[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Fwd: Eodromaeus, new basal theropod from Triassic in Argentina
One example that's often overlooked is _Caudipteryx_. Some specimens
preserve scales on the ventral manual digits. Obviously, these
coincide with the advanced-stage feathers anchored to the dorsal part
of the same digits.
Jason has used evo-devo to argue that feathers and scales *are*
mutually exclusive many times before but this is easily falsified by
looking at a number of fossil specimens. Even if feathers do
"highjack" the developmental pathways used by scales, and even if the
tarsal scutes (which are different from scales) of birds are actually
modified feathers, there is plenty of proof that it's not an
all-or-nothing trade. Feathers or filaments can and did coincide with
typical dinosaurian scales in a number of specimens from all up and
down the coelurosaurian tree, so there's no reason to think this
couldn't be true of more basal taxa.
For what its worth, _Pterodactylus_ specimens also show scales and
pycnofibres coinciding in the same way.
On Sun, Jan 16, 2011 at 6:00 AM, Jaime Headden <firstname.lastname@example.org> wrote:
> Â At the point to which "extent" becomes a variable, pure speculation leaves
> the question unanswerable as to "Which dinosaurs had what type of
> integumental covering?" We cannot answer this question without direct
> evidence, and this is lacking in depositions which fail to preserve anything
> but the bones.
> Â I would also remind readers that the general artistic trend, as promoted by
> Greg Paul, is to render theropods half-and-half squamous and "fuzzy," or
> squamous and plumed when it comes to taxa he's argued to be derived from
> *Archaeopteryx*-type "protobirds." This artistic device is based on little
> _hard_ evidence, although some exists:
> Â *Juravenator* is known from material with both "fuzzy" and squamous
> Â Dave NGMC 91 has regions of the snout and limbs that do not appear to
> possess "fuzz";
> Â *Scansoriopteryx*' holotype has impressions of squamous skin as well as
> traces of preserved "fuzz."
> Â Theagarten Lingham-Soliar argues that the "quills" in *Psittacosaurus* sp.
> are coincident with traces of squamous skin, although he objects to the
> identification of the nature of the "quills" being related to "fuzz."
> Â So there is evidence in some specimens of both integument types, while in
> others it may be argued at least that ontogeny may play a role.
> Jaime A. Headden
> The Bite Stuff (site v2)
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
>> Date: Sat, 15 Jan 2011 14:59:16 -0300
>> Subject: Re: Eodromaeus, new basal theropod from Triassic in Argentina
>> From: email@example.com
>> To: firstname.lastname@example.org
>> CC: email@example.com; firstname.lastname@example.org
>> As long as both squamous integument and "fuzz" may be reconstructed for
>> dinosaurs on the basis of bracketing (the first because of the state in
>> crocs, bird feet, ornithischians, sauropods, theropod Carnotaurus; the
>> second because of the state in pterosaurs, small ornithischians, and
>> coelurosaurs), it may be inferred that both were present, because they
>> can be both present as long as the organism is not covered by only one
>> integumental type. The question would be to which extent each
>> integumental type was present, which seems difficult to ascertain as we
>> often do not have complete integumental coverings. Of course, size may
>> explain the extent of each coverage.