2010 GSA Denver Annual Meeting (31 October 3 November 2010)
Paper No. 125-7
Presentation Time: 3:00 PM-3:15 PM

KILLER SPERM WHALES: EXPLORING THE LIFE HISTORY AND ECOLOGY OF NEOGENE PHYSETERIDS FROM THE ATLANTIC COASTAL PLAIN

GILBERT, Kwasi, Earth Sciences, Syracuse University, Heroy Geology Lab, Syracuse, NY 13244, kngilber@syr.edu, IVANY, Linda, Department of Earth Sciences, Syracuse University, Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, and UHEN, Mark D., Atmospheric, Oceanic and Earth Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030

The Family Physteridae (sperm whales) attained great diversity during the Miocene and Pliocene. Fossil specimens suggest the occurrence of at least 31 distinct species. Within the past decade, several studies have attempted to reconstruct the ecology and phylogeny of these early physeterid taxa, an endeavor made difficult by the scarcity and often poor preservational condition of remains. The Neogene phosphatic sands of the US Atlantic Coastal Plain (ACP), in particular at the Lee Creek Mine, North Carolina, lay claim to one of the largest early physeterid fossil assemblages in the world. Physeterid remains, especially teeth, are common in these strata along with a host of marine vertebrates ranging from turtles to crocodilians. Teeth are known for their archival properties, here we examine the teeth of two physeterid genera, Physeterula and Scalidcetus, to constrain the respective life histories and ecologies of these taxa.

Rhythmically accreted growth structures (‘growth layer groups’), analogous to tree rings, are visible in longitudinal cross sections of the teeth. As physeterid teeth grow continuously over ontogeny, these structures can be used to ascertain the age of the animal at death. Tallies of growth increments from multiple individuals reveal that life spans of both Physeterula and Scalidcetus were significantly shorter than the 65+ years noted in modern sperm whales. A relationship between tooth diameter and body size, as established in modern odontocetes, is used to approximate the body size of these early physeterids. Rather than attaining the large body sizes observed in the modern sperm whale, Physeter macrocephalus, these early physterids were comparable in size to modern killer whales, Orcinus orca. Functional upper and lower jaw dentition, not present in the modern taxon, is indicated by wear facets on teeth, suggesting an ecological analog with Orcinus as well. Despite similarities in ecology and body size, life spans of the Lee Creek whales are markedly shorter than those of Orcinus orca. To attain body sizes comparable to those of modern Orcinus in half the time requires rapid growth conceivably facilitated by an abundance of food. The highly productive waters of the ACP at this time likely supplied the resources necessary to sustain the high growth rates and metabolic demands of this top predator.

2010 GSA Denver Annual Meeting (31 October 3 November 2010)
General Information for this Meeting
Session No. 125
Paleontology V - Predation and Biological Interactions
Colorado Convention Center: Room 503
1:30 PM-5:30 PM, Monday, 1 November 2010

Geological Society of America Abstracts with Programs, Vol. 42, No. 5, p. 321

© Copyright 2010 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.