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One last thing on the bitten _Edmontosaurus_

I continued my discussion with Ken Carpenter and Kevin Padian about
what Jerry Harris' favorite hadrosaur's tail shows us and Jack
Horner's state of knowledge about it.  I'm going to excerpt from all of our
comments here.

Kevin wrote:

   Mickey, thanks, would you please post my apologies to the list [for
   unintentionally spreading the apparently false rumor that Jack has
   never seen the "bitten" hadrosaur at DMN&S (formerly DMNH) -- MPR].
   Jack and I were talking about this specimen before our "debate,"
   and when I mentioned that I hadn't seen it, I thought I understood
   Jack to say that he hadn't seen it either.  (He's in South America
   for the rest of the month.)  And obviously Ken has cleared up the
   matter.  I guess then that the question comes down to how one knows
   it is or isn't a bite mark.  The slides Jack showed were of a
   specimen that had no clear tooth marks or broken teeth in it, and
   he opined that it might have just had its tail stepped on (they
   can't fold them around themselves because of the ossified tendons).
   I think we would all agree that clear tooth marks or embedded
   broken teeth on subsequently healed bone would establish an
   individual incident, though repeated incidents would be even more
   persuasive.  Without this evidence, as in any traces of behavior
   (such as footprints), it's tough to know what you've got in many
   cases, isn't it?  And it's equally hard to think of definitive
   evidence of fossilized behavior that would support scavenging.
   Jack is pretty tenacious in defending his case, but he (and we)
   don't lose sight of the fact that this problem, though it may be
   scientifically difficult to determine, has a lot of potential to
   inform the public about how we approach these kinds of questions in
   the fossil record.  And, in fact, that science isn't a monolithic
   march to "prove" a "theory"!  Thanks -- kp

I did some more digging after that and found a message I sent to the
list on Ken's behalf back in 1995:


The most relevant bit (written by Ken) was:

     Actually, the height is 13 feet. The top 1/3 of one neural spine
     is obliquely sheared off leaving a U-shaped groove. There is some
     remodeling of the bone indicating some healing occured prior to
     death. Other neural spines are mangled, with at least two tooth
     punctures. These and the missing spine form a nice U-shape that
     conforms well with the cast of the T. rex skull we have. Jack has
     seen it and agrees that it most likely was done by a T rex,
     however, argues that it was a rare attack.

I interpret that to mean that one spine has a small U-shaped groove
that looks like it was formed by a single tooth biting through it, and
the overall pattern of damage forms a larger U-shape that looks like
outline of the Tyrannosaur's jaw.  Jerry should comment if I've biffed
that description, but I think that comports with the clarification Ken
sent me today:

     The tail in question is described in the Gaia volume on Theropod
     paleobiology. [...]  There are 3 adjacent neural spines in
     question, one that is sheared off obliquely, and two on each side
     with tooth punctures. They three for[m] an arc that pretty well
     matches the front of a T. rex mouth (based on the AMNH skull on
     display 10 feet away). The spacing of the three features also
     matches well the T. rex teeth.

     I find it more incredulous to image that a hadrosaur managed to
     get one neural spine on the tail sheared off by another's blunt,
     wide toe nail. I suppose the "tooth marks" were also by toe nails
     piercing through skin, muscle and ossified tendon? Perhaps a
     roving gang of delinquent hadrosaurs (with pierced beaks) had
     surrounded an adult hadrosaur and repeatedly kicked it?

For those who haven't met him, Ken's a funny guy :-)

I also discovered this:

    Evidence of hadrosaur tail vertebrae damaged by T. rex attacks:
    There's an Edmontosaurus at the Denver Museum of Natural History
    that appears to have had a bite taken out of the top of its
    tail. Ken Carpenter took some thin sections of the neural spines
    and found a fragment of tyrannosaur tooth embedded in one of
    them. The fact that the bone shows evidence of healing after it
    was broken indicates that the damage was inflicted while the
    animal was alive, and thus is not the result of scavenging.



What I elided from Ken's quote above was:

     I did no thin sectioning and have no idea where this myth came

Hence I'm CC'ing this message to the person who apparently wrote that
section for the Tate Museum.  I include the quote above to warn you of
the inaccuracy in case you hear of this "myth" anywhere else.

Without having seen Ken's response (and hence probably thinking the
bit on sectioning was real; though I'm not sure how much that should
change your conclusions about what caused the damage...) Kevin wrote:

     Okay, so in correcting my previous message to you, Ken's evidence
     seems pretty definitive.  I'm not sure that Jack admitted this
     but we may have been talking about different specimens (the one
     he showed was a different one that he had), and in any case, as
     we noted before, the question is how regular the behavior is (how
     often are you going to get the "fighting dinosaurs" preserved --
     especially less than five years after someone predicts that this
     is how the dromaeosaurs used their claws?).

That's probably a good place to leave this, which is probably exactly
where Ti... I mean Tom and most other theropod experts are sitting
with respect to this "debate".  The question probably shouldn't be
whether Tyrannosaurs hunted or scavenged.  The question should be how
often did they do each.  However, the hadrosaur skeleton in Denver
strongly suggests they at least one Tyrannosaur tried to start eating
at least one animal when it was alive :-)

My thanks again to Ken and Kevin for taking the time to answer

Mickey Rowe     (rowe@psych.ucsb.edu)