Camarasaurus

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Camarasauridae

Genus: Camarasaurus

Species: Camarasaurus supremus

Introduction

Edward Cope and Othniel Charles Marsh were nineteenth-century dinosaur hunters engaged in what became known as the Bone Wars. Each wanted to earn the honor of finding and naming the most dinosaurs. In 1877, Edward Cope purchased bones discovered by O. W. Lucas, a teacher and excavator, in what came to be known as the Morrison Formation, a rock layer rich in fossils covering 700,000 square miles and spanning eleven states. He named the bones Camarasaurus. In 1925, a more complete juvenile Camarasaurus was discovered by American paleontologist Charles W. Gilmore.

The name Camarasaurus means “chambered lizard” due to the pneumatic bones found in many of the dinosaur's cervical (neck) and dorsal (back) vertebrae. The bones were thin and hollow to accommodate air sacs that were part of the Camarasaurus’ respiratory system. Camarasaurus was a plant-eating dinosaur.

Classification

Paleontologists use different classification schemes to understand and describe dinosaurs. Because of the dynamic nature of this field of study, they sometimes disagree, and it is not unusual for a discovery to alter the placement of a dinosaur within a given system.

Linnaean classification is a hierarchical system that classifies plants and animals into categories such as phylum, class, and order. There are two basic infraorders of saurischian dinosaurs from the Jurassic period: theropods, which were meat-eaters, and sauropods, which were plant-eaters. Linnaean classification puts Camarasaurus in the class Sauropsida. Sauropods have extra vertebrae in the neck (at least twelve cervical vertebrae) with weaker back vertebrae. Additionally, sauropods are characterized by having five “toes” on their front and back feet, large, thick limbs, and substantial abdomens to digest large amounts of plant matter. While their necks and tails were long, their heads were small. More than a dozen different types of long-necked sauropods have been found in the Morrison Formation. Camarasaurus is further classified in the Camarasauridae family largely due to its spine formation, which in Camarasauridae, is characterized by split neural spines.

A second classification scheme is cladistics, or phylogenetic classification. The system is based on physical characteristics indicative of shared ancestry. Scientists create family trees called “cladograms” to indicate relationships between genera and species. Cladistics place Camarasaurus and other camarasaurids in the Macronaria clade, dinosaurs with large, crested nares, or nostrils, placed high on the head, spoon-shaped teeth, and elongated metacarpals. Titanosaurs like Brachiosaurus also belong to Macronaria.

Anatomy

Camarasaurus is one of the few dinosaurs about which the structure of the bones and the anatomy, what scientists call the osteology, is fully known.

The dinosaur's forelegs were slightly shorter than its hind legs, but because of their position on the body, Camarasaurus's posture was fairly level and not as sloped as some creatures with shorter front limbs. The legs resembled those of modern elephants; they were straight columns, which allowed the dinosaur to support its great weight using its bones rather than muscles. Its hips were lizard-like. (Unlike true lizards, though, dinosaurs’ legs did not extend out to the side). Camarasaurus's inner toe took the shape of a sharpened claw, used supposedly for protection. Unlike its sauropod relatives, it is noted that Camarasaurus had a shorter tail and neck than others.

Camarasaurus's skull was blunt and short, containing about fifty teeth. Nostrils were large and located in front of the eyes, which were also large. The structure of Camarasaurus's neck is another point of contention. Sauropods are usually pictured as having giraffe-like necks. The structure of the cervical vertebrae, however, seems to indicate a linear extension. The vertebrae at the base of a giraffe's neck are wedge-shaped; this is not the case for Camarasaurus. Nor does the dinosaur have keystone-shaped vertebrae as do the dinosaurs known to have necks that extended upward.

Scientists disagree as to whether Camarasaurus's metabolism was cold-blooded, warm-blooded, or something in between. Warm-blooded animals, such as mammals, need more food than do cold-blooded ones such as reptiles, but previous theories that supposed that dinosaurs were cold-blooded have, in recent years, come in question. Scientists are now exploring whether dinosaurs may have had more complex metabolic systems than previously understood.

Intelligence

An alligator of the present day has an EQ of 1.0. One of the most intelligent dinosaurs, Troodon, had an EQ of 5.8. Scientists assume that Camarasaurus had enough intelligence to find food, to escape predators, and to mate.

At one point, scientists believed that an enlargement of the sauropod spinal cord at the hips was a “second brain.” The “second brain” was thought to be even larger than the brain in the dinosaur's skull. This theory has since been debunked, as many vertebrates have an enlargement in the hip area.

Reproduction and Population

Scientists know almost nothing about mating habits of dinosaurs. Nor is it well understood how sauropods laid their eggs without damage from the height of the drop and the weight of the mother laying the eggs. Fossilized nests of eggs suggest that sauropods could not have brooded their eggs, as the placement of other nests was too close and the weight of the dinosaur too great. Dinosaur egg expert Gerald Grellet-Tinner and Lucas Fiorelli conducted research in Argentina in 2010, which showed that some sauropods returned to the same nesting area each year and laid their eggs in depressions or holes; and the research indicated that eggs may have been laid close to geothermal vents. The sauropod eggs found there measured 21 centimeters (8.27 inches) in diameter and were laid in moist environments over time; the egg shells became thinner as they matured. Evidence suggests that parents might have guarded the nests, possibly in herds and from a short distance, and they might have fed their young.

Diet

The largest of all the herbivorous dinosaurs, Camarasaurus had spoon-like teeth. These were located on most of the upper and lower jaws and used to pull leaves from shrubs and trees. Based on the wear marks of Camarasaurus teeth, scientists think that it ate coarse plants, such as conifers. However, the wear marks on teeth of juveniles suggest that the young ate soft plants. Scientists theorize that the diet of the dinosaur changed as it aged.

One major concern is the nutritional value of what Camarasaurus ate. Scientists have studied the energy from plants related to those of the Jurassic era and have concluded that conifers, ferns, and ginkgoes would have provided the most nutrition.

Behavior

Camarasaurus may have traveled in groups or perhaps in herds. Because food supplies were seasonal, they may have migrated long distances. One study estimated that Camarasaurus might have traveled nearly 3 million meters (1,800 miles) each year.

Like most plant-eating creatures, Camarasaurus was probably not aggressive. The chief concern of the dinosaur would have been finding enough to eat.

Habitat and Other Life Forms

At one time, the earth contained a single landmass known as Pangaea. During the Jurassic period, this supercontinent began breaking up into smaller continents. The climate during the Jurassic age may have resembled a hothouse, with less variation in seasons than is common today. Some researchers liken the western United States during the Jurassic (then Laurasia), where many of the Camarasaurus fossils have been found, to a contemporary East African savannah.

Fossil evidence at Douglass Quarry, where the Dinosaur National Monument is located, indicates that several types of sauropods, including Camarasaurus, lived there. Among the sauropods were Apatosaurus, Barosaurus, Diplodocus, and Haplocanthosaurus. Other contemporaries included Dryosaurus, Camptosaurus, and Stegosaurus.

Sauropods, such as Camarasaurus, were prey for carnivorous dinosaurs, such as Allosaurus. In fact, one sauropod pelvic bone retrieved from the Morrison Formation shows traces of gouging from Allosaurus.

Research

Scientists have revised their estimates of how dinosaurs grew and how long they lived. Earlier studies believed that dinosaurs grew slowly, as reptiles do, and thus dinosaurs might have lived for centuries, given their huge size. Paleontologists now believe that dinosaurs grew more rapidly, as contemporary mammals and birds do. They have studied bone fossils, which add new bone material to the outsides of existing bones. This is the way all vertebrates grow their bones. Thus bone growth can be studied based on these growth lines, just as a tree's age can be determined by its rings. Doing so has led scientists to conclude that dinosaurs had an adolescent growth spurt, just as humans do.

In 1983, scientists first looked at the growth lines of a Late Jurassic sauropod's bones. Based on their observations, they concluded that the large herbivorous dinosaurs, such as Camarasaurus, might have lived for seventy or eighty years. They theorize that smaller, carnivorous dinosaurs, like large birds today, might have lived for 20 or 30 years.

From an unusually complete Camarasaurus find, Emanuel Tschopp and his team modeled the animal's forefeet and hindfeet and made impressions from the 3-D models. In so doing, they concluded in a 2015 Palaeontologia Electronica paper that it had no hooves and that, despite its ubiquity, no known dinosaur footprint matched that of Camarasaurus.

Much research on Camarasaurus has focused on its teeth. Scratches, or wear patterns, suggest that unlike its distant relative Diplodocus, Camarasaurus ate coarser vegetation. Other research has focused on how high sauropods might have lifted their heads; some scientists hypothesize that Camarasaurus might have grazed higher vegetation than Diplodocus did. Some research also indicates it had a greater bite force, also suggesting a woodier diet than that of Diplodocus.

By comparing the oxygen isotope concentrations in Camarasaurus teeth to those from rock formations in different areas, Henry Fricke and his colleagues concluded that Camarasaurus likely migrated seasonally from lowlands to uplands. Those migrations would likely have been mass events as seen in modern herbivores.

By counting daily dentin lines present in Camarasaurus teeth, Michael D’Emic and his colleagues learned the ages of the extant teeth and computed the time needed to form new teeth. Based on that assessment, Camarasaurus replaced teeth every sixty-two days, about half as fast as Diplodocus, suggesting less need for replacement, perhaps because of grazing on higher, less gritty material.

Furthermore, impressions of soft tissues found with a Camarasaurus jaw may indicate deep gums and a beak-like keratin structure, according to a 2017 paper by researchers Kayleigh Wiersma and Martin Sander. In a 2019 follow-up, they compared Camarasaurus jaws to those of other sauropods and suggested sauropods more broadly had such features, given that wear patterns were present only on top half of the teeth.

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