Carotid circulatory development in turtles: Using existing material to seek critical developmental stages that localize establishment of clade-specific patterns

Abstract

Recent re-evaluation of variation in the carotid circulation of turtles has revealed that the phylogenetic signal contained in this character complex may indicate different patterns of relationship than have previously been hypothesized. Herein we document cranial circulatory development in Apalone spp. and Chrysemys picta for the first time, with the objective of stimulating future, intensive study of the source of observed circulatory variation in turtles. Both species studied exhibit a nearly identical circulatory pattern, resembling that of adult Trionychia, in later developmental stages. This is an unexpected finding given their highly divergent adult conditions. Further study is required to elucidate the means by which the adult circulatory pattern is attained in these taxa. © 2008 Brill Academic Publishers.