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I was re-reading Spinar and Currie's _The Great Dinosaurs_ and in the
early section about defining dinosaurs is the statement:
Some of the most important characteristics used to define
the Dinosauria are found in the hind limb. This is because
dinosaurs were more efficient walkers than more primitive
cousins like thecodonts, crocodiles and pterosaurs (flying
reptiles). The upper leg bone (femur) has a ball-like head
that fits into the hip socket and brings the leg under the body.
I have two questions about the statement:
1) Does this mean pterosaurs did not have a ball/socket pelvic
2) Did plesiosaurs, mosasaurs, and ichthyosaurs also lack the
Often the popular books on dinosaurs exclude pterosaurs and marine
dwelling reptiles of the Mesozoic from the Dinosauria because they didn't
live on the land. That may be true of plesiosaurs, but it's a weak
argument for pterosaurs, especially if I'm going to try to convince the
kids at my school (and colleagues) that birds are dinosaurs.
So, the two questions above can probably be summarized as one:
What specific characteristics exclude pterosaurs and marine
dwelling archosaurs from the Dinosauria?
(On another tangent: There was a lot of discussion a while back about
pterosaur locomotion, but isn't part of the reason they were less
efficient walkers due to the awkwardness of dealing with the wings?)
Thanks from me and my "constituents" for any enlightenment.
----- Amado Narvaez