Name:
Brontomerus
(Thunder thigh).
Phonetic: Bron-toe-meh-rus.
Named By: Michael P. Taylor, Matthew J. Wedel
& Richard L. Cifelli - 2011.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropoda, Macronaria, Camarasauromorpha.
Species: B. mcintoshi (type).
Type: Herbivore.
Size: Approximately 14 meters long.
Known locations: USA, Utah, Cedar Mountain Formation.
Time period: Aptian to Albian of the Cretaceous.
Fossil representation: Two fragmentary specimens,
representing two animals of different ages.
Brontomerus
has been given its name for good reason, it had possibly the largest
thigh muscles of all the known sauropods.
This has been established
from the proportionately large ilium that also projects forward. The
ilium is where the thigh muscles attach and this enlargement not only
suggests enlarged muscles but a degree of strong forward motion,
possibly even being able to deliver a kick.
One
theory, and easily the most popular since its description was
published, is that these powerful legs were used to fight back against
predators like Deinonychus
that would have been common during the time
of that location. Such a kick might have also been used in dominance
contests where two males might stand side to side and kick each other
until one concedes defeat for mating rights over the herd. A
second is that it was an evolutionary adaptation for walking up and
down slopes in hilly environments. As Brontomerus
went up steep
inclines it would inevitably have to go down them, and a thigh that
provided strong support either way would give it a significant
advantage over its other sauropod relatives.
The
ilium also has attachments for abductor muscles which allow a leg to
draw away from the body. These muscles may have allowed Brontomerus
to
steady itself as it reared up on its legs to reach up and feed on
higher vegetation in a tree canopy. All
of the above theories are good, and more than one could be correct.
Although given the specialisation in the hip of Brontomerus
which does
not appear in other sauropods, it could be more likely that it
developed to deal with environmental factors of the location, and any
other secondary usages a result of this specialisation.
Unfortunately
the dig team that discovered and named Brontomerus
were not the first
to the dig site, and not only were many specimens removed, others lay
around broken. Only partial remains of the two individuals have been
recovered and between them, the legs are still unknown. Without further
fossil finds, the exact function of the powerful thigh muscles of
Brontomerus can only remain as theory.
Further reading
- Brontomerus mcintoshi, a new sauropod dinosaur
from the Lower
Cretaceous Cedar Mountain Formation, Utah, USA - Michael P. Taylor,
Mathew J. Wedel & Richard L. Cifelli - 2011.
- The early evolution of titanosauriform sauropod dinosaurs - M. D.
D'Emic - 2012.