Edwin H. Colbert, a former paleontologist with the American Museum of Natural History in New York who died in 2001, presented the first evidence for dinosaur cannibalism 1989. Colbert described two adult specimens of Coelophysis bauri, found with the skeletons of young Coelophysis in their rib cages. The small meat-eating dinosaur lived in North America during the Late Triassic period 228 to 208 million years ago.
Colbert's find was questioned, however, when Robert Gay, a paleontology student at Northern Arizona University in Flagstaff, presented evidence at a conference in October 2002 suggesting the larger animals were merely lying on top of the younger ones, casting evidence of cannibalism into doubt.
Several bones of carnivorous dinosaurs with tooth marks on them from other meat-eating dinosaurs have been found in Alberta, Canada. But scientists have yet to narrow down who was eating who, said Rogers.
The latest find suggests cannibalism owing to bones found with distinctive sets of tooth marks that match both the size and spacing of teeth in Majungatholus' jaws and similar grooves that match the sharp serrations on Majungatholus' blade-like teeth.
The researchers were careful to compare the tooth-scored Madagascar bones to the teeth of other animals living on the island 65 to 70 million years ago. One two-footed, meat-eating dinosaur named Masiakasaurs was ruled out because of its small size: It only grew to one-fifth the size of 30-foot (9-meter) Majungatholus.
Other possible candidates include two large crocodiles (Mahajangasuchus insignis and Trematochampsa oblita). But both animals had teeth too variable in size, spacing, and location to have made the evenly-spaced tooth marks observed on the fossils, said Krause. Nor did the ancient crocodiles have tooth serrations of correct size and spacing to have made drag marks observed on some of the best-preserved bones.
"With these other candidates eliminated, Majungatholus atopus stands accused of cannibalism and is presumed guilty until proven innocent, which, in my opinion, is unlikely to happen," said Krause.
Hans-Dieter Sues, associate director for science and collections and curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, originally described Majungatholus in 1979. He said he was not the least bit surprised to learn of new evidence pointing to cannibalistic behavior by Majungatholus.
"I fail to see what the big deal is," he said. "Cannibalism is very common among reptiles and Coelophysis has long been established as eating small members of its own speciesthe unpublished recent claims of a student from Arizona notwithstanding."
Rogers agrees that finding evidence for cannibalism among dinosaurs is no big surprise. The behavior is common among living reptiles and mammals, fish, birds, even insects. "But I would certainly like to see comparable evidence presented for Coelophysis," he said.
More than making the case for cannibalism, the evidence collected by Rogers and colleagues helps paint a picture of Majungatholus' life as a hard and stressful venture that caused it eat its own kindnot out of dietary preference but out of a bid to stay alive.
According to Rogers' analysis of rocks and soils where the fossils were found, Late Cretaceous Madagascar was marked by a seasonal and semi-arid climate, much like that of Madagascar today. Flooding occurred periodically. In addition, times of severe drought forced animals to gather around the few remaining sources of water.
"There might have been times of plenty for Majungatholus, but there also might have been times of need, and these stressful episodes could have led to this behavior," he said.
Many of the fossils collected in Madagascar came from large bone beds, where in addition to Majungatholus, the researchers found frogs, turtles, and the remains of long-necked sauropods called titanosaurs that were also a staple in Majungatholus' diet.
The beds suggest to Rogers an oasis, perhaps the remaining source of water and forage that a variety of animals migrated towards in a hard scrabble effort to survive. Such a lean environment can push animals that might not regularly practice cannibalism to seek sustenance in the flesh of their neighbors.
"I think that periodically in this ecosystem animals were pushed to feed on whatever was remaining to feed on," said Rogers. "They were hard times. Majungatholus had to strip all remaining flesh from bones."
This intense feeding behavior, Rogers said, would account for the unusual concentration of tooth-marked bones and suggests that the dinosaurs were so hungry they sought every available bit of flesh.
"The evidence indicates that Majungatholus was a methodical carnivore, capable of focusing on particular behaviors," said Curry Rogers. "It worked long and hard to procure a meal."
More National Geographic News Stories on Dinosaurs:
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
Study Paints New Picture of Dinosaur's Nose
Skeleton of New Dinosaur "Titan" Found in Madagascar
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
"Feathered" Fossil Bolsters Changing Image of Dinosaurs
Oddly Angled Teeth Make Masiakasaurus Stick Out
New Find: Pterosaur Had Strange Crest, Fishing Style
Dinosaur Beak Probably Used to Strain Food, Not Kill Prey
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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