Daryl P. Domning (Howard University, Washington, DC) Lawrence G. Barnes (Natural History Museum of Los Angeles County, CA)
Abstract: PIs propose to collect fossils of seacows (Sirenia; herbivorous marine mammals related to modern dugongs and manatees) at fossil localities in Mexico and Puerto Rico that are threatened, respectively, by natural erosion and human disturbance. This fieldwork will also support the research of J. Vélez, a Puerto Rican graduate student at Howard University. The fossils known to be at these sites are crucial to his doctoral dissertation, which will revise the classification and clarify aspects of the evolutionary history, paleoecology, and geographic distribution of fossil Sirenia from Puerto Rico, the wider Caribbean, and adjoining areas of the New World. The localities to be visited include ones that produced the type specimens of several sirenians whose identities and affinities need to be clarified by much more adequate fossil material. Besides analyses of their feeding adaptations and evolutionary relationships, the newly-collected fossils will also provide samples of tooth enamel for stable-isotope analysis important for interpreting their feeding ecology. Baja California Sur, México: In the North Pacific, seacows have been present at least since the early Miocene (circa 25 million years ago), and are represented by all three subfamilies of the family Dugongidae: Halitheriinae, Hydrodamalinae, and Dugonginae. Important fossils of each of these groups have been collected in Baja California. The coexistence of all three groups is very interesting from the standpoint of paleoecology, and a major goal of our research is to understand how these herbivores shared the marine plant resources of the North Pacific coastline. PIs seek better specimens of these sirenians, as well as more information about the other marine animals among which they lived. Puerto Rico: Fossil seacows in Puerto Rico include both halitheriines and dugongines. Vélez has recently collected important new specimens of both, and the potential of recovering more fossil sirenians (as well as other vertebrates) from the Tertiary deposits in Puerto Rico is high. It also provides a rare opportunity to recover sirenians from the Oligocene, an important but otherwise poorly sampled period in their evolution and diversification. Seacow remains have been collected from other parts of the Caribbean, but they are mostly either from older (Eocene) or younger (Miocene) deposits. Several species of seacows are expected to be found in the different rock layers around the island, further documenting the former existence of multi-species sirenian communities, and possibly including early manatees (Trichechidae).
