Evolutionary Trends of Chiropteran Dentitions

The paleontologist\u27s obsession with teeth may be a cause for wonder to the neo-mammalogist accustomed to utilizing knowledge of habits as well as the whole suite of physical characters when evaluating an animal. The occasional more-or-less complete fossil skeleton is most welcome, but more often only isolated skeletal elements are recovered. Teeth being constructed of relatively hard and resistant material are more readily preserved and usually reflect dietary habits and relationships better than other isolated elements. Horizontal classification faces a real possibility that two groups with a common ancestor have greatly diverged in their dietary habits and consequent tooth-pattern. The primary problem in vertical classification lies in the fact that in the distant past a large group of related forms shared the same dental patterns, but only one gave rise to the modern group under study, while others left no descendants at all. Moreover, after the basic eutherian pattern was established, additional cusps, such as the hypocone, were added in the same position independently by different groups at different times. Furthermore, suggesting formal lineages by evaluation of contemporary forms can be misleading, although such studies have their value. Very few cave deposits predate the Pleistocene, and forest faunal elements are extremely rare as fossils. As caves and forests are the primary habitats of chiropterans, they have the poorest fossil record of any major group, even though they are second only to rodents in numbers of living forms. Working with what we have seems preferable to begging the whole question. By a careful examination of the dentitions of modern forms and the few available pre-Pleistocene fossils, one can plot the probable route each type has taken to arrive at the dentition it possesses. Using taxonomic units as representatives of stages in dental evolution seems preferable to numbering hypothetical stages. Even if the procession of stages is not 100% accurate, in most cases such an exercise can eliminate certain types of dentitions from the ancestry of others