Functionally significant aspects of skull morphology were examined in Eocene miacids and in early members of the modern carnivore families to see if functional craniology might shed light on factors involved in the origin and early evolution of the modern carnivores. No key innovations are apparent at the beginning of the modern carnivore radiation, and an alternative hypothesis to account for that radiation is proposed: the radiation represents the filling of niches vacated by the extinction of several groups of archaic carnivores in the late Eocene. Differences that distinguish modern viverrids, canids, felids, and mustelids from each other today were less pronounced in the Oligocene, when these families first appeared, and provide no insights into possible ecological differences at the family level. However, body size differences among the early members of the modern carnivore families suggest that partitioning of prey resources by size may have been a factor in their initial radiation. Comparison of cranial morphology in Eocene miacids, early members of the modern carnivore families, and living carnivores allows reconstruction of the primitive conditions of carnivore skull morphology and determination of the pathways of morphological transformation that resulted in the diversity of skull morphology seen in modern carnivores.
Endocranial casts of 12 genera of extinctcanids, covering a time span of 30 million years, and of all living canid genera provide information on brain evolution in that carnivoran family. The oldest canid brains had only suprasylvian and coronolateral sulci, a widely exposed cerebellum with a straight posterior vermis, a high rhinal fissure and a strikingly undeveloped frontal lobe. By 25 million years ago, ectosylvian, ectolateral and presylvian sulci had appeared, and by about 12 million years ago, a Sylvian sulcus had developed, expansion of the temporal lobe and of orbital and sigmoid gyri was noticeable, and lobule VII of the cerebellar vermis had enlarged and twisted in the line leading to modern canids. Ansate, postcruciate and cruciate sulci developed along with the expansion of the sigmoid gyri. Canid brains 15–30 million years old average slightly smaller relative to body size than do modern canid brains, while later fossil canid brains are about the same relative size as modern ones. Modern canid brains are relatively uniform in external morphology, differing mainly in the relative size of the prorean gyrus.
Journal Article Basicranial axis length v. skull length in analysis of carnivore skull shape Get access LEONARD B. RADINSKY LEONARD B. RADINSKY 1Anatomy Department, University of Chicago, Chicago, Illinois 60637, U.S.A Search for other works by this author on: Oxford Academic Google Scholar Biological Journal of the Linnean Society, Volume 22, Issue 1, May 1984, Pages 31–41, https://doi.org/10.1111/j.1095-8312.1984.tb00797.x Published: 14 January 2008 Article history Received: 23 March 1983 Accepted: 23 March 1983 Published: 14 January 2008
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Elongate canines evolved independently at least four times among mammalian carnivores, and each time skulls were modified in similar ways. We have compared the cranial morphology of sabertooths to that of their non-sabertoothed relatives, living and extinct, and applied simple biomechanical models to elucidate the functional significance of the morphological differences. Our analysis suggests that (1) sabertooth morphology represents modification for wider gape with retention of a powerful bite force at the carnassial; (2) sabertooths probably used a throat or ventral neck slash to kill prey; and (3) elongate canines and retractile claws may have facilitated the exploitation of relatively larger prey by sabertooths compared to non-sabertooth carnivores.
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