Meeting Abstract

23.4  Saturday, Jan. 4 14:15  Implications for the origin of baleen as revealed by palatal vascularization of a gray whale calf (Cetacea, Mysticeti) EKDALE, E.G.; San Diego State Univ eekdale@projects.sdsu.edu

The origin of baleen in Mysticeti was a major transition during cetacean evolution. All extant baleen whales are edentulous in adulthood, but teeth develop in utero within open alveolar grooves. The teeth are resorbed prenatally and the alveolar grooves close as dermal papillae associated with baleen differentiate on the palate. Lateral nutrient foramina in place of the maxillary alveolar groove transmit arteries to the highly vascularized epithelium from which baleen develops. The vessels through the foramina are hypothesized to be branches of the superior alveolar artery given the position of the foramina in relation to the embryonic alveolar groove, and presence of the foramina often is used to reconstruct baleen in extinct taxa. However, branches of the greater palatine arteries that supply blood to the hard palate also may play a role in baleen vascularization. Baleen has epidermal and dermal origins, and medially positioned sulci radiating from the greater palatine canal towards developing baleen are observed in some fetal mysticetes. In order to identify the blood source to the baleen, the hard palate of a gray whale neonate was injected with latex and CT scanned. Vessels that supply blood to the baleen and surrounding tissues are in fact those within the superior alveolar canal. The greater palatine artery is restricted to its own passage that diverges within the maxilla posterior to the superior alveolar canal and opens onto the hard palate medial to the baleen. No direct connections between the palatine artery and vessels passing through the lateral foramina of the palate were observed. The results indicate that the presence of lateral nutrient foramina in mysticete fossils can be used as bony correlates for the presence of baleen in extinct taxa.