BALTIMORE, Oct. 29 (UPI) -- New evidence offers further proof that tyrannosaurs ate their own kind.
The latest evidence comes from Wyoming. Researchers were there looking for fossils when they unearthed a 66-million-year-old tyrannosaurus bone with gashes that could only have been made by another hungry tyrannosaurus.
"We were out in Wyoming digging up dinosaurs in the Lance Formation," recalled Matthew McLain, a paleontologist with the Loma Linda University in Southern California. "Someone found a tyrannosaur bone that was broken at both ends. It was covered in grooves. They were very deep grooves."
The bone's groves were deep and perpendicular, made by a large predator pulling meat from the bone.
One particular laceration proved especially important in the paleontologists analysis of the bone. Toward the end of the bone are the marks of a tooth dragged sideways across the bone, as if the hungry dino turned its head to look up from its meal. The move imprinted the tooth's serrations in the bone.
The grooved teeth rule out a massive prehistoric crocodile as the culprit, leaving only two theropod dino species from the Lance Formation -- Tyrannosaurus rex or Nanotyrannus lancensis.
"This has to be a tyrannosaur," said McLain. "There's just nothing else that has such big teeth."
Many scientists believe N. lancensis is not a separate species, but simply a juvenile T. rex, thus leaving cannibalism as the only explanation for the massive grooves. Researchers can't say whether the tyrannosaur was scavenging or actually tracked down and killed its meal.
McLain and his colleagues are preparing to present their latest findings this weekend at the annual meeting of the Geological Society of America in Baltimore.
Scientists have previously used bone markings to suggest a variety of large dinosaur species were willing to eat their own kind, but McLain and his colleagues claim theirs is the most compelling evidence yet.