Daspletosaurus
Name: Daspletosaurus
(Frightful lizard).
Phonetic: Das-pleet-oh-sore-us.
Named By: Dale Alan Russell - 1970.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Tyrannosauria, Tyrannosauridae .
Species: D. torosus (type), D.
horneri, D. wilsoni .
Type: Carnivore.
Size: 8-9 meters long.
Known locations: Canada, Alberta, Judith River
Group - USA, Montana, Judith River Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Six well preserved specimens
as well as other scattered bones.
Until
1970, Daspletosaurus was thought to be another
specimen of
Gorgosaurus.
Both were active at the same time and location as one
another, yet closer study of the Daspletosaurus
revealed a much more
powerful animal than the more lightly built Gorgosaurus.
It has been
surmised that the two predators may have focused their attention to
different prey groups with Daspletosaurus favouring
slower and more
durable prey items that may necessitate the need for extra power.
Possible dispute for this would come from a hadrosaur known to have
been killed by a Daspletosaurus, or it may just
be proof that as a
predator, it would take whatever it had chance too.
Although
older, Daspletosaurus is remarkably similar to Tyrannosaurus
with the main differences being smaller but heavier build, the feet
shorter and the teeth proportionally larger. This has led some to
conclude that Daspletosaurus was the ancestor of Tyrannosaurus,
while
others consider it to be a sub species, although no definitive
Tyrannosaurus remains have been found to date from
the same time as
Daspletosaurus.
Daspletosaurus
is a possible contender for social interaction leading
to pack hunting. At least two skulls show tooth marks that were
inflicted to the face, with one of the skulls belonging to a juvenile
showing that the tooth marks had healed over, indicating that the
bite was not intended to be fatal. Face biting occurs in other
predators, and can relate to a number of reasons including dominance
over a group subordinate, territorial dominance or possibly even
being inflicted during the mating process. An alternative explanation
however is that these marks were caused by an ailment such as a
parasitic infection.
In
Montana, the remains of three Daspletosaurus and
five hadrosaurs
have been found in a bone bed together. It’s unlikely that the bones
had been washed together via a river flow, and some consider this
evidence that Daspletosaurus may have formed
packs. Of the three
remains, one was an adult, another juvenile, but the age of the
third cannot be determined. However this only really proves that
three Daspletosaurus died in the same location.
The fact that the
hadrosaur remains outnumber the predators lends a little weight to this
as it asks the question, how can just three predators kill at least
five prey items in the same locale? If the hadrosaurs had been
trapped, it’s possible. Alternatively the hadrosaurs might have
been killed by something else such as a volcanic event involving the
discharge of toxic gas. Then roaming Daspletosaurs
happened upon
the bounty and were then themselves killed by further discharges of
gas. Another possibility is that the Daspletosaurs
were killed by
other predators in competition for the carcasses. The only other
explanation is that the hadrosaurs were killed and dragged to some kind
of lair. But why would three large predators waste energy by doing
that when they could eat their fill where they made the kill? While
there is other evidence to suggest the pack hunter theory in other
large theropods, here in this instance it is at best circumstantial.
Further reading
- Tyrannosaurs from the Late Cretaceous of western Canada. - National
Museum of Natural Sciences, Publications in Paleontology 1:1-34. - Dale
Russel - 1970.
- Gut contents from a Cretaceous tyrannosaurid: implications for
theropod dinosaur digestive tracts. - Journal of Paleontology 75 (2):
401–406. - David J. Verricchio - 2001.
- An unusual multi-individual tyrannosaurid bonebed in the Two Medicine
Formation (Late Cretaceous, Campanian) of Montana (USA). by Philip J.
Currie, David Trexler, Eva B. Koppelhus, Kelly Wicks & Nate
Murphy.
In The Carnivorous Dinosaurs, Indiana University Press. pp. 313–324,
Kenneth Carpenter eds. - 2005.
- Pre- and postmortem tyrannosaurid bite marks on the remains of
Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial
Park, Alberta, Canada. - PeerJ 3: e885. - D. W. E. Hone & D. H.
Tanke - 2015.
- A new tyrannosaur with evidence for anagenesis and crocodile-like
facial sensory system. - Scientific Reports. 7. - Thomas D. Carr, David
J. Varricchio, Jayc C. Sedlmayr, Eric M. Roberts & Jason R.
Moore - 2017.
- A transitional species of Daspletosaurus Russell, 1970 from the
Judith River Formation of eastern Montana. - PeerJ. 10. e14461. - El�as
A. Warshaw & Denver W. Fowler - 2022.
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