Hadrosaurus
Name:
Hadrosaurus
(Sturdy lizard).
Phonetic: Had-roe-sore-us.
Named By: Joseph Leidy - 1858.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ornithopoda, Hadrosauridae, Hadrosaurinae.
Species: H. foulkii (type).
Diet: Herbivore.
Size: Uncertain due to a severe lack of remains.
Known locations: USA, New Jersey - Woodbury
Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Skull fragment and partial
post cranial remains including parts of the limbs, pelvis and
vertebrae.
In
terms of paleontological study, Hadrosaurus was a
genus of firsts.
One of the things that the genus is famous for is that it was the
first dinosaur to have a skeleton mounted for public display. Earlier
reconstructions such as the now outdated dinosaurs of Crystal Park in
England are brick and concrete models of what the dinosaurs were
thought to look like in life. The first mounted skeleton of
Hadrosaurus however also had to be completed by
making up many of the
missing bones to what they were thought to be like.
The
partial remains of Hadrosaurus were first
discovered in 1838 when a
man named John Estaugh Hopkins was digging in a marl pit (a marl pit
is essentially a deposit of mudstone). Parts of many of the
important body parts were such as partial limbs and the pelvis were
found, but the ribs, most of the vertebrae and most importantly a
skull were not found. These missing parts are what makes it difficult
to not only establish the true length of Hadrosaurus,
but also how
the genus relates to other later named hadrosaurs, more detail on
this though further down.
As
already mentioned above, Hadrosaurus was the
first cast skeleton to
be put together for public display. This mounting took place in
1868 and was overseen by the famous American palaeontologist Joseph
Liedy who had described the remains ten years earlier. This mount had
to be completed with additional sculpted parts, and the end result
was what would have been a common rendition of an ornithopod dinosaur
from the late nineteenth century until the latter decades of the
twentieth. Liedy interpreted Hadrosaurus as being
an obligatory
bipedal dinosaur due to the greatly enlarged rear legs, and since
dinosaurs were still being treated as exceptionally large lizards back
then, the tail hung limply behind the body where it was dragged along
the floor. The overall posture was that of a creature that walked
with its spine nearly vertical to the ground.
Today
we now know that such reconstructions are to be blunt wrong, though
to be fair they were still more accurate than the first dinosaur
renditions at Crystal Park. Hadrosaur dinosaurs are now known by
dozens of different genera, some of which are almost complete and
even show impressions of soft tissues like skin and muscle. For a
start, Hadrosaurus would have been a primarily
quadrupedal dinosaur
as while the rear legs were the main weight bearing features, the
fore legs were also adapted for weight bearing as well. This means
the spine of Hadrosaurus would have actually of
been nearer horizontal
to the ground rather than vertical in the older reconstructions. It
should be pointed out though that while Hadrosaurus
mostly walked
around in a quadrupedal stance, Hadrosaurus could
have still reared
up on their hind legs to reach higher food. They may have also been
able to ‘run’ on just the rear legs when escaping predators.
Hadrosaurus
was the first named hadrosaur,
in fact that is why hadrosaurs are
called hadrosaurs, the name of a group of animals is always based
upon the first named genus. As such Hadrosaurus
is the type genus of
the Hadrosauroidea and the Hadrosauridae. The latter group is for
true hadrosaurs like Maiasaura
and Edmontosaurus,
while the
Hadrosauroidea was for genera that are hadrosaurid like but not quite
like Tanius
and Jeyawati.
Hadrosaurids
can be divided into two groups of hollow and solid crested genera.
The hollow crested genera are usually referred to as lambeosaurines
after the genus Lambeosaurus.
Solid crested genera, or even those
without crests, used to be referred to as hadrosaurines after the
type genus. However as already stated, the skull of Hadrosaurus
is
unknown and the remaining bones are too undiagnostic to prove it was
anything other than a hadrosaur, so there is no telling what kind or
indeed if any crest was present in Hadrosaurus.
For this reason a new
sub group was created called the Saurolophinae after Saurolophus,
and
this contains all of the current solid/no crested genera. At the time
of writing, Hadrosaurus sits alone within the
Hadrosaurinae, and
unless new and more complete fossils of Hadrosaurus
are found, this
is how things will remain.
Principal
predators of Hadrosaurus would have been large tyrannosaurs,
but
giant
crocodiles
were also in North America during the late Cretaceous.
Other theropod dinosaurs such as dromaeosaurs
and troodonts
could have
also posed a threat, especially to not yet fully grown juvenile
Hadrosaurus.
Further reading
- Revised diagnoses of Hadrosaurus foulkii
Leidy, 1858 (the type
genus and species of Hadrosauridae Cope, 1869) and Claosaurus
agilis Marsh, 1872 (Dinosauria: Ornithopoda) from the Late
Cretaceous of North America, A. Prieto-M�rquez - 2011.
- The dinosaur Hadrosaurus foulkii, from the
Campanian of the East
Coast of North America, with a reevaluation of the genus, A.
Prieto-M�rquez, D. B. Weishampel & J. R. Horner
- 2006.
Random favourites
 |
 |
 |