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leg injuries in large theropods, etc



 I've been offline for the past week and a half due to some continuous and
rather nasty infections related to a wisdom tooth extraction, but in my
pained and groggy state have read thru most of the postings which included
comments on actual evidence of falling tyrannosaurs, or tyrannosaurs whacked
on the leg by ankylosaurs, Cheetahs, etc. In my still dizzy and feverish
condition I thought I'd add a few comments.

 An earlier writer noted something to the effect "that Cheetahs just brush
off the dust and walk away following a wipe-out incurred during a failed
predation attempt". This is not always so. In Adamson's 1969 book THE
SPOTTED SPHINX, she notes on page 207 that leg injuries among juvenile
Cheetahs are the leading casuse of mortality in this species. Leaping from
trees caused leg sprains and other trauma was incurred during predation
attempts. Unfortunately nothing is said about adult Cheetah wipe-outs and
any resultant injuries.

 Evidence for injuries specifically incurred during a fall in any fossil
vertebrate is of course impossible to know for sure, as we were not there to
see it actually happen. So any traumatic injuries in a tyrannosaurid or
other large theropod that are ascribed to a fall incurred while chasing prey
could have actually resulted from a variety of factors (a simple fall
unrelated to pursuing prey, intraspecific fighting, accident, etc). As we
all know, bones are also frequently fractured well after fossilization, so a
true fatal leg fracture (or skull fracture for that matter) might be
misinterpreted or masked as erosion, ground movement, etc.

 I'm working on a new subadult Albertosaurus skeleton for Tyrrell which will
be exhibited this summer. It appears to have suffered a fractured right
dentary- now hard to see due to bone repair (a CT scan soon should tell us
for certain), a fractured and healing right fibula (mid-shaft) and a muscle
or ligament injury (avulsion) on one of the right pedal phalanges. Popular
books would have us believe that ankylosaurs could whack a predator on the
jaw or leg and cause injuries. While I cannot envision the former, the
latter seems probable. I don't have hard numbers to present here, but
through my work, I get the feeling that more subadult tyrannosaurs show
fibular fractures than full adults. This I've believed was due to hunting
inexperience of the young tyrannosaur and getting whacked by an ankylosaur-
much like a yearling Coyote, etc might erroneously try to tackle a Porcupine
or Skunk with equally disasterous results. In Dinosaur Provincial Park we
find either subadult or fully grown tyrannosaurid skeletons- there was a
high mortality rate at the subadult stage. Some of these subadults show
fractured and partly healed fibulae- evidence for ankylosaur tail club
whacks to the lower leg??? Evidence of jaw injuries are there too, but don't
get excited- all but the example noted above appear to be dentigerous cysts,
intraspecific bites, broken teeth, etc. Nothing else that would suggest
injuries incurred from a fall while chasing prey.

 I am curious to know whether those motorbike riders who related their
accident experiences could enlighten us on any differing injuries between
pavement wipe-outs versus those suffered by dirt-bike riders who are wiping
out on softer and more yielding substrate (which would be more akin to the
ground a tyrannosaur would land on in the event of a fall). I would expect a
rider on smooth, regular pavement would be more likely to slide along,
whereas softer irregular ground would invite more rolling, digging in and
flipping over such as seen in racecars which get off the track and onto the
grassed infield.

 There may be one way of finding out about tyrannosaurid fibular fractures
being incurred by whacks from ankylosaur tailclubs. As a paleopathology and
Late Cretaceous ceratopsian man, I don't know if there were ankylosaurs with
clubs in the Late Jurassic. I believe not, yet there were large theropods
around then (ie. Allosaurus). I have not seen any, but has anyone come
across fibular fractures in Allosaurus or other large theropods predating
the earliest known tail-clubbed ankylosaur? If enough examples of these
exist, it might preclude the concept of tyrannosaurids fibular fractures
being incurred through tail club clouting.

 Enough delerious rambling..... off to bed for rest and recuperation!

 Darren Tanke
 Darren Tanke, Technician I, Dinosaur Research Program, Royal Tyrrell Museum
of Palaeontology, Box 7500, Drumheller, AB, Canada T0J 0Y0. (403) 823-7707;
(403) 823-7131 (fax). Paleo Interests: fossil identification, collection and
preparation, centrosaurine ceratopsians, Upper Cretaceous vertebrate faunas
of North America and East Asia, paleopathology; senior editor on annotated
bibliography of extinct/extant vertebrate dental pathology, osteopathy and
related topics (9,300 entries as of Feb. 7, 1996).