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Re: BURROWING SEGNOSAURS
In a message dated 96-02-29 15:12:00 EST, firstname.lastname@example.org (Darren Naish)
>One question that arises, however, is 'Are segnosaur claws like those of
>megatheres?'. Though I've seen a fair few megathere claws, I'm none too sure
>here, but my recollection is that they are far more hook-like than those of
>_Segnosaurus_ et al. Though this certainly doesn't rule out the analogy, it
>opened different interpretations for others. Uncle Bob, for example, insists
>that segnosaurs have ideal digging claws - long and straight, like those of
>badger, he says. Somehow I just can't imagine a 2 ton dinosaur merrily
>tunnelling its way beneath the Cretaceous topsoil.
Except for their relative size, segnosaur claws aren't very similar to
edentate claws. For example, I don't think segnosaurs walked on all fours
with their manual claws turned under. Also, the manual claws for _Alxasaurus_
and _Therizinosaurus_, the only two taxa for which the manual claws are
known, are quite different in proportions, curvature, and absolute size. One
hallmark is that they are strongly compressed transversely (both manual and
pedal claws, actually), which is one way Nessov was able to identify them in
the fossil record.
I can't be certain, but the longest and strongest manual digit seems to be
the _first_ (the "brontosaur" pattern), even though the corresponding
metacarpal is shortest. This seems to be the case with the type specimen of
_Alxasaurus_--though it was not restored that way in the mounted cast in the
_Greatest Show Unearthed_ traveling dinosaur exhibition. _Alxasaurus_ is the
only segnosaur known with a more or less complete manus.
Burrowing seems out of the question, not only because of the sheer size of
the animals but because transversely compressed claws would be rather useless
for digging with--like trying to dig a hole with a scythe. Claws designed for
digging would probably be shorter and thicker, so as to get some shoveling
action and leverage. But I can see segnosaur claws as useful for ripping open
termite and ant colonies (or marauding tarbosaurinids).