On "SICK DINOSAURS" (RESEARCH UPDATE)

["Darren Tanke" <dtanke@dns.magtech.ab.ca>]

 There was a recent posting asking about sick dinosaurs and evidences for
this, so I thought seeing how I am into dinosaur paleopathology (the study
of ancient disease, injuries and related topics), I would take this
opportunity to bring the group up to speed on some of the latest
knowledge/research:

 1. Illness. Dinosaurs could have (and probably did) suffer from a wide
variety of illnesses, many of which we will never be able to diagnose
successfully, if ever. Simply put, we need some evidence of the illness and
without physical proof of the disease process (as manifested on teeth,
bones, skin impressions, footprints) we can never really know. For example,
dinosaurs could have suffered from colds, but colds do not leave any lesions
(marks) on bones. Dinosaurs could have suffered from liver cancer, but we'd
never know it. I was once told that over 99% of current diseases leave no
traces of their passing on bones so we are limited to less than 1% to deal
with. Given the rarity of animals developing massive bone pathologies and
the taphonomic and preservational bias against all bones ever being
fossilized (let alone found before modern erosion destroys them) it is
remarkable that we ever find anything. But we do. I have the fortune of
living in Alberta, Canada where dinosaur remains (single bones, skeletons,
bonebeds) abound so my comments below will rely heavily on Albertan material.

 2. Skin impressions. These do not show pathological conditions so far, but
I think it is just a matter of time before healing/healed cuts and tears
show up on fossil specimens. Possible external parasite damage was suggested
in one British specimen. Also, dinosaur skin impressions show a highly
beaded texture with lots of nooks and crannies which would have been ideal
niches for ectoparasites to lodge.

 3. Parasites. Fully modern-appearing ticks, mosquitoes and gnats (family
Ceratopogonidae) and others were around in the Late Cretaceous and could
have fed on dinosaurs and spread a variety of pathogens. Several species of
gnats preserved in amber show specialized mouthparts which the researcher
thought indicated they were adapted to feeding on dinosaurs, especially on
the softer tissues, for example around the eyes of hadrosaurs or the
underside of horned dinosaur frills. Internal parasites are of course
unknown, but given every animal today is the host of some sort of internal
parasite, it is certain dinosaurs were similarly affected. 

 4. Footprints. Surprisingly, footprints can also show evidences of
pathology. Missing or deformed toes are known from some trackways. In
theropods, the affected toe is usually the outside one (Digit IV). Most
surprising to some is evidence of limping dinosaur trackways. These are
known in theropods and sauropods. These types of trackways are the only
circumstantial evidence that dinosaurs probably suffered pain. See:

 Lockley, M.G., Hunt, A.C., Moratalla, J. and Matsukawa, M. 1994. Limping
Dinosaurs? Trackway Evidence for Abnormal Gaits. Ichnos, 3:193-202.

 5. Teeth. Isolated teeth are very common as fossils. Most striking to me
for the Albertan material is the total absence of dental caries or tooth
decay. Dinosaurs replaced their teeth on a continuous and regular basis and
because of this, the teeth were lost before caries could develop. Tooth
fractures, especially in large theropods (ie. tyrannosaurs) are quite
common. Often the tip, tip and side, or tip and both sides of the tooth
crown were snapped off while feeding or fighting. Sometimes the tooth is
snapped off right to the base. Many of these broken teeth were retained in
the jaws and show post-trauma wear facets, indicating even though they were
broken, they were retained in the mouth for an extended period. Some teeth
show anomalous serration patterns of either the occluding tooth, or the
impacting tooth of an aggressor. An unusual basal divergence of the
serration row into 2 rows (nicknamed "splitters") may have a genetic basis; see:

 Erickson, G.M. 1995. Split Carinae on Tyrannosaurid Teeth and Implications
of Their Development. Jour. Vert. Paleo., 15(2):268-274. 

 A theropod tooth fracture paper: Farlow, J.O., Brinkman, D.L., Abler, W.L.
and Currie, P.J. 1991. Size, Shape and Serration Density of Theropod Lateral
Teeth. Mod. Geol., 16:161-198.

 6. Bones. Bones tell us the most about dinosaur disease and injuries. Bone
is not static and unchanging, but a living tissue that is continuously
resorbed, remodelled and restructured. It reacts in a variety of ways to
certain pathological conditions. These reactions are often similar over vast
geologic time and taxonomically diverse extinct and extant vertebrates. This
commonality allows us to extrapolate and compare disease processes in
extinct vertebrates to those living today, although such interpretations
(especially in older literature) were often incorrect. Despite modern
medical technological advances (CT scans, MRI, etc.), and our increased
knowledge-base of pathology gained over time, diagnosis of bone pathology
due to disease (ie. non-fracture) processes continues to be a challenge to
this day. Often such diagnoses are contentious; this is why I am more
interested in occurrences of fractures- where they are on the skeleton, with
what frequency, what age group is affected, and combining this all to ask
the question: WHY? What behavior or repetitive activity does the dinosaur
family engage in to cause these injuries?
  a. Most bone pathologies I have seen are healing/healed fractures or
healing/healed fractures with subsequent infection (osteomyelitis).
Distribution and relative frequency of healed fractures tells a story. I
won't get into all of them here, but I'll relate a couple. Hadrosaurs show
much evidence for bone trauma. I have seen some very serious ones, such as
jaw fractures or massive pelvic fractures. It is indeed remarkable these
animals survived such injuries, considering the total absence of veterinary
care. Injured animals probably crawled off into the heavy vegetation and
remained stationary. They would then live off body fat reserves in order to
recover from major bone traumas. In herding species, injured animals were
likely afforded some degree of protection by remaining relatively anonymous
among a large herd of many thousands. Hadrosaurs also show much damage on
their tails. Most telling are massive crush fractures to the end of the
tail, where each individual vertebrae are broken into as many as 5 pieces
(typically 2) which have then fused back together, or series of up to 4
(again typically two) crushed and fused vertebrae. Many of these specimens
show marked angulation which would have imparted a "kink" to the end of the
tail. Tyrannosaurs suffered numerous fractures too. Fibula fractures are
often attributed to being whacked on the lower leg by an ankylosaur tailclub
although other interpretations, such as a twisting fall should be
considered. Tyrannosaurs often show healed/healing fractures of the ribs and
gastralia- no doubt due to high impact falls. Remember, tyrannosaurs did not
have arms long enough to break a fall and would have landed with much force.
The saying "The bigger they are, the harder they fall" would suit
tyrannosaurs admirably! See:

 Farlow, J., Smith, M.B. and Robinson, J.M. 1995. Body Mass, "Strength
Indicator", and Cursorial Potential of Tyrannosaurus rex. Jour. Vert.
Paleo., 15(4):713-725.

  b. DISH. Diffuse idiopathic skeletal hyperostosis or "DISH" is often seen
in sauropod tail vertebrae. One poster on this list called this "arthritis",
but this is NOT so. True cases of arthritis in dinosaurs are EXTREMELY RARE.
Despite its nasty appearance, DISH is actually not a true osteopathy, but
rather, the bodies way of dealing with stress points along the vertebral
column. DISH can be found in Man. For good articles on DISH, see:

 Rothschild, B.M. 1985. Diffuse Idiopathic Skeletal Hyperostosis:
Misconceptions and Reality. Clin. Rheum. Prac., 4:207-211.

 Rothschild, B.M. and Berman, D. 1991. Fusion of Caudal Vertebrae in Late
Jurassic Sauropods. Jour. Vert. Paleo., 11(1):29-36.

 c. Arthritis is often mentioned as occurring in dinosaurs, especially in
regards to vertebral fusions. Arthritis affects joints (ie. fingers/toes,
wrist/ankle, elbow/knee, shoulder/hip), and not vertebral articulations. The
misuse of this term "arthritis" is one of semantics. Vertebral fusions are
either DISH or another pathological condition called "spondylitis
deformans". Arthritis is known in 2 members of the IGUANODON herd in
Belgium, where the foot is affected. Gout in an unspeciated tyrannosaur from
Dinosaur Provincial Park, Alberta and the T. REX popularily called "Sue" is
known, but these are all rare cases. For the gout paper see:

 Rothschild, B.M., Tanke, D.H. and Carpenter, K. 1997. Tyrannosaurs Suffered
>From Gout. Nature, 387:357.

 For the paper on true "artritis" in dinosaurs, see: 

 Rothschild, B.M. 1990. Radiologic Assesment of Osteoarthritis in Dinosaurs.
Ann. Carnegie Mus., 59:295-301.

 d. Osteomyelitis. Osteomyelitis or generalized bone infections are known.
It is often secondary to a bone fracture that has become infected. Often
massive new amounts of bone are developed, and with a characteristic bubbly
texture, sometimes with larger holes to allow the drainage of pus (a
pyogenic infection).
 e. Face-biting in theropods. Dr. Philip Currie has co-authored a paper with
me on excellent evidence of intraspecific (same species) fighting in some
large theropods, particularly tyrannosaurids and the Chinese theropod
SINRAPTOR. This paper is "in press" in the upcoming GAIA theropod
paleobiology volume. Look for:

 Tanke, D.H. and Currie, P.J. "in press". Head-Biting Behavior in Theropod
Dinosaurs: Paleopathological Evidence. GAIA, Theropod Paleobiology Volume.

 Skulls of some large theropods often show bite marks. These lesions are
virtually identical to toothmarked dinosaur prey (ie. hadrosaur) bone, but
with one major and compelling difference- the wounds show signs of healing!
So we know for sure that some large theropods fought and were biting each
other on the head. More on the SINRAPTOR face-bite injuries can be found at
my homepage: 

   http://dns.magtech.ab.ca/dtanke  

 Click on the link "About the fighting dinosaurs". Why are they doing this?
We considered various possibilities, and concluded that territoriality or
fighting for food or status within a grouping likely causes. Fights for
mates were ruled out in those cases where the animals were only half grown
(and unlikely to be engaging in reproductive behaviors). Most interesting
were healing bite marks on T. rex. I think you'd all agree the only animal
big and brave enough to bite a T. rex on the head would be another T. rex.
Which brings up the question of whether T. rex was a pure scavenger or
predator. I feel that if a T. rex had the gumption to bite another T. rex on
the head (and risk retaliatory bites causing injuries/death) there is no
reason to reject the possibility that T. rex was fully capable of biting
prey animals (ie. hadrosaurs) on the head too. The study of paleopathology
provides a powerful tool for determination of some aspects of dinosaurian
bvehavior pattterns.

 f. Hemangioma. Benign bone tumors in an unspeciated dinosaur from the
American Jurassic has recently been published; see:

 Rothschild, B.M., Tanke, D.H., Hershkovitz, I. and Schultz, M. 1998.
Mesozoic Neoplasias: Origins of Haemangioma in the Jurassic Age. Lancet,
351(9119):1862.

 g. Some sort of "bone-eating disease". Horned dinosaur frills sometimes
show "extra" holes which completely pierce through the bone. This are
typically ascribed to horn thrust injuries incurred during fighting.
However, I am finding unusual bone lesions on the inside of the frill that
erode down into the bone, often quite deeply. Given time these lesions could
erode and expand forming classic "horn thrust injuries". Unfortunately there
is no comparable disease today that I am aware of. Just like how life
evolves and goes extinct, diseases (and their effects on bone) come and go,
leaving us now with some perplexing questions. These types of lesions are
not infection-related.
 h. New research. A colleague of mine is presently pursuing an exciting line
of research which involves the comparison of dinosaur fracture callus with
that of modern vertebrates of known physiologies. It is hoped that direct
comparison at the histological level with provide clues as to the
physiologies (ie. "warm/cold-blooded") of dinosaurs. Hopefully we will learn
some day how fast (or slow) dinosaurs repaired their bone injuries.

 Finally, a couple other more recent citations for those interested in
pursuing this subject further. These papers provide a broad overview as to
the current status of this interesting field:

 Rothschild, B.M. and Martin, L.D. 1992. Palaeopathology- Disease in the
Fossil Record. CRC Press, Boca Raton, Florida. 386 pp.

 Rothschild, B.M. 1997. Dinosaur Paleopathology. pp. 426-448. In: The
Complete Dinosaur. Edited by J. Farlow and M.K. Brett-Surman. University of
Indiana Press, Bloomington.

 Rothschild, B.M. and Tanke, D.H. 1992. Paleopathology: Insights Into
Lifestyle and Health in the Geological Record. Geoscience Canada, 19(2):73-82. 

 Tanke, D.H. and Rothschild, B.M. 1997. Paleopathology. pp. 525-529. In:
Encyclopedia of Dinosaurs. Edited by P.J. Currie and K. Padian. Academic
Press, San Diego. 869 pp.

 Best,

 Darren Tanke

 
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FAEVUS QUAESITOR SCIENTIA                                  FODERE AUT CADERE

DARREN TANKE, Technician I, Dinosaur Research Program, ROYAL TYRRELL MUSEUM
OF PALAEONTOLOGY, Box 7500, Drumheller, Alberta, CANADA  T0J 0Y0 and:

Senior editor of: Annotated Bibliography of Paleopathology, Dento-Osteopathy
and Related Topics. 12,702 citations as of January 28, 1999.
For details, visit the bibliography homepage at: http://dns.magtech.ab.ca/dtanke
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