Sauropelta
Name:
Sauropelta
(Lizard shield).
Phonetic: Sore-oh-pel-tah.
Named By: John Ostrom - 1970.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ankylosauria, Nodosauridae.
Species: S. edwardsorum (type).
Diet: Herbivore.
Size: Around 5 to 6 meters long.
Known locations: USA, Wyoming and Montana -
Cloverly Formation.
Time period: Aptian to Albian of the Cretaceous.
Fossil representation: Many specimens.
Sauropelta
is one of the better known nodosaurids,
armoured dinosaurs that are
thought to be ancestral to the later and more heavily armoured
ankylosaurids. This armour was in the form of lots of osteoderms
(bony plates that are held within the skin that are also sometimes
called scutes) that varied greatly in size over different parts of
the body. The largest of these were huge spines that were attached to
the neck, and while earlier reconstructions conceived these to belong
to a single row on each side of the neck, new interpretations have
the spines forming two parallel rows on each side of the neck. The
upper row of spines pointed up and backwards, while the lower row
pointed out to the side at a backwards angle, together forming an
exceptional defence for what is traditionally one of the most
vulnerable areas of an animal’s body.
As
a relatively slow dinosaur, the armour would have been the single
best chance that Sauropelta had of surviving attack
from predators.
One predator from the Cloverly Formation that Sauropelta
may have had
contact with is Deinonychus.
The large spines that rose up from the
neck and shoulders in particular would have made it incredibly
difficult for a dromaeosaurid like Deinonychus to
jump onto the back of
Sauropelta and stab at its neck, a tactic that is
thought to have
been favoured by dromaeosaurids,
and may have been the reason why
Sauropelta evolved to have such a defence around its
neck.
Sauropelta
also had an exceptionally long tail, in fact half of its body length
was actually tail. This tail was supported by a network of tendons
that kept it off the ground, but it is uncertain if it could have
used its tail to strike at attacking predators, something that has
been proposed for the earlier Gastonia.
As with other nodosaurids,
Sauropelta had forelegs that were shorter than the
rear legs,
something that would have given it a posture where its mouth was
closer to ground which would have helped it in its life as a low
browser.
Study
of the fossil sites that Sauropelta is from has
indicated that these
parts of Montana and Wyoming would have been low lying wetland that was
an expanse of rivers and floodplains during this stage of the
Cretaceous. The narrow mouth and leaf shaped teeth of Sauropelta
suggest that it would selectively browsed upon the low growing soft
vegetation that would have been in this area. Other herbivorous
dinosaurs from the Cloverly Formation that Sauropelta
would have shared
this habitat with are the ornithopods Tenontosaurus
and Zephyrosaurus.
Further reading
- Stratigraphy and paleontology of the Cloverly Formation (Lower
Cretaceous) of the Bighorn Basin area, Wyoming and Montana. - Bulletin
of the Peabody Museum of Natural History 35: 1–234. - John H. Ostrom -
1970.
- Skeletal reconstruction and life restoration of Sauropelta
(Ankylosauria: Nodosauridae) from the Cretaceous of North America. -
Canadian Journal of Earth Sciences 21 (12): 1491–1498. - Kenneth
Carpenter - 1984.
- Description of a new skull of Sauropelta cf. S.
edwardsi Ostrom, 1970
(Ornithischia: Ankylosauria). - Journal of Vertebrate Paleontology 21
(Supplement to 3 - Abstracts of Papers, 61st Annual Meeting of the
Society of Vertebrate Paleontology): 87A. - William L. Parsons
& Kristen M. Parsons - 2001.
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