| Chapter 1. An ecomorphological study of extant small extant carnivorans demonstrates that dietary groups can be distinguished using quantitative morphological characters. Small (<10kg) modern carnivorans were divided into three dietary classes: carnivores, insectivores, and omnivores/hard-object feeders. Statistical analyses revealed trends in differences between these classes including longer carnassial blades in carnivorans, as opposed to larger molar grinding areas, larger post-canine dentitions, and wider fourth premolars in omnivores/hard-object feeders. Insectivores are not consistently distinguished from other dietary types, although they do tend to have weaker dentaries and shorter temporalis muscle moment arms. These trends can be used to help interpret morphologies that include taxa of uncertain ecologies.; Chapter 2. An ecomorphological study of small mammalian carnivores from the North American Eocene strengthens the case for possible competition between carnivorans and creodonts. Generic diversity curves demonstrate the classic "double-wedge" pattern of diversity overlap between the two orders. Morphological analyses show both groups evolving from mainly generalized, small forms into larger, more hypecarnivorous forms. In carnivorans this is accomplished with an expansion of ecomorphological space, while in creodonts this occurs at the expense of generalized ecotypes. This ecological similarity enhances the case for competition, although the turnover itself may have been triggered by a climatic change.; Chapter 3. The Rancho La Brea tar seeps are well known for their abundance of large carnivores. A taphonomic analysis of a single tar seep from Rancho La Brea, Pit 91, reveals a complex history of deposition and diagenesis. Radiometric dating of bones documents at least two episodes of deposition, one from 45,000 to 35,000 yr and another, shorter, interval from 26,500 to 23,000 yr. Strikingly, the law of superposition was not upheld consistently. Bones are distributed as disarticulated elements in two large concentrations that span both depositional episodes. In general, long bones are oriented horizontally, with little or no preference for cardinal orientation. Bone-on-bone contact ("pit wear") increases with depth, suggesting a possible compaction of the bones over time. These results suggest a post-entrapment journey for the bones that is unique to these deposits. |
