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RE: Dinosaurs with Guts
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
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
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
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
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
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