Apatosaurus
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Apatosaurus (pronounced /əˈpæ.təˌsɔː.rəs/), often mistakenly referred to as Brontosaurus, is a genus of sauropod dinosaurs that lived about 140 million years ago, during the Jurassic period. They were some of the largest land animals that ever existed, about 4.5 metres (15 feet) tall at the hips, with a length of up to 21m (70 feet) and a mass up to 35 metric tonnes (40 tons). Their name means "deceptive lizard", because the chevron bones were like those of Mosasaurus (Greek apatelos or "apatelios" = deceptive + sauros = lizard).
The cervical vertebrae and the bones in the legs were bigger and heavier than that of Diplodocus but they both had a long neck and tail. The tail was held above the ground during normal locomotion. Like most sauropods, Apatosaurus had only a single large claw on each forelimb. The skull was first identified in 1975, a century after this dinosaur acquired its name.
Discovery and species
Fossils of this animal have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming, and at sites in Colorado, Oklahoma, Utah, USA.
- A. ajax is the type species of the genus, and was named by the paleontologist Othniel Charles Marsh in 1877 after Ajax, the hero from Greek mythology. It is the holotype for the genus and two partial skeletons have been found, including part of a skull.
- A. excelsus (originally Brontosaurus) was named by Marsh in 1879. It is known from six partial skeletons, including part of a skull, which have been found in the United States, in Oklahoma, Utah, and Wyoming.
- A. louisae was named by William Holland, in 1915. It is known from one partial skeleton, which was found in Colorado, in the United States.
Paleobiology
Early on, it was believed that Apatosaurus was too massive to support its own weight on dry land, so it was theorized that the sauropod must have lived partly submerged in water, perhaps in a swamp. Recent findings do not support this. In fact, like its relative Diplodocus, Apatosaurus was a grazing animal with a very long neck, and a long tail that served as a counterweight. Fossilized footprints indicate that it probably lived in herds. To aid in processing food, Apatosaurus may have swallowed gizzard stones (gastroliths) the same way that many birds do today, as its jaws lacked molars with which to chew tough plant fibers.Neck
Apatosaurus browsed the tops of trees, on riverbanks. Scientists believe that these sauropods could not raise their necks to an angle of 90 degrees, as doing so would slow blood flow to the brain excessively; blood starting at the body proper would take two or more minutes to reach the brain. Furthermore, studies of the structure of the neck vertebrae have revealed that the neck was not as flexible as previously thought.Physiology
With such a large body mass, combined with a long neck, physiologists encounter problems determining how these animals managed to breathe.Beginning with the assumption that Apatosaurus, like crocodilians, did not have a diaphragm, the dead-space volume (the amount of unused air remaining in the mouth, trachea, and air tubes after each breath) has been estimated at about 184 liters for a 30kg specimen.
Its tidal volume (the amount of air moved in or out during a single breath) has been calculated based on the following respiratory systems:
- 904 liters if avian
- 225 liters if mammalian
- 19 liters if reptilian
Furthermore, an avian system would only need a lung volume of about 600 liters compared to a mammalian requirement of 2,950 liters, which would exceed the available space. The overall thoracic volume of Apatosaurus has been estimated at 1,700 liters allowing for a 500-liter, four-chambered heart (like birds, not three-chambered like reptiles) and a 900-liter lung capacity. That would allow about 300 liters for the necessary tissue.
Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism (it certainly could not fly), it would need to consume only about 262 liters (69 gallons) of water per day.
It is not known how Apatosaurs ate enough food to satisfy their enormous bodies. It is likely that they ate constantly, pausing only to cool off, drink or to remove parasites. It is surmised that they slept standing upright. They likely relied on their enormous size and herd behavior to deter predators.
Lips
According to Robert Bakker, it is a major possibility that Apatosaurus may have had thick, moose-like lips.Apatosaurus/Brontosaurus controversy
In 1877, Othniel Charles Marsh published notes on his discovery of Apatosaurus ajax, and then in 1879 described another, more complete dinosaur species, which he speculated to represent a new genus and named Brontosaurus excelsus. In 1903, it was discovered that Brontosaurus excelsus was in fact an adult Apatosaurus, and the name Apatosaurus, having been published first, was deemed to have priority as the official name; Brontosaurus was relegated to being a synonym. In the 1970s, it was proven that the traditional "Brontosaurus" image known to all was, in fact, an Apatosaurus excelsus with a Camarasaurus head incorrectly placed on its body.
In Popular Culture
Film and television
- Apatosaurus are featured in the Walking with Dinosaurs special The Ballad Of Big Al and in When Dinosaurs Roamed America.
- Littlefoot from the popular 1988 film, The Land Before Time was an Apatosaurus.
Reference
See also
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