The oldest known turtle might not have looked much like a turtle at all.

This chubby, 260-million-year-old ancestor called Eunotosaurus -- without a shell and with a long tail -- more closely resembled an extremely fat lizard, according to a new study by anatomy expert Gaberiel Bever at New York Institute of Technology and three other researchers.

After four years, thousands of hours of research and myriad CT scans, Bever and his colleagues made an important discovery: Turtles are more like lizards, crocodiles and snakes than scientists previously thought.

The new information could spur bigger questions and deeper research into topics such as the evolution of DNA and the key to turtle longevity. The findings were published this month in the journal Nature and proved an earlier hypothesis by Bever, an assistant professor of anatomy at NYIT's College of Osteopathic Medicine in Old Westbury, and one of the researchers.

"There has been a lack of transitional fossils," Bever said, explaining why the research is being done now. "Finding the early, early turtles has been the Holy Grail."

The findings made "a bit of a splash" in the turtle research community, said Hofstra biology Professor Russell Burke, a vertebrate ecologist whose studies include diamondback terrapin turtles in Jamaica Bay Wildlife Refuge.

The Eunotosaurus specimens were special because of their exceptional age and how well-preserved they were, Burke said. In addition, their skulls were mostly intact.

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Eunotosaurus first was found in South Africa in the late 1800s, but there has long been debate about whether it was a turtle.

About 50 specimens have been discovered, though few of those have skulls. Three were carefully shipped from South Africa to the United States and scanned with a high-powered CT scanner to produce images of what the inside of a Eunotosaurus skull looked like without damaging it. A fourth was scanned in South Africa.

Bever studied the scans, put the information into data sets and analyzed it against other data collected from turtles and other reptiles. The four-year process supported a hypothesis that Eunotosaurus was an early turtle and helped researchers place it in the evolutionary tree.

"Science itself and scientists are incredibly conservative," Bever said. "It takes a lot to get them to accept something new. You have to overwhelm them with evidence."

Turtles, unlike other reptiles, do not have openings in their skulls through which the muscles that control their jaws pass. The muscles are completely encased in bone. Eunotosaurus, however, had these openings, indicating that turtles are more closely related to lizards, crocodiles and other reptiles, as well as birds, than previously thought.

Bever noted that Eunotosaurus was to turtles what Archaeopteryx was to birds, in terms of linkage in the fossil record between the creatures' forms millions of years ago, compared with today. Archaeopteryx, discovered in 1861 in southern Germany, was about the size of a common raven and is considered by paleontologists to be a transitional fossil between dinosaurs and modern birds.

Modern turtles, whose shells are unique in the animal kingdom, were thought to be much different from other creatures, Bever pointed out. The new research, however, highlights the similarities between turtles and other animals -- an important distinction, he said.

Such commonalities mean the findings could have implications for mammals, including humans, which share some characteristics with turtles. Those could include studying why turtles live so long and whether findings from such research could help in lengthening human life spans.