Correction Appended

A new dinosaur species, one of the largest known carnivorous dinosaurs, has emerged from the red sandstone of Patagonia, in Argentina, where reptilian giants seem to have thrived 100 million years ago.

Paleontologists reported yesterday that they had found the fossils of seven to nine individuals of a species they are naming Mapusaurus roseae.

An analysis of the bones showed that an adult exceeded 40 feet in length, which the discoverers said was slightly larger than specimens of both its close relative, Giganotosaurus, and Tyrannosaurus rex. Some scientists think that a Spinosaurus species from North Africa is the largest meat-eating dinosaur, but that is still debated.

The discovery was made in sediments of a 100-million-year-old water channel at a site 15 miles south of Plaza Huincul, Argentina. It was reported at a news conference in Plaza Huincul and described in the French journal Geodiversitas.