Neck motion in turtles and its relation to the shape of the temporal skull region

摘要: Abstract Extant turtles are characterized by diverse marginal reductions in their temporal skull region. Among other minor factors, modes of neck retraction were hypothesized to have a key influence for shaping that region through evolution. A recent study on the mobility turtle highlighted possibility stem turtles, such as Proganochelys quenstedti able easily retract necks laterally tucking under anterior edge shell. small emargination “cheek” this species could be correlated its mode retraction. In present study, using geometric morphometric approach, I curve shapes retracted and positions with expansion skulls. hypothesize based morphospace distributions evolved only once within evolution pleurodiran cryptodiran directly independently derived from ancestral tucking. Pleurodires middle kink elongated lateral At dawn evolution, associated ancestrally (laterally rotated) neck, cervicals less specialized than extant taxa. For cryptodires, condition may permitted transitional, intervertebral rotation towards vertical orientation found group during It retained characteristically oriented curvature cervical column. ventral flexion all strongly occiput emargination. Pleurodiran retraction, however, does not shape degree. The is “occiput” appears occur correlation fixation palatoquadrate braincase crown turtles. Neck related forces acting also crucial factors reduction potential fenestration inherited potentially fenestrated ancestor.