JAMNICZKY, Heather A.; BRINKMAN, Donald B.; RUSSELL, Anthony P.; University of Calgary, Canada; Royal Tyrrell Museum of Palaeontology, Drumheller, Canada; University of Calgary, Canada: The Utility of Cranial Arterial Canals and Foramina in the Resolution of Problems in Turtle Phylogeny

Turtles have long been considered to be representative of the primitive amniote condition and have been used to polarize characters in phylogenetic analyses of other groups of amniotes. There has been much recent debate surrounding both the relationships of turtles to other vertebrates, and relationships within turtles themselves. The employment of various suites of characters, both morphological and molecular, has resulted in the production of alternate classifications. The inclusion of fossil taxa in phylogenetic analyses has posed the additional problem of missing data and how to treat these. The difficulties of dealing with fossil forms has led to disagreement about the relative positions of such taxa within turtles. An examination of the crania of extant turtles revealed that patterns of cranial circulation vary among turtle groups. The vessels employed in these studies are represented by foramina and canals in the intact skull, and these were used to reconstruct patterns of cranial circulation in fossil forms. This has revealed that putative patterns of homology may be nominal rather than physical. A re-evaluation of turtle phylogeny based on morphological characters derived from cranial circulatory patterns will help to elucidate both the relationships among members of this group and the relationships of turtles to other vertebrates.