Team discovers Jobaria tiguidensis of Cretaceous Period

A primitive, long-necked dinosaur that weighed an estimated 20 tons and grew to a length of 70 feet is the newest species to be plucked from the African Sahara by a team led by Chicago paleontologist Paul Sereno.

“With 95 percent of its skeleton preserved, the new species stands as the most complete long-necked dinosaur ever discovered from the Cretaceous Period,” said Sereno, Professor in Organismal Biology & Anatomy.

The species, discovered in the Republic of Niger and described in the Nov. 12 issue of the journal Science, was unveiled last week at a news conference at the National Geographic Society, a sponsor of the project.

Toiling in temperatures exceeding 120 degrees, Sereno’s team excavated tons of bone and rock during a 1997 expedition and spent two years cleaning and studying the fossilized bones. The team has constructed two full-size cast skeletons: a 60-foot-long adult, rearing to a height of more than 30 feet, and a juvenile, posed in mid-stride.

The new dinosaur, named Jobaria tiguidensis, lived about 135 million years ago during the Cretaceous Period, when open forests and broad rivers characterized the region. Jobaria (JO-BAR-E-YA) refers to “Jobar,” a creature in the legends of the local Tuareg nomads. The Tuareg legend grew out of the fact that the creature’s exposed bones were in plain view. Tiguidensis (TI-GI-DEN-SIS) refers to a cliff near the excavation sites.

The main graveyard contained bones of several adults and juveniles, suggesting that Jobaria once roamed in herds of mixed age, Sereno said. Although an ancient flash flood quickly buried the animals, some may have died at the hands of the chief meat-eating dinosaur of the time, Afrovenator, a 27-foot-long predator previously discovered in the same area by Sereno’s team. Tooth marks are present on the ribs of one of the juvenile skeletons.

Jobaria does not fit into any recognized family of long-necked dinosaurs, or sauropods. Rather, Jobaria represents an ancient sauropod lineage that survived and flourished only in Africa during the Cretaceous Period.

Unlike other Cretaceous sauropods, Jobaria has spoon-shaped teeth and a relatively short neck composed of only 12 vertebrae. Jobaria’s backbone and tail are simple compared to the complex vertebrae and whiplash tail of the older, North-American sauropods Diplodocus and Apatosaurus.

“Jobaria is a real survivor, a relic in its own day,” said Jeff Wilson of the University of Michigan, a sauropod expert on Sereno’s team. A general analysis of the dinosaur record by Sereno and his Science co-authors revealed an uneven pace of skeletal change.

“Some dinosaurs change a lot in a short amount of time, whereas others change very little over millions of years,” Wilson said. Jobaria is an example of the latter.

Sereno’s team has studied modern elephants in an attempt to more realistically reconstruct the Jobaria skeletons. The team believes that despite its enormous size, Jobaria moved gracefully, with its feet set close to each other under the body.

“Its proportions were elephant-like, and its bones could have supported its body mass when rearing during feeding or in courtship contests,” Sereno said. Jobaria’s flexible neck and spoon-shaped teeth were well adapted for nipping the smaller branches of trees.

Sereno’s field and lab work was supported by the National Geographic Society, the David and Lucile Packard Foundation, the Pritzker Foundation and the Women’s Board of the University. Sereno also won additional support by competing in the 1999 Chicago Marathon Celebrity Challenge and from pledges from children and other contributors.

The skeletons will be on display at a free exhibit, “Dinosaur Giants,” in the Crystal Gardens of Navy Pier in Chicago from Jan. 14 to March 19.

For more information, see www.jobaria.org.