Re: MORE ON BCF

["Matthew Troutman" <m_troutman@hotmail.com>]

<<You know, I'm getting tried of this argument. You must know and 
relized that the fossil record is poor for the early to middle 
Jurassic.>> 

I know that it is poor, but we cannot use that as some sort of 
scientific "cushion" to shield ourselves from the fact that we still 
have not found any unequivocal bird or dino/bird bones.  

<<And why is it, I've asked this on the list before, that if a skeletal
element that might belong to an non-avian theropod OR an avian-theropod 
that it's always placed into the non-avian theropod? Case in point, 
Jensen & Padian, 1989, they're going over Jensen's 'birds' Palaeopteryx, 
the proximal tibia is refered to either a Deinonychosaur or BIRD, and 
BYU 2033, a right femur might be a Deinonychosaur or BIRD!, but everyone 
will say it's a Deinonychosaur. I say, lest get some balls here and say 
it's a BIRD (or avian-theropod, what ever)!!!>>

It still is not unequivocably known that they are birds or not. Paul 
(1988) has questioned the avian assignment.  Even if they are birds, SO 
WHAT?  Still, it is close enough to the Jurassic/Cretaceous boundry that 
it makes no real difference.  

>There are Archaeoptryian teeth from the Kimmeridgian of Portugal.

I have not yet seen this paper, but what about the possibility that they 
are crocodilian?  Was this addressed?

<<And what about ichnology? The forgotten science. There are thousands 
and thousands of small theoropod prints from the early Jurassic to the 
late Jurassic. With some early Jurassic prints that are so small they'll 
fit under a quater. What about the bird (or bird like prints?just forget 
them? Not good enough?)>>

Let me quote parts of Padian and Chiappe 1997 pertaining to this issue:

"Lockley et al. (1992) argue that there are some possible bird tracks in 
the fossil record as early as the late Early Jurassic (e.g. 
_Trisauropodiscus_ from Arizona and South Africa), but their criteria 
are somewhat vague, and have not been demonstrated as unique characters 
of bird tracks, or of certain taxa within birds (Chiappe, 1995a; Padian, 
1997).  The degree of divarication of the second and fourth toes figures 
prominently in their discussions, but other morphological features of 
the tracks are not clearly diagnostic of Aves; the authors also 
acknowledge the problematic lack of skeletal evidence of birds until the 
Late Jurassic.  It is not clear that the authors are identifying these 
tracks as avian; they are noting presumably avian features.  Still, 
'avian features' can only be either those of true birds of convergent 
features of other taxa (presumably, in this case, small non-avian 
theropods), so either way some intriguing questions and doubts are 
raised."  Padian and Chiappe 1997; p.14

Molnar (1985) has questioned the birdiness of Ellenberger's South 
African tracks, saying that the "feather imprints" are actually 
invertebrate trails that trod over regular tracks.

Matt Troutman

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