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Re: pterosaurs, pre-K/T theropods, and Certhiidae



Stephan Pickering (stefanpickering2002@yahoo.com) wrote:

<Has anyone yet done an osteological comparison (with myological
extrapolations) between pterosaurs and pre-K/T feathered, flying and
secondarily flightless, theropods, and the extant species within Certhia,
the "treecreepers"? These interesting dinosaurs are adapted to "walking"
up the sides of trees, feeding on insects.>

  There aren´t that many myological studies on pterosaurs out there,
considering there are very few rather complete 3-D skeletons available.
Otherwise, work is cobbled together from a variety mis-sized specimens
that must be assembled allometrically. S. Christopher Bennett has done
several papers on the osteology and inferred musculature in *Pteranodon*,
but this was general. Bird skeletal anatomy is inherently different, and
there are bones and bone associations that make the two fairly different,
but the mechanichs are essentially the same except that pterosaurs lack an
equivalent m. supracoracoideus elevator as distinct as in enantiornithines
or ornithurines. Pterosaurs make do with a huge m. deltoideus, and this is
the reason why the deltopectoral crest in pterosaurs is so much larger
than in birds.

  As for *Certhia*, there are numerous treecreepers and honeycreepers, as
well as most all other arboreal piciforms, that are well-suited to
harvesting on the trunks of trees, either wood, investing food storage,
grubs, or the soft pulpy cork beneath the bark. This appears to be enabled
largely through the pedal and tail design, with paired bracing raches in
the tail, and zygodactyle feet with specialized claws. Among Mesozoic
theropods, only *Scansoriopteryx* (a non bird) seems to have any features
of the Anomoluridae (scaly-tailed squirrels, which are leaping gliders)
and tree-hugging piciforms, including large claws to foot size, a scaly
tail (no evidence of feathery integumental covering whatsoever), and a
limb apparatus suitable for "scrambling" and climbing. My illustration on
Dinosauricon also has this behavior in side view, and I have another that
will be appearing on my website that is much more ... illustrative ... of
this behavior as I infer from the anatomy.

  Hmm ... tree-hugging pterosaurs ... one would have to find climbing
adaptations in the limbs (all of them) along with presumably short wings
as is usually found in species of birds living in forested areas, good for
maneuvering close-quarters flying.

  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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