Dinosaurs > Apatosaurus

Apatosaurus, meaning “deceptive reptile”, is an extinct genus of sauropod dinosaur that lived in North America during the Late Jurassic period. The genus was first described in 1877 when Othniel Charles Marsh named A. ajax, and many species have since been described. They range in age from about 154 to 150 million years ago throughout the Kimmeridgian and early Tithonian ages of the Morrison Formation. Among the species is A. excelsus, long considered to be separate under the genus Brontosaurus, which is now considered a junior synonym of Apatosaurus. It had an average length of 22.8 m (75 ft) and a mass of at least 16.4 metric tons (18.1 short tons), although a few specimens indicate a length up to 30% greater and a weight of 33–73 t (32–72 long tons; 36–80 short tons). Apatosaurus was one of the more common sauropods in the Morrison, along with Diplodocus and Camarasaurus.

The cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and the bones of the leg were much stockier despite being longer, implying that Apatosaurus was a more robust animal. The tail was held above the ground during normal locomotion. Like all sauropods, Apatosaurus had only one claw on the forelimbs and three on its hindlimbs. The skull of Apatosaurus, long thought to be similar to Camarasaurus, is much more similar to that of Diplodocus.

Apatosaurus is a genus in the family Diplodocidae. It is more basal than other genera like Diplodocus and Barosaurus, and is sometimes included in its own subfamily, Apatosaurinae. Apatosaurus is one of the more common sauropods in the Morrison Formation, and is often found associated with skeletons of Allosaurus, Camarasaurus, Stegosaurus and Diplodocus. Apatosaurus is also one of the longer genera, although Supersaurus exceeds it.

Apatosaurus was a large, long-necked quadrupedal animal with a long, whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. Most size estimates are based on specimen CM 3018 (the type specimen of A. louisae), which reached 21–22.8 m (69–75 ft) in length and 16.4–22.4 t (16–22 long tons; 18–25 short tons) in weight.


Clade: Dinosauria
Suborder: Sauropoda
Family: Diplodocidae

Size: 22.8 m (75 ft) long

Weight: 22 metric tons

When: Jurassic Period
154 to 150 million years ago

Where: North America

Diet: Herbivore

The skull was small in comparison with the size of the animal. The jaws were lined with spatulate (chisel-like) teeth, suited to a herbivorous diet. The snout of Apatosaurus and similar diplodocoids are squared, with only Nigersaurus having a squarer skull. The braincase of Apatosaurus is well preserved in specimen BYU 17096. The bones are articulated, and their fusion indicates that the bones are mature. The braincase was placed in a phylogenetic analysis, and its morphology was found to be very similar to that of other diplodocoids. Some skulls of Apatosaurus have been found still in articulation with their teeth. Those teeth that have the enamel surface exposed do not have any scratches on the surface, and instead display a sugary texture and little wear.

It was historically believed that sauropods like Apatosaurus were too massive to support their own weight on dry land, so it was theorized that they must have lived partly submerged in water, perhaps in swamps. Recent findings do not support this, and sauropods are thought to have been fully terrestrial animals.

A study of diplodocid snouts showed that the square snout, large proportion of pits, and fine subparallel scratches in Apatosaurus suggests it was a ground-height nonselective browser. It may have eaten ferns, cycadeoids, seed ferns, horsetails, and algae. Kent Stevens and Michael Parrish (1999 and 2005) suggest that Apatosaurus had a great feeding range as its neck could bend into a U-shape laterally. The neck’s range of movement would have also allowed the head to graze below the level of the body, leading some scientists to speculate on whether these sauropods grazed on submerged water plants, from riverbanks.

Source: Wikipedia