Correlations between craniodental morphology and feeding behavior in ungulates: reciprocal illumination between living and fossil taxa.

By: Dr. Christine M. Janis

Abstract

The diversity of living and fossil ungulates provides multiple examples of evolutionary adaptations to the challenge of herbivory. In this paper I review modern studies on ungulate craniodental anatomy in the historical context of conceptual and technological advances. The important influences on the modern studies include (1) the renaissance in biomechanical studies of form and function dating from around the middle of this century; (2) the emergence of new techniques such as scamming electron microscopy and electromyography; (3) the later rise of comparative method studies, aided by the prior accumulation of ecological data on living taxa; and (4) the appearance of the personal computer for easy and rapid data analysis. An understanding of the correlation between form and function in living ungulates of known ecology and behavior can be extended to the reconstruction of the dietary behavior and mode of mastication of extinct taxa. Studies of individual fossil taxa or lineages include both those with living representatives, such as horses and pigs, and those without living relatives or analogs, such as arsinotheres. Comparative method studies of a broad spectrum of living ungulates have provided anatomical correlates of precise herbivorous dietary categories such as grazer, browser, and mixed feeder. This information can not only provide evidence about the diets of individual extinct taxa, but can also be extended to the study of paleocommunities, including habitat reconstruction and environmental change over evolutionary time. Some outstanding problems are the difficulty in distinguishing mixed-feeding ungulates from the more specialized grazers and browsers, the precise functional reason for high-crowned cheek teeth, and the reason for the isometric scaling of dental dimensions. Although much of the flow of information has been from living taxa to extinct ones, the diversity of form in fossil taxa and the timing of events in the fossil record has resulted in the reinterpretation of hypotheses of form and function based on extant taxa alone.

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