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Tyrannosaur paleopathologies, updates.



 I've been following the "falling down tyrannosaurs" discussion with some
degree of mirth. I'd thought this discussion had died out long ago....

 Anyhow, as I work on (dig up and prepare) tyrannosaurs here at Tyrrell and
study paleopathology (ancient disease and injuries) I thought I'd add a few
points.

 1. Someone was asking about articles on bipeds falling. I searched my
ongoing osteopathy bibliography and came up with nothing really relevant
short of apes falling out of trees and suffering arm injuries, or Mountain
Sheep falling off of high cliffs (no survivors there I'm afraid).

 2a. Tyrannosaurus "Sue" injuries. I saw the actual specimen just before it
was taken away. The fractured and HEALING leg bone was the fibula. There was
also a fusion of two mid-caudal vertebrae, and associated healed/healing
facial bites, presumably intraspecific in origin. 
 2b. I have seen people commenting on the T. rex tooth embedded in Sue's
neck and must protest. I saw this and held it in my hands. The bone was an
elongated rib section with an enlarged, swollen end that was hollowed out on
one end. Inside was a foreign object that could not immediately be
identified. I am suspicious about this being an injury incurred by Sue for
the following reasons:
     The internal structure and surface texture of the bone did not even
look tyrannosaurid- it looked like ornithischian (ie. duck-billed dinosaur)
bone.   
     The bone had a fresh break (ie. broken during excavation) on one end.
When I asked BHIGR staff as to the whereabouts rest of the bone they
shrugged their shoulders. They said it came from the quarry (which has
already yielded hadrosaur bone), but they were not sure which bone it came
from. As I recall, the piece did not remind me of a tyrannosaur neck rib or
neck vertebra.
     The pathological swelling did not fully encapsulate the tooth.
     The "tooth" looked like a tooth at first glance, but under differing
light angles it also appeared to be an ironstone nodule that had simply
become lodged inside the cavity. In a case of a mosasaur having its tail
bitten by a Shark, the Shark tooth was firmly embedded in the vertebrae and
locked into position by reactive bone tissue. In Sue's case, the "tooth"
could have rattled around inside- it was not encapsulated.
     The bone had all the appearances of a hadrosaur rib with an improperly
healed fracture- a pseudoarthrosis, which in some cases forms a deep
pocket-like structure on the end of the rib (at the fracture site), with a
small stone finding its way inside through the open end.   

 3. Getting back to 2a, I emphasize HEALING as the fibula fracture callus
had not been remodeled/resorbed so the injury had not fully HEALED.
Tyrannosaur fibula fractures appear to be not uncommon. I have not had the
opportunity to examine all tyrannosaur skeltons known, but I can say that
based on what I have seen, fibular fractures in tyrannosaurs are not that
rare, perhaps 10-15% so affected. I want to give a higher percentage number
but I am being cautious here. In fact, when a new tyrannosaur fibula or
skeleton with fibula is found, I am not the least bit surprised when someone
tells me it was injured in life. Fibular fractures are known in subadult and
adult animals. I know of no femur or tibia fractures showing any sign of
healing. The tyrannosaur I finished mounting in May had a lesion on its
tibia, but only because of a spur-like exostosis growing from the fibula
fracture callus that had projected into the tibia shaft and irritated the
bone tissue there. While a fibula fracture is serious, I suspect that, like
modern animals in a forested area, the injured animal would lay down and
hide in the undergrowth and wait for 14 or so days for healing to take
place. I don't know what the healing rate would be in theropod dinosaurs,
but given their widely accepted active lifestyle, "warmbloodedness" and
bird-like status I would suspect healing rate would be more akin to extant
birds (which take about 12-14 days for leg and wing fractures to heal). All
the tyrannosaur fibular fractures I've seen are healed back into a straight
or relatively straight line. Amazing, considering no medical help back
then.... This indicates the animal was immobilized for some time. Any animal
that repeatedly moves a fractured bone will form a "pseudoarthrosis" or
"false joint". For example, if I break a rib and don't immobilize the
fracture site, the rib can heal as two separate sections. This is well known
in horned dinosaur posterior dorsal ribs here at Tyrrell. What I find
particularly interesting about tyrannosaur fibula fractures is that all are
in HEALING mode, but not close to, or fully HEALED. I imagine the animal
breaking its leg, hiding in the undergrowth, healing its fracture, only to
die of other causes, such as infection, starvation, intraspecific predation
(yes, tyrannosaurs ate tyrannosaurs- we have tyrannosaur bone with
undisputed unhealed tyrannosaur toothmarks on them), thirst, or other
complications. Once the leg was healed enough to put weight on it, I can't
see the hungry animal suddenly running off in search of prey. I can see the
pained animal with a stiff leg limping or walking slowly at first. Potential
prey could run away, so scavenging might have been the only source of food
for the first little while. It would also be exposed to the predations of
rival tyrannosaurids. Tough times back then......

 4. Humeri fractures are known in tyrannosaurs. It was suggested they
fractured during sleep or copulation- perhaps they are fall-related.

 5. Tyrannosaurs were obviously built for speed. While, like modern fast
predators they probably walked or simply laid about most of the time, they
certainly could run when the need arose. They were large, active animals.
And as big, active animals they fell down from time to time. Remember: "The
bigger they are the harder they fall". Some fell and died or were injured.
Don't deny it. Some were even killed by their prey (it happens today). But
such events were rare and had no real impact (no pun intended) on the
tyrannosaur population structure as a whole. If falls were so detrimental to
tyrannosaurs, they would have evolved a "safety device" long ago or gone
extinct from falling down all the time.

 6. While on the topic of tyrannosaurs, some new updates from Tyrrell:

 A). The possible new tyrannosaur from Edmonton did not turn out to be
anything significant.
 B). Another tyrannosaur skull has been found in Drumheller. This is an
adult skull, the top of the head is showing. This is not the same as the new
tyrannosaur from Drumheller reported in my last posting- so we now have two
new tyrannosaurs from the Drumheller valley area in just the past 1.5
months. All these tyrannosaurs........ we must be the world capital for them. ;)
 C). During SVP'96 Phil Currie was looking at tyrannosaur material at the
AMNH. All times previously he looked at cranial material only.
Well........... on this trip he looked at postcrania only and discovered
this amazing piece of information: In 1910, Barnum Brown found a tyrannosaur
bonebed near Drumheller, containing articulated skeletons! But........ there
was so many specimens that he could high-grade, so he just collected one
hind leg and about 6 left feet! A tyrannosaur pack mass mortality event??
Site locality information is poor, but we have some photographs which show
surrounding scenery so we might be able to relocate the site. Keep
posted........
 D). I'm to mount a cast of the AMNH T. rex between now and the next field
season. It will be mounted crouched low down and mean-looking.
 E). Also during this time, I'll be preparing a virtually complete,
disarticulated and largely uncrushed juvenile/subadult DASPLETOSARUS skull.   
 F). Previously I reported on a tyrannosaur jaw with embedded tyrannosaur
tooth and healing. I may have jumped the gun on that one. The embedded tooth
is tyrannosaur, but the "healing" appears to be a combination of hard
iron-rich silt/sandstone and bone with unusual texturing. So we have the
bullet but no smoking gun..........  

 7. I read somewhere once that most fibula fractures in Man are related to
twisting falls, such as falling down while skiing.

 Darren Tanke, Tyrrell Museum.
 Darren Tanke, Technician I, Dinosaur Research Program, Royal Tyrrell Museum
of Palaeontology, Drumheller, Alberta, Canada. 
 Interested in all aspects of centrosaurine ceratopsians, paleopathology,
recent and fossil dento- and osteopathy; senior editor on annotated
bibliography of extinct/extant vertebrate dental pathology, osteopathy and
related topics (10,035 entries as of Oct. 16, 1996). 

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