Mamenchisaurus ungual

Having mentioned the other day the sheer size of some sauropod claws, it seemed long overdue that I drag out this photo from about five years ago. It’s an ungual of that great long-necked beast Mamenchisaurus. Unfortunately I don’t have with me any of the shots that would put this close-up in context so I’m not sure if it’s a manual or pes one, though memory tells me it’s in the hand. Regardless the two key issues are relate to it’s dimensions.

First of all, it’s big. Really quite big. OK, so this is a very large animal (this individual was around 15 m as I recall) but even so, that claw is getting on for some 20 cm in length. That’s pretty huge, even in context. Secondly, it’s also big compared to the phalanx it articulates with. Given how sauropod hands and feet are built, you can’t imagine that this ever really had to swing around on that joint but instead poked out of a fleshy foot. Yet it’s nearly twice the height of it’s articulating phalanx so it’s hard to imagine that the claw is just big as some kind of evolutionary hangover, but was actively being selected or maintained at this big size, despite its discrepancy with the rest of the foot. In short, yeah, that’s pretty huge.

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