RE: Dinosaurs with Guts

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

        Don't be too bashful Randy, I felt you had some good points.

        I don't feel too bad commenting on this, as I have already voiced some 
of my concerns to Dr. Varricchio. In all fairness, he did not linger to discuss 
them at length, so he may have been a bit rushed at the time. However, I am 
sure that reviewers would have brought them up as well:

Modest Randy Irmis wrote:

> The most obvious problem with their diagnosis is that none
>of the remains found are articulated.
        Check. I am not convinced that the bone assemblage represents the 
original structure of the skeleton. I'd like to see the locations compared to 
the hydraulic properties of the elements themselves, or a rose diagram for the 
orientation of (the few) long elements, or a test for randomness of the 
assemblage. Note that even finding one specimen articulated within another does 
not PROVE ingestion (as some point out regarding the infamous "cannibal" 
ceolophysis... but don't ask me, I've never seen the thing).

>My second problem is, why would a predator ingest the skeletal elements that
>are found?  The area of the skull that contains the dentary has almost no
>meat.
        Actually, the mid- and distal caudals were probably not that meaty 
either. The more proximal ones would have anchored the caudofemoralis 
musculature, and those would've been tasty... but I'm not sure you couldn't 
just strip that off the bone (I am reminded, in a purely non-homologous way, of 
chicken thighs).
        On the other hand, I don't think the author is under any burden to 
prove that the alledged meal was "worthwhile." I've seen toothmarks on some 
awfully untasty-looking hadrosaur bits.

        Interestingly, my own research suggests that the dentary and caudal 
vertebrae of hadrosaurs may be considered part of the same "representation 
group" (after Voorhies) for hadrosaur skeletal elements. In general, 
ornithischian vertebrae are easily transported elements. This is a bit 
suspicious.

Ever-thoughtful Mickey Mortimer wrote:

>"None of the bones exhibit any surface modification such as weathering
>or abrasion-induced damage. Except for breakage resulting from recent exposure,
>elements appear complete."
> 
>So yes, I agree that an acidic environment cannot be the reason for the
>etching.
        It is not at all uncommon for different bones in a quarry, often bones 
from the same animal, and sometimes even two fragments of the SAME BONE to 
exhibit different weathering styles. Sometimes, this indicates locally 
differeing chemical "micorenvironments" (either in burial, or exposure), 
sometimes it indicates that some of the bones sat around longer, or were 
transported further, prior to burial.
        In Big Bend, we see weathering similar to that observed on Dr. 
Varricchio's hadrosaurs, often side-by-side with well preserved bones, and 
concretion-covered bones, and abraded bones, in bone beds where a "digestive" 
interpretation is less likely. We also find sites which (are interpreted to) 
consist of one individual, with only a few isolated elements of others.

        I highly recommend that EVERYONE interested in studying dinosaurs go 
out RIGHT NOW and get a copy of Pat Shipman's book _Life History of a Fossil_. 
It is a little old, but it will bring you up to (1981) date on the important 
and rigorous study of taphonomy. This is the discipline that Dr. Varricchio, 
and most other paleontologists, use to "filter" the geologic information we 
get. No one should attempt to draw inferences from the geologic record without 
it.

        Wagner
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     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
  "Why do I sense we've picked up another pathetic lifeform?" - Obi-Wan Kenobi