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RE: did Jurassic dinosaurs have feathers?



> From: Mike Taylor [mailto:mike@indexdata.com] 
>
> Thomas R. Holtz, Jr. writes:
>  > > ....and while all the "birds" had feathers, in both the 
> Jurassic  > > and Cretaceous (the book was arranged by era 
> *then* by  > > clade)...the maniraptors and other predatory 
> dinosaurs only were  > > illustrated with feathers in the Cretaceous.
>  > >
>  > > is there reason to think that Jurassic predatory 
> dinosaurs  > > would/wouldn't be feathered?
>  >
>  > Jurassic maniraptorans would have almost certainly have 
> been  > feathered.  Compsognathids and tyrannosauroids would 
> be fuzzy. More  > basal theropods (including Allosaurus, 
> Ceratosaurus, etc.) would be  > scaled.
> 
> WHat's our reason for being confident that Allosaurus didn't 
> have feathers?  My understanding is that we have some 
> preserved tyrannosaur skin impressions that show scales and 
> no feathers, but that this is not taken as evidence that 
> tyrannosaurs were not feathered -- only that they had scales 
> but that these could have been as well as, rather than 
> instead of, feathers.  What's to stop the same being true of 
> Allosaurus or Ceratosaurus, or for that matter Brachiosaurus 
> or Triceratops?

Okay, to be fair it is ambiguous (a Type II inference) for Allosaurus: we
have no indication of scales over the whole body within Carnosauria, so the
presence of Allosaurus scales on the limited skin impressions could be a
tyrannosaurid-type situation or a lepidosaur-type situation.

Nearly the entire surface of Carnotaurus is (alledgedly) known from skin
impressions, and these are scales-only. So at least in the adult stage of
one ceratosaur there are only scales, and no evidence within Ceratosauria or
basal-ward [with respect to Coelurosauria] to it of protofeathers. Inference
of protofeathers is at present a Type III inference with no supporting
evidence. Could easily change with a single discovery, but that's the
situation now. Hence putting protofeathers on Ceratosaurus or abelisaurs (or
more basal theropods) is AT PRESENT unsupported by confirmatory evidence,
and contradicted by both observational evidence and phylogenetic inference.

Same goes for all dinosaurs basalward [again, with respect to
Coelurosauria]. And no, there are NOT protofeather impressions of
coelophysoids/dilophosaurids in the Newark Supergroup: those are algal mat
drag marks, as Tony Martin has shown. (This does not demonstrate lack of
protofeathers in these guys, but is simply not evidence FOR protofeathers.)



Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Fax: 301-405-0796

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA