A key difference to later sauropods is in Antetonitrus' limbs. "The hand was not transformed into the tubular weight supporting device that it is in later sauropods, it had kept a crude grasping [thumb] seen in earlier two-legged dinosaurs," said Yates, also noting that Antetonitrus' "hind feet were not quite the stumpy broad elephant-like feet of later sauropods. The toes were still quite long."
"We now know [sauropods] were present in the early history of the dinosaurs. We just hadn't recognized them," he said. Yates and Kitching will publish their new description of the species in an upcoming print edition of London's Royal Society Journal Biology Letters.
Kitching has built his reputation since the 1950s uncovering great quantities of Triassic and older Permian fossils in South Africa's Karoo region.
While Antetonitrus was larger than any land animal living today and its contemporaries, it pales in comparison to the monumental dinosaurs that would follow millions of years later. Brachiosaur species from the Jurassic period (200 to 144 million years ago) ranged from 22 to 30 meters (72 to 98 feet) in length and weighed a whopping 30 to 80 tons (27 to 73 metric tons). Even larger dinosaurs followed in later periods until their extinction 65 million years ago.
But the newly discovered species was the first dinosaur giant, said Michael Benton, a dinosaur expert at the University of Bristol in England who commended the find.
"[Antetonitrus] is a quadruped because it has to be," said Benton. "At that size it couldn't continue as a biped." The new fossil shows that the four-footed dinosaurs evolved from two-footed ancestors earlier than thought and, surprisingly, retained some grasping function in their forelimbs, Benton said. "All later sauropods have [hands] designed solely to support their weight," he said.
And that transition to four-feet allowed sauropods to attain great size, and reap the benefits in more ways than one. Huge animals are more challenging snacks for predators, rarely get cold, and are able to break down large quantities of otherwise low quality plant food, by slowly fermenting it in their massively elongated guts.
Naming a new dinosaur is the "realization of a lifelong dream," said Yates. While ingenipes means massive paw, Antetonitrus comes from the Latin for before the thunder, and is fitting for an early ancestor of BrontosaurusGreek for thunder lizard.
More National Geographic News Stories on Dinosaurs:
Dinosaur Cannibal: Fossil Evidence Found in Africa
Bizarre Dinosaurs Shed Light on Adaptation
Robots Designed to Show How Dinosaurs Moved
Dino Dung: Paleontology's Next Frontier?
Do They Really Look Like That? The Science of Dino Art
Dinosaur Footprints: Tracks Tell Prehistoric Secrets
Four-Winged Dinosaurs Found in China, Experts Announce
Utah Dinos May Have Been Killed By Drought
Cuban Dinosaur: First Confirmed Remains Discovered
Dinosaur Cannibal?Mystery in New Mexico
Tetrapod Fossil FoundFirst Ever in Asia
New Picture of Dinosaurs Emerging
Fossil Implies Our Early Kin Lived in Trees, Study Says
Weird Buck-Toothed Dinosaur Found
Dinosaur Tracks Preserved on Scottish Island
Dinosaur Tracks Shed Light on Sauropod Evolution
Comets May Have Led to Birth and Death of Dinosaur Era
Fossil of Dog-Size Horned Dinosaur Unearthed in China
Tyrannosaurus rex Was a Slowpoke
Researchers Rethink Dinosaur Die Off Scenario
Researchers Melt Polar Dinosaur Mysteries
Scientist's Finds Spur New Thinking on Dino Evolution
Dino-Era Vomit Fossil Found in England
Additional Dinosaur Resources from National Geographic:
Paul Sereno: National Geographic Explorer-in-Residence and Dinosaur Hunter
Destinations: Dinosaur National Monument
RELATED LESSON PLANS
Use this National Geographic News article in your classroom with these Xpeditions lesson plans and student activity:
K-2: Dinosaur Bodies
3-5: How Do Scientists Find Dinosaur Fossils?
6-8: The Science of Digging Up Dinosaurs
9-12: The Evolution of Dinosaurs Over Geologic Time
K-2: Those Fussy Dinosaurs!
9-12: Physical Characteristics of Places: The Fossil Record
Activity: A Dinosaur's Neighborhood
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