Horned Variety : Fossils Found of Small Type of Dinosaurs

Fossils of a previously unknown type of horned dinosaur have been discovered in the 75-million-year-old Judith River Formation in south-central Montana, paleontologist Peter Dodson of the Philadelphia Academy of Natural Sciences announced Thursday.

The 7 1/2-foot-long, 3-foot-high plant eater, named Avaceratops lammersi , probably was a juvenile weighing about 400 pounds, Dodson said. Adults could have grown to 12 feet in length. “It challenges the notion that all dinosaurs were large,” Dodson said.

The Judith River formation was the source of many dinosaur fossils in the 19th Century, but the new fossil is the first major discovery of this century.

Carries Bony Frill

The distinctive feature of Avaceratops , Dodson said, is the shape of the bony frill projecting from the back of the animal’s skull. All horned dinosaurs possess this frill, but previously discovered specimens all had a pair of large openings, while the frill of the new specimen is solid.

Parts of the skeleton were first found in 1981 by professional fossil hunter Eddy Cole, who removed about 700 bones from the site. Dodson subsequently examined Cole’s finds and recognized the significance of the Avaceratops fossils. Cole and Dodson later excavated more bones from the site with support from the National Geographic Society.

Dodson said that 40% of all known dinosaurs have been discovered since 1970, and that about seven new species are discovered each year.