Dreadnoughtus
Name:
Dreadnoughtus
(Fearing nothing).
Phonetic: Dread-nort-us.
Named By: K. J. Lacovara, L. M. Ibiricu,
M. C. Lamanna, J. C. Poole, E. R. Schroeter, P.
V. Ullmann, K. K. Voegele, Z. M. Boles, V. M.
Egerton, J. D. Harris, R. D. Mart�nez, F. E. Novas
- 2014.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropoda, Titanosauria.
Species: D. schrani (type).
Diet: Herbivore.
Size: Up to 26 meters long and around 59
tons in weight for the holotype individual, fully grown adults would
have been larger, but total size cannot yet be confirmed.
Known locations: Argentina, Santa Cruz Province.
Time period: Campanian/Maastrichtian of the
Cretaceous.
Fossil representation: Roughly half of the post
cranial skeleton and a maxilla of the skull. Remains are of a younger
and not yet fully grown individual.
Titanosaurs
like most sauropod
dinosaurs are usually only known from partial
remains such as one or two legs, a sequence of vertebrae or the
occasional isolated skull. This is because their inherent large size
makes it unlikely that the whole body will be buried and preserved
before scavengers and environmental effects scatter the bones of an
individual so that the skeleton is only preserved in a few pieces.
But in 2005 a new discovery was made in Argentina, a new
titanosaur with roughly half the skeleton preserved in a semi
articulated fashion. At the time of naming in 2014 Dreadnoughtus
was the most complete titanosaur known from South America, and
worldwide only genera such as Rapetosaurus
from Madagascar are known to
be more complete.
Dreadnoughtus
is yet another example of the large titanosaurs that were living in
South America all the way to the end of the Cretaceous period. The
holotype individual of Dreadnoughtus was estimated
to be about
twenty-six meters long, just over eleven meters of which was neck.
The body weight of this dinosaur has also been established to around
the fifty-nine metric tons mark. However the absence of an outer
layer of bone on the vertebrae (external fundamental system) but
instead continued presence of a fast growing bone type indicates that
the holotype individual was not fully grown at the time of death.
This reveals that fully grown adults of Dreadnoughtus
would have been
longer and heavier than what we know the holotype to have been.
Because
of the completeness of the Dreadnoughtus remains it
has been possible
to infer a few things about this dinosaur. The Dreadnoughtus
holotype
has the largest known scapula (shoulder blade), ilium (upper
hip bone) as well as forearms that are proportionately longer
than any other known titanosaur at the time of writing. However while
the humerus (upper arm bone) of Dreadnoughtus
is also long, it is
actually shorter than the humerus of Paralititan
from Egypt, which is
amongst the largest known. Fully grown Dreadnoughtus
may have had a
humerus that was longer, but the measurements from the holotype at
least indicate that there can be a broad difference in features amongst
titanosaurs and sauropods even though they all have the same basic body
plan of four legs and long neck. In an addition to the proportional
notes, many of the bones particularly those associated with the
neck, show the presence of pneumatic air sacs. This is yet further
proof that dinosaurs had an avian-like respiratory system.
The
Dreadnoughtus holotype seems to have been deposited
in a flood event
perhaps as
part of a river changing course. The teeth of large theropod
dinosaurs (possibly megaraptoran)
were found amongst the holotype
skeleton, though given the context of the rock deposits these may be
a sign of scavenging as opposed to hunting.
Further reading
- A Gigantic, Exceptionally Complete Titanosaurian Sauropod
Dinosaur from Southern Patagonia, Argentina. - Scientific
Reports - K. J. Lacovara, L. M. Ibiricu, M. C.
Lamanna, J. C. Poole, E. R. Schroeter, P. V.
Ullmann, K. K. Voegele, Z. M. Boles, V. M. Egerton,
J. D. Harris, R. D. Mart�nez, F. E. Novas - 2014.
- Rates of Dinosaur Body Mass Evolution Indicate 170 Million
Years of Sustained Ecological Innovation on the Avian Stem Lineage.
- PLoS Biol 12(5) - Roger B. J.Benson, Nicol�s E.
Campione, Matthew T. Carrano, Phillip D.Mannion, Corwin
Sullivan, Paul Upchurch, David C. Evans - 2014.
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