A comparative analysis of the tibia of Paralouatta varonai, an extinct Cuban primate

The Caribbean islands were home to primates for millions of years, potentially from the Miocene through the early Holocene. Paralouatta varonai was a species endemic to the island of Cuba whose fossil remains have been well described. While all known platyrrhines are arboreal, it has been proposed that Paralouatta may have been semiterrestrial. This work provides comparative analyses of the fossilized tibia of P. varonai, specifically looking at the distal articular surfaces to determine the locomotion of this extinct platyrrhine, as well as its relation to the extant platyrrhine families. Our sample consisted of 154 extant platyrrhines (from 14 primate families) and 6 extinct platyrrhines. We used three-dimensional geometric morphometric shape data in two different principal components analyses, one utilizing all individuals, and one utilizing taxon means. We found that Paralouatta possesses a flattened trochlear surface, a characteristic associated with suspensory primates. Paralouatta also resembles arboreal primates in having an oval-shaped trochlear surface, as opposed to the trapezoidal shape seen in terrestrial primates. However, the medial malleolus is short and blunt, a trait that typically provides stability but restricts flexibility and is often found in terrestrial primates. Thus, the distal tibia of Paralouatta exhibits a mix of morphological characteristics that are typically associated with terrestrial and suspensory primates. It occupies a unique position in the platyrrhine morphospace; however, this position is most similar to extant atelids, lending support to earlier assertions that Paralouatta is most closely related to this taxon