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VEXING PROBLEMS WITH FORELIMB POSTURE



I just read the 1995 paper R. Johnson senior authored on Torosaurus forelimbs
in Functional Morphology in Vertebrate Paleontology. I am not a happy camper.

At one point it is stated that I have argued ceratopsid arms were erect
because I believe they were fast runners and endothermic.  My works cited by
JR are PredDinoWorld1988 which is largely irrelevant because it covers
theropods, and a short1991 SVP-JVP abstract. I wish to state that Johnson's
assertions are grossly incorrect. 

I do not argue that any given dinosaur had a certain limb posture because of
its supposed locomotary abilities or metabolic status. To do so would be bad
science. In DinosPast&Present1987 I presented detailed anatomical and
functional arguments and diagrams showing why ceratopsid arms were erect. In
Modern Geology 1991 I published a detailed skeletal restoration showing a
Triceratops or Torosaurus (not certian which it is) skeleton walking out a
known trackway with erect arms. Neither of these papers is cited in RJ's 1995
study. I have concluded that all quadrupedal dinosaurs had erect arms solely
on the combined basis of anatomy and especially trackways. From these
conclusions I derive further conclusions regarding their metabolics, gaits
and speeds, but that is a very different matter. 

When I said in another posting that "people do not listen" to what I
say, this is an example of what I mean. What is the point of
publishing data in peer reviewed papers (as the 1987 and 1991 studies
were) if it gets ignored in favor of misrepresentations of other
unreviewed works? Very odd and extremely frustrating.

As for the conclusion that Torosaurus had sprawling arms, this has been
disproven by trackways published a number of years ago by Lockley. These
trackways almost certainly were made by a giant ceratopsid, probably
Triceratops or possibly the rarer Torosaurus. In JR's 1995 paper the
trackways is not figured. This is probably because the Torosaurus skeleton
mounted by JR has both the fore and hindlimbs much too far apart to fit the
trackways. Although the shoulder of dinosaurs were fairly narrow, Torosaurus
was a very big animal with shoulders almost three feet across. The hand
prints in the trackways are a little over three feet apart. Ergo, the hands
were almost directly below the shoulders, not sprawling far out to the sides
as Johnson's skeleton shows. Actually, unlike sauropods and stegosaurs,
ceratopsids may have been able to sprawl their arms, perhaps to drink or
feed, or as a combat posture. The trackways, however, show that they normally
walked with the hands under the shoulders. There are anatomical reasons to
think that the elbow were only a little bowed out when they walked this way,
but you will have to take the time to look up and read my studies and check
out the nice figures (and others by Ken Carpenter) to find out why. 

GSPaul