 2012).
Repositories and institutional abbreviations.—American
Museum of Natural History, Fossil Mammals (AMNH FM),
New York, USA; Museo Argentino de Ciencias Naturales
“Bernardino Rivadavia,”Ameghino and Paleovertebrata col-
lections (MACN-A/Pv), Buenos Aires, Argentina; Museo di
Geologia e Paleontologia (MGP), Università degli Studi di
Padova, Italy; Museo de La Plata (MLP), La Plata, Argentina;
Museo de Ciencias Naturales de Mar del Plata “Lorenzo
Scaglia”(MMdP), Mar del Plata, Argentina; Muséum national
d’Histoire naturelle, Casamayoran collection (MNHN-CAS),
Paris, France; Museo Paleontológico “Egidio Feruglio”, Verte-
brate Paleontology collection (MPEF-PV), Trelew, Argentina;
Colección Paleontología de Vertebrados Lillo, Instituto Miguel
Lillo (PVL), Tucumán, Argentina; Yale Peabody Museum,
Vertebrate Paleontology Princeton University Collection
(YPM-PU), New Haven, Connecticut, USA.
Systematic background
In this section, all erected extinct species into the family
Archaeopithecidae are comprehensively reviewed. The type
species of the family, Archaeopithecus rogeri, is based on the
specimen MACN-A 10816 (Fig. 2.1), catalogued as holotype
Table 2. Dimensions (mm) of lower dentition of Archaeopithecus rogeri.MD=mesiodistal diameter; LL =labiolingual diameter; SW =stage of wear: 1, little;
2, middle; 3, heavy; CV (coefficient of variation) =100 × (SD/mean). Approximate values in parentheses. Dashes represent not measured dimensions (broken tooth or
alveolus).
p2 p3 p4 m1 m2 m3
Specimen SW MD LL MD LL MD LL MD LL MD LL MD LL
AMNH FM 28705 3 3.9 2.3 4.0 2.9 4.0 3.3 4.1 3.2
AMNH FM 28782 3 4.4 2.7 4.7 3.1 5.0 3.6 4.5 3.9 4.8 3.9 5.9 3.4
AMNH FM 28801 2 4.3 3.0 4.5 3.3 4.2 3.5
AMNH FM 28803 1 4.7 3.5 4.6 3.5 5.0 3.8
AMNH FM 28804 1 (4.8) 3.1 5.3 3.5
AMNH FM 28805 1 (4.2) (2.8) 5.0 3.3
AMNH FM 28840 3 4.4 3.3 4.5 3.3 4.6 3.8
AMNH FM 28842 2 4.3 3.0 4.4 3.2
AMNH FM 28872 1 4.8 2.9
AMNH FM 28884d 3 4.2 (3.1) 4.4 (3.3) (6.3) (3.0)
AMNH FM144688 1 4.6 3.4 4.2 3.2
AMNH FM144689 1 4.8 3.7 6.2 3.1
AMNH FM 144690 2 5.0 3.5
AMNH FM 144691 1 4.6 3.1
AMNH FM 144693 2 4.4 3.0 4.4 3.4
AMNH FM 144694 3 5.6 3.2
MACN-A 10824a 1 4.2 3.0 (4.7) 3.1
MACN-A 10841c 2 4.0 3.1 5.6 3.3
MGP 29028 2 4.5 3.5 5.7 3.3
MGP 29056 2 3.7 2.9 - - 5.4 2.9
MGP 31596 2 4.5 3.3
MGP 31597 2 3.4 3.1
MGP 31598 1 4.5 3.3
MGP 31599 2 5.4 3.1
MGP 31601 1 4.6 -
MGP 31657 2 4.4 3.5
MGP 31658 2 3.6 2.8 4.9 2.7
MGP 31720 2 4.6 3.3
MGP 31727 1 5.8 3.4
MGP 31759 1 4.6 3.1
MGP 31767 3 4.2 3.2
MLP 12-1529 1 4.9 4.1
MLP 66-V-10-19 1 6.5 3.7
MLP 75-II-3-20 1 5.0 3.8
MLP 93-XI-22-3a 2 4.7 3.6 5.0 3.8
MLP 93-XI-22-3b 2 5.4 3.2
MLP 93-XI-22-3c 1 5.3 3.1
MLP 93-XI-22-3d 1 5.5 3.5
MLP 93-XI-22-3e 1 6.6 3.4
MLP 93-XI-22-3h 1 5.4 3.2
MNHN-CAS 741 3 4.1 3.2
PVL 162 2 4.6 3.4 (4.9) -
PVL 163 2 4.6 3.5 4.9 3.1 6.6 3.4
PVL 165 3 4.2 2.8 4.6 3.3
PVL 166 1 4.4 3.4 4.5 3.6
PVL 167 2 5.1 2.9
PVL 199 1 5.2 3.3
PVL 232 3 (4.8) -
Number 2 2 6 6 14 14 22 19 20 19 17 17
Range 3.9–4.4 2.3–2.7 4.0–4.8 2.9–3.1 4.0–5.3 2.8–3.6 3.4–5.0 2.9–3.9 3.6–5.6 2.8–4.1 4.8–6.6 2.7–3.7
Mean 4.1 2.5 4.5 3.0 4.6 3.2 4.4 3.3 4.7 3.5 5.7 3.2
SD 0.3 0.3 0.3 0.1 0.4 0.2 0.4 0.2 0.4 0.3 0.6 0.2
Vera—Eocene archeopithecids from Patagonia 5
and consisting of a maxillary fragment with six teeth, here
recognized as right P1–M2, coming from the Casamayoran
levels of Sarmiento Formation (Patagonia, Argentina), but
without specific locality information. Originally, Ameghino
described upper premolars and molars for this species, giving
the P1–M3 length (27 mm), and he also described a mandible
fragment, providing several dimensions. Unfortunately, this
mandible is presently lost and only the maxilla was originally
figured (Ameghino, 1897, fig. 8; 1904, fig. 402). Although he
described the complete upper molar series, the M3 is missing in
the maxilla. It is worth noting that M3 is dotted in Ameghino’s
figure, which means that this molar was always absent.
Although MACN-A 10816 is poorly preserved, it is pos-
sible to distinguish the following features: triangular upper
premolars; low and well-developed mesial cingulum on P2–4
and upper molars; very undulating ectoloph in P2–4; upper
molars wider than longer (LLD >MDD); and deep lingual sul-
cus in M1–2, very shallow in P4, and absent in P2–3. This
combination of features is observed in AMNH FM 28782
(Acropithecus rigidus sensu Simpson, 1967b), MACN-A 10813
(lot catalogued as Archaeopithecus rigidus, see below), and
MACN-A 10851a (type of Acropithecus plenus), although the
presence of a lingual sulcus in P4 cannot be corroborated in
the last specimen. In addition, the measurements of all these
specimens are comparable (Table 1).
The holotype of the species Archaeopithecus alternans is
the specimen MACN-A 10815 (maxillary fragment with left
M1–3; Fig. 2.2), which comes from ‘Oeste de Río Chico’
(Ameghino’s locality from Chubut Province, Fig. 1; Simpson,
1967a). Ameghino (1901, p. 359) described Archaeopithecus
alternans as a larger species than A.rogeri and provided the
length of M1–3 (14 mm). M1 of MACN-A 10815 is squarer
than that of MACN-A 10816 (A.rogeri), which is more rec-
tangular certainly due to its greater degree of wear, although the
length in both is practically the same (Table 1). Indeed,
dimensions of M2 and M3 in MACN-A 10815 match the M3s
of MACN-A 10850 (type specimen of Acropithecus tersus, see
below) and of other specimens, such as MLP 79-I-17-20
(Table 1). In addition, MACN-A 10815 (Fig. 2.2) is morpho-
logically very similar (fossettes configuration, undulated ecto-
loph, lingual sulcus on molars, mesial and distal cingula) to
MACN-A 10813 (Fig. 2.3, 2.6, 2.10).
Archaeopithecus rigidus was defined by Ameghino (1901,
p. 359) basically by its larger size compared with A.rogeri and
by having squared upper molars with faintly undulating labial
face and lingual sulcus. Ameghino also provided the length of
P2–M3 (30 mm). The material catalogued as type of A.rigidus
has the number MACN-A 10813 (Fig. 2.3–2.11) and it is a lot
with seven maxillary fragments and two isolated teeth, coming
from ‘Oeste de Río Chico’(Fig. 1). The lot consists of: MACN-
A 10813a, maxillary fragment with left P2–M2 (Fig. 2.3);
MACN-A 10813b, maxillary fragment with left P4–M2 (Fig.
2.4); MACN-A 10813c, maxillary fragment with right P4–M2
(Fig. 2.5; P4, presently broken, probably corresponds to that
figured by Ameghino, 1904, fig. 404); MACN-A 10813d,
maxillary fragment with right M1–3 (Fig. 2.6); MACN-A
10813e, maxillary fragment with right P1–3 (Fig. 2.7); MACN-A
10813f, maxillary fragment with right P4 (Fig. 2.8; similar to the
P4 pictured by Ameghino, 1904, fig. 403); MACN-A 10813g,
maxillary fragment withright M1–2 (Fig. 2.9); MACN-A 10813h,
Table 3. Body masses (mean values in kg) for Archaeopithecus rogeri and notopithecids based on different authors (dataset taken from Vera, 2013b). FLML,
first lower molar length; SUML, second upper molar length; LMRL, lower molar row length; SLML, second lower molar length; TLML, third lower molar
length; Li1, transverse width of the tibial trochlea; Li2, proximodistal length of the lateral trochlear ridge of the tibial trochlea; Li5, proximodistal length of the
astragalus; Li9, dorsoventral thickness of the medial part of the astragalus; Ar1 =Li1 x Li2; Ar3 =Li1 x Li9.
Janis (1990) Scarano et al. (2011) Tsubamoto (2014)
Taxon/allometric equation FLML SUML LMRL FLML SLML TLML SUML Li1 Li5 Ar1 Ar3 Average total
Archaeopithecus rogeri 1.47 1.25 1.36 1.75 1.43 2.57 1.51 1.62
n 21 18 2 21 12 10 18
sd 0.40 0.32 0.41 0.38 0.29 0.45 0.31
Notopithecus adapinus 1.06 0.87 0.67 1.35 1.03 1.99 1.13 1.80 1.85 1.82 1.82 1.40
n 79 63 22 79 77 64 63 1111
sd 0.38 0.21 0.18 0.37 0.25 0.35 0.22
Antepithecus brachystephanus 1.71 1.53 0.99 1.97 1.39 2.40 1.79 1.68
n 47 12 8 47 44 33 12
sd 0.51 0.35 0.14 0.44 0.21 0.35 0.34
Transpithecus obtentus 1.75 1.35 1.30 2.01 1.52 3.17 1.61 1.82
n893812139
sd 0.48 0.27 0.18 0.42 0.26 0.28 0.26
Guilielmoscottia plicifera 2.63 1.92 1.83 2.76 2.14 3.20 2.15 2.38
n11381112113
sd 0.67 0.34 0.27 0.55 0.40 0.80 0.31
Figure 2. Archaeopithecus rogeri.(1) MACN-A 10816, holotype: maxillary fragment with right P1–M2, occlusal view; (2) MACN-A 10815, holotype of
Archaeopithecus alternans: maxillary fragment with left M1–3, occlusal and lingual views; (3–11) MACN-A 10813, material catalogued as type of Acropithecus
rigidus:(3) MACN-A 10813a, maxillary fragment with left P2–M2; (4) MACN-A 10813b, maxillary fragment with left P4–M2; (5) MACN-A 10813c, maxillary
fragment with right P4–M2; (6) MACN-A 10813d, maxillary fragment with right M1–3; (7) MACN-A 10813e, maxillary fragment with right P1–3?;
(8) MACN-A 10813f, maxillary fragment with right P4; (9) MACN-A 10813g, maxillary fragment with right M1–2; (10) MACN-A 10813h, right M1 or M2;
(11) MACN-A 10813i, left P4; (12–14) MACN-A 10850, material catalogued as type of Acropithecus tersus:(12, 13) two left M3 and (14) right M3, not
associated, occlusal and lingual views; (15) MACN-A 10851a, holotype of Acropithecus plenus: maxillary fragment with left M1–2, occlusal view; (16) MACN-
A 10851b, fragment with right m2–3, occlusal view; (17) MACN-A 10824a, holotype of Notopithecus fossulatus: mandible fragment with left p4–m1 and roots
of p3 and m2, occlusal and labial views; (18) MACN-A 10824b, Notoungulata indet: mandible fragment with two extremely worn right teeth, occlusal and labial
views. Abbreviations in the text. Scale bar is 5 mm.
6Journal of Paleontology
Vera—Eocene archeopithecids from Patagonia 7
right M1 or M2 (Fig. 2.10); and MACN-A 10813i, left P4 (Fig. 2.11;
this matches the P4 figured by Ameghino, 1904, fig. 405).
Simpson (1967b, p. 65) identified the same number of
specimens in lot MACN-A 10813; he selected the maxilla, here
named MACN-A 10813b, as the lectotype of Archaeopithecus
rigidus and mentioned that the other specimens in the lot could
all be syntypes. Bearing in mind that Ameghino (1901) pro-
vided only the length of a P2–M3 series, and there is not such a
series represented among the specimens in lot MACN-A 10813,
two explanations are possible: the maxilla on which Ameghino
based his description (and measurements) is lost or, more likely,
Ameghino used several elements in combination, as he did for
Archaeopithecus rogeri (see above). Whatever was the case, the
decision of the first reviewer (Simpson, 1967b) is here accepted
and MACN-A 10813b (Fig. 2.4) is considered the lectotype of
Archaeopithecus rigidus.
Specimen MACN-A 10813b (Fig. 2.4) is characterized by
a narrow mesial cingulum and a high distal cingulum on molars;
P4 with very undulating ectoloph and narrow lingual face
showing a deep sulcus; and M1–2 with less undulating ectoloph
than P4, hypocone lingually more developed than the protocone
and both lingually separated by a deep sulcus. MACN-A
10813b is similar to MACN-A 10813a (Fig. 2.3) and MACN-A
10813c (Fig. 2.5). MACN-A 10813e (Fig. 2.7) shows very little
wear; P2 has a low and reduced mesial cingulum and cannot be
compared directly with MACN-A 10813a or MACN-A 10813c,
but the premolars are similar to those of MACN-A 10813b as
P3 has a deep lingual sulcus and P4 a clearly undulating
ectoloph and high distal cingulum. The same is observed in
MACN-A 10813f and MACN-A 10813i, where the P4s are
comparable to those of MACN-A 10813b. In turn, MACN-A
10813d shows a more advanced stage of wear than MACN-A
10813b (e.g., M2 has protocone and hypocone united by
entoloph), while MACN-A 10813h has a more developed
mesial cingulum than MACN-A 10813b. All specimens in lot
MACN-A 10813 can be considered as several individuals of the
same taxon in different ontogenetic stages.
Based on specimen MACN-A 10813b (Fig. 2.4), Simpson
(1967b) considered Archaeopithecus rigidus as a senior
synonym of Acropithecus tersus; he proposed the combination
Acropithecus rigidus, and also included Archaeopithecus
alternans in the genus Acropithecus. Simpson (1967b, p. 65)
incorporated in the hypodigm of Acropithecus rigidus several
specimens from the AMNH collection (such as AMNH FM
28782, AMNH FM 28884, AMNH FM 28895), as well as seven
partial mandibles with teeth, around 150 identified isolated
upper cheek teeth and around 150 identified isolated lower
cheek teeth (with no number or description).
As stated by Simpson (1967b, p. 63–65), the differences
between Acropithecus and Archaeopithecus were based mainly
on P1–3: Acropithecus has asymmetrically triangular premolars,
a P1 longer than wide and a P2 less transverse; in contrast,
Archaeopithecus has more transverse, more symmetrical and
less pronounced ectoloph in P1–3. Interestingly, Simpson
described the P2 of Acropithecus based on nine individuals in
different stages of wear and mentioned a vertical groove
immediately anteroexternal to the protocone and a sinuous
protoloph; he also mentioned a mesial cingulum on the P2, on
three of 23 P3s, and on 12 of 26 P4s; when present, the cingulum
is very weak, evidencing a high variability in this character. The
same features (lingual sulcus, mesial cingulum, and sinuous
ectolophe) are observed on the premolars of MACN-A 10816
(holotype of Archaeopithecus rogeri; Fig. 2.1); in addition, the
dimensions of MACN-A 10813e (Fig. 2.7) are similar to those
of MACN-A 10816, and differences in transverse and ante-
roposterior diameters are not significant between specimens
(Table 1). This clearly demonstrates that both the specific
differentiation between A. rogeri and A.rigidus proposed initi-
ally by Ameghino (1901) and the generic distinction between
Acropithecus and Archaeopithecus pointed out by Simpson
(1967b) cannot be supported based on the dimensions and
morphology presented here.
According to the MACN catalogue, the type specimen of
Acropithecus tersus, MACN-A 10850 (Fig. 2.12–2.14), comes
from Casamayoran levels of Patagonia. Lot MACN-A 10850
includes three upper molars, two left M3 (Fig. 2.12, 2.13) and
one right M3 (Fig. 2.14), with disparity in wear stage and,
hence, belonging to different individuals. Ameghino (1904, p.
204, fig. 231) figured the left M3s but identified them as M2–3
of the same individual. Simpson (1967b) considered the asso-
ciation incorrect and synonymized the name Acropithecus
tersus with Archaeopithecus rogeri, despite of the type
specimen of the latter (MACN-A 10816; Fig. 2.1) has no M3
preserved. The left M3s MACN-A 10850 (Fig. 2.12, 2.13) are
very similar to each other; they have a very reduced mesial
cingulum and their lingual sulcus is mesially placed; in turn, the
right M3 MACN-A 10850 (Fig. 2.14) has less wear than the
previous molars (the lingual valley is open, separating proto-
cone from hypocone) and the mesial cingulum is more devel-
oped. The three molars have a trapezoidal outline and are
comparable in morphology and size (Table 1) to the M3s of
MACN-A 10813d (Fig. 2.6) and other specimens, such as
AMNH FM 28782 (Fig. 3.3) and MMdP-M 727 (Fig. 4.1), so
that that there is no enough evidence to consider a different
species based only on these three upper molars (Table 1;
Supplemental Data 3). Herein, indirect evidence (morphological
and metrical similitudes between MACN-A 10850 and
MACN-A 10813d, and between the latter and MACN-A 10816)
allows establishing a comparison between Acropithecus tersus
and Archaeopithecus rogeri, in agreement with the synonymy
proposed by Simpson (1967b).
As mentioned before, Ameghino (1903) transferred
Adpithecus plenus Ameghino, 1902 to the genus Acropithecus,
establishing Acropithecus plenus. The specimen catalogued as the
type of Adpithecus plenus has the number MACN-A 10851,
which consists of a lot including a maxillary fragment with left
M1–2 (here numbered MACN-A 10851a; Fig. 2.15) and a man-
dibular fragment with very worn right m2–3 (MACN-A 10851b;
Fig. 2.16). Adpithecus plenus, however, was described based on
upper dentition (Ameghino, 1902, p. 8), which implies that the
specimen MACN-A 10851a is actually the holotype of this
species. Strong evidence for this assumption is the metrics of M1
MACN-A 10851a (Table 1), which matches almost exactly
with the dimensions provided by Ameghino (5.0 × 7.5 mm). The
mandibular fragment MACN-A 10851b does not belong to the
same individual and, therefore, it is not part of the holotype; it is
probably a different taxon. Besides, MACN-A 10851a shows
morphologic (Fig. 2.15) and metrical (Table 1) similitudes with
8Journal of Paleontology
Figure 3. Skull and mandible AMNH FM 28782 (Acropithecus rigidus sensu Simpson, 1967b): (1) lateral view, (2) dorsal view, (3) ventral view, (4) detail of
right I1–3 and left I1–3, occlusal view (not at scale); (5) isolated lowermost anterior teeth; (6) right dentary and detail of p2–m2, occlusal and labial views.
Abbreviations in the text. Scale bars are 5 mm.
Vera—Eocene archeopithecids from Patagonia 9
10 Journal of Paleontology
MACN-A 10816 (holotype of Archaeopithecus rogeri;Fig.2.1),
MACN-A 10815 (holotype of Archaeopithecus alternans)and
MACN-A 10813b (lectotype of Archaeopithecus rigidus;
Fig. 2.4), as well as with the maxilla AMNH FM 28782 (Fig. 3.3).
In turn, MACN-A 10851b (Fig. 2.16) is very different from the
associated mandible AMNH FM 28782 (Fig. 3.6) and other
specimens with lower teeth (Fig. 4.17, 4.19–4.22). Actually, the
smaller size of MACN-A 10851b and some characteristics, such
as straight protolophid and metalophid, longer paralophid and
absence of hypoflexid in m3, make it resembles Notopithecus.
Simpson (1967b, p. 64) considered Acropithecus plenus
a junior synonym of Archaeopithecus rogeri based on the
similarity that he observed between both holotypes, MACN-A
10851a and MACN-A 10816, although he mentioned that the
lingual sulcus on the M2 of A.rogeri (MACN-A 10816;
Fig. 2.1) is stronger than that of Acropithecus plenus (MACN-A
10851a; Fig. 2.15). On this point, both M2s under discussion
show a strong lingual sulcus, which is more evident in MACN-A
10816 due to its lesser wear in comparison with MACN-A
10851a, whose M1 is almost erased occlusally (Fig. 2.15). Thus,
considering this evidence as well as the similarities between
MACN-A 10851a (holotype Adpithecus plenus) and MACN-A
10816 (holotype of Archaeopithecus rogeri), two different
species are not supported here (see below for priority).
Finally, the case of Archaeopithecus fossulatus deserves a
special attention. Ameghino (1897) described Notopithecus
fossulatus within Notopithecidae, but Simpson (1967b) trans-
ferred it to the genus Archaeopithecus in the Archaeopithecidae,
establishing the combination A.fossulatus (Ameghino, 1897).
It is important to note that Ameghino (1897, p. 18, figs. 6a–d)
described the species based on a right mandibular fragment
with p3–4 (according to his interpretation, but see below),
which differs from Notopithecus adapinus Ameghino, 1897, in
having a larger size (dimensions for every tooth were the
same, 4 mm × 3 mm). The material catalogued as the type of
Notopithecus fossulatus has the number MACN-A 10824
(Fig. 2.17, 2.18) and is a lot composed of three specimens.
MACN-A 10824a is a mandibular fragment with left p4–m1 and
roots of p3 and m2 (Fig. 2.17), which agrees with Ameghino’s
illustration (1897, fig. 6a–b); it was designated lectotype of
N.fossulatus by Simpson (1967b), though he identified the teeth
as p3–4. MACN-A 10824b (Fig. 2.18) is a mandibular fragment
with two extremely worn right teeth (not figured by Ameghino,
1897), which Simpson (1967b, p. 64) described as p4–m1, not
associated with MACN-A 10824a. Last, MACN-A 10824c is an
isolated left P2, figured, but not described by Ameghino (1897,
figs. 6c–d), and referred by Simpson (1967b) as uncertain P2
(not associated). Later, Vera (2012a) considered the specimen
MACN-A 10824c as a P2 of the notopithecid Transpithecus
obtentus Ameghino, 1901; thus, Notopithecus fossulatus
became a synonym (in part) of T. obtentus.
Simpson (1967b, p. 64) pointed out that both mandible
fragments (MACN-A 10824a and MACN-A 10824b) are
practically indeterminable, and that they could be either
Archaeopithecus rogeri or Acropithecus rigidus. He explained,
on the one hand, that the lower premolars are morphologically
identical to but shorter in length than the specimens assigned
to Acropithecus rigidus housed at the AMNH. On the other
hand, a direct comparison with the species of Archaeopithecus
was impossible because no lower dentition is known for this
genus (the only mandible described by Ameghino is lost, see
above). Briefly, because Simpson (1967b) was not very
confident in establishing synonymy, he proposed tentatively the
combination ?Archaeopithecus fossulatus.
A recent revision and comparison of specimens MACN-A
10824a and MACN-A 10824b enable me to suggest a different,
more conservative position. Firstly, both specimens do not
correspond to the morphotype of the genus Notopithecus or any
other member of the notopithecid group. MACN-A 10824a
(Fig. 2.17) is very similar to AMNH FM 28705 and AMNH FM
28801, two specimens catalogued as Acropithecus rigidus; thus,
it is grouped with the Archaeopithecidae. On the other hand, the
extreme wear of specimen MACN-A 10824b (Fig. 2.18) has
erased all features on the occlusal surface of p4–m1 to allow any
comparison; although it could be considered Archaeopithecidae
based on its association and similar size to MACN-A 10824a,
it is here regarded as Notoungulata indet.
As a final point, with respect to more recent mentions of
archaeopithecids, Cladera et al. (2004, p. 317) listed the pre-
sence of Archaeopithecus? sp. nov. in Gran Hondonada (Chubut
Province), a locality referred to the Mustersan SALMA (late
Eocene); however, the authors did not provide either a catalogue
number or a figure of these specimens. Tejedor et al. (2009)
referred to Archaeopithecus cf. A.rogeri some maxillary
and mandibular remains and isolated teeth from the Paso del
Sapo fauna (late early Eocene, Woodburne et al., 2014a)
represented in La Barda and Laguna Fría localities (west of
Chubut Province). More recently, some remains from Las
Violetas locality (Chubut Province) were assigned as
Acropithecus rigidus (Gelfo et al., 2010; Bauzá et al., 2016),
which were recovered from a sequence overlaying Las Violetas
Formation (Río Chico Group); according to these authors,
this faunal assemblage is early Eocene in age (Ypresian) and
shows affinities with those of the Paleocene Itaboraian and
‘Sapoan’biochrons (Woodburne et al., 2014b and references
therein).
Figure 4. Archaeopithecus rogeri.(1) MMdP-M 727, maxillary fragment with right P1–M3, occlusal view; (2) MNH CAS 739, maxillary fragment with right
P3–M2, occlusal view; (3) AMNH FM 28841, maxillary fragment with left P2–3?, occlusal view; (4) MLP 93-XI-22-16a, right P4, occlusal view; (5) MACN-
PV 11237, maxillary fragment with left M1–2, occlusal view; (6) MGP 31362, maxillary fragment with right M1–3, occlusal view; (7) MLP 93-XI-22-3, left P4
and upper molar, occlusal view; (8) AMNH FM 28534, maxillary fragment with right M1–M2, occlusal view; (9) MACN-A 10831, right upper molar, left M1?
and two right M3, occlusal view; (10) MGP 31595, right M2?, occlusal view; (11) MACN-A 10847, left M3, occlusal view; (12) AMNH 28827, maxillary
fragment with left P4–M2, occlusal view; (13) MPEF 1580b, maxillary fragment with M1–3, occlusal view; (14) AMNH FM 28840, dentary with left p4–m2,
occlusal view; (15) AMNH FM 28705, dentary with left p3–m1 and right p2–3, occlusal view; (16) AMNH FM 28801, dentary with left p3–m1, occlusal and
labial views; (17) MACN-A 10841c, dentary with left m1–2, occlusal view; (18) MLP 93-XI-22-16b, left lower molar, occlusal view; (19) MLP 93-XI-22-3a,
dentary with right m1–2, occlusal view; (20) AMNH FM 28884d, dentary with right m1–3, occlusal view; (21) PVL 163, dentary with left m1–3, occlusal view;
(22) MGP 29028, dentary with right m2–3, occlusal view; (23) MGP 31599, left m3; (24) MLP 66-V-10-19, dentary with right m3, occlusal view. Abbreviations
in the text. Scale bar is 5 mm.
Vera—Eocene archeopithecids from Patagonia 11
Systematic paleontology
Anatomical and dimensional abbreviations.—AP, antero-pos-
terior; C/c, upper/lower canine; c.f, central fossette; c.ftd, central
fossettid; c.o, cristid oblique; entyd, entostylid; d.c, distal cin-
gulum; d.ftd, distal fossettid; end, entoconid; H, height; hy,
hypocone; hylfd, hypolophid; I/i, upper/lower incisor; L, length;
LLD, labiolingual diameter; lb.sul, labial sulcus; M/m, upper/
lower molar; Mc, metacarpal; m.c, mesial cingulum; m.cgd,
mesial cingulid; MDD, mesiodistal diameter; m.f, mesial
fossette; med.f, medial fossette; mtd, metaconid; P/p, upper/
lower premolar; par, paracone; prty, parastyle; pr, protocone;
pryd, protostylid; T, transversal; W, width.
Order Notoungulata Roth, 1903
Family Archaeopithecidae Ameghino, 1897
Genus Archaeopithecus Ameghino, 1897
Type species.—Archaeopithecus rogeri Ameghino, 1897.
Diagnosis.—Archaeopithecus differ from Notopithecus in
having a taller cranium and longer rostrum, moderate-sized
tympanic bullae, not reduced jugal and external expansion of
lacrimal; the symphysis is very short and wide and the man-
dibular bone is robust. The dentition is complete, rooted
and brachydont, but relatively higher-crowned than in other
brachydont early notoungulates, such as notopithecids and
oldfieldthomasiids. Archaeopithecus differs from notopithecids,
oldfieldthomasiids and interatheres in having conical upper and
lower incisors and canines, and short diastemata between these
teeth and P1. P1 is not reduced and has parastyle, differing from
notopithecids, Notostylops and Oldfieldthomasia. P/p1 are not
overlapped by C/c and P/p2 and lowers molars with a reduced
paralophid, differing from typotherians. A lingual sulcus divides
protocone in two lobes in P3–4, differing from Notopithecus and
Antepithecus. Upper molars are approximately square in
young specimens (TD ~MDD), but the transverse diameter
increases towards the base, becoming rectangular (TD >MDD)
when worn. M1–M2 have hypocone lingually more developed
than the protocone (like in Transpithecus). M3 has hypocone,
unlike notopithecids, oldfieldthomasiids and other Eocene
notoungulates. P4–M3 are characterized by having a central
fossette with a mesiodistally elongated section and a narrow
labial projection, which becomes an isolated ‘third labial’
fossette with wear (like molars of Archaeohyrax suniensis).
Lower incisors have non-procumbent implantation, unlike
Notostylops, and there is no groove in i1, differing from
notopithecids. p2–4 have a well-developed protostylid
fold, unlike Notopithecus,Antepithecus,Notostylops and
oldfieldthomasiids. Archaeopithecus has a well-developed
postmetacristid on p3–4, a feature shared by notopithecids, but
not by oldfieldthomasiids, hericosborniids and notostylopids.
Archaeopithecus contrasts with other Eocene notougulates by
having lower molars with a well-developed entostylid (shared
with Pleurostylodon) and a deep hypoflexid on talonid of m3
(except Henricosbornia).
Remarks.—Diagnosis emended from Ameghino (1897) and
Simpson (1967b).
Archaeopithecus rogeri Ameghino, 1897
Figures 2–5
1897 Notopithecus fossulatus Ameghino, p. 18, figs. 6a–d.
1901 Archaeopithecus alternans Ameghino, p. 359.
1901 Archaeopithecus rigidus Ameghino, p. 359.
1902 Adpithecus plenus Ameghino, p. 8.
1903 Acropithecus tersus Ameghino, p. 194.
1903 Acropithecus plenus; Ameghino, p. 195.
1904 Archaeopithecus rigidus; Ameghino, figs. 403–405.
1904 Acropithecus tersus; Ameghino, figs. 231, 280.
1967b Archaeopithecus fossulatus; Simpson, p. 64 (part).
1967b Acropithecus rigidus; Simpson, p. 65.
Holotype.—MACN-A 10816, maxillary fragment with right
P1–M2 (Fig. 2.1). This specimen lacks locality data, but it
probably comes from south of Colhué Huapi lake, Chubut
Province (Simpson, 1967b).
Diagnosis.—As for the genus, by monotypy.
Materials.—Materials are listed below by locality.
Bajo Palangana.—MGP 29056, left m3 and right m1?;
MGP 31657, right m2?; MGP 31658, right dentary m2–3 and
left M3; MGP 31663, left maxilla with broken M1–2; MGP
31717, right maxilla M2 (broken); MGP 31718, right upper
molar, broken; MGP 31719, left lower molar; MGP 31720, right
lower molar; MGP 31727, right m3; MGP 31729, right M1?;
MGP 31753, right P3?; MGP 31759, left m2?; MGP 31763, left
upper premolar; MGP 31767, right m1?; MGP 31768, right
molar; MGP 31769, left P3?; MGP 31777, left P3?; MLP 34-
V-22-7, right M2?; MLP 61-VIII-3-145, left maxilla P2–3?;
MLP 61-VIII-3-146, left maxilla P3–M1; MLP 61-VIII-3-148,
left maxilla P2–M2; MLP 61-VIII-3-176, right maxilla P4–M2;
MLP 61-VIII-3-177, left maxilla P4–M2.
Bahía Solano.—MGP 31595, right M2?; MGP 31596,
right m2?; MGP 31597, left m1?; MGP 31598, right m2?; MGP
31599, left m3; MGP 31600, left P3; MGP 31601, left m2?;
MGP 31602, recently erupted left lower molar; MGP 31603, left
m3; MGP 31604, left talonid m3; MGP 31605, broken right
upper premolar; MGP 31606, left P3?; MGP 31607, right m1?.
Northeast Cabeza Blanca.—AMNH FM 28824, right
maxilla P4–M2; AMNH FM 28871, isolated left M1?, M3?, two
right upper molars; AMNH FM 28872, isolated left p4 and m3,
and right molar; MLP 79-I-17-10, right maxilla P4–M2; MLP
79-I-17-12, right maxilla P3–M2; MLP 79-I-17-20, right
maxilla P4–M2; MLP 79-I-17-22, right maxilla P3–M3; MLP
79-I-17-36, left P3?; MLP 79-I-17-37, left P4?; MLP 79-I-
17-41, left maxilla M1–2; MLP 79-I-17-48, left maxilla P4–M2;
MLP 79-I-17-50, left maxilla P4–M2.
Campo Muriette.—MLP 61-VIII-3-425 to 446, 3 upper
premolars, 8 upper molars, 3 lower premolars, 7 lower molars;
MLP 66-V-10-4, left M2?; MLP 66-V-10-19, right m3.
Cañadón Hondo.—AMNH FM 28534, right maxilla M1–
M2; MACN-A 10824a, left dentary p4–m1 and rows p3 and
m2; MMdP-M 727, right maxilla P1–M3.
Cañadón Blanco.—MLP 12-1529, left m2?.
12 Journal of Paleontology
Colhué Huapi.—AMNH FM 144694, left m3; MACN-A
10833c, right M2; MACN-A 10841c, left dentarym1–2; MACN-
Pv 11237, left maxilla M1–2; MACN-Pv 12842, left maxilla
M1–3.
Cerro Solo.—MPEF-PV 1570, left M2 and M3, right P4
and M1; MPEF-PV 1580: a, right maxilla P4–M2; b, right
maxilla M1–3; c, left maxilla P4.
Cañadón Vaca.—AMNH FM 28534, right maxilla M1–
M2; AMNH FM 28705, left dentary p3–m1 and right p2–3;
AMNH FM 28782, skull with left I1–3, P1 (broken), P2–M2,
and right broken I1–3, P3–4, M1 and M3; AMNH FM 28801,
left dentary p3–m1; AMNH FM 28803, left dentary p4–m2;
AMNH FM 28804, right dentary p3–4; AMNH FM 28805,
right dentary with talonid of m1 and erupting m2; AMNH FM
28827, left maxilla P4–M2; AMNH FM 28840, left dentary
p4–m2; AMNH FM 28841, left maxilla P2–3?; AMNH FM
28842, left dentary p3–4; AMNH FM 28868, right maxilla
P2–M1; AMNH FM 28884: a, right maxilla M1–3; b, left
maxilla M1 (broken)–M2; c, left maxilla P2–3 and broken
P4–M2; d, right dentary m1–3; AMNH FM 28895, right
Figure 5. Morphological variation of M1 and m1 of Archaeopithecus rogeri throughout ontogeny: occlusal (1, 3) and labial (2, 4) views. From left to right, (1,
2) M1: MACN-A 10813c, MLP 93-XI-22-3b, MACN-A 10813a, AMNH FM 28782; (3, 4) m1: MLP 93-XI-22-16b, MLP 93-XI-22-3a, AMNH FM 28840 and
AMNH FM 28782. SW =stage of wear: 1, little; 2, middle; 3, heavy. From SW 1 to 3: occlusal surface becomes featureless and crown diminishes in height; M1
shortens and m1 widens (see text for details).
Vera—Eocene archeopithecids from Patagonia 13
maxilla P3–4; right Mc II-III, Mc IV?, left ulna, fragment of
phalanx; AMNH FM 144693, right dentary p4–m1; AMNH FM
144695, right maxilla P4–M2; AMNH FM 144696, right max-
illa M2–3; AMNH FM 144688, left dentary p4–m1; AMNH FM
144689, right dentary m2–3; AMNH FM 144690, left m1;
AMNH FM 144691, right p3?; AMNH FM 144692, isolated
and associated right M1, M2 and M3; AMNH FM 144693, right
dentary p4–m1; AMNH FM 144694, left m3; AMNH FM
144695, right maxilla P4–M2; AMNH FM 144696, right max-
illa M2–3; MGP 29028, right dentary m2–3; MLP 75-II-3-19,
left P4; MLP 75-II-3-20, left m1 or m2; PVL 162, left dentary
p4–m1; PVL 163, left dentary m1–3; PVL 165, left dentary
p4–m1; PVL 166, right dentary m1–2; PVL 167, right p4,
alveolus c and i3; PVL 199, right p4?; PVL 210, right M2?; PVL
232, left m1?; PVL 242, left P3?.
El Pajarito.—MLP 66-V-9-16, right P4?.
Lomas Blancas.—AMNH FM 28886, right P4?.
Las Cascadas.—MLP 93-XI-22-3, 22 lower teeth and 38
upper teeth, isolated; MLP 93-XI-22-16, 7 lower teeth and 12
upper teeth.
Oeste Río Chico (Ameghino’s locality).—MACN-A
10813: a, left maxilla P2–M2; b, left maxilla P4–M2; c, right
maxilla P4–M2; d, right maxilla M1–3; e, right maxilla P1–3; f,
right maxilla P4; g, left maxilla M1–2; h, right M1?; i, left P4;
MACN-A 10815, left maxilla M1–3; MACN-A 10831, right
upper molar, left M1? and two right M3.
Pico Salamanca.—MGP 31362, right maxilla M1–3.
No locality data.—AMNH FM 15902c, right maxilla P4–
M1; MACN-A 10816, right maxilla P1–M2; MACN-A 10843,
left lower molar; MACN-A 10847, left M3; MACN-A 10850,
a-b) two left M3; c) right M3; MACN-A 10851a, left maxilla
M1–2; MNHN-CAS 739, right maxilla P3–M2; MNHN-CAS
741, left m1; MNHN-CAS 751, right maxilla P4–M2.
Occurrence.—Las Flores Formation (?56–47 Myr, early
middle Eocene; Krause et al., 2017) and Sarmiento Formation
(Cañadón Vaca Member, 45–42 Myr, and Gran Barranca
Member, 41.7–38.45 Myr, middle Eocene; Ré et al., 2010;
Dunn et al., 2013; Bellosi and Krause, 2014; Krause et al.,
2017). The fossiliferous localities with archaeopithecids
are geographically located in Chubut Province, Argentina
(Figure 1).
Description.—The following description for the cranium is
based on specimen AMNH FM 28782 (Fig. 3.1–3.6), an adult
individual with associated skull and mandible and much worn
dentition; although partially restored, it is the most complete
individual known for archaeopithecids.
As regards cranium size, the rostrum is short and high, but
the cranium is taller and the rostrum longer and taller than in
Notopithecus (MACN-A 10787, MACN-A 10790); the dorsal
profile rises backwards. The maxillary bone is concave on its
rostral portion, in front of the orbit (Fig. 3.1). The infraorbital
foramen is circular and large, placed above the P4 level. The
orbits, posteriorly open, are very large in relation to the skull;
their most anterior border is at M1–2 level, just behind the
infraorbital foramen (Fig. 3.1, 3.2). Nasals are rectangular,
narrow and long. The zygomatic arches are laterally high and
apparently (by restoration) much expanded in dorsal view
(Fig. 3.1). In ventral view, the most anterior part of the pre-
maxillaries is semi-circular and its width increases slightly from
I to P1 level; posteriorly, the palate is not significantly wider
than the premaxillaries (Fig. 3.3, 3.4). Simpson (1967b,
p. 61) noted that the jugal bone forms the external and anterior
parts of the zygoma, continuing towards the lacrimal as a narrow
splint, both different features from oldfieldthomasiids and
notopithecids. Unfortunately, the poor preservation of AMNH
FM 28782 does not allow differentiating main bones around
orbital borders and defining the real extension of the lacrimal.
The tympanic bullae are moderately sized in relation to cranium
size, differing from other Eocene notoungulates such as Noto-
pithecus,Oldfieldthomasia, and Colbertia.
The mandibular bone is robust; its height increases gra-
dually backwards, from p2 (H =10.1 mm) to m2
(H =15.1 mm). The inferior border is convex up to m2–3 level,
where there is a concavity, and after this point the height
increases significantly (Fig. 3.6). The symphysis is very short
and wide; its posterior border is at p2–3 level. There is a labial
foramen below p2 and another one below talonid of p3.
Concerning the teeth, Archaeopithecus has a complete,
rooted, brachydont (Fig. 3.3), but relatively higher-crowned
dentition than other brachydont early notoungulates, such as
notopithecids and oldfieldthomasiids. The enamel is continuous
around the crown. Cementum is absent. The premolar series is
longer than molar series, as in notopithecids; this ratio is
characteristic of browser artiodactyls (Mendoza et al., 2002). No
deciduous dentition was identified with certainly among the
sample, probably because most of the sample corresponds to
isolated teeth; thus, the following description refers to perma-
nent teeth.
The morphology and size of archaeopithecid teeth
are variable throughout ontogeny (Fig. 5.1–5.4), which led
Ameghino to originally consider the presence of distinct
species. The present revision and comparison of many archae-
opithecid specimens permit establishing a wide intraspecific
variation rather than interspecific differences, which was like-
wise observed in archaeohyracids (Croft et al., 2003; Billet
et al., 2009; Cerdeño et al., 2010) and other notoungulate groups
(Francis, 1960; Madden, 1997; Billet et al., 2008; Cerdeño
et al., 2008). Indeed, Simpson (1967b) also recognized a
highly variable morphology on crown pattern and dimensions
in the archaeopithecid teeth samples he studied, such as the
extremely variable mesial cingulum in premolars and molars.
In Archaeopithecus, the upper teeth (mainly molars) are
labiolingually narrow at occlusal level (TD ≈MDD), but
the transverse diameter increases to the base, modifying
the dimensions on the tooth (TD >MDD). Another peculiarity
is that the presence of mesial cingulum and the lingual and
mesial sulci are variable in the upper dentition of archaeo-
pithecids.
Upper dentition.—The I1–3 of AMNH FM 28782 are
cylindrical in outline (Fig. 3.4). I1 is the greatest incisor
(2.6 × 2.4mm) and differs from the other incisors in having a
labiolingualy flattened tip and a lingual wear facet; I2
(2.0 × 2.2 mm) is a bit less compressed than I1 and the wear facet
is less developed; I3 (2.4 × 2.0 mm) is conic, pointed, and has
two smooth facets on the mesial and distal sides. The canine in
AMNH FM 28782 is broken at alveolar level, but the preserved
crown fragment indicates a cylindrical tooth, with approxi-
mately the same diameter as I3. There are short diastemata
14 Journal of Paleontology
separating incisors and canine, and between the canine and first
premolar. Conic-shaped incisors and canine and the presence of
diastemata distinguish Archaeopithecus from notopithecids,
oldfieldthomasiids, and interatheres.
From P1 to P4 (Figs. 2.1, 3.3, 4.1), the series is pre-
molariform, clearly distinguished from molars (see below). As a
whole, the distal cingulum is high, wide, and well developed
throughout the face, and it fuses with the metaloph in much-
worn teeth; the mesial cingulum can be absent (Fig. 4.1, 4.3) or,
when present, it is very narrow, near the base of the crown
(Fig. 2.1); both cingula descend lingually. The parastyle, para-
cone, and metacone folds form a very undulate ectoloph and
delimit deep labial sulci. There are mesiolabial and central fos-
settes in all premolars; on P1–2 the central fossette is small and
circular, but on P3–4 it also has a labial portion that forms an
isolated mediolabial fossette in worn teeth. A distolabial fossette
was only observed in P4. The mesial and distal borders of P2–4
are undulate.
P1 and P2 (Figs. 2.1, 4.1) are triangular in outline, with
conical protocone, centrally placed. They lack a lingual sulcus;
instead, there is a sulcus in the middle of the mesial face, as in
Transpithecus (Vera, 2012a), connecting to the central fossette
on unworn teeth (Fig. 2.7). P1 is much narrower than P2
(Table 1), but the difference is not so significant between P2 and
P3–4; P1 has a narrow and mesiodistally enlarged central
fossette (Fig. 2.7) and a parastyle fold, in contrast to other
notoungulates (e.g., Notopithecus,Colbertia) in which the P1 is
much reduced or canine-like. In addition, P1 is non-overlapping
by C and P2 (Fig. 3.3), differing from typotherians.
P3 is very similar to P1–2, but differs in having a lingual
sulcus dividing the protocone column in two lobes (Figs. 2.7,
4.2), although in some cases, the lingual sulcus is absent (Figs.
2.1, 4.1). A smooth sulcus in the mesial face is also observed in
some specimens (Fig. 2.7).
P4 has a wider protocone than P3, lacks the characteristic
triangular shape of the preceding premolars, and its mesial face
can be singularly concave (Fig. 2.3, 2.11). The lingual sulcus
is deep, forming two well-folded (Fig. 4.2) or softly folded
(Figs. 2.4, 3.3) columns. In AMNH FM 28841, the paracone and
metacone folds are not as undulate as in other specimens
(Fig. 2.7). There are mesio- and distolabial fossettes, the latter
being the shallowest and the first one to disappear. The central
fossette can be circular or elongated and has a narrow labial
extension; in some cases, there are internal crests in the central
fossette and the mesial extension can be also variable in shape
(Fig. 4.4).
As the wear advances in P2–4, the metaloph starts to con-
nect with the distal cingulum at a middle point (Fig. 4.1, 4.2),
forming two small pits, lingually and labially to the union; the
lingual pit, just posterior to the protocone, is deeper than the
labial pit and becomes a shallow fossette when worn (Fig. 2.11).
In a very old individual (AMNH FM 28782; Fig. 3.3), M1
shows only the central fossette, while P2 and P3 also have a
mesial fossette.
Compared with the premolars, the molars are squared or
rectangular in outline, depending on the wear stage. M1 and M2
are very similar to each other, and it is difficult to identify them
among isolated teeth. Unworn or very little worn molars have
the central valley completely open on the lingual face and
separating protocone from metacone (SW =1 in Fig. 5.1).
When wear increases, these lingual cones fuse through a crest
(entoloph), isolating the central fossette, and a sulcus on the
lingual face is formed, which differentiates protocone and
metacone columns (SW =2 in Fig. 5.1). This peculiarity is
shared with some notopithecids (Vera, 2012a, 2012b; Vera and
Cerdeño, 2014). On P4 and molars, the central fossette is
mesiodistally elongated and has a narrow labial projection,
which extends from the most anterior part of the central fossette
in the M1 and from the middle part on M2 and M3 (Fig. 4.1).
This labial projection becomes isolated as well, separated from
the central fossette and forming an independent mediolabial
fossette (Fig. 3.3) or internal fossette in Archaeohyrax suniensis
(Billet et al., 2009). However, in Archaeopithecus, the isolation
of this fossette seems to be independent from the increase of
wear. There are much-worn specimens preserving the labial
projection united to the central fossette (Figs. 2.15, 4.5, 4.6) and
little-worn specimens showing the mediolabial fossette com-
pletely separated from the central part (Fig. 4.7, 4.9). As with the
premolars, the distal cingulum in molars is much more devel-
oped than the mesial cingulum. M1–2 have hypocone more
developed than protocone and lingually protruding (Fig. 4.8,
4.12), a feature also described for the notopithecid Antepithecus
(Vera and Cerdeño, 2014; Vera, 2016), but in contrast to noto-
pithecids, the protoloph-protocone are inclined and curving
posteriorly in Archaeopithecus; there are some exceptions,
however, in which the protocone protrudes lingually more than
the hypocone, giving a ‘bilobed’shape (Fig. 4.10). In some
specimens (Fig. 4.12), M1 has a small ‘cuspule’at the base of
the sulcus between paracone and metacone, such as occurs in
Notopithecus (Vera, 2013b). Besides the ‘complex’central
fossette, molars have mesio- and distolabial fossettes, which are
irregular in shape and similarly sized. The occlusal surface
shows the typical ‘face’described for other groups of notoun-
gulate, with fossettes occupying the eyes, mouth, and nose of
this virtual face. These fossettes disappear in much-worn spe-
cimens (Fig. 3.3; SW =3 in Fig. 5.1). The ectoloph is not as
undulate as on premolars.
The M3 is characterized by its trapezoid shape, with the
distal face narrower than the mesial face, producing a distally
inclined labial face (Fig. 4.13); it differs from notopithecids,
oldfieldthomasiids and other Eocene notoungulates in having a
developed hypocone. The protocone is wider and more devel-
oped than the hypocone (Fig. 4.11, 4.13), whereas the opposite
condition is observed in M1–2; in some cases, the protocone is
pointed (Fig. 2.13). The wider protocone causes the central
valley to be displaced distally. The mesial cingulum is low and
short (Fig. 2.14), little to moderately developed, although also it
can be absent (Fig. 2.13). The distal cingulum is as well devel-
oped as in M1–2, but differs in being more convex distally. The
general pattern of fossettes is similar to that on M1–2: two labial
fossettes, and the central fossette formed by two transverse and
vertical parts; occasionally small fossettes form when the mesial
and distal cingula merge with the occlusal surface. In worn spe-
cimens (Fig. 2.12), M3 assumes a nearly square outline and sev-
eral fossettes are formed: the mesiolabial and distolabial fossettes,
the shallow fossette between the mesial cingulum and protoloph,
and a deeper fossette between the distal cingulum and metaloph,
just below the distolabial fossette.
Vera—Eocene archeopithecids from Patagonia 15
Lower dentition.—There are three isolated teeth in lot
AMNH FM 28782 (Fig. 3.5), here identified as most anterior
lower incisors and/or canine. Two of them are conical and sin-
gle-rooted; they do not have any lingual or labial sulci, unlike in
notopithecids. One tooth (2.0 × 1.6 mm) is a bit more labiolin-
gually flattened than the other (1.9 × 1.8 mm) and has a beveled
distal crest. The third tooth is smaller and has a very low crown
in comparison with the other teeth; its tip is rounded; it has a
slightly concave internal face, whereas the external is convex.
According to the size of the preserved alveolus in the lower jaw
AMNH FM 28782, i1 is the smallest of the series, and c is
approximately equal in size to i3. Their position demonstrates
that the implantation of incisors is non-procumbent, which
differs from Notostylops.
The premolars are characterized by having the trigonid
longer than the talonid and a well-developed protostylid
fold distally extended (Fig. 3.6), as described for p3–4in
Transpithecus (Vera, 2012a), but contrasting with Notopithecus,
Antepithecus,Notostylops, and oldfieldthomasiids. Molars,
instead, have trigonid much shorter than premolars and a longer
talonid; the trigonid is particularly narrow and labially convex,
with a lingually inclined protolophid. Occasionally, a very low
conulid behind protoconid, between trigonid and talonid, is
present on molars.
The p1 was not identified in the sample. On p2 (Fig. 3.6),
the trigonid is narrower than the talonid, with two crests
forming a V; the protolophid is mesiolingually very inclined; and
the metalophid ends in a distally directed metaconid. The
mesiolingual cingulid is narrow and low. The talonid is trian-
gular in shape. The distal cingulid is low and wide, limiting a
deep pit.
The p3–4 are similar to each other, premolariform (Fig. 3.6;
Table 2), differing from molars as the homologous teeth in
upper series (see above). The metalophid is a much-curved crest,
and the metaconid is, in consequence, distally displaced in a
postmetacristid; thus, the latter approaches to the entolophid,
forming a fossettid in the talonid when worn. This well-developed
postmetacristid is shared by notopithecids, but not by old-
fieldthomasiids, henricosborniids, and notostylopids. The cristid
oblique touches the metalophid at the middle point of the labial
face. The protostylid can be absent (Fig. 4.15); such variability
was also observed in Transpithecus (Vera, 2012a). There is a well-
developed and low mesial cingulid, which merges with the pro-
tolophid and forms a long linguodistally oriented crest. The
p3 of AMNH FM 28801 (Fig. 4.16) has an unworn conulid
(entostylid) in the talonid basin, in contact with the entolophid;
with wear, this conulid merges with the entolophid, giving it the
mesial expansion observed on p4 and the molars; with more
advanced wear, this expansion reaches the metaconulid, isolating
a circular fossettid (Fig. 4.14). Comparing to the wear stage of
premolars of AMNH FM 28782 (Fig. 3.6; Table 2), p2 is less
worn than p3, and the latter has less wear than p4, although the
difference in wearis more evident between p2–3thanp3–4. Based
on this observation, it is assumed that p2 is the last premolar to
erupt, and the sequence of eruption can be established as p4, p3,
and p2. The same pattern was described for notopithecids, the
henricosborniid Henricosbornia, some interatheriines (Vera and
Cerdeño, 2014; Vera, 2016), and the hegetotheriid Paedotherium
(Cerdeño et al., 2017).
The m1 and m2 are similar to each other, and it is difficult
to differentiate them when they are isolated because it occurs
with upper molars. A short-lived hypolophid is present
(Fig. 4.16) and a tiny lingual cingulid connects hypolophid with
entolophid, isolating a distal fossettid on the talonid
(Fig. 4.17; SW =1 and 2 in Fig. 5.3). In older individuals, how-
ever, the hypolophid and fossettids ‘disappear’due to the merging
of hypolophid and entolophid, and the talonid becomes sub-
circular (Fig. 4.15; SW =3 in Fig. 5.3). The fossettid located
between entolophid and hypolophid is more ephemeral than the
central fossettid placed between metalophid and entolophid
(Figs. 3.6, 4.14, 5.3). Molars have a well-developed entostylid,
which is shared only with Pleurostylodon. The entostylid is highly
variable in shape according to wear stage, being either hook-
shaped (Fig. 4.18) or bilobed (Fig. 4.19).
The m3 differs from m1–2 in the talonid. It is longer, has a
long and well-developed hypolophid and a labial sulcus (hypo-
flexid), which is deeper than in other Eocene notoungulates
(except Henricosbornia). Although absent in some individuals,
there is a low lingual cingulid uniting entoconid and hypolophid
and forming a distal fossettid, which is more evident when worn;
differing from m1–2, it is a deeper and long-term fossettid
(Fig.4.20).Asinm1–2, the entostylid touches the metaconid and
forms a mesial fossettid on the talonid; however, this entostylid is
wider and can have small extra crests (Fig. 4.22). In some speci-
mens (Fig. 4.21, 4.23), there is a small and low lingual cingulid
that closes the valley between trigonid and talonid. In younger
individuals (Fig. 4.24), trigonid and talonid are occlusally sepa-
rated, but with wear the cristid oblique touches the metalophid at
mid point. Molars have a short paralophid that merges in early
stages of wear with the mesial cingulid, forming a long crest
(Figs. 4.15, 4.16, 4.18, 5.3).
Postcranium.—Specimen AMNH FM 28895 includes the
right Mc II and Mc III in anatomical connection (Fig. 6.1–6.3),
an isolated metapodial (Fig. 6.4–6.7), a fragment of phalange,
and a fragment of left ulna (Fig. 6.8, 6.9). The metacarpals are
poorly preserved. Mc II is distally incomplete, but it would be
shorter than Mc III (Fig. 6.1; Table 4); the proximal articular
surface of Mc II is deeper and wider than that of Mc III
(Fig. 6.2); the proximointernal face is broken.
Mc III has a laterally compressed proximal half (AP >T),
an anteroposteriorly flattened distal half (AP <T), and is
approximately square at the midpoint (Fig. 6.1; Table 4); there is
a concave proximoexternal facet for Mc IV, formed by two
lunate sections, with the anterior being larger than the posterior
part (Fig. 6.3); the proximal articular surface is asymmetrically
triangular. The length of Mc III is comparable to the dimensions
of the Mc III of Colbertia magellanica (Bergqvist and Fortes
Bastos, 2009). Dimensions of Mc II–III (Table 4) are larger than
those reported by Vera (2012b, table 4) for the metapodials of
Notopithecus adapinus.
The isolated metapodial AMNH FM 28895 is significantly
shorter than Mc II–III (Table 4). This difference in size
occurs, for example, among metacarpals of the Interatheriinae
Protypotherium,Miocochilius, and Federicoanaya, in which
Mc V has almost half the length of Mc III (Sinclair, 1909;
Stirton, 1953; Hitz et al., 2008). Based on this comparison
(Eocene associated metapodials are practically unknown) and
by association with the other metacarpals present in the lot
16 Journal of Paleontology
AMNH FM 28895, the isolated bone is here tentatively con-
sidered a right Mc V (Fig. 6.4–6.7). It is complete, but fractured;
the body is nearly straight and quadrangular in section (Fig. 6.4,
6.5); the proximal epiphysis is laterally compressed and the
distal epiphysis is anteroposteriorly flattened (Fig. 6.6). The
proximal facet is rectangular in shape, anteroposteriorly very
convex, and laterally inclined (Fig. 6.7); posteriorly, the surface
extends downwards in a small fan-shaped area (Fig. 6.5).
Internally, just below the surface, there is a thin ridge that
borders a concavity. The external face is convex and has no
distinctive facet. The distal articular surface is anteriorly convex
and has a moderately developed keel on the posterior face
(Fig. 6.7); in anterior view, a semi-circular sulcus separates the
articulation from the shaft.
The ulna fragment (Fig. 6.8, 6.9) has a moderately concave
and nearly vertically oriented articular facet for the humerus,
similar to the ulna of Notopithecus adapinus (Vera, 2012b) and
differing from the curved surface observed in Protypotherium
(YPM-PU 0-15828, YPM-PU 0-15341; also see Sinclair, 1909).
Discussion
Variation throughout ontogeny and systematic implications.—
It is widely known that wear modifies the dimensions and
morphology of the dentition of herbivorous mammals through-
out ontogeny. In particular, among native ungulates from South
America, ontogenetic sequences based on extreme morpholo-
gical changes on dentition were described for Archaeohyracidae
(Croft et al., 2003; Billet et al., 2009; Cerdeño et al., 2010), the
notopithecid Transpithecus (Vera, 2012a), and other groups of
notoungulates (Francis, 1960; Madden, 1997; Billet et al., 2008;
Cerdeño et al., 2008).
Concerning archaeopithecids, the morphological changes
on the occlusal surface of upper and lower dentition became
really noticeable as wear progresses. However, these changes
were originally assumed to represent taxonomic differences,
therefore Ameghino (1897, 1901, 1902, 1903) erected at least
six species of archaeopithecids. Simpson (1967b) regarded the
same criteria, but he reduced the number of species and
recognized variation. On this aspect, Croft et al. (2003) provided
the basis for interpreting wear-related metric variation in
archaeohyracids tooth dimensions and demonstrated that most
cheek teeth decrease in length and increase in width through
Figure 6. Archaeopithecus rogeri. AMNH FM 28895: (1–3) right Mc II-III,
(1)anterior,(2) proximal (anterior face to bottom) and (3) lateral views; (4–7)
right Mc V, (4) anterior, (5) posterior, (6) internal, (7) proximal and distal views;
(8, 9), fragment of left ulna, (8)anteriorand(9) lateral views. Scale bar is 5 mm.
Table 4. Measurements (mm) of the metapodials of AMNH FM 28895.
APD =anteroposterior diameter; diap =diaphysis; dist =distal; L =length;
px =proximal; W =width. Dashes represent not measured dimensions.
Mc III Mc II Mc V
L 34.5 - 15.9
W px 6.5 6.1 2.6
W dist 7.0 - 3.9
APD px 6.3 8.2 3.7
APD dist 4.5 - 2.7
W diap 6.5 - 2.4
APD diap - - 1.7
Vera—Eocene archeopithecids from Patagonia 17
increasing wear, which should be taken into account when
interpreting the systematic significance of metric differences
among specimens of different wear states.
The present revision of archaeopithecid teeth highlights,
for example, that in barely worn teeth (e.g., 1 in Fig. 7) the
mesial cingulum is low (nearly at the base of the crown), the
protocone and the hypocone are separated (the entolophe is not
formed or incipient), and the central fossette preserves its
vertical part (Figs. 2.4, 2.5, 4.11; SW =1 in Fig. 5.1); in
contrast, in much more worn teeth (e.g., 3 in Fig. 7), the
cingulum merges with the occlusal surface until disappearing,
and the protocone and hypocone are occlusally joined by the
entoloph at the same level (Figs. 2.15, 3.3, 4.12; SW =2in
Fig. 5.1). The same occurs with fossettes and sulci: they are
present in younger individuals and disappear or are attenuated in
older individuals. All these alterations throughout ontogeny
modify the occlusal surface appearance. Nevertheless, the most
striking changes with wear concern tooth metric variations.
Unworn upper molars (M1–2) are nearly square (MDD ≈LLD),
but with wear, the width increases much more than the length
(MDD <LLD), and consequently become rectangular (see open
triangles 1–3, Figure 7). In turn, P4 changes in both dimensions
with wear: the younger specimens are narrower and shorter
(e.g., 1 in Fig. 7) than those with moderate wear (e.g., 2 in
Fig. 7), while the older teeth are the longest and widest (e.g., 3 in
Fig. 7). With respect to lower dentition, the tendency is not as
clear as for the upper homologous teeth due to an overlapping
among wear categories; in general, however, m1 and m2 tend to
widen and shorten with increasing wear, although this is not as
evident as in archaeohyracids (Croft et al., 2003). These authors
suggested that the coefficient of variation (CV) has important
implications to distinguish species using metric values alone in
the absence of other corroborating morphological distinctions.
In the Archaeopithecidae sample, the coefficient of variation
assumes values below 11% for all cheek teeth, disregarding
wear (Table 1), and below 13% considering wear separately (see
Supplemental Data); this translates as low variation on teeth
dimensions. The higher variation (CV <13%), which considers
wear categories, emphasizes the difficulty to classify individual
teeth to a particular stage of wear.
In addition, despite the fact that the dentition of
Archaeopithecus is brachydont and develops roots, height
varies markedly through increasing wear (Fig. 5. 2, 5.4), from
relatively high-crowned teeth (SW =1 in Fig. 5.2, 5.4) to very
low-crowned teeth (SW =3 in Fig. 5.2, 5.4). With respect to
this peculiarity, Simpson (1967b, p. 62) observed how the age of
an individual influenced tooth dimensions and argued that the
accelerated hypsodonty revealed by archaeopithecids might hint
at a possible relationship with archaeohyracids. On this aspect,
however, it is important to distinguish that archaeopithecids
have brachydont-rooted dentition, which is relatively higher
crowned than in other typical short-crowned Eocene notoungu-
lates, whereas archaeohyracids are characterized by rootless,
ever-growing teeth (hypselodont dentition; Simpson, 1970).
Regardless of the ontogenetic stage of the individual, the
presence of mesial cingulum on upper dentition is a variable
feature in the archaeopithecid sample studied, and is here
considered an intraspecific variation or a polymorphic character
in phylogenetic terms. This variation was also mentioned by
Simpson (1967b) for the teeth sample referred to Acropithecus
rigidus (see above). This statement is crucial because the
presence of a mesial cingulum was one of the characteristics
alluded to by Tejedor et al. (2009) for assigning their material to
Archaeopithecus rogeri.
The present revision, based on more than 200 catalogued
specimens, including the type material of the species defined by
Ameghino and several collections (e.g., AMNH, MGP, MNHN,
MLP), does not support the differentiation of archaeopithecids
into two genera and three species as proposed by Simpson (1967b)
or two monospecific genera as suggested by Vera (2013b). On the
contrary, the present work identifies only one morphological
pattern showing morphological transformations throughout onto-
geny, from unworn to much more worn teeth, and presenting
some polymorphic characters that reflect intraspecific variation.
This documented difference in shape of the occlusal surface is
associated with wear-related metric variation in teeth dimensions.
Thus, a previous taxonomic overestimation is evident, and only
one monotypic genus, Archaeopithecus rogeri, is validated.
It should be noted that the Scarritt Pocket collection at
AMNH also includes uncatalogued isolated teeth (~200 pieces),
which have field numbers and were previously identified as
archaeopithecids by Simpson (1967b, p. 63–65), who collected
them in Patagonia. As part of the present revision, all these teeth
were studied during two visits to the AMNH and compared with
the type specimens of the Ameghino collection, which allowed
me to recognize on them the morphometric characteristics
described for Archaeopithecus rogeri.
Concerning nomenclature, Archaeopithecus rogeri is the
type species and the first one described by Ameghino (1897) in
Archaeopithecidae; in addition, the type specimen is a nearly
complete maxilla (P1–M2), enough to represent the morphologi-
cal characteristics of the taxon. Further, the name Archaeopithecus
Ameghino, 1897 has nomenclatural priority over Acropithecus
Ameghino, 1901, according to the ICZN (2000). Based on the
above-mentioned explanations, Archaeopithecus rogeri is here
considered as the valid name for the single recognized species.
Under this proposition, the name Acropithecus rigidus, resulting
from transferring Archaeopithecus rigidus to Acropithecus
(Simpson, 1967b), is consequently discarded.
Figure 7. Bivariate plot of eight specimens preserving P4–M2 row-teeth in
different stages of wear (SW). (1) MACN-A 10813c, SW =1; (2) MMdP-M
727, SW =2; (3) AMNH FM 28782, SW =3.
18 Journal of Paleontology
Phylogenetic analysis.—Exhaustive revision of many speci-
mens of Archaeopithecus rogeri has permitted improved codi-
fication of some characters with respect to Vera’s (2016) matrix.
Sixty-nine of 87 characters were scored for Archaeopithecus
rogeri (Supplemental Data 1). For example, the eruption
sequence of permanent premolars follows a postero-anterior
direction as in notopithecids (4
1
), P/p1 are not overlapped by
P/p2 or C/c (12
2
and 37
0
), i3 is larger than i2 (31
0
), c is larger
than incisors (35
1
), and the paralophid is reduced on molars
(51
1
). Other characters, such as those related to the mesial
cingulum on P3–4 and M1–2 (characters 18 and 19), the
development of hypocone versus protocone on M1–2 (character
22), and the lingual sulcus on P3–4 (characters 25 and 26), were
coded as polymorphic (Supplemental Data 1).
The phylogenetic analysis yielded 204 most-parsimonious
trees, 289 steps long, with a consistency index (CI) of 0.38, and
a retention index (RI) of 0.69. In the strict consensus (Fig. 8.1),
two basal polytomies are recovered; node A gathers Colbertia
and Notostylops as the most basal genus of node B. This latter
includes Archaeopithecus rogeri and other Eocene notoungu-
lates, such as Kibenikhoria,Henricosbornia,Oldfieldthomasia,
Pleurostylodon, and two clades: notopitheciids and node
C (grouping interatheriids, hegetotheres, mesotheres, and
archaeohyracids). Nodes B and D (Fig. 8.1) are well supported
Figure 8. (1) Strict consensus from the 204 most parsimonious trees (289 steps, CI =0.38, RI =0.69) obtained under equally weighted characters. (2) Tree
0/204, showing a particular arrange for Acropithecus rogeri in relation to other Eocene notoungulates. Synapomorphies are shown above branches. Numbers
below branches, from left to right, correspond to absolute BS, relative BS and Symmetric Resampling values. Letters A–F refer to nodes, which are explained in
text; (*) indicates synapomorphies 1, 13, 17, 25, 26, 61, 64, 65, 68, 69, 80.
Vera—Eocene archeopithecids from Patagonia 19
by, respectively, 11 synapomorphies (5, 7, 10, 12, 28, 29, 33,
35, 42, 52, and 66) and 12 synapomorphies (3, 13, 17, 20, 25,
26, 27, 34, 36, 40, 49, and 66).
It should be highlighted that Archaeopithecus rogeri is not
grouped into the notopithecid clade, being the most noteworthy
difference with respect to Vera’s (2016, fig. 2B) cladogram, where
A.rogeri is the sister taxon of the clade gathering Transpithecus
and Guilielmoscottia. In fact, in one of the most parsimonious
topologies (tree 0 of 204; Fig. 8.2), Archaeopithecus rogeri (with
10 autapomorphies) splits from node A as sister taxon of a most-
inclusive clade (node B), gathering the notopithecid clade (node
C) and node D, which groups some oldfieldthomasids (node E)
and node F (interatheriids, hegetotheres, mesotheres, and archae-
ohyracids). Node A (Fig. 8.2) links Archaeopithecus rogeri with
node B by two synapomorphies: 52 and 62. According to this
result, Archaeopithecus rogeri is a basal notoungulate, not directly
related to any group (family) of this order; therefore, previous
hypotheses linking this taxon to Oldfieldthomasia (Reguero and
Prevosti, 2010) or notopithecids (Vera, 2016) are discarded.
The strict consensus (Fig. 8.1) yielded relatively good branch
support and a good fit with the stratigraphic record of the taxa
included, in agreement with the topology obtained by Vera (2016,
fig. 2B). However, the relationships among Eocene taxa are not
well established, as shown the polytomies on nodes A and B (Fig.
8.1), in comparison with the better resolution of more-derived
notoungulate groups. These particular polytomies are due to the
shifting position mainly of the oldfieldthomasiids members, such
as Kibenikhoria and Oldfieldthomasia (Fig. 8.2; node E).
Despite recognizing only one taxon, the family Archaeopithe-
cidae as a Linnaean hierarchical rank is here maintained until new
studies of basal groups are undertaken, and the relationships among
Paleogene notoungulate families are identified more clearly.
Body mass estimation and paleoecological inferences.—Size,
which is one attribute of niche differentiation in herbivorous
mammals (Jarman, 1974; Owen-Smith, 1988), also allows
understanding the paleobiology and paleoecology of a fossil
organism (Elissamburu, 2012). The most common way to esti-
mate body mass in fossil ungulates is applying allometric equa-
tions derived from extant mammals, using linear regression based
on dental, craniomandibular, and postcranial measurements
(Damuth, 1990; Janis, 1990; Scott, 1990; Mendoza et al., 2006;
Tsubamoto, 2014). Particularly for ungulates, Janis (1990) rea-
lized that the parameters with less variation and greater correlation
with body mass on herbivorous ungulates were the lengths
(MDD) of each lower molar (m1, m2, and m3), M2, and the series
m1–3, with the last being the most reliable. Several estimations
were carried out for different groups of South American notoun-
gulates (Madden, 1997; Elissamburu, 2004; Elissamburu and
Vizcaíno, 2004; Croft and Anderson, 2008; Reguero et al., 2010;
Vizcaíno et al., 2010; Scarano et al., 2011; Cassini et al., 2012a;
Elissamburu, 2012), including a geometric morphometric
approach by Cassini et al. (2012b). Based on several allometric
equations from different authors, Elissamburu (2012) estimated
body size for 50 genera of Notoungulata and proved that lower
molar row length (LMRL) and first lower molar length (FLML)
offer more stable estimation values, with Janis’(1990) predictors
being best for notoungulate taxa with unknown postcranial bones,
such as most of the Eocene groups. Specifically, regarding early
Paleogene Patagonian taxa, Elissamburu (2012; table 2) provided
mean body mass values for archaeopithecids (Acropithecus)and
notopithecids (Notopithecus). In turn, Scarano et al. (2011)
proposed new linear regression models that proved to be most
successful for small herbivorous ungulates with body mass under
13kg; for larger ungulates, the equations postulated by other
authors (Damuth, 1990; Janis, 1990) worked better.
Following these inferences, body mass was estimated for
Archaeopithecus rogeri and notopithecids (Notopithecus,
Antepithecus,Transpithecus, and Guilielmoscottia) using
Vera’s (2013b) dataset and applying equations from Janis
(1990) and Scarano et al. (2011). In particular for Notopithecus,
body mass was also inferred from astragalar parameters
(Tsubamoto, 2014) based on one specimen (MPEF-PV 1113,
Vera, 2012b). Mean values for each model and taxon, as well as
the average total, are listed in Table 3.
Taking into account average total values (Table 3), the
estimated body mass of Archaeopithecus rogeri (1.62 kg) falls
between the estimated values for the notopithecids Notopithecus
adapinus (1.40 kg) and Antepithecus brachystephanus Ame-
ghino, 1901 (1.68 kg), and is surpassed by Transpithecus
obtentus (1.82 kg) and Guiliemoscottia plicifera (2.38 kg).
However, after exploring each model separately and applying
second lower molar length (SLML), third lower molar length
(TLML), and m1–3 length (LMRL) models, the body mass of
the archaeopithecid is higher than that of N.adapinus and
A.brachystephanus, but is still surpassed by the predicted mass
values for T.obtentus and G.plicifera (Table 3). In summary,
the body mass values obtained for Archaeopithecus rogeri fall
within the range between 1.43 kg and 2.57 kg, overlapping the
values for notopithecids (Table 3) and the hegetotheriids
Pachyrukhos and Paedotherium (~2 kg, Cassini et al., 2012a,
2012b; Elissamburu, 2012), but below the body mass estimated
for the interatheriinae Protypotherium australe (~8 kg, Scarano
et al., 2011; Cassini et al., 2012a; 3–5 kg, Cassini et al., 2012b;
~7 kg, Elissamburu, 2012). Indeed, the body mass estimates of
the present study for Notopithecus and Archaeopithecus
(Table 3) are very close to those previously reported by
Elissamburu (2012, table 2). In contrast, when considering
models based on postcranial remains, body mass values are
higher than those based on dental models, as it is corroborated
for Notopithecus (Table 3; Elissamburu, 2012); in this case,
when applying Tsubamoto (2014) models based on astragalar
lineal measurements, body masses predicted for Notopithecus
do not vary between equations (Table 3), and their values are
closer to those estimated using humerus length than those based
on other long bones (Elissamburu, 2012).
Archaeopithecus rogeri is a brachydont notoungulate
restricted to the Casamayoran SALMA, but characterized by
having relatively higher crowns than other contemporaneous
brachydont groups, such as notopithecids and oldfieldthoma-
siids. Explaining this incipient protohypsodonty (Mones, 1982)
is not easy, given that Archaeopithecus is ancestral to any other
notoungulate group; phylogenetic effects and an adaptive
differential use of feeding source (substrate preference) should
be considered, particularly during the middle Eocene when a
global cooling occurred and open-vegetation habitats expanded
in central Patagonia (Bellosi and Krause, 2014, and references
therein).
20 Journal of Paleontology
Biostratigraphic context.—Within Ameghino’s published
work, all of his Archaeopithecidae members (excepting
Guilielmoscottia, which was later transferred to notopithecids,
see above), were described for the Casamayoran levels (Eocene)
of the Sarmiento Formation (Patagonia). Ameghino usually
differentiated specimens based on their origin, either from the
‘low’or ‘upper’sections of the Casamayoran, but unfortunately
many of his specimens presently lack this important strati-
graphic information. Cifelli (1985) recognized two distin-
guishable sections in the traditional Casamayoran age, which
later were referred to the Vacan and Barrancan subages. At
present, the Vacan (the lower section or Cañadón Vaca Member,
43.1–46.9 Myr; Bellosi and Krause, 2014) and the Barrancan
(the upper section or Gran Barranca Member, 42–39 Myr;
Bellosi and Krause, 2014) are considered to be Lutetian-
Bartonian, respectively (Woodburne et al., 2014a, 2014b, and
references therein). In turn, all the specimens referred by
Simpson (1967b) to Acropithecus rigidus come from the Casa-
mayoran lower levels of Cañadón Vaca, which is the type
locality of the Vacan subage (Cifelli, 1985). This locality is very
near to ‘Oeste de Río Chico,’which produced some of the
Ameghino type specimens (Simpson, 1967a; Fig. 1). According
to Simpson (1967a, p. 65), the assemblage from Cañadón Vaca
is more similar to Ameghinos’specimens from ‘Oeste de Río
Chico’than those from Colhué Huapi. In addition, many other
specimens recognized here as Archaeopithecus rogeri derive
from localities at Barrancan levels, such as Colhué Huapi
(where the Cañadón Vaca section is absent; Bellosi and Krause,
2014), and are contemporaneous with the notopithecid remains.
The specimens in the Egidio Feruglio collection, curated at the
MGP, have information about locality, but the stratigraphic
origin is not precise.
Simpson (1935a, 1935b) referred to a Notopithecidae indet.
and ?Transpithecus sp. from Cañadón Hondo; however, Vera
(2012a) determined that the specimen mentioned by Simpson
(1935a) does not correspond to Transpithecus or any member of
the notopithecid group (or any other specimen from the
Cañadón Hondo fauna in the AMNH collection), and referred
it instead to the archaeopithecid morphotype (AMNH FM
28534). This is the only fossil from Cañadon Hondo recognized
as an archaeopithecid after several years of research and two
visits to the AMNH. Particularly for the Cañadón Hondo area,
Raigemborn et al. (2010) postulated that the Gran Barranca
Member of the Sarmiento Formation is equivalent to the
Cañadón Hondo Formation (Andreis, 1977) and that it overlies
the Las Flores Formation. In turn, Bellosi and Krause (2014)
proposed a correlation between the Cañadón Vaca Member (of
the Sarmiento Formation) and the lower and middle sections of
the Cañadón Hondo Formation, as well as between the Gran
Barranca Member and the upper section of Cañadón Hondo
Formation. This means that Simpson’s fossil from Cañadón
Hondo (AMNH FM 28534) could have come from levels younger
than Itaboraian age. The same situations could apply to the
specimens coming from the Bajo Palangana, and Cerro Blanco
localities, where there are levels of both the lower section of the
Sarmiento Formation (Gran Barranca Member) and the Río Chico
Group (Riochican SALMA, late Paleocene–middle Eocene;
Raigemborn et al., 2010, and references therein), but the
stratigraphic origin of these specimens is unclear.
Concerning new records of archaeopithecids (Cladera et al.,
2004; Tejedor et al., 2009; Gelfo et al., 2010; and Bauzá et al.,
2016), it is necessary to clarify some points. In the case of
Acropithecus remains from the Las Violetas fauna, these were
recovered from outcrops, uncomformably overlying the Las
Violetas Formation (Gelfo et al., 2010), assigned to Las Flores
Formation (Río Chico Group), and referred to early Eocene (Bauzá
et al., 2016). In turn, the presence of Archaeopithecus in the fauna
from Paso del Sapo (Tejedor et al., 2009) is not discarded, bearing
in mind that the Paso del Sapo fauna fills the gap between the
Riochican SALMA and Vacan subage (Woodbourne et al., 2014b;
but see Krause et al., 2017); however, the taxonomic affinities of
these remains need to be corroborated. Finally, if the record of
Archaeopithecus in the Mustersan levels of Gran Hondonada
(Cladera et al., 2004) is confirmed, it would imply the youngest
record and the biochronological extension of this taxon.
In sum, although Archaeopithecus rogeri is present in the
Cañadón Vaca and Gran Barranca members, it is more common
in the Vacan than the Barrancan subage. The first (Riochican
SALMA) and last (Mustersan SALMA) appearances proposed
for Archaeopithecus still need to be confirmed (see discussion
above).
Conclusions
This systematic revision of hundreds of specimens referred to
archaeopithecids has permitted identifying only one morpho-
type, which shows ontogenetic variation in both size and mor-
phology, and intraspecific variability for some characters.
Consequently, only one taxon is recognized among the many
species originally described for the group.
Nomenclatorial priority supports Archaeopithecus rogeri
as a valid name. In this sense, the names of all species described
by Ameghino into Archaeopithecidae (Archaeopithecus
alternans,A.rigidus,Acropithecus tarsus, and Ac.plenus)
become synonymous with Archaeopitecus rogeri, including the
combination Acropithecus rigidus proposed by Simpson (1967b).
Regarding the lectotype (MACN-A 10824a) of Notopithecus fos-
sulatus, this specimen is here recognized as an archaeopithecid;
thus, the name N.fossulatus (and Archaeopithecus fossulatus sensu
Simpson, 1967b) is considered synonymous with Archaeopithecus
rogeri.
In contrast to the other Casamayoran brachydont taxa, such
as notopithecids and oldfieldthomasiids, Archaeopithecus dis-
plays incipient higher-crowned dentition, conical upper/lower
incisors and canines, short diastemata between anterior teeth, a
parastyle on P1, non-overlapping P/p1, hypocone developed on
M3, non-procumbent lower incisors, a well-developed proto-
stylid fold on p2–4, a reduced paralophid and well-developed
entostylid on lower molars, and a deep hypoflexid on talonid of
m3. Archaeopithecus shares the eruption sequence of permanent
premolars and the well-developed entostylid on lower molars
with notopithecids and Pleurostylodon, respectively. Some
characters are polymorphic, such as presence/absence of the
mesial cingulum and lingual sulcus on upper teeth. Addition-
ally, Archaeopithecus teeth show variable occlusal morphology
throughout ontogeny, which is associated with a wear-related
variation in dental dimensions. With increasing wear, upper
Vera—Eocene archeopithecids from Patagonia 21
molars became wider, while lower molars tended to widen and
shorten.
Based on the phylogenetic analysis, Archaeopithecus rogeri
is not recovered as a member of the notopithecid clade or together
with Oldfieldthomasia, contrary to previous hypotheses (Reguero
and Prevosti, 2010; Vera, 2016). In fact, Archaeopithecus
rogeri occurs in basal position in relation to Typotheria, forming
a polytomy with other Eocene taxa, such as the isotemnid Pleur-
ostylodon modicus,Henricosbornia, and some oldfielthomasiids.
The body masses for Archaeopithecus rogeri and the
notopithecids were estimated using different regression models
based on dental measures, and on postcranial parameters in the
case of Notopithecus. The mean value calculated for Archae-
opithecus rogeri (1.62 kg) is very close to those for Notopithe-
cus adapinus (1.40 kg) and Antepithecus brachystephanus
(1.68 kg), and slightly lower than Transpithecus obtentus
(1.82 kg) and Guiliemoscottia plicifera (2.38 kg), all of which
have body sizes comparable to those of the hegetotheriids
Pachyrukhos and Paedotherium.
Archaeopithecus rogeri currently has been reported only
from Eocene localities of Chubut Province (Argentina). Its
biostratigraphic range is from Vacan (early middle Eocene)
through Barrancan (late middle Eocene) subages. Older records
from the Riochican SALMA need to be stratigraphically
confirmed. In addition, purported archaeopithecids from the
Paso del Sapo fauna, Gran Hondonada (Mustersan SALMA),
and Las Violetas localities, lack published descriptions to verify
their taxonomic designation. Therefore, the lower and upper
limits of the archaeopithecid biochron are still tentative.
Acknowledgements
Thanks are due to the editors of the Journal, D. Croft, and an
anonymous reviewer for their constructive suggestions that
improved the manuscript. I am also grateful to the following insti-
tutions and people who provided access to the collections under their
care: J. Meng, J. Galkin, and A. Gishlick (AMNH); A. Kramarz and
S. Álvarez (MACN); M. Fornasiero and L. del Favero (MGP);
M. Reguero and M. Bond (MLP); C. Argot (MNHN); F. Scaglia
and A. Dondas (MMdP); E. Ruigómez (MPEF); and D. García
López and J. Powell (PVL). I am indebted to C. Bottero, who
revised the English language, P. Meglioli (IANIGLA), who helped
with statistical analysis, R. Bottero (IANIGLA), who prepared
Figure 1, and F. Magliano for technical assistance. The Campo
Muriette location (Fig. 1) was kindly provided by M. Krause and
P. Puerta (MPEF). This research was financially supported by:
“Consejo Nacional de Investigaciones Científicas y Técnicas”
(CONICET, Argentina), postdoctoral scholarship for short stays
abroad (Resolution D Nº4778); the scholarship committee of the
Field Museum of Natural History, USA (grant 2010-P305326); a
Williams Foundation travel grant (2011); and two “Proposte di
finanziamento per azioni di cooperazione universitaria”grants (2011
and 2014) by the University of Padova, Italy.
Accessibility of supplemental data
Data available from the Dryad Digital Repository: http://doi.
org/10.5061/dryad.h2900
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Accepted 2 May 2017
24 Journal of Paleontology
