The Earliest Known Radiation of Pitheciine Primates

Abstract

Two of the more interesting and controversial platyrrhine primate taxa from the Miocene of Patagonia are Soriacebus and Mazzonicebus. Although they are known basically from isolated teeth and partial mandibles and maxillae, their morphology is highly distinctive. Opinions about their phylogenetic relationships differ widely. We interpret these fossils as belonging to the lineage of the anatomically derived, living pitheciine seed-predators; others hold the view that they are stem platyrrhines with convergent adaptations with pitheciines (with the single exception of Proteropithecia among the Patagonian forms), somewhat distant relatives converging coincidently with pitheciines. Here we tested these hypotheses in two ways: (1) by summarizing a character analysis of taxonomically informative traits; (2) we implemented "blind" parsimony analyses using the software package TNT, including a combined matrix of both morphological and molecular data, and replication studies of other matrices. We make some criticisms on the applied methodology of Parsimony in our analysis. Soriacebus and Mazzonicebus resulted sister-taxa nested deeply within the pitheciid clade; thus, and according to our inferences, they are not stem platyrrhines. Most of the differences separating them from the younger and uniformly recognized pitheciine fossils Proteropithecia, Nuciruptor and Cebupithecia are explained as being of more primitive character states; the vast majority of resemblances and their broader functional patterns are definitively pitheciine, as typified by the living pitheciines (sakis and uakaris). We therefore found that none of the Miocene Patagonian genera treated here can be reliably interpreted as stem platyrrhines. Rather, they tend to ratify the Long Lineage Hypothesis.

Keywords: Miocene; Patagonia; Pitheciinae; Platyrrhini; parsimony; phylogeny.

Figure 1

Dentition of living pitheciines. Occlusal view of the right upper (left) and right lower dentition (right) of Cacajao calvus (FMNH 88813, cast). Scale bar = 2 mm.

Figure 2

Occlusal views of (a) MACN Pv SC2 (cast), holotype of Soriacebus ameghinorum; (b) MPEF PV 6752, holotype of Mazzonicebus almendrae; and (c) MLP 91‐IX‐1‐125 (modified from Kay et al. 1998), holotype of Proteropithecia neuquenensis. Scale bar = 1 cm.

Figure 3

Occlusal views of the upper M1s of Mazzonicebus almendrae (a, MPEF‐PV 7063), Soriacebus ameghinorum (b, MACN Pv SC67, cast), Cebupithecia sarmientoi (c, UCMP 38762), and Cacajao calvus (d, FMNH 88813, cast). Scale bar = 1 mm.

Figure 4

Occlusal views of the lower m1 of Soriacebus ameghinorum (a, in holotype, cast), Mazzonicebus almendrae (b, MPEF‐PV 5348), Proteropithecia neuquenensis (c, MLP 91‐IX‐1‐127), Cebupithecia sarmientoi (d, UCMP 38762), and Cacajao calvus (e, FMNH 88813, cast). Scale bar = 1 mm.

Figure 5

Right upper molar series of Mazzonicebus almendrae (MPEF‐PV 10970); modified from Novo et al. 2017). Scale bar = 1 mm.

Figure 6

Cebupithecia sarmientoi, upper left (left) and lower right (right) dentitions in occlusal views. Scale bar = 1 mm. (Courtesy of Alfred L. Rosenberger).

Figure 7

Tree resulted from the analysis of molecular data of living taxa, and the DNA obtained from Xenothrix.

Figure 8

Strict consensus tree obtained from combined molecular and morphological data.