A Forrest Gump of the dinosaur era.

Nature does not always favor the fleetest or most sophisticated.

Paleontologists have unearthed the remains of a huge, strangely shaped mollusk from the Cretaceous period that succeeded in spite of its ungainly body.

While digging on Seymour Island off the coast of Antarctica, Anton Oleinik (left) and William Zinsmeister from Purdue University in West Lafayette, Ind., discovered a 6-foot-long fossil belonging to a 65-million-year old ammonite called Diplomoceras maximum, shown between the two researchers. Scientists had found only fragments of the animal in the past and therefore did not realize it had a long, awkward shell shaped like a giant paper clip (see sketch below).

Relatives of the chambered nautilus, ammonites filled the seas during the Mesozoic era, the age of the dinosaurs. Because 95 percent of ammonites had beautifully coiled bodies, paleontologists have traditionally considered the uncoiled forms as evolutionary dead ends that could not compete well, says Zinsmeister.

But the Diplomoceras proliferated near Seymour Island, and the new find shows that some grew quite large. "They seemed to have competed as well as their swift and agile cousins. That's why I refer to the fossil as the Forrest Gump of the ammonites," says Zinsmeister.