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Re: John Bois on Armadillos at the K/T!
I think that the giantism is a "background" phenomenon in pterosaur history.
The fact that "giant" pterosaurs are very large [giantism is relative: a
"rhamphorhynchoid" pterosaur with a 2.5 m wing span was a giant, but who
cares about it?] in the Cretaceous depends upon the shift of Cretaceous
pterosaurs to larger sizes with respect to Jurassic pterosaurs.
The pterosaur sample is rather small, thus all considerations should be
taken with care, but in my opinion Ornithocheirid and Pteranodontid giants
seem to have been gone sometime before the late[st] Cretaceous, later being
supplanted by Azhdarchid giantism just because Azhdarchids supplanted
Ornithocheirids and Pteranodontids during latest Cretaceous times. Thus the
question is: why Azhdarchids supplanted Ornithocheirids and Pteranodontids?
The answer is probably unrelated to size but possibly lies in the different
wing structure, in something related to the ecological pressure or simply
in historical contingencies difficult to identify.
P.s. - What about Wann?
- For those of the list unaware of:
Martill, D.M., Frey, E., Green, M. & Green, M.E., 1996, Giant pterosaurs
from the Lower Cretaceous of the Isle of Wight, UK. N. Jb. Geol. Paläont.
Mh., 1996, 11: 672-683.
You wrote: <<Hi, Fabio. What you say is quite correct, but I'd like to
point out that the earlier Ornithocheirid and Pteranodontid giants seem to
have been gone sometime before the late Cretaceous, later being supplanted
giantism. I wonder if there may have been some common connection related to
the demise of one and the eventual arising of the other. Perhaps a decline
in oxygen levels between the two episodes of giantism? Or a period of
reduced convective activity? Or? I don't have a clue what the reason(s)
may have been. Any thoughts, anybody?
Best wishes, Jim>>