The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Size and external morphology of the brains of the large fossil platyrrhines Protopithecus and Caipora


1Anatomical Sciences, Stony Brook University, 2Museu de Ciencias Naturais, Pontificia Universidade Catolica de Minas Gerais

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Protopithecus brasiliensis and Caipora bambuiorum are large fossil platyrrhines from Pleistocene caves of Brazil. They were much larger than any extant platyrrhines with estimated sizes over twice the mean size of any extant New World monkeys. Protopithecus shows similarities to extant howling monkeys while Caipora resembles extant atelins. Although the cranial and postcranial anatomy of the fossil monkeys have been described in several studies, to date there have been no descriptions of either the size or external morphology of their brains.

We measured the endocranial volume of the fossil crania of both taxa using pellets and a graduate cylinder. We also made endocasts of the fossil crania using liquid latex and compared the external morphology of these with endocast molds of a wide range of extant primates, including most platyrrhines.

The endocranial volume of Caipora (156 cm3) was larger than that of Protopithecus (129cm3) even though Protopithecus was a larger taxon. Thus, Caipora had a greater Encephalization Quotient than Protopithecus. The endocasts show that Caipora had a more globular cerebrum than Protopithecus with a larger temporal lobe and more rounded frontal and occipital lobes. In overall shape, the endocast of Protopithecus resembles that of Alouatta whereas the endocast of Caipora resembles that of extant atelins such as Ateles. The development of sulci and gyri on the surface of the two endocasts was similar, but most sulci were longer in Caipora. The morphology of the brains of these taxa support previous taxonomic allocations of Protopithecus with Alouatta and Caipora with Ateles.

Funded in part by the LSB Leakey Foundation

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