Camarasaurus lentus is a sauropod dinosaur, a member of the group that contained long-necked herbivorous dinosaurs such as Apatosaurus, Diplodocus, and Brachiosaurus. It lived in the Late Jurassic period, approximately 150 million years ago. This dinosaur could reach up to 15 m in length and weighed close to 15000 kg. While this is large compared to land animals alive today, about the weight of three large male African elephants, C. lentus was only middling in size among sauropods (1). It is likely that C. lentus traveled in herds, a behavior predicted for other sauropod dinosaurs (2).
Through the study of bone microstructure, paleontologists have been able to learn about the growth patterns of Camarasaurus. Some species of dinosaurs, as well as many animals alive today, laid down yearly rings in their bones. By counting the number of rings and measuring the spaces between them, paleontologists are able to estimate how long an animal lived and how fast it might have grown. In 2013, Griebeler et al. studied the bones of Camarasaurus for this purpose. The species is unknown, but given the close relatedness of all Camarasaurus species, it is likely that growth patterns would have been similar among them (1).
They estimated that Camarasaurus lived for approximately 26 years and reached sexual maturity at around 20 years of age. Camarasaurus likely became sexually mature before they were fully-grown. This is not unusual in the natural world and can also be seen in female elephants (2).
Camarasaurus lentus lived 150 million years ago in the Jurassic Period. It has been found in locations such as Wyoming, Colorado, and Utah in the Morrison formation. When it was alive, the environment would have looked very different from what can be seen in these areas today. The habitat represented by the Morrison Formation was semiarid with short wet seasons. It contained a mix of floodplain prairies and riverine forests. A wide variety of dinosaurs shared this environment, including predators like Allosaurus and Torvosaurus and other sauropods, such as Apatosaurus and Brachiosaurus (1).
This was a very different environment than seen in similar modern ecosystems. C. lentus lived before flowering plants evolved, meaning that grasses and many tree varieties did not yet exist. Insects were similar to those found today, but mammals were far less abundant. The largest mammal in this environment would have been no bigger than a rat and probably laid eggs rather than giving live birth (2).
There are generally four species recognized in the Camarasaurus genus. Camarasaurus fossils are relatively abundant in deposits, but species identification remains problematic for this group. This is due to a variety of factors, such as the wide degree of anatomical change seen between juvenile and adult Camarasaurus skeletons. Another problem is the lack of knowledge on sexual dimorphism in Camarasaurus, whether male and females of these species had different appearances. Additionally, there is wide amount of variation in morphology between individuals. All of these factors combined sometimes make it difficult to place a specimen within one Camarasaurus species or another (1).
C. lentus is especially similar to the species Camarasaurus supremus, distinguished only by its smaller size. Making this case even more ambiguous is that the original specimens discovered of C. lentus and C. supremus are both juveniles, causing comparisons to adult forms to be imprecise at best (2).
Like all other sauropod dinosaurs,Camarasaurus lentus was an herbivore. Despite its long neck, it would have been difficult for C. lentus to feed at ground level like a cow or a horse. Instead, C. lentus browsed at medium and high levels in bushes and trees (1). It had teeth larger than most sauropods, and its skull would have supported large jaw muscles. These adaptations allowed C. lentus to feed on tough and coarse plant matter. Sauropods such as Diplodocus had much smaller teeth and weaker jaws. They probably fed on much softer vegetation than C. lentus (2). The diet of Camarasaurus was so abrasive on its teeth that each tooth was replaced every 62 days (2).
Polished pebbles have sometimes been found within the body cavities of fossilized sauropod dinosaurs. This led paleontologists to believe that some dinosaurs, including C. lentus, swallowed stones to help grind tough plant material and help digestion. This is a behavior seen in birds today. However, comparison between these fossil stones and the stones that serve this function in modern birds has shown that this interpretation is most likely false. Instead of swallowing stones to process food, sauropods probably kept food within their digestive system for longer periods of time (4).
Camarasaurus lentus is part of the Sauropoda group. This evolutionary lineage contains long-necked dinosaurs such as Apatosaurus and Diplodocus. Within Sauropoda, C. lentus is further classified in the Macronaria clade. This is a much smaller group containing fewer individuals and indicating closer relatedness to those within. A recent analysis of the sauropod lineage shows that Camarasaurus is a primitive member of Macronaria. More derived members of this group include Brachiosaurus and all titanosaurs (1).
