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Theses Doctoral

Phylogeny and Evolution of Locomotor Modes in Carnivoramorpha (Mammalia)

Spaulding, Michelle

Contained in this thesis are seven chapters, five each with a specific scientific focus relating to the study of basal carnivoramorphans or the evolution of locomotion. Presented here is the first detailed description of the only known postcranial skeletal elements of "Miacis" uintensis, found to differ markedly from previously described "miacids" (a paraphyletic assemblage of early fossil Carnivoramorphans), invalidating the notion that all "miacids" were very similar in their postcranial morphology and locomotor styles. The majority of the differences indicate an animal less well adapted to an arboreal lifestyle than has been inferred for other early "miacid" carnivoramorphans. A new genus and species of basal non-Viverravidae Carnivoramorpha, Dawsonicyon isami, is named and described. This new taxon is dentally compared to all known genera of nonviverravid basal carnivoramorphans, as well as with all known species of the problematic genus Miacis. Both "Miacis" uintensis and Dawsonicyon isami are incorporated into a phylogenetic analysis and preliminary functional interpretations of a scansorial locomotor mode are offered for both of these taxa. Following these two descriptive chapters, over 100 postcranial characters are added to the existing data set, which is dominated by cranio-dental characters. The addition of these new characters permits the inclusion of a large number of basal carnivoraforms known solely or predominantly from postcranial characters, that previously would have been `unplaceable' in a phylogenetic analysis. The resultant phylogeny recovers most of the same clades identified in previous studies, but resolves some relationships differently within the basal carnivoraforms. A novel (unnamed) monophyletic subclade of the Carnivoraformes is recovered, supported in part by characters from both the prior and new data sets. The inclusion of a substantial suite of postcranial characters expands the ability to assess the relationships of basal carnivoramorphan taxa, and permits the inclusion of many taxa represented only by incomplete material. Subsequent to the additional of post-cranial characters the matrix is enlarged again, creating the largest anatomical matrix to date for Carnivoramorpha, with 60 extant and fossil taxa and 243 morphological characters. Taxon sampling emphasizes basal carnivoramorphans, and this matrix includes almost every early species for which significant postcranial or non-dental cranial material is known. Resulting trees support the monophly of Carnivoramorpha, Carnivoraformes, and Carnivora as successively diverging clades, as has been found in previous studies, with excellent resolution of interrelationships of taxa within basal Carnivoraformes. Pangolins are found to be the sister clade of Carnivoramorpha to the exclusion of Creodonta. Basal carnivoramorphan taxa previously used to represent a putative basal condition for the group (e.g., species of Vulpavus) are instead found to be highly nested within a monophyletic subclade that is sister-group to most other carnivoramorphans. Nimravidae is strongly supported as a noncrown Carnivora lineage, in contrast to most prior studies. Finally, the evolution of prehensile tails is examined via the identification of phylogenetically independent osteological correlates of prehensility. These features are examined in all living taxa therian known to have independently evolved a prehensile tail, and a close relative that lacks a prehensile capability. This examination reveals that the distal caudal vertebrae are more reliable for the identification of prehensility in a taxon than the more anterior, though there are general trends observed in more proximal caudals. When these indicator features are examined in a complete fossil Cimolestidae from the Green River Formation they allow for the confident identification of prehensility in this specimen. This specimen represents the first known postcranial morphology for the clade Cimolestidae and is the oldest known Eutherian with a prehensile tail.

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More About This Work

Academic Units
Earth and Environmental Sciences
Thesis Advisors
Flynn, John J.
Degree
Ph.D., Columbia University
Published Here
May 30, 2013
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