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

Re: Feathered/scaly theropods: trying to make the point.



Information on theropod skin impressions is only available for a little
over half a dozen taxa. These include two scaly forms (the abelisaurid
ceratosaurs _Carnotaurus_ and _Aucasaurus_) and a bunch of feathered or
proto-feathered forms (coelurosaurs such as _Sinosauropteryx_,
_Protarchaeopteryx_, _Caudipteryx_, _Beipiaosaurus_, _Microraptor_,
_Sinornithosaurus_, and avians).

The most parsimonious explanation, based on these data and the most
commonly accepted phylogenies, is that feathery integument was present in
all members of Clade(_Sinosauropteryx_ + _Passer_*), and possibly
originated earlier, as far back as basal _Tetanurae_ (Clade(_Passer_ <--
_Ceratosaurus_)).

It is currently ambiguous as to whether such taxa as _Tyrannosauroidea_,
_Ornithomimosauria_, _Coelurus_, _Ornitholestes_, _Scipionyx_, etc. are
inside Clade(_Sinosauropteryx_ + _Passer_) or not. However, since feathery
integument may well be a feature of a wider clade, it is quite likely to
have occurred in these forms.

It is also possible that feathery integument extends even further than
_Neotheropoda_ (Clade(_Ceratosaurus_ + _Passer_)), and the aforementioned
carnotaurines are secondarily featherless. At the other end of the range
of possibilities, it may be that feathery integument is restricted to
Clade (_Sinosauropteryx_ + _Passer_), and that certain members of that
clade may have been secondarily featherless, either during part or all of
their lives.

Apparently there are some new discoveries of non-avian theropod integument
being written up. Perhaps we'll know more soon.

Personally, I choose to depict all coelurosaurs with feathery integument,
although it's possible that gigantic forms lost it as adults. Carnosaurs
and other tetanurans may have had similar structures, too. (See Brett
Booth's carnosaur depictions on my site.)

(* _Passer_ is an extant passeriform neornithean avian (sparrow,
specifically))

_____________________________________________________________________________
T. MICHAEL KEESEY
 Home Page               <http://dinosauricon.com/keesey>
  The Dinosauricon        <http://dinosauricon.com>
   personal                <keesey@bigfoot.com> --> <tmk@dinosauricon.com>
    Dinosauricon-related    <dinosaur@dinosauricon.com>
     AOL Instant Messenger   <Ric Blayze>
      ICQ                     <77314901>
       Yahoo! Messenger        <Mighty Odinn>