Thesis (Ph. D.)--Columbia University. / Includes bibliographical references (p. 58-60).

Thesis (M.S.)--University of Kentucky, 2004. / Title from PDF t.p. (viewed Jan. 5, 2005). Includes vita. Includes bibliographical references (p. 45-54).

This thesis deals with a phylogeny of living Equidae based on an available evidence (morphology, behaviour, chromosomes, mitochondrial and nuclear genes) and using maximum parsiomony and Bayesian approaches; and ILD, PBS analyses which are able to recognise incongruences between specific character partitions. My results are relatively very robust and rational in comparison with published studies. My thesis consists of a review (literature, GenBank) and obtaining of many sequences by myself.

This thesis deals with a phylogeny of living Equidae based on an available evidence (morphology, behaviour, chromosomes, mitochondrial and nuclear genes) and using maximum parsiomony and Bayesian approaches; and ILD, PBS analyses which are able to recognise incongruences between specific character partitions. My results are relatively very robust and rational in comparison with published studies. My thesis consists of a review (literature, GenBank) and obtaining of many sequences by myself.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: John Kappelman. Vita. Includes bibliographical references. Also available from UMI.

The social intelligence hypothesis states that the main selection pressures driving increases in brain-to-body ratio are social rather than ecological. The domestic horse is an ideal animal to study within this framework because horses possess rich social lives but inhabit simple ecological environments. Here I assess the abilities of horses within two broad areas of social cognition; the classification of, and the use of information obtained from, social partners. In Section One I demonstrate that horses are capable of cross-modal individual recognition of conspecifics, an ability not previously demonstrated conclusively outside of humans. This ability extends to identifying familiar human companions suggesting that recognition systems are highly plastic in the individuals they can encode. These results also provide the first insights into the brain mechanisms involved in this process by revealing a clear left hemisphere bias in discriminatory ability. In Section Two I investigate the extent to which horses are capable of reading human attentional and communicative cues. It has been suggested that this skill was selected for through the process of domestication, however there have been no systematic studies of domestic animals other than the domestic dog. I found that horses were indeed highly skilled at determining if people were paying attention to them. In contrast they tended to only use basic stimulus enhancement cues to choose a rewarded bucket. A further study of young horses indicated that the ability to detect human attention requires significant experience to develop fully whereas the ability to use stimulus enhancement cues in an object choice task appears to require far less (if any) experience to develop. Overall my thesis extends our knowledge of comparative social cognition and in particular our knowledge of social cognition in horses. Taken together, these results clearly demonstrate that horses do indeed possess some complex socio-cognitive skills.

We report here a sample of 5 cheek teeth of a primitive hipparion from the early late Miocene Ethiopian locality of Chorora. This sample represents the oldest hipparion known from Ethiopia, and probably East and South Africa. The sample exhibits a number of distinctly primitive characters that suggest its provisional referral to "Cormohipparion" sp. The Chorora hipparion has none of the more advanced features typical of the latest Miocene-Pleistocene African hipparionine lineage Eurygnathohippus, maintaining a low crown height, lack of ectostylids and pli caballinids. The Chorora hipparion does exhibit a mesowear signal, suggesting that it was a mixed-feeder. The carbon isotope signal also suggests that it was a mixed-feeder that included both browse and C4 grass in its diet.

Since changes in chromosome morphology contribute to the knowledge of evolution as well as to chromosome dynamics, this study looks specifically at one chromosome compared in twelve different species of Perissodactyls: Equus caballus (ECA), E. przewalskii (EPR), Equus africanus somaliensis (EAF), E. asinus (EAS), E. hemionus onager (EHO), E. h. kulan (EHK), E. h. kiang (EKI), E. zebra hartmannae (EZH), E. grevyi (EGR), E. burchelli (EBU), Tapirus indicus (TIN), and Rhinoceros unicornis (RUN). While chromosome morphology studies have been done in some of the extant equids, none have followed the evolution of this chromosome, homologous to Equus caballus chromosome 20 (ECA20), which contains the major histocompatibility complex (MHC). The gene order on the chromosome arm homologous to human chromosome six in most Equidae is reversed with respect to the centromere in comparison to humans. Multicolor fluorescence in situ hybridization was used to show that four probes from ECA20 hybridized to ECA20 (control), SWA5, EAS8, EHO16, EHK14, EKI16, EZH10, EGR11, EBU13, TIN4, and one of RUN12, 14, 15, or 22. The order for the four genes in the horses, zebras, and rhinoceros were as follows: cen-EDN1-MHC-ITPR3-MUT. Hybridization to the ass and tapir chromosomes displayed a possible neocentromere formation. It is apparent the chromosome has gone through several morphological changes while undergoing speciation in the Equidae, yet the overall gene order is conserved.

Four groups of equids, "Anchitheriinae," Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, and only the Equini remains after 16 million years of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes controlling the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. I investigated two methods of quantitative analysis, Occlusal Enamel Index for shape and fractal dimensionality for complexity. I used analyses of variance and an analysis of co-variance to test hypotheses of process. Results suggest that enamel shape was controlled by phylogeny, tooth position, and climate. The lower taxonomic levels are shown to have a strong effect on complexity, suggesting behavior is driving complexity rather than overarching phylogenetic constraint.

A morphometric analysis of third metapodials and first phalanges of Middle Awash and Hadar hipparions dating from the 6.0-3.0 Ma interval was conducted using two methods. Morphological comparisons using standard metrics were made using: 1) log10 ratio diagrams; 2) size independent variables developed with reference to scaling trends for hipparions in general. Results of these analyses suggest that hipparion diversity during this temporal interval was relatively low. A single dominant gracile lineage of Eurygnathohippus Van Hoepen, 1930, most plausibly derived from the Lothagam (Kenya) species Eurygnathohippus feibeli (Bernor & Harris, 2003), would appear to have persisted throughout this interval and is marked by increases in size with measured change in metapodial and phalangeal morphology. A rarer, more robust form is found in the Ethiopian sample at 4.0 Ma and is morphometrically similar to Eurygnathohippus turkanense Hooijer & Maglio, 1973 from late Miocene horizons of Lothagam. Another smaller form, of uncertain systematic status, appears likely late in the Kada Hadar sequence, c. 3.0 Ma.