[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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






> Date: Mon, 14 Nov 2011 10:08:24 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: 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.
 
 Then I wonder how theropods (those that weren't on the large end of the scale) 
managed to not only hold their own, but to thrive worldwide for over a hundred 
million years.
 
If that's not a good argument for assuming theropods are ecologically 
versatile...
 
> 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.
 
Catch-22.
 
It can't enter an arboreal setting without those novel traits.
 
And it won't have those novel traits* if it can't take the first step toward 
finding a new source of food in or near trees.
 
* = beyond the fractionally-different-from-its-parent-species mutation.
 
 
> 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.
 
 Committed?  How committed was Ankarapithecus or Sahelanthropus to being an 
intelligent tool-user?   For the same reason, we can't and shouldn't expect the 
same level of "committment" from the early attempts at arboreality/flight, as 
we find in the later, more successful attempts at the same.
 
 
> They remained cursorial, terrestrial bipeds.
 
 I can buy that feathered protoavian theropods were terrestrial.
 
 But the "ornately-feathered limbs were like a stag's antlers or peacock's 
tail" answer for _Microraptor_* suggests to me that _Microraptor_ only had what 
we assume were four gliding wings during certain times of the year (and we only 
have fossils from those annual events).
 
So, unless there were kjopes, cliffs, or ravines in _Microraptor_'s habitat, 
then trees are the only remaining option  (that and sauropod-climbing)
 
 
* = no, nobody made that argument, but it's what I think of when I try to 
imagine _Microraptor_ running around on the ground.
 
 
> 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".

> 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).
 
 Weren't stem-mammals traditionally regarded as reptiles?
 
Odd, strange reptiles, but still reptiles.