Efraasia
Name: Efraasia
(Named after the palaeontologist Eberhard Fraas who discovered the
first remains).
Phonetic: E-frayz-e-ah.
Named By: Peter M. Galton - 1973.
Synonyms: Sellosaurus fraasi,
Teratosaurus minor, Thecodontosaurus diagnosticus.
Classification: Chordata, Sauropsida,
Dinosauria, Sauropodomorpha.
Species: E. minor (type).
Diet: Herbivore.
Size: About 6 to 7 meters long.
Known locations: Germany - L�wenstein Formation.
Time period: Norian of the Triassic.
Fossil representation: Partial skull and post
cranial remains of juveniles.
The
early study of Efraasia was to say the least one
born out of
misconceptions. The first remains of this sauropodomorph
dinosaur
were being found way back in the latter half of the nineteenth
century, but they were being assigned to different genera. Some of
these genera were sauropodomorphs too, such as Sellosaurus
and
Thecodontosaurus,
though later revisions of the species created when
these fossils were added found the species did not actually compare
well to the type species of those genera. A species of
Thecodontosaurus, T. diagnosticus
has now been found to be
synonymous (the same as) the Efraasia type
species, while a
Sellosaurus species, S. fraasi
is also
synonymous. On a quick
side note the Sellosaurus type species is also now
treated as a synonym
to the famous Plateosaurus
which means that the whole Sellosaurus genus
is no longer valid. Perhaps most bizarre of these early mix-ups was
the adding of sauropodomorph remains that would later be identified as
belonging to Efraasia as to the rauisuchian
genus Teratosaurus,
creating a then new species called T. minor,
which is now a
synonym to Efraasia, though the actual Teratosaurus
genus is still
treated as valid thanks to the earlier named type species.
So
far Efraasia is only known from partial skull and
post cranial skeletal
remains, and probably those of juveniles, meaning that they were
not fully grown. This is why early size estimates of the genus credit
Efraasia as being between two and three meters
long, they were being
based upon the size of the known juvenile remains. Needless to say,
juveniles grow up into adults and adults would have been larger than
this two to three meter estimate. The first realistic adult size
estimate for Efraasia came to light in 2003 in
a subsequent study
of the genus by Adam Yates which suggested six and a half meters.
There
is still debate over whether Efraasia was bipedal
or quadrupedal. The
development of the wrists suggest that Efraasia may
have been able to
put weight on the forelimbs, but others have pointed out that the
forelimb bones (ulna and radius) could not pronate to point
straight down. The latter hints at a more bipedal mode of
locomotion, and the hands that were capable of grasping branches also
suggest that the forelimbs were of more use in feeding instead of
bearing weight. A middle ground could be Efraasia
being bipedal when
walking around, but then balancing upon the forelimbs when browsing
upon low growing vegetation or bending forward to drink. Balancing
though may only mean light weight bearing, with the majority of the
body weight being counterbalanced by the tail with the force of the
weight transmitted to the hips and down the rear legs.
As
a sauropodmorph Efraasia already shows signs of an
elongated neck
though not even close to the extremes of later sauropods. Despite the
slight elongation, the neck was still thin, with the bones
indicating only the minimum of necessary muscle support. With this in
mind Efraasia may have been at its developmental
limit before the more
radical skeletal changes of later sauropodomorphs. Gastroliths found
in association to Efraasia also indicate a more
exclusively herbivorous
diet for this dinosaur.
Further reading
- Die Dinosaurier der Europ�ischen Triasformation mit
ber�cksichtigung der Ausseurop�ischen vorkommnisse. - Geologische
und Palaeontologische Abhandlungen Suppl. 1(1): 1-419 -
Friedrich von Huene - 1908.
- On the anatomy and relationships of Efraasia
diagnostica (Huene)
n.gen., a prosauropod dinosaur (Reptilia: Saurischia) from the
Upper Triassic of Germany - Pal�ontologische Zeitschrift
47(3/4): 229-255. - Peter M. Galton - 1973.
- The cranial anatomy of the prosauropod dinosaur "Efraasia
diagnostica", a juvenile individual of Sellosaurus
gracilis from
the Upper Triassic of Nordw�rttemberg, West Germany - Stuttgarter
Beitr�ge zur Naturkunde B, 117: 1-15 - P. M. Galton
& R. T. Bakker - 1985.
- The species taxonomy of the sauropodomorph dinosaurs from the
L�wenstein Formation (Norian, Late Triassic) of Germany -
Palaeontology 46(2): 317-337. - Adam M. Yates -
2003.
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