[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
<<Moving toward rather less dodgy ground, there have been occasional
references in the technical literature to occasional arboreality in
crocs. In one of his papers (either 1972, 1974 or 1977: haven't had time
to check) Alick Walker cited arboreality in primitive
crocodylomorphs as a character shared with birds, and noted
that extant crocodile juveniles apparently preserve this primitive
behaviour. Reviewing Walker's phylogenetic proposals, Tarsitano and
Hecht (1980) listed Walker's crocodile-bird characters, and, as
character (14), wrote..>>
His 1972 paper outlines this. Actually an extremely interesting paper
(and before Ostrom 1973; wonder why it didn't catch on :-)), he lists a
1961 Cott paper (Cott, H. B., Trans. Zool. Soc., 29, 211 (1961)), as a
reference to arboreality in baby crocs. Also very interesting, crocs
have a motion in their wrists very similiar to the wing-folding
mechanism in bird wrists (functional linkage of wrist and forelimb
joints of Molnar, 1985). Walker sites this an arboreal specialization
(actually a primitive, hold-over specialization). Wonder why it wasn't
interpreted that way in theropod=>bird circles (some are working on
this). He goes on to list several other arboreal specializations in
_Sphenosuchus_ (which are also present in maniraptoriforms).
<<'(14) Crocodilians were originally arboreal as evidenced by the
climbing ability of juvenile crocodilians, the morphology of the
tarsus, long humerus, pneumatization of the skull and limbs of
fossils crocodilomorphs, marked inward and forward curvature of the
lower half of the tibia and reduction of the first metatarsal.'>>
Don't forget Martin's _Current Ornithology_ paper in 1983. He lists
this feature as equivocal for some reason.
I think that arboreality as being primitive among crocodylomorphs to be
quite an interesting notion, though I will hold out making radical
speculations until more evidence is found.
Now to the birdy croc section of this post.....
There are actually two versions of the crocodile => bird scenario. 1)
The Walker hypothesis where birds are the sister-group to
crocodylomorphs and (in later papers) _Sphenosuchus_ is closer to birds
than crocs. 2) The Whetstone hypothesis where birds share a special
common ancestor with Crocodylia (Crocodyliformes actually) and
sphenosuchids are the sister to the bird+croc clade. If there was no
evidence for the maniraptoriform => bird theory, I would go with the
croc hypothesis and the Whetstone version, but, as noted in a recent
post by Darren, the braincase evidence, which the croc hypothesis hinges
on, is more in line with the theropod hypothesis (kick ass!).
Anyway, while birdy crocs are interesting, I doubt that anybody
(including me) can part with the birdy theropod image.
Get Your Private, Free Email at http://www.hotmail.com