The Evolutionary History of the Feliformia: Contingency, Constraint, Disparity
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Date
2022-10-04
Authors
Barrett, Paul
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Publisher
University of Oregon
Abstract
Constraint is a fundamental concept in evolutionary theory. The possibilities are not endless for what shape an organism can take, nor ecology of one generation to the next. Cat-like carnivorans (Feliformia) offer a unique opportunity in investigating aspects of evolutionary constraint, given several of their constituent clades are purported to experience this phenomenon in terms of limited evolutionary potential, but also in the presence of some clades with extreme durophagous (bone-crushing) and sabertooth morphology. I investigated the evolutionary history of feliforms by considering their phylogeny, ecology and cranial morphology. I recover results that suggest there are three distinct ecospaces within which feliforms reside. The first is occupied by those small in overall size, covering a wide dietary and ecological spectrum, up to but not including hypercarnviory. These broad ecologies are facilitated by a narrow band of similar cranial shapes, evocative of “one to many mapping”. The second ecopace is occupied by soft-flesh specialists, such as felids (cats) and nimravids. These hypercarnivores possess distinct (non-overlapping) crania from the first ecospace, optimized for bite force and large gape angles. The evolutionary end member of this ecospace are those taxa possessing sabertooth morphology and the most disparate cranial shapes of all. The third ecospace is that of hyaenids, with a diverse ecological breadth optimized for dental toolkit and body mass, channeled by postcranial cursorial adaptations. The evolutionary end member of this ecospace are those taxa possessing durophagous morphology. In all three ecospaces, constraint exists in what cranial morphology and ecological transitions are possible. Large size nor hypercarnivory are achievable within the small feliform ecospace, and thus require transitions into the other two zones. Soft-flesh specialization is a road of no return that does not facilitate ecospace transitions. The hyaenid ecospace does not facilitate transitions into the ‘soft flesh’ ecospace, nor by extension sabertooth morphology. These limitations are a result of phylogenetic baggage and functional challenges, but fruitfully channel extreme cranial shapes (soft-flesh specialist) and diverse ecologies (hyaenids) that couldn’t exist without these constraints.
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Keywords
Carnivora, Ecology, Evolution, Feliformia, Morphology, Phylogeny