Camarasaurus

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**