Barosaurus lentus

Barosaurus lentus was a giant diplodocid sauropod from the Late Jurassic Morrison Formation of the western United States. It shared the long, low body plan of Diplodocus but carried an even more elongated neck and a proportionally shorter tail. The vertebrae were extensively hollowed by air spaces, reducing the weight of the enormous neck, while sturdy limbs supported the body. No skull has been securely associated with Barosaurus, so every mounted or illustrated head is reconstructed from related diplodocids. The species is comparatively rare, yet several partial skeletons together reveal much of its body and support an adult length of roughly 24 to 27 metres.

Its fossils occur between approximately 155 and 150 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The neck consisted of highly elongated, air-filled vertebrae supported by complex bony struts and extensive soft tissues. The torso was compact for such a long animal, and the forelimbs were somewhat longer and more slender than those of Diplodocus. A long tail balanced the front of the body, although it was proportionally shorter than in Diplodocus. Forked chevrons hung beneath many tail vertebrae. The narrow, peg-toothed head shown in reconstructions is inferred from close relatives because a Barosaurus skull remains unknown.

• Extremely elongated cervical vertebrae forming a very long neck
• Air-filled vertebrae reinforced by internal bony struts
• Proportionally shorter tail than Diplodocus
• Relatively long and slender forelimbs
• Forked chevrons beneath much of the tail
• No securely identified skull

The first Barosaurus fossils were collected from the Morrison Formation of South Dakota in 1889 and consisted chiefly of tail vertebrae. Othniel Charles Marsh named Barosaurus lentus in 1890. Later skeletons from Dinosaur National Monument supplied much more of the neck, trunk and limbs. One of these individuals, nicknamed Gordo, remained partly unrecognized in the Royal Ontario Museum's collections until staff assembled its bones into Canada's largest mounted dinosaur. The American Museum of Natural History created its famous rearing group from casts representing material held by several institutions rather than one complete individual.

Naming authors: Othniel Charles Marsh.

Barosaurus lived on the broad river floodplains and seasonally dry woodland mosaics recorded by the Morrison Formation. Ferns, horsetails, cycads and conifers supplied vegetation at many heights. It shared these environments with other giant sauropods, stegosaurs and ornithopods, while Allosaurus and other large theropods were potential predators. The map marker represents the public Carnegie Quarry region at Dinosaur National Monument, not a precise fossil coordinate.

Its long neck allowed Barosaurus to reach vegetation across a wide feeding envelope while moving its heavy body less often. How high it normally held the neck remains debated. Rearing on the hind limbs, as shown in famous museum mounts and the selected artwork, is mechanically conceivable but has not been observed and cannot be established as routine behaviour from fossils. No direct evidence reveals herd structure, mating displays or parental care.

• No Barosaurus skull has yet been securely identified.
• The Royal Ontario Museum's Gordo mount is about 27 metres long.
• A limb bone associated with the ROM skeleton preserves a rare impression of sauropod skin.
• The American Museum of Natural History displays a dramatic rearing Barosaurus family group made from casts.
• Its neck was longer and its tail proportionally shorter than those of Diplodocus.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Barosaurus lentus

   Dinosaur National Monument, U.S. National Park Service

   Open source
2. 02
   Iconic: Barosaurus

   Royal Ontario Museum

   Open source
3. 03
   Saurischian Dinosaur Fossils

   American Museum of Natural History

   Open source
4. 04
   Barosaurus dinosaur directory entry

   Natural History Museum, London

   Open source