You can call it a Triassic titan. Or a pre-Jurassic juggernaut. Just don’t call it a dinosaur. Despite its appearance, this burly behemoth was a completely different prehistoric beast: a dicynodont.

Early relatives to present-day mammals, dicynodonts dominated Earth more than 200 million years ago, living first before, and then alongside, dinosaurs. Unlike dinosaurs, these herbivorous animals had short necks and large skulls. They were stocky like rhinos, toothless and had tusks and turtle-like beaks. Many ranged in sizes from pigs to hippos, though some were small enough to burrow into the ground.

Now, scientists have uncovered a new species of dicynodont that towered over the rest, comparable in size to an elephant.

The newly discovered species, known as Lisowicia bojani, was 8.5 feet tall and about 15 feet long, and weighed 9 tons. It is both the largest and youngest dicynodont found so far and its discovery provides further evidence that these proto-mammals survived into the late Triassic Period, past the point when many scientists had previously thought they went extinct.

The finding was published recently in the journal Science.

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A team of paleontologists began uncovering the new dicynodont bones from a clay pit in the village of Lisowice in southern Poland in 2006.

“We found the first bones in ten minutes,” said Grzegorz Niedźwiedzki a paleontologist from Uppsala University in Sweden and an author on the study. “It was so clear to us that it’s a kind of El Dorado.”

At first, the researchers thought the bones belonged to long-necked dinosaurs called sauropodomorphs, a group that includes brachiosaurus and titanosaurs. During a dig, one of Dr. Niedźwiedzki’s colleagues unearthed a humerus which was found to belong to a dicynodont, not a dinosaur.

That was a surprise because the site had been dated to the late Triassic Period, and many paleontologists believed dicynodonts had died out by that time. The bones, the team said, provided further evidence that dicynodonts lived at least another 10 to 15 million years. That suggests that they did not go extinct before dinosaurs began conquering the land, but instead coexisted with them for some time.

But Dr. Niedźwiedzki said it wasn’t until 2011 when another colleague found a 3-foot-long scapula that the researchers began to comprehend the beast’s true size.

“It was so obvious to us that this was a really big animal,” said Dr. Niedźwiedzki. “It’s a monster. We don’t have something like this in the fossil record.”

Since then they have found hundreds of bones belonging to different gigantic individuals.

They compared the bones to previous dicynodont specimens, trying to better understand how it stood and moved. The team thinks the new dicynodont had a fully erect gait, like what you would see in a horse or elephant, as opposed to an intermediate crocodile-like or lizardlike sprawl.

Christian Kammerer, a paleontology curator at the North Carolina Museum of Natural Sciences who was not involved with the study, said he agreed that the latest dicynodonts may have had a more upright gait than their Permian ancestors. But he noted that because we don’t know how the tendons, ligaments and cartilage caps were attached to its limbs, we can’t be sure.

“It’s questionable if it was really that mammal-like in its posture.” Dr. Kammerer said. “There’s a lot of wiggle room there.”

The team plans to continue excavating the Lisowice site. And Dr. Niedźwiedzki thinks there might be dicynodonts that are even more colossal buried there.

“Something really big is waiting for us in Poland,” said Dr. Niedźwiedzki.

Nicholas St. Fleur is a science reporter who writes about archaeology, paleontology, space and other topics. He joined The Times in 2015. Before that, he was an assistant editor at The Atlantic. @scifleur Facebook

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