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Re: Origin of Birds-arboreal biped




On Mon, 8 Dec 1997, G & J Bloomfield wrote:

(various snips)
>      The upper Triassic archosaur Scleromochlus taylori had been 
> suggested as one such beast by Von Huene  in 1914.*  He apparently was 
> exploring the possibility of it being a pterosaur ancestor, but it seems 
> to me that it would "work better" as a bird/dinosaur type as is being 
> discussed.  I've rearranged the published skeleton(from Wellnhofer's 
> pterosaur book) and attempted to restore it as an arboreal, 
> "protofeathered," obligate biped, with its small forelimbs free to help 
> it balance itself as it jumped and clambered about in branches.  The 
> recent findings of possible primitive feathers are seeming to make this 
> more and more plausible.  It would seem to fill the bill in many ways, 
> and some form like this does seem to me to be the most likely candidate 
> for a "proto-bird."  

Actually it has long been accepted that pterosaurs had some sort of
epidermal insulation.  I am wondering if this covering is similar to that
found on _Sinosauropteryx_.  If this is the case, then would _Lagosuchus_
not be a good candidate for these "proto-feathers" as well (assuming of
course that it is the most recent ancestor of pterosaurs (and
_Scleromochlus_) and dinosaurs)?  Greg Paul restored his _Lagosuchus_ with
proto-feathers (perhaps filoplume like structures) back in PDW, which I
thought was fitting.

> I realize that this particular animal was not 
> well-preserved, but is there anything known for certain about it that 
> would rule this out?  It does seem to be a perfectly good, tiny archosaur 
> in the right time slot.

_Scleromochlus_ is preserved only as an impression.  Dr. James Clark has
told me that about all we have to argue with on this little creature are
limb proportions.  

jc