Fossils of 14 lumbering titanosaurs that died in a volcanic eruption near Moab at least 100 million years ago cast doubt on the origin of the species.
The fossils of the 40-foot-long, 12-foot-tall plant eaters are the oldest ever found in North America. Earlier samples, dating back 98 million years, had been found in South America, Africa and India.That made scientists believe the Titanosauridae family migrated to Utah and New Mexico from South America. Now, said Brooks Britt, speaking Friday during the Society of Vertebrate Paleontology's annual meeting, that theory is in doubt.
The new find of the 100 million- to 120 million-year-old titanosaurs at Dalton Wells quarry near Moab means there were titanosaurs living in North America at the same time they were in the Southern Hemisphere, Britt said.
"That calls into question this theory titanosaurs invaded from the Southern Hemisphere," he said. "We can say equally well they came from North America and went south."
Paleontologist Catherine Forster of the State University of New York-Stony Brook, said the Utah finds could be the base of the titanosaur family tree.
"Once we figure out how titanosaurs are related, we can tell which way the migration went," she said.
Britt dug and studied the titanosaurs with Rod Scheetz from the Grand Junction museum, Kenneth Stadtman from Brigham Young University and John McIntosh of Connecticut's Wesleyan University.
So far, 2,900 bones have been excavated representing eight species, five of which are new, including the titanosaur species.
Other plant eaters at Dalton Wells include the armored Gastonia, Iguanodontid and new species of camarasaurid and brachiosaur, Britt said. Meat eaters include Utahraptors and two new species of small carnivore. Most were announced last year, but Britt gave many new details of titanosaurs on Friday.
Less than a tenth of the quarry has been excavated.
Titanosaur fossils found at the site include 8- to 10-inch-long brain cases - the back part of the skull that housed the dinosaur's small brain - and most other bones. There is no complete skull, but a nearly complete skeleton could be built from the 14 individuals.
The Utah titanosaurs were among a dozen dinosaur fossil discoveries highlighted during the Snowbird meeting. Others included titanosaurs from Madagascar and Malawi, the first duck-billed dinosaur fossils found in Antarctica, the first occurrence of an African meat eater in South America and beautiful Velociraptors from Mongolia with bird-like features.