Thursday - TODAY - 7th April, Neil Chalmers Seminar Room, DC2, 16:00
Dr. Jennifer Lane, Bayerische Staatssammlung für Paläontologie und Geologie, Munich
The growing field of palaeontological CT scanning has only recently begun to be applied to fossil chondrichthyan fishes (i.e., sharks, rays, and chimaeroids). In recent years, CT scan-based studies have provided new information on chondrichthyan cranial morphology, particularly regarding internal features such as the interior surface of the braincase and the inner ear.
Many of these features have turned out to be significant in shedding new light on patterns of chondrichthyan evolution. Hybodonts, the sister group of modern sharks, are of particular interest in what they can reveal about the evolutionary history of their living relatives.
The inner ear of modern sharks (neoselachians) is highly adapted toward low-frequency semi-directional sound detection (LFSDP). New investigations of two fossil hybodonts (Tribodus limae and Egertonodus basanus) using high-resolution CT scanning confirms that the structure of the inner ear in these sharks was also adapted for LFSDP. However, this adaptation is absent in earlier chondrichthyans (e.g., symmoriiforms, ctenacanths, Pucapampella), suggesting that it arose only after the divergence of the hybodont/neoselachian lineage from these earlier groups. Other features of evolutionary interest include.the loss of the cranial fissures and elaboration of the vagal and glossopharyngeal nerve canals; development of a medial capsular wall; and changes in patterns of cranial arterial circulation.
In facilitating identification of key features such as positions of nerve and blood vessel pathways and foramina, CT scanning and digital reconstruction techniques may also pave the way for future developmental studies (such as reconstructing the positions and growth patterns of the embryonic cranial cartilages).
Contact: Greg Edgecombe firstname.lastname@example.org