The Vertebrate Paleontology from the Cenozoic of Bryn Gwyn, Gaiman (Patagonia, Argentina)?

Capitulo de Libro

Resumen *

The evolutionary history of platyrrhines has been a matter of debate especially over the last four decades, with several research teams having made new findings that remarkably increased fossil collections. Their basal radiation is obscured by the lack of a continuous record postdating the oldest discoveries in the late Paleogene of Peru, where two primate lineages are documented. The Early to Middle Miocene Patagonian primates are not only among the most primitive representatives, but their phylogenetic status is quite controversial. In particular, the position of Dolichocebus gaimanensis, from the Early Miocene of Sarmiento Formation, including the Bryn Gwyn locality, Gaiman city (Chubut Province, Argentina) has been at the center of the controversy. Dolichocebus is one of the oldest primate records in Patagonia, together with Mazzonicebus and Tremacebus, with an age of about 20 Ma. It is represented by a cranium discovered in the 1940s near Gaiman city, as well as subsequent findings of a talus and isolated teeth from Bryn Gwyn. Dolichocebus is central to a discussion surrounding two opposing positions: one called the Long Lineage Hypothesis (LLH), and another alternative called the Stem Hypothesis (SH). The phylogenetic relationships of the Patagonian primates play a central role in these discussions. The SH argues that all Patagonian primates except Proteropithecia are stem platyrrhines. The authors who have supported the SH undertook a phylogenetic analysis that has been used in several successive works, but the character states are in urgent need of revision and correction, and these changes might strongly affect the conclusions. On the other hand, the LLH suggests that Dolichocebus is a crown platyrrhine, specifically part of the cebine lineage with living representatives. Upon careful revision, our interpretation is that Dolichocebus has affinities with the Cebidae, and even all Patagonian primates belong to the crown Platyrrhini. Información suministrada por el agente en SIGEVA