Geotimes - September 2003 - Dinosaur skeletons in the closet

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Paleontology
Dinosaur skeletons in the closet

More than 20 years after unearthing a 215 million-year-old skeleton, paleontologists are realizing the value of their find. A researcher at the University of Witwatersrand in Johannesburg, South Africa, has discovered that the bones belong to a previously unseen dinosaur — becoming the oldest known species among the giant, four-legged sauropods.

At the South African site of the original discovery of a new dinosaur, Antetonitrus ingenipes, Lukas Huma surveys the fossil skeleton. Photo courtesy of Bernard Price Institute for Palaeontological Research.

Paleontologist James Kitching of the University of Witwatersrand discovered the bones in 1981 in late-Triassic sediments of the Karoo region of South Africa. He brought the bones back to his laboratory at the Bernard Price Institute for Palaeontological Research (BPI) for study. Yet, after he cleaned and prepared the bones, Kitching associated them with prosauropods, ancient “cousins” of the enormous long-necked dinosaurs that would become the largest land animals on Earth.

Not until 2001 did Adam Yates, a post-doctoral researcher at BPI, arrive at the university and notice that the fossils warranted further investigation. Yates recognized that the bones were much more similar to actual sauropods than any of their relatives. In fact, the new species may represent a link between sauropods and prosauropods.

Yates, who specializes in vertebrate evolution, has named the dinosaur Antetonitrus ingenipes, as described in the July 3 Proceedings of the Royal Society: Biological Sciences. The genus name Antetonitrus means “before the thunder” — a reference to the dinosaur’s descendant Brontosaurus, or “thunder lizard”; and the species name ingenipes means “massive paw.”

Antetonitrus had a flexible, clawed thumb akin to the ones on prosauropods, probably used for gripping or defense against predators. Prosauropods had shorter front legs than rear legs, while Antetonitrus had nearly equal-length legs, indicating that it is the earliest example of a dinosaur that walked solely on four feet (a sauropod trait). Other skeletal traits revealed that Antetonitrus was also probably a strict herbivore, not an occasional meat-eater — the earliest example of a vegetarian sauropod.

Forelimb bones of a new species of sauropod — the earliest example of a dinosaur that walked solely on four feet. Photo courtesy of Bernard Price Institute for Palaeontological Research.

Although Yates can tell from the dinosaur’s backbones that the Antetonitrus specimen at Witwatersrand is a juvenile, the dinosaur still would have weighed 1,800 kilograms (3,900 pounds), stood two meters (6.5 feet) high at the hips, and stretched 8 to 10 meters (26 to 33 feet) long. As with later sauropods, Antetonitrus is far larger than its contemporaries — truly a giant for its time.

Josh Chamot
Geotimes contributing writer

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