Systematics, Zoogeography and Phylogenetics of Skates (Chondrichthyes, Rajoidei)

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This proposal is a request for funds to continue a long term study on the systematics, distribution, and evolutionary relationships of skates and rays (flattened cartilaginous fishes). The overall objectives of the study are to clarify the evolutionary relationships within and among the subgenera and genera of skates, to use this information to construct distributional and evolutionary patterns for skates, and to speculate on the evolutionary relationships of skates and the other taxa of rays (sawfishes, guitarfishes, electric rays and sting rays). Specifically, the proposed research will: 1) test, elaborate and revise as necessary the current hypothesis of evolutionary relationships of skates by comparative analysis of the skull, gill arches, shoulder girdle, pelvic girdle, intromittent organs, and tooth morphology of all subgenera and genera and a majority of the species; and 2) compare these structures, and the gill arch musculature, cranial nerves, and head and gill arch blood vessels of skates with those of other rays. Detailed systematic and evolutionary studies of skates over the past 30 to 40 years have set the stage for a comprehensive and in-depth evolutionary study of skates. These studies have clarified most of the species level systematic problems and recognized most of the subgenera and genera. However, the evolutionary relationships remain uncertain. Successful completion of the proposed study will contribute to: 1) clarification of the evolutionary interrelationships of the cartilaginous fishes (chimaeras, sharks and rays); 2) the understanding of the distributional patterns of benthic fishes; and 3) knowledge of the evolutionary patterns of a diverse but morphologically conservative group of organisms.