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Should the fifth metatarsal be considered in comparison to Odontochelys or other turtles? Its homology is disputable (Lee 1997, Fabrezi et al. 2009, Lyson et al. 2013). In some turtles, the fifth distal tarsal forms most of the hooked element (pleurodires) which is not the same as in other diapsid reptiles, while in others (cryptodires), the hooked element is mostly made up of the the fifth metatarsal after all. Since AFAIK no one has yet examined the fifth metatarsal of very basal turtles to be certain whether it is made up of the fifth metatarsal (as in cryptodires and other reptiles) or a composite of the fifth distal tarsal and fifth metatarsal (as in pleurodires), this probably should not be taken as definitively homologous.71.61.150.32 (talk) 17:29, 28 June 2015 (UTC)
- For instance, in Odontochelys, the fifth distal tarsal is already lost (Li et al., 2008; pers. obs.; but scored as unknown in Lyson et al. and subsequent papers), but Eunotosaurus has both distal tarsal V and no hooked metatarsal (see scorings in various Lyson et al. papers, Schoch and Sues 2015). If the metatarsal is NOT hooked in Eunotosaurus, then it probably evolved convergently in which Testudines do have it.71.61.150.32 (talk) 17:42, 28 June 2015 (UTC)