Brachychampsa
Name:
Brachychampsa.
Phonetic: Brak-y-cham-sah.
Named By: Charles W. Gilmore - 1911.
Synonyms: Brachyuranochampsa.
Classification: Chordata, Reptilia,
Crocodylomorpha, Crocodylia, Alligatoroidea, Globidonta.
Species: B. montana
(type), B. perrugosus, B. sealeyi?
Diet: Carnivore.
Size: About 2.5 to 3 meters long.
Known locations: Across the USA including Colorado,
Montana, New Jersey, New Mexico, North Dakota, South
Dakota, Texas and Wyoming. Also Saskatchewan of Canada and now
also Kazakhstan.
Time period: Turonian of the Cretaceous through to
the Lutetian of the Eocene.
Fossil representation: Well over a hundred
individuals of varying degrees of completeness.
The
crocodiles seem to have been quite resilient to the effects of the KT
extinction sixty-five million years ago that marked the death of the
dinosaurs, as Brachychampsa is yet another genus
of crocodylian that
is known to have existed for several million years before and after
this extinction event. Dyrosaurus
is another crocodile genus also
known to have lived before and after the KT extinction.
The
snout of Brachychampsa was short, blunt and
rounded across the
front, and is immediately alligator-like at first glance. The teeth
of Brachychampsa are not only conical and robust,
but have round
pommel-like caps on the tips. These teeth are not for puncturing and
holding flesh like the teeth of other crocodiles, but for breaking up
the hard shells of invertebrates like crustaceans. Similar teeth can
be found on some other reptiles that are shelled prey, the mosasaur
genus Globidens
being one particularly good example.
This
ties in
well with the known distribution of Brachychampsa
in North America
which mostly seems to follow the coastlines of the old Western Interior
Seaway that submergered the central portion of North America in the
late Cretaceous and Paleocene. Also of interest is that the
disappearance of the genus Brachychampsa also
loosely coincides with
the gradual closing off and disappearance on the Western Interior
Seaway.
Classification
wise, Brachychampsa has often been considered as
an aliigator-like
crocodile, and in the past the genus has even been placed within the
Alligatoridae and Alligatorinae. Most modern analysis however places
the Brachychampsa genus within the Alligatoroidea,
so that the genus
is referred to as an alligatoroid. Within this group Brachychampsa
is
considered a globidont. There is some conetention about the species
B. sealeyi becasuse not everyone considers it to
be valid. Those
who do not count it as a synonym of the species B. montana,
on the
basis that the type specimen of B. sealeyi is a
juvenile of B.
montana. However not everyone agrees with the
identification of the
B. sealeyi specimen as a juvenile B.
montana, and so B. sealeyi
continues to be listed.
Further reading
- A new fossil alligator from the Hell Creek Beds of Montana -
Charles W. Gilmore - 1911.
- Fossil vertebrates from the Late Cretaceous Lance Formation,
eastern Wyoming - R. Estes - 1964.
- The Late Cretaceous alligatoroid Brachychampsa montana
(Crocodylia): new material and putative relationships - M.
A. Norell, J. M. Clark & J. H. Hutchison -
1994.
- ?Brachychampsa sealeyi, sp. nov.,
(Crocodylia,
Alligatoridea) from the Upper Cretaceous (Lower Campanian)
Menefee Formation, northwestern New Mexico - T. E.
Williamson - 1996.
- Brachychampsa montana Gilmore (Crocodylia,
Alligatoroidea)
from the Kirtland Formation (upper Campanian), San Juan Basin,
New Mexico - R. M. Sullivan & S. G. Lucas.
- Alligatorine phylogeny and the status of Allognathosuchus
Mook,
1921 - C. A. Brochu - 2004.
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