Saurornitholestes
Name:
Saurornitholestes
(Lizard bird thief).
Phonetic: Sore-or-nif-o-les-teez.
Named By: Hans-Dieter Sues - 1978.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Dromaeosauridae, Eudromaeosauria,
Saurornitholestinae.
Species: S. langstoni (type),
S.
robustus, S. sullivani.
Diet: Carnivore.
Size: Around 1.8 meters long.
Known locations: Canada, Alberta - Dinosaur
Park Formation, Oldman Formation. USA, Montana - Two Medicine
Formation, New Mexico - Kirtland Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Several specimens.
First
discovered in the Canadian Province of Alberta by Irene Vanderloh in
1974 and named by Hans-Dieter Sues in 1978, Saurornitholestes
was a small dromaeosaur that is thought to have been similar to the
Asian Velociraptor
in form. In 2006 a second species called
Saurornitholestes robustus was named by Robert
Sullivan. The
‘robustus’ part is in reference to the more robust build of the
thicker bones of this specimen which indicates that this species was
more heavily and powerfully built than the more northern types species
S. langstoni.
Like
with many other members of the Dromaeosauridae, Saurornitholestes
would have had a small skull and jaws, but did possess the large
sickle shaped claws that are a signature feature of this group that
were probably the primary killing weapons. Saurornitholestes
is
usually depicted as a low level predator that would have focused upon
hunting similarly sized dinosaurs and other small vertebrates like
mammals and lizards. There is fossil evidence however that upon at
least one occasion a Saurornitholestes fed upon the
giant pterosaur
Quetzalcoatlus,
although the specimen of this pterosaur is thought to
have come from a juvenile and hence smaller individual. It’s also
possible that the Quetzalcoatlus in question may
have already been dead
and that the Saurornitholestes had scavenged the
body, commonplace
behaviour for predatory animals today that rarely pass up the chance
for a free meal.
Saurornitholestes
would have faced predatory competition from other small theropods like
Dromaeosaurus
and Troodon
that were actually distantly related to
Saurornitholestes. However none of these dinosaurs
were the apex
predators of Late Cretaceous North America, that title belongs to the
tyrannosaurs and there is fossil evidence to lend some support to
this. A dentary (lower jaw bone) from the Dinosaur Park Formation
was described in 2001 by Aase Roland Jacobsen as having tooth marks
in the form of grooves across the bone. Although the size and spacing
of the marks is similar to that of another dromaeosaur, the shape is
closer to that of tyrannosaur teeth. Together this leads to the
conclusion that Saurornitholestes was eaten by a
juvenile tyrannosaur,
something which is actually quite likely when you consider that
juvenile tyrannosaurs had proportionately longer legs than adults
which means that they could have run faster by comparison and with some
juvenile tyrannosaurs showing similar leg proportions to ornithomimid
dinosaurs (thought to possibly be the fastest dinosaurs), a
dromaeosaur like Saurornitholestes would have had
no chance of escape
by running away.
The
exact culprit of this kill is still unknown, but two tyrannosaur
genera that are from the Dinosaur Park Formation at the same time as
Saurornitholestes are Daspletosaurus
and Gorgosaurus
(a third
tyrannosaur called Albertosaurus
is also known from this formation but
from a later period in the Cretaceous). Gorgosaurus
is of
particular interest since this had a more gracile build than
Daspletosaurus meaning it would likely have been the
faster of the
two. Southern populations of Saurornitholestes
would have also had to
live in the shadow of a different kind of tyrannosaur, the slightly
shorter snouted Bistahieversor.
Further reading
- A new small theropod dinosaur from the Judith River Formation
(Campanian) of Alberta Canada. - Zoological Journal of the Linnean
Society 62:381-400. - Hans-Dieter Sues - 1978.
- Saurornitholestes robustus is a troodontid
(Dinosauria: Theropoda).
- Canadian Journal of Earth Sciences, v. 51, p. 730–734. - D. C. Evans,
D. W. Larson, T. M. Cullen & R. M. Sullivan - 2014.
- Cranial Anatomy of New Specimens of Saurornitholestes langstoni
(Dinosauria, Theropoda, Dromaeosauridae) from the Dinosaur Park
Formation (Campanian) of Alberta. - The Anatomical Record. 303 (4):
691–715. - Philip J. Currie & David C. Evans - 2020.
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