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Lots of Zuni stuff (was RE: Little video blurb on the new Zuni theropods)



> From: John Bois [mailto:jbois@umd5.umd.edu]
>
> On Tue, 19 Jun 2001, Thomas R. Holtz, Jr. wrote:
>
> > The support for the feathered nature of therizinosaurs, oviraptorosaurs,
> > dromaeosaurids, and basal birds (duh) is considerably better than many
> > cherished aspects of dinolore, such as:
> >     *pack hunting in various theropods
> >     *predation in most theropods
> >     *herd behavior in sauropods
> >     *long-term post-nesting parental care in non-avian dinosaurs
> >     *sexual display in stegosaurs
>
> Just wondering if you consider parental care _during_ nesting
> better or less supported.

Good catch!  Parental care DURING nesting (and even just post hatching) is
strongly supported on phylogenetic evidence.

>From Tracy Ford:
>But dinosaurs are KNOWN to have had scales, a great majority of them.
>Mammals are not (some do have scales like armadillos, but that is of a
>different structure (I think), they have hair. We do not know for sure that
>all Dromaeosaurs, oviraptors, etc had scales or feathers. We do know that
>some had them and other theropods had scales. We can not for a minute say
>without a doubt that all small theropods had feathers or feather like
>structures. Now, I'm not arguing against this. I had for a long time been
>against this, but now I'm sliding more and more toward this. What I am
>saying is that it is still debatable.

This is part of the danger of working from a typological context rather than
a historical (phylogenetic) context.  While it is true that the majority of
Mesozoic dinosaurs for which body impressions are known are scaled, these
are representatives of ornithischians and sauropodomorphs and the occasional
neoceratosaur.  In fact, given this information we can be confident for the
moment in saying that illustrations feathered baby hadrosaurids or
hypsilophodonts are non-scientific: treating (as we should) feathers as
evolutionary novelties no different from any other, the historical context
is that feathers currently seemed to have been distributed soley among
coelurosaurian dinosaurs.

On the flip side of this, treating again feathers as an evolutionary
novelty, these structures are very securely placed as present basally in
Maniraptora, and fairly securely further down in Coelurosauria.  Without
positive evidence to the contrary, the simplest assumption is that all
maniraptorans were feathered.

By the same token, many fossil bat species are known only from teeth and
skulls.  However, because they fit phylogenetically within the clade
comprised of modern bats and of ones known to have wings (_Icaronycteris_
and company), we are confident that all of those species had wings.  We
haven't seen their wings, and there is nothing in evolution to prevent any
individual lineage from becoming a flightless bat, but it is unscientific to
assume any of these were flightless bats without additional positive
evidence.

In other words, the burden of proof has now shifted.  Any claimants on
featherless dromaeosaurids and oviraptorsaurs and avialians and so forth
must demonstrate their claim.  Otherwise, the proper default is that
maniraptorans (minimally) were all feathered.

There is an important point to make here, though: it is "maniraptorans" or
more broadly "coelurosaurs" for which we have evidence of feathers.  In
other words, particular branches of the tree of life: historical entitities.
It is NOT some sort of essentialist grouping like "small theropods" or
"small dinosaurs".  There is currently no phylogenetic evidence that
_Eoraptor_ or _Coelophysis_ (for instance) were feathered, and they should
be kept scaled for the moment.

Judy Horan indicates that the interview I did for @discovery.ca is available
online at http://exn.ca/discovery/index.asp, under the heading "Vegan
dinosaur".  One slightly misleading, although unintentional, video cut: when
talking about _Nothronychus_ (a name I am constantly mispelling!!) I'm
talking about the massive hand claws, and the clip they are showing moves
from _Notrho_ to the feet of the dromaeosaurid.  No, the therizinosaur
didn't have sickle foot claws (the next image in the documentary is a wider
shot, from above, of the dromaeosaur looking nervously up at _Nothro_).

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796