Scientists found two individual animals on the site that appeared to have gut contents that included young of the same species.
The skeletons were too far developed to be unborn fetuses, so the late Edwin H. Colbert, chair of the department of vertebrate paleontology at AMNH, reached another conclusion.
Colbert determined that the remains were the last meals of larger Coelophysis—and dramatic evidence of dinosaur cannibalism.
For decades the find has been considered one of the very few examples of cannibalism among theropods.
But an odd-looking bone led researchers to revisit the Coelophysis case.
"You could see [the bone] on exhibition, and right from the beginning we felt that this didn't really look like a dinosaur," said Alan Turner, another Columbia University graduate student studying at AMNH.
The juvenile femur and other bones found in one of the accused Coelophysis's gut contents revealed leg and hip characteristics that are shared by crocodilians, not dinosaurs.
Studies of the femur's growth rate confirmed that it was crocodilian, because the reptiles exhibit very different growth characteristics from dinosaurs.
"I think it's pretty evident that this animal had not fed on its own young but on something else," said Peter Makovicky, dinosaur curator at the Field Museum in Chicago, Illinois.
The second animal's "last meal" may not have been a meal at all.
The study suggests that the gut contents were actually found outside the rib cage and were big enough to raise eyebrows.
"The [size of the] gut contents was very, very large and not likely to be a meal that this animal could have consumed," said AMNH's Turner.
It's possible that, during whatever calamity caused the mass deaths at Ghost Ranch, an adult dinosaur may have fallen on top of the remains of a juvenile beast.
If so, their bones could have mingled over the eons and created the mistaken impression that one animal had swallowed the other.
Given the new analysis, experts say that no one can be sure if therapod dinosaurs ever indulged in cannibalism.
"The best evidence was the Coelophysis find, and I think that's now largely refuted," said the Field Museum's Makovicky.
"It doesn't necessarily mean that Coelophysis would have not have acted cannibalistically given the opportunity. It just means that we're back to a state where we have no evidence."
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