Estemmenosuchus
Name:
Estemmenosuchus
(Crowned crocodile).
Phonetic: Ess-teh-men-oh-soo-kuss.
Named By: Chudinov - 1960.
Synonyms: Anoplosuchus tenuirostris,
Estemmenosuchus uralensis, Zopherosuchus luceus.
Classification: Chordata, Synapsida,
Therapsida, Dinocephalia, Estemmenosuchidae.
Species: E. uralensis, (type)
E. mirabilis.
Diet: Herbivore.
Size: E. uralensis about 4.5
meters long, E.
mirabilis about 3 meters long.
Known locations: Russia, Perm region.
Time period: Wordian of the Permian.
Fossil representation: Several specimens of complete
and partial remains of individuals, including skin impressions.
Although
other herbivorous therapsids like Styracocephalus
also had head
crests, Estemmenosuchus had by far the most
elaborate head
ornamentation. These crests varied between the two species, but
superficially the head ornamentation resembled short deer antlers.
The horns of Estemmenosuchus grow upwards from the
frontal skull bones
and seem to have primarily been display devices.
As
with many of the therapsids the exact diet of Estemmenosuchus
is still a
subject of debate amongst palaeontologists. Some have pointed to the
sharp canines and incisors and declared Estemmenosuchus
to be a
carnivore. However many of the herbivorous tharapsids still support
carnivore like teeth, and the sheer bulk and size of the body suggest
that it was shaped to incorporate a large digestive system. As a
general rule herbivores have larger bodies to accommodate a longer and
more complex digestive system because plant matter takes longer to
digest than animal meat. This is why most palaeontologists consider
Estemmenosuchus to be a herbivore, although some
concede that it may
have supplemented its plant diet with meat and if this were true,
then Estemmenosuchus would be an omnivore.
Another
piece of evidence to support the herbivore theory is how the legs are
orientated. The rear legs are situated directly under the hips
supporting the body weight from underneath. By themselves this would
suggest that Estemmenosuchus spent a lot of time
walking as it would
provide a more energy efficient form of locomotion. The front legs
however sprawl out to the sides similar to how you see them in modern
lizards. While this has been suggested to improve manoeuvring so that
the head ornamentation is pointed towards a rival Estemmenosuchus,
or
even a potential predator, a more obvious benefit is that these legs
would allow Estemmenosuchus to lift its forward
upper body up and
down, kind of like it was doing push ups. This pairing of different
limb attachments would suit a herbivore better than a carnivore because
it would still allow for more efficient walking when Estemmenosuchus
searched for suitable food, while also allowing Estemmenosuchus
to
lower its head to the ground for easier low level browsing.
The
large size and bulk of Estemmenosuchus have also
brought the suggestion
that Estemmenosuchus was gigantothermic. This is
where an animal has
a low surface area to body mass ratio resulting in the outer tissue
layers insulating the inner layers. This increases the base
temperature of the animal giving it a metabolism close to a warm
blooded creature without the usual adaptations that would suggest it
was warm blooded.
Further reading
- Diagnosen der Therapsida des oberen Perm von Ezhovo [Diagnoses of
Therapsida of the Upper Permian of Ezhovo]. - Paleontologischeskii
Zhural, 1960, n. 4, p. 81-94. - P. K. Chudinov - 1960.
- New facts about the Fauna of the Late Permian of the U.S.S.R. -
Journal of Geology, v. 73, p. 117-130. - P. K. Chudinov - 1965.
- Estemmenosuchus and primitive theriodonts from
the Late Permian. -
Paleontological Journal 34 (2): 184–192 - M. F. Ivakhnenko - 2000.
- Tetrapods from the East European Placket—Late Paleozoic Natural
Territorial Complex.. - Proceedings of the Paleontological Institute of
the Russian Academy of Sciences 283: 200. - M. F. Ivakhnenko - 2001.
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