Re: dinos and birds

["Jaime A. Headden" <qilongia@yahoo.com>]

Mickey Mortimer (Mickey_Mortimer111@msn.com) wrote:

<I had forgotten about these scales or scutes in Scleromochlus.  They are
placed above the dorsal column in the three specimens where they are
preserved.  But I don't think their presence can be used to argue against
filamentous integumentary derivitives, given the numerous mammals with
both fur and osteoderms/scales, even on the same area of skin (e.g.,
opossums, armadillos, sloths).>

  Well, as I am currently away from my references, taking a vacation in
dry, hot Las Vegas for the 4th, I cannot confirm specimen identities, but
at least one specimen has ventral, belly scutes. These are arranged in
gastrale-like series mediolaterally and in a pattern in a sterno-vent
orientation as in crocs and aetosaurs. The surface is not well preserved,
so that, unlike mammals, pitting of the surface as in mammals for
folicular evidence is unknown. The osteoderms of the few sloths that have
them, and the glyptodonts, show clear folicular channels. That of
armadillos, though not as well-ossified, show the same. That of crocs does
not. The comparison is not evident in *Scleromochlus.* Evidence for
fluffy-like integument is absent despite the fine details of the bone.
While this is not evident, it is also constrained by the bracketing of
other basal archosaurs, including *Lewisuchus* and sphenosuchians, which
show a more croc-like or irregular sagittal dermal skeleton, and in the
latter, show no evidence of folicular invasion of the dermal bones, or
bony growth around the folicular channel. In this case, given archosaurian
evolution even if pterosaurs are included, *Scleromochlus* has little to
non positive inferrence it would have a "pelage." No other tetrapod shows
scalation in the same place as folicular activity other than scalation,
even birds, which show feathered replacement rather than scales around the
feet (as in ptarmigan, swifts, or some owls). This, unlike other data,
show that it is not really likely, though not imposible, that the armor in
*Scleromochlus* included a pelage. Unlike the hairy sloths, the dermal
armor does not occur as nodules, but as plates; as in the plated
armadillos, hair and armor take an alternating position for the most part:
where there is armor, there is little hair ... and where there is much
hair, there is nil armor. This would provide that a very fluffy
*Scleromochlus* is unlikely. IF it were a mammal -- we have no idea if any
other animal would be remotely likely to show such a condition since there
are no other animals aside from mammals with a non-hair folicular
structure (aka, scale, hair, feather, nail) growing in the same place and
region as the hair, or interspersed. This, rather than supporting a "We
don't know any better, so all bets are off and let's draw fluffy
*Scleromochlus* anyway" idea, and supports a "Look at plated, scaly
animals, and if they were haired, look at animals with hair, THEN look at
animals that don't have hair (all non-cynodonts) and see what the pattern
THERE is..." idea. There is NO positive evidence or even "weak" inference
to support a furred *Scleromochlus,* mammals [which it is not]
notwithstanding.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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