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Re: ACROCORACOIDS AND REPTILE PHYLOGENY
<<You`re sure you want to stick with this one??? I`ve heard that the AM
ankle was a defining Characteristic of the Ornithodirans, (ie.
Dinosaurs, Pterosaurs, Birds, Lagosuchus, Herrerasauridae). Never heard
of Lepidosaurs being in that group!>>
Lepidosauromorphs have an Advanced Mesotarsal ankle joint and it is a
synapomorphy of that group according to Olivier Rieppel. Turtles also
show the AM joint (this is one of the characters linking turtles to
lepidosauromorphs). I can't remember whether or not it is of a similiar
construction to the ornithodiran kind but if memory serves, they are an
awful lot alike. And nobody has ever said that lepidosaurs are in the
ornithodiran group, everybody thinks that it is a convergence. Whoever
said that homoplasy is rampant sure did know what they are talking
Anyway, on to acrocoracoids...
In the other reply to my previous post, Larry said that the presense and
elevation of the acrocoracoid process is a sure way to tell whether or
not various maniraptoriforms are secondarily flightless. Fair enough,
although I guess that _Sphenosuchus_, which is one step away from being
a crocodile, is secondarily flightless! The _Sphenosuchus_ coracoid not
only shows a biceps tubercle in the theropod position, the coracoid is
elongate in the manner of the various maniraptoriforms. Walker (1972)
regarded the shoulder of _Sphenosuchus_ to be very birdlike, possibly
more so than _Archaeopteryx_!
Secondarily flightless sphenosuchids? Keep it coming...
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