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Re: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx

Anthony Docimo <keenir@hotmail.com> wrote:

> But in the radiations which include the ancestral line working to overcome 
> the limitation?  That seems to be what we have with the
> protobirds.

I'm perfectly fine with the idea that certain basal paravians spent at
least some time in trees.  But if we are going to put these particular
dinosaurs in trees, it has to be for the RIGHT REASONS.  Intuitive
notions about how small theropods should be as ecologically versatile
as goats, frogs, lizards, or snakes aren't good enough by themselves.
We need compelling morphological support to put basal paravians in an
arboreal setting - such as novel traits in the skeleton (or unguals)
that can be tied to scansorial or arboreal locomotion.

It is possible that taxa such as _Microraptor_ and _Archaeopteryx_
were indeed "working" to overcome their limitations.  And it may be
that the novel skeletal features in these taxa  (along with their
small body size) might have been adequate for tree-climbing.  After
all, to use an analogy from elsewhere in the Dinosauria, the burrowing
ornithopod _Oryctodromeus_ shows novel features of the snout, shoulder
girdle and hip bones consistent with digging habits while retaining
cursorial hindlimbs.  It is only because _Oryctodromeus_ was preserved
in a burrow that these novel features were inferred to be involved in
digging.  Then, the same or similar features in related ornithopods
(_Zephyrosaurus_, _Orodromeus_, _Koreanosaurus_) could be viewed in
the same light.  My personal view is that certain basal paravians were
experimenting with scansorial/arboreal behavior, but were hardly
committed.  They remained cursorial, terrestrial bipeds.

David Marjanovic <david.marjanovic@gmx.at> wrote:

> Scales are probably a sauropsid autapomorphy. Sauropsida is what Tim
> Williams appears to mean when he says "reptiles".

Actually, when I said "reptiles" I meant reptiles.

As defined by Modesto and Anderson (2004), Reptilia is the most
inclusive clade containing _Lacerta agilis_ and _Crocodylus niloticus_
but not _Homo sapiens_.  So turtles, lizards, snakes, tuatara,
crocodiles and birds are all members of the Reptilia - irrespective of
whether turtles are anapsids, euryapsids, or diapsids.

I'm not saying this definition is the final word on how Reptilia
should be defined.  But it's the definition I'm most comfortable with.
 It allows Reptilia to include extant forms traditionally regarded as
reptiles, and pointedly excludes those amniotes on the mammal line
(including stem-mammals).