Camarasaurus
Name:
Camarasaurus
(Chambered lizard).
Phonetic: Cam-ah-rah-sore-us.
Named By: Edward Drinker Cope - 1877.
Synonyms: Cathetosaurus, Caulodon,
Morosaurus, Uintasaurus.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha, Sauropoda, Macronaria.
Species: C. supremus (type),
C.
grandis, C. lentus.
Diet: Herbivore.
Size: Between 15 and 23 meters long,
depending upon the species.
Known locations: USA, Wyoming, New Mexico,
Colorado & Utah - Morrison Formation.
Time period: Oxfordian to Tithonian of the Jurassic.
Fossil representation: Many specimens.
Although
not as famous as some sauropods
like Apatosaurus
and Diplodocus,
Camarasaurus actually appears to have been the most
common judging by
the large numbers of remains. Some Camarasaurus
specimens are
actually almost complete and the genus also has one of the largest
numbers of sauropod skulls attributed (for those who haven’t realised
the skull you see rotating at the top of every web page on this site is
actually a replica of a Camarasaurus skull).
Camarasaurus
was named in 1877 after Edward Drinker Cope bought the first
fossils from Oramel W. Lucas. These remains were of an incomplete
individual but were still valuable to Cope because the vertebrae had
hollow chambers, something that gave rise to the name of ‘chambered
lizard’. Back then these chambers were more a curiosity and were
presumed to have been a weight saving feature that considerably reduced
the weight of such a large dinosaur. Today however these chambers are
interpreted as being air sacs that were actually part of the
respiratory system of Camarasaurus. These
features are seen in other
sauropods, as well as similar systems in other dinosaur groups such
as in the theropod Aerosteon,
and would go to be called an avian-like
respiratory system as birds also have similar air sacs inside their
bodies. Back to Camarasaurus, the air sacs are
thought to have
allowed for a far more efficient flow of air down the long neck so that
fresh air went down one network of sacs, while oxygen depleted air
went up another. Thus a constant supply and exchange of breathable
air was still taking place despite the distance of the lungs from the
mouth and nostrils.
In
1925 Charles W. Gilmore retrieved a much better Camarasaurus
specimen which was for lack of a better word complete. The main
reason why it was so well preserved is because it was a younger and not
fully grown individual, which meant that the body was probably buried
before scavengers and environmental conditions could scatter and damage
the skeleton. Unfortunately some took this specimen to be the literal
size of all Camarasaurus, something which
resulted in many
Camarasaurus reconstructions being smaller than they
really were in
life.
The
largest number of Camarasaurus fossils is
attributable to C. lentus,
which is seen as having an average length of fifteen meters. The
biggest species of Camarasaurus is the type C.
supremus which grew up
to twenty-three meters long. The shape of Camarasaurus’s
body looked
like it was something in between Apatosaurus and Brachiosaurus.
The
front limbs were shorter than the rear limbs, but the position and
placement of the shoulder girdle meant that Camarasaurus
still walked
tall with a slight slope down the back towards the hind quarters. The
neck appears to have been held up high so that the head and mouth were
placed at a level where Camarasaurus could have
comfortably browsed from
the tree canopy and while the skull has many large fenestra it is
remarkably robust and solid, possibly explaining the high standard of
preservation that has come to be associated with Camarasaurus
skulls.
Overall this has led to Camarasaurus being
declared a primitive
(basal) macronarian, the grounp of high necked sauropods that
included members such as Brachiosaurus, Giraffatitan
and Lusotitan.
Even
though the skull has many large fenestra it is remarkably robust and
solid, possibly explaining the high standard of preservation that has
come to be associated with Camarasaurus skulls.
The teeth are also
very large and spatulate in form so that they could crop off vegetation
from the coarser branches and growths. This is quite different from
other sauropods such as Diplodocus which had weaker
teeth, but a head
position that saw them capable of easily feeding from softer low
growing vegetation.
As
with many genera that have multiple species assigned to the genus,
not all of the species would have been active for the entire run of
the genus. C. grandis was the first Camarasaurus
species to appear
and was eventually joined by C. lentus to which
it coexisted until it
disappeared after a few million years. C. lewesi
also appears to
have been present but not until the end of the genus. Paradoxically
the first species of Camarasaurus named, C.
supremus, appears to
have actually been the last to live, and probably evolved from C.
lentus. The Camarasaurus genus ending
in the largest species is a
trait that is commonly seen in other groups were the largest form is
the last to appear, but also reveals a possible limit to the extent
of that animal’s specialisation, as for further adaptation often
ceases to take place.
Unlike
some similar kinds of dinosaurs like Saltasaurus
that have
been found to lay eggs in nests, Camarasaurus
eggs have been found in
lines which suggest that Camarasaurus did not spend
extensive amounts
of time rearing young. They may have instead laid their eggs near
undergrowth so that the newly hatched young could go straight to cover
where they would have stayed until they grew large enough to venture
into more open areas.
Some
Camarasaurus bones and fossil sites have yielded
valuable insights into
their behaviour, biology and placement within the late Jurassic
ecosystems of North America. One well documented case from Wyoming is
the presence of two Camarasaurus adults and a
single juvenile that
appear to have been drowned while crossing a river that may have been
in flood. The presence of individual Camarasaurus
of different ages
dying together has been taken as evidence of herding behaviour in
Camarasaurus, with the three individuals
suggesting that Camarasaurus
lived in at least small groups, although the full extent of a herd’s
size remains unknown. Similar bone beds are known for some
ceratopsian dinosaurs like Centrosaurus
and Styracosaurus
from the
Cretaceous, although in these deposits the individuals can number in
hundreds.
A
partial Camarasaurus grandis skeleton from Wyoming
includes a humerus
(upper 'arm’ bone of the fore limb) that has been designated
DMNH 2908. This humerus has an eighteen by twenty-five centimetre
lesion on the bone that is composed of what seems to woven bone
fibres. Analysis of this legion (by McWhinney, Carpenter, and
Rothschild) suggests that the bone healed but with a growth that
would have caused discomfort as the individuals muscles flexed around
it. Many causes of this injury have been put forward, but the most
likely seems to have been an avulsion, an injury where the muscle
attachment has been torn free, removing some of the bone in the
process. This could have been caused by a slip or a fall, or even
repetitive strain, and may indicate that this individual Camarasaurus
was living in area of uneven terrain that saw it going up and down
inclines.
A
Camarasaurus pelvis from Utah shows signs of damage
that could have
feasibly been caused by an Allosaurus,
a dinosaur that was quite
possibly the top predator of North America in the Jurassic. A problem
here is that the fossil does not prove that the Camarasaurus
was killed
by an Allosaurus, just that an Allosaurus
possibly fed upon the body
after the time of death whatever the cause may be, including a
dinosaur attack. A long held belief about sauropods was that they
were near invulnerable because they were just too big to attacked by
any of the predators. This idea however is no longer accepted without
question, with some sauropods appearing to have armoured skin, and
the fact that some predators, including Allosaurus,
show signs of
skeletal injuries that could have conceivably been caused by grappling
with large and powerful prey. Strong fossil evidence also
exists for Allosaurus attacking the armoured
dinosaur Stegosaurus,
and if Allosaurus could think to attack a
herbivorous dinosaur that
could have killed it with a strike from its spiked tail, then it does
not seem entirely out of the question that an Allosaurus
might have
attempted to take down a Camarasaurus, especially
if the Camarasaurus
was sick or already injured.
Further reading
- Notice of new dinosaurian reptiles from the Jurassic formation. -
American Journal of Science and Arts 14:514-516. - O. C. Marsh - 1877.
- Notice of new American Dinosauria. - The American Journal of Science
and Arts, series 3 38:331-336. - O. C. Marsh - 1889.
- The dorsal vertebrae of Camarasaurus Cope. -
Bulletin of the AMNH ;
v. 33, article 17. - Charles Craig Mook - 1914.
- Notes of Camarasaurus Cope - Annals of the New York Academy of
Sciences vol 24, iss 1 - Charles Craig Mook - 1914.
- Camarasaurus, Amphicoelias,
and other sauropods of Cope. - Bulletin
of the Geological Society of America 30:379-388. - H. F. Osborn
& C. C. Mook - 1921.
- A nearly complete articulated skeleton of Camarasaurus,
a saurischian
dinosaur from the Dinosaur National Monument, Utah. - Memoirs of the
Carnegie Museum 10(3):347-384. - C. W. Gilmmore - 1925.
- Camarosaurus annae-a new American sauropod
Dinosaur. - The American
Naturalist, v. 84, p. 225-228. - T. U. H. Elinger - 1950.
- A fourth new sauropod dinosaur from the Upper Jurassic of the
Colorado Plateau and sauropod bipedalism. - The Great Basin Naturalist
48(2):121-145 - J. A. Jenson - 1988.
- The Osteology of Camarasaurus lewisi (Jensen,
1988). - Brigham Young
University, v. 41, p. 73-116. - J. S. McIntosh, W. E. Miller, K. L.
Stadtman & D. G. Gillette - 1995.
- Dental micro wear patterns of the sauropod dinosaurs Camarasaurus
and
Diplodocus: Evidence for resource partitioning in
the late Jurassic of
North America. - Historical Biology: An International Journal of
Paleobiology. - col 13, iss13 - Anthony R. Fiorillo - 1998.
- A New Nearly Complete Skeleton of Camarasaurus. -
Bulletin of Gunma
Museum of Natural History, n. 1, p. 1-87. - J. S. McIntosh, C. A.
Miles, K. C. Cloward & J. R. Parker - 1996.
- Evolution of High Tooth Replacement Rates in Sauropod Dinosaurs. -
Plospme - Michael D. D’Emic, John A. Whitlock, Kathlyn M. Smith, Daniel
C. Fisher & Jeffrey A. Wilson - 2013.
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