Eotrachodon
Name:
Eotrachodon
Eotrachodon (Dawn Trachodon/Dawn rough tooth).
Phonetic: E-oh-trak-oh-don.
Named By: Albert Prieto-Marquez, Gregory M.
Erickson& Jun A. Ebersole - 2016.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ornithopoda, Hadrosauridae.
Species: E. orientalis
(type).
Diet: Herbivore.
Size: Holotype skull reconstructed to be about 42
centimetres long. Total body length estimated at between six and
nine meters long, but this is highly speculative.
Known locations: USA, Alabama - Mooreville
Chalk Formation.
Time period: Santonian-Coniacian of the Cretaceous.
Fossil representation: Almost complete skull,
lower jaws, some vertebrae and fragmentary limb bones.
By
the start of the Late Cretaceous the central portion of North America
had been submerged by a shallow sea. This created two landmasses out
of the North American continent, Laramidia in the west and Appalachia
in the east. Most Cretaceous era dinosaurs from North America have
been found in what was once Laramidia, but a few are known from
Appalachia. With respect to the hadrosaurs
(a.k.a. the duck
billed dinosaurs), for over one hundred and fifty years the only
known member of this group of dinosaurs present in Appalachia was the
Hadrosaurus
genus itself (discovered in New Jersey in 1858).
Then in 2016, a second genus of hadrosaur was identified as living
in Appalachia: Eotrachodon.
Eotrachodon
is so far known from an almost complete skull, lower jaws as well as
some vertebrae and fragmentary elements of the limbs. The genus is
actually the first hadrosaurid dinosaur from Appalachia to be known
from skull material, with the earlier named Hadrosaurus
only known
from very partial post cranial fossils. Eotrachodon
was discovered in
the Mooreville Chalk Formation of Alabama, a fossil bearing formation
that is actually best known for marine animals such as sharks, bony
fish and mosasaurs. This may well suggest that the holotype
individual of Eotrachodon was actually washed out
to sea, which in
turn might mean that this animal lived elsewhere from Alabama.
Eotrachodon
means ‘dawn rough tooth’ and is a reference to the earlier
appearance of Eotrachodon compared to the genus Trachodon
(today
regarded as a highly dubious hadrosaurid dinosaur genus). The
authors of the description have speculated that Eotrachodon
may have
been amongst the first true hadrosaurs to appear upon the face of the
planet, suggesting that the hadrosaurid dinosaurs may have first
appeared in Appalachia. However, with a growing number of
hadrosauroid dinosaurs (evolutionary close to true hadrosaurs,
though not quite them) being discovered in other parts of America,
Asia as well as possibly Africa, it may well be too soon to jump to
a conclusion as to where the first true hadrosaurs appeared.
Further reading
- A primitive hadrosaurid from southeastern North America and the
origin and early evolution of 'duck-billed' dinosaurs. -
Journal of Vertebrate Paleontology: e1054495. - Albert
Prieto-Marquez, Gregory M. Erickson& Jun A. Ebersole
- 2016.
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