Piveteausaurus
Name:
Piveteausaurus
(Piveteau’s lizard - after the French palaeontologist Jean
Piveteau).
Phonetic: Piv-e-tew-sore-us.
Named By: P. Taquet & S. P. Welles
- 1977.
Synonyms: Eustreptospondylus divesensis,
Proceratosaurus divesensis.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Megalosauridae, Afrovenatorinae.
Species: P. divesensis
(type).
Diet: Carnivore.
Size: Uncertain due to lack of remains, though
comparisons to other theropod fossils indicates that it was at least a
large theropod, possibly around the nine meter mark.
Known locations: France, Lower Normandy -
Marnes de Dives Formation.
Time period: Upper Callovian of the Jurassic.
Fossil representation: Braincase.
The
history of Piveteausaurus is one that is littered
with comparisons to
other theropod genera. The braincase that is the holotype fossil of
Piveteausaurus was first described in 1923 by
Jean Piveteau.
Fossils of other dinosaurs had been discovered in the same region as
this braincase all the way back to 1808 when fossils began to be
studied by Georges Cuvier (though the fossils were actually collected
many years before this). In 1861 another palaeontologist named
Richard Owen created a new species for the genus Streptospondylus
as
S. cuvieri from some of these fossils. To
Piveteau it seemed a
logical conclusion that the braincase he was studying belonged to this
species of Streptospondylus.
The
above remained unchallenged until 1964 when Alick Walker studied
the braincase (referenced as MNHN 1920-7) and declared it to
belong to a new species of Eustreptospondylus,
E. divesensis.
However the additional skeletal remains previously assigned to
Streptospondylus cuvieri were also assigned to the
new species of
Eustreptospondylus. In 1977, a new study by
Taquet and Welles
found the braincase to be unique enough to require its own genus and
hence the genus Piveteausaurus was created. A
2001 study by R.
Allain also found that there was no definitive link between the
braincase and other fossils, the result being that now only the
braincase is a valid specimen of Piveteausaurus.
Since this
creation Gregory S. Paul has considered the brain case to actually
represent a species of Proceratosaurus,
though thus far everyone else
continues to credit Piveteausaurus as a valid genus.
As
an actual living dinosaur Piveteausaurus was your
classic theropod,
bipedal, reduced fore arms, large skull mounted on a relatively
short S-curved neck. The brain case that is now the holotype of
Piveteausaurus has been considered to be comparable
to the brain cases
of larger specimens of Allosaurus.
Most larger specimens of
Allosaurus are just under the ten meter mark for
length (some
specimens suggest bigger but these are already discussed on the
Allosaurus page), so an estimate of around nine
meters long, give
or take one meter could be a realistic proposition for Piveteausaurus.
It should also be remembered that there are other theropods from the
Jurassic of France such as Poekilopleuron
and Dubreuillosaurus
that do
seem to have comfortably grown to nine meters long as well.
While
Piveteausaurus has been considered to be similar to
Eustreptospondylus, Proceratosaurus
and Ceratosaurus,
a 2004
study of another dinosaur named Piatnitzkysaurus
has found that this
was possibly one of the closest relatives of Piveteausaurus.
Further reading
- L'arri�re-cr�ne d'un dinosaurien carnivore de l'Oxfordien de Dives
[The braincase of a carnivorous dinosaur from the Oxfordian of
Dives], Jean Piveteau - 1923.
- Redescription du cr�ne de dinosaure th�ropode de Dives
(Normandie) [Redescription of a theropod dinosaur skull from Dives
(Normandy)], P. Taquet & S. P. Welles - 1977.
- Triassic reptiles from the Elgin area: Ornithosuchus and the
origin of carnosarus, A. D. Walker - 1964.
- Braincase structure of the Middle Jurassic theropod dinosaur
Piatnitzkysaurus, Rauhut - 2004.
- Redescription de Streptospondylus altdorfensis,
le dinosaure
th�ropode de Cuvier, du Jurassique de Normandie [Redescription of
Streptospondylus altdorfensis, Cuvier's theropod
dinosaur from the
Jurassic of Normandy], R. Allain - 2001.
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