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Systemtic and phylogenetic reconstruction of the bivalve genus Pitar

Mills, Jayme
Abstract
The genus Pitar is an infaunal shallow marine bivalve in the family Veneridae (subfamily Pitarinae) and is one of the most abundant and diverse genera of the Cenozoic (Figure 1) (Allen 1985). The taxonomy and systematics of the genus have largely been ignored in the paleontological literature; producing a “wastebasket” taxon that is poorly diagnosed. Despite the diversity of Pitar and its importance in shallow marine environments, few researchers have focused on the evolutionary history of the group. Individual species placed in the genus Pitar have, however, been described in some detail (Jukes-Browne 1908; Palmer 1927; Harte 1993). The genus Pitar ranges from the early Paleocene to the Recent (Palmer 1927; Moore 1969; Harte 1993) and is cosmopolitan in distribution. Members of this genus are adept at burrowing and are extremely mobile filter-feeders. The genus is economically important as a food source. The purpose of this project is to: (1) revise the major subgenera comprising the genus Pitar, (2) determine what characters are most useful for diagnosing this genus, and (3) to construct a phylogenetic tree as a framework to reconstruct the evolutionary history of the group. This project focuses on the shell morphology of several species, including both fossil and modern representatives, within the genus. Pitar is an ideal taxon for systematic and phylogenetic study because it is well preserved, has a lengthy fossil record, and exhibits a great deal of morphological diversity (Shimamoto 1986). Since the genus Pitar has never been systematically revised, it is unclear whether the species included in the genus represent a monophyletic group (i.e., a true phylogenetic assemblage of a taxa that share a common ancestor). Without a phylogeny, it is virtually impossible to reconstruct the evolutionary relationships among species in a genus (Wilkinson 2001). This study will represent the first attempt to reconstruct a phylogenetic tree for the genus Pitar.
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2003-01-01
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Geology Capstones
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Geology
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https://scholarworks.wm.edu/handle/internal/9984
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