American Journal of Primatology 45:317–336 (1998)
© 1998 Wiley-Liss, Inc.
RESEARCH ARTICLES
A New Pitheciin Primate From the Middle Miocene
of Argentina
RICHARD F. KAY,1* DEREK JOHNSON,1 AND D. JEFFREY MELDRUM2
1Department of Biological Anthropology and Anatomy, Duke University Medical Center,
Durham, North Carolina
2Department of Biological Sciences, Idaho State University, Pocatello
We report here a new fossil primate from the middle Miocene of Argentina.
The material consists of isolated teeth, mandibular fragments, and a talus.
The fossils were collected in the Collón Cura formation at Cañadón del
Tordillo in Neuquén Province. An age of 15.71 ± 0.07 Ma has been reported
for the Pilcaniyeu Ignimbrite, which lies just below the paleosols in which
the fossils were found. This material is thus the youngest occurrence of
fossil primates in Argentina (hitherto documented in the Santacrucian and
older land mammal ages) but still is older than the middle Miocene platyr-
rhine primates from La Venta, Colombia, in particular the pitheciins
Nuciruptor and Cebupithecia. The material is recognized as a new genus
and species of Pitheciinae, Propithecia neuquenensis. The mesiodistally com-
pressed, high-crowned incisors are specialized and similar to species in the
tribe Pithecini and to the nonpitheciin Soriacebus (early Miocene, Patagonia).
We rule out a phylogenetic relationship to the latter because of differences
in molar morphology. Propithecia does, however, fit well into the pattern of
pitheciin evolution, being more derived than the middle Miocene pitheciin
Nuciruptor but not as much as another middle Miocene taxon, Cebupithecia.
As such, this makes Propithecia the oldest taxon that can be confidently
placed within this modern New World monkey subfamily. By analogy with
the molar structures and diets of extant platyrrhines, Propithecia has a
molar structure consistent with a variety of low-fiber diets ranging from
fruit and gum to seeds. Its incisors suggest seed-eating in much the same
way as extant pitheciins, like Pithecia. The talus resembles that of
Callicebus, suggesting arboreal quadrupedal locomotion. Am. J. Primatol.
45:317–336, 1998. © 1998 Wiley-Liss, Inc.
Key words: Pitheciinae; Platyrrhini, Collón Cura formation; Miocene;
Argentina; dental anatomy
Contract grant sponsor: CONICET; Contract grant number: PID3-005900; Contract grant sponsor:
National Science Foundation.
*Correspondence to: Richard F. Kay, Department of Biological Anthropology and Anatomy, Duke Uni-
versity Medical Center, Durham, NC 27710.
Received 15 June 1997; revision accepted 2 February 1998

318 / Kay et al.
INTRODUCTION
In 1991, Pardiñas reported a fossil primate found by him in 1985 in the
Collón Cura formation in the valley of Río Limay in southern Neuquén Province,
Argentina [Pardiñas, 1991]. This and other fossil vertebrates had been discov-
ered while he was undertaking archaeological studies in areas expected to be
flooded by a hydroelectric project on the Río Limay. In 1990 and 1991, a group
from Museo de La Plata (MLP) and Duke University returned to Cañadón del
Tordillo and made another, larger collection of fossil vertebrates, including addi-
tional primate specimens. While fragmentary in preservation, being composed of
isolated teeth, jaw fragments, and a talus, the collection is significant in docu-
menting the first occurrence of primates from a faunal interval of the Miocene
known as the Colloncuran that slightly postdates the Santacrucian South Ameri-
can Land Mammal Age (SALMA) [Madden et al., 1997]. As such, this is the young-
est fossil occurrence of primates in Argentina, while still being slightly older
than middle Miocene Colombian primates [Madden et al., 1997; Flynn et al.,
1997]. Based on the Cañadón del Tordillo material, we name a new species of
pitheciine and offer some notes on its age and adaptations.
The monophyly of the modern Pitheciinae, Pithecia (the saki), Chiropotes (the
bearded saki), and Cacajao (the uakari), is well established [reviewed in Kay, 1990].
Rosenberger advocated inclusion of Callicebus (the titi) and Aotus (the owl monkey)
in the Pitheciinae [Rosenberger, 1979, 1981]. Rosenberger’s allocation of Callicebus
to the Pitheciinae is supported by recent phylogenetic analyses of DNA nucleotide
sequences, but the molecular evidence does not support the hypothesis that Aotus is
related to pitheciines [Schneider et al., 1993, 1995; Meldrum, 1995]. The classifica-
tion of Schneider et al. [1993] reflects these cladogenetic events and is followed here.
The subfamily Pitheciinae represents a clade including the monophyletic tribe
Pitheciini with the extant genera Pithecia, Chiropotes, and Cacajao and the tribe
Callicebini Pocock, 1925, for Callicebus alone.
Several fossil primates have been suggested as possible pitheciines. Meldrum
and Kay [1997] present strong evidence that Cebupithecia and Nuciruptor (both
middle Miocene, Colombia) are early members of the pitheciin clade, whereas
Soriacebus and Mohanamico (early and middle Miocene of Argentina and Colom-
bia, respectively) present significant “crossing specializations” making them less
likely candidates for membership in Pitheciinae. Tremacebus (early Miocene, Ar-
gentina) has been proposed as related to Aotus and for that reason included in
pitheciines [Rosenberger, 1990], but, with removal of the latter from pitheciines,
the former should be removed as well. Homunculus (early Miocene, Argentina)
too has been accorded pitheciine status based upon cranial and dental similari-
ties to Callicebus [Rosenberger et al., 1990; Tauber, 1991]. We defer comment on
such an allocation pending description of new material and restudy of other fos-
sils. (Should Homunculus (early Miocene, Argentina) prove to be the sister group
to Callicebus, [see Rosenberger et al., 1990], the correct nomen for the Callicebini
should be Homunculini Ameghino, 1894.)
GEOLOGY AND PALEONTOLOGY
The new primate fossils occur in the Collón Cura formation at Cañadón del
Tordillo (40°23´30´´ S, 70°12´20´´ W), a narrow, dry valley of the Río Limay ap-
proximately 40 km southwest of the town of Piedra del Aguila, Neuquén Prov-
ince [Pardiñas, 1991]. The Collón Cura formation with its contained fauna crops
out extensively in Neuquén and Río Negro Provinces and is commonly quite fos-
siliferous but has hitherto yielded no primate fossils. In this valley, the Collón