Comparing primate crania: The importance of fossils

Abstract

The morphospace outlined by living primates largely includes that occupied by fossil taxa, suggesting that the cranial diversity of living primates generally encompasses the total diversity that has evolved in this Order. The evolution of the anthropoid cranium was a significant event allowing anthropoids to achieve significantly greater cranial diversity compared to strepsirrhines. Fossil taxa fill in notable gaps within and between clades, highlighting their transitional nature and eliminating the appearance of large morphological distances between extant taxa, particularly in the case of extant hominids.

Cranial and endocranial diversity in extant and fossil atelids (Platyrrhini: Atelidae): A geometric morphometric study

“…Halenar et al () explored cranial shape variation in extant and fossil platyrrhines and showed that several fossil specimens, including Cartelles , do not overlap with the distributions of extant atelid genera, but occupy a unique position in shape space, intermediate between Alouatta and the rest of the family. Similar results were found for Cartelles by Fleagle et al () using a comparative sample expanded to all primates. This suggests that the overall anatomy, and hence probably the niche occupied by Cartelles , have no equivalent among extant platyrrhine primates.…”

“…The pattern of variation seen in the extant atelid species for cranial and endocranial shape, form, CAC and RSC is similar to the variation observed in previous studies on the cranium alone, showing a large difference between Alouatta and the other atelid genera (Aristide, dos Reis, et al, ; Fleagle et al, ; Halenar et al, ; Perez et al, ). Regarding the fossil species, we show that whereas Caipora bambuiorum is within the observed range of variation of extant Brachyteles , Cartelles coimbrafilhoi occupies a region of endocranial form and endocranial shape space that does not overlap with the range of variation seen in any of the extant taxa.…”

“…The results of this study show the importance of considering both extant and fossil species when exploring diversification in complex traits, such as endocranial and cranial shape variation. Several recent studies analyzed cranial and mandibular shape variation in extant and fossil species of primates and other mammalian clades (e.g., Álvarez, Perez, & Verzi, ; Fleagle et al, ; Gunz et al, ; Püschel, Gladman, Bobe, & Sellers, ; Rocatti et al, ), and they also show the importance of fossil variation for understanding clade evolution. In particular, the joint use of data from fossil and extant species allows us to consider variation from periods predating or concomitant with events of mass extinction.…”

“…These techniques allow one to study features such as the relative position and the size of individual structures seen in the endocast in addition to overall absolute and relative brain size/endocranial volume. Based on previous cranial results using different configurations of data and comparative samples (i.e., Fleagle et al, ; Halenar, ; Halenar et al, ; Krupp, Cartelle, & Fleagle, ), we expect variation in cranial and endocranial size and shape in the fossil species to be within the range of that already observed in the extant family Atelidae, but not necessarily within the range of each of the extant genera.…”

“…Here, we perform an exhaustive morphometric study of variation in cranial and endocranial size and shape in Cartelles coimbrafilhoi and Caipora bambuiorum , within the context of the Atelidae as a whole. Despite the existence of these and other relatively well‐preserved specimens of platyrrhine fossil crania, detailed studies of morphological variation have generally not been systematically pursued using extant and fossil species together (but see Fleagle, Gilbert, & Baden, who address this issue across primates). Specifically, the main aim of this work is to more comprehensively explore the pattern of variation in cranial and endocranial morphology in atelid primates.…”