pig nosed turtle
Arvinachelys goldeni - the pig nosed turtle Victor Leshyk

What has been dubbed the weirdest turtle to have ever lived has been discovered in Utah, named so because of its pig nose. Arvinachelys goldeni lived 76 million years ago alongside tyrannosaurs, armored ankylosaurus and giant duck-billed dinosaurs.

The extinct pig-nosed turtle was around two feet long and had a streamlined shell ideal for living in rivers. However, it also had a broad snout with two bony nasal openings – all other turtles have just one external nasal opening, with the division between the nostrils being just flesh.

Its scientific name derives from "arvina", the Latin word for pig fat or bacon, and "chelys", which is Latin for tortoise. Many ancient turtle species are represented by fossils consisting of just an isolated skull or shell – having the two is a rare occurrence. Pig nose turtle, however, was found with its skull, shell and almost a complete forelimb, partial hindlimbs and vertebrae from its neck and tail.

Arvinachelys goldeni
Snout view of the skull of the fossil turtle Arvinachelys goldeni with its shell in the background. Natural History Museum of Utah

Joshua Lively, who is now at the University of Texas at Austin, reported the species in the Journal of Vertebrate Paleontology. He said: "It's one of the weirdest turtles that ever lived."

The find fills in gaps relating to the evolution of turtles. Randall Irmis, curator of palaeontology at the museum, said: "With only isolated skulls or shells, we are unable to fully understand how different species of fossil turtles are related, and what roles they played in their ecosystems."

The turtle was discovered in the Grand Staircase-Escalante National Monument by scientists from the Natural History Museum of Utah. This area in the US is abundant with fossil remains and at the time Arvinachelys lived, western North America was a large island continent called Laramidia, with a sea stretching from the Arctic to the Gulf of Mexico separating it from eastern North America.

Dinosaurs living in southern Laramidia – southern Utah, New Mexico and Texas – appear to have diversified from their relatives in the northern part of the continent. Arvinachelys fits in with this pattern, the scientists note. "It really helps add to the story emerging from dinosaur research carried out at the Natural History Museum of Utah," Lively said.

Why these species were kept separate from one another remains a mystery but scientists think rising sea levels and climate change might have created barriers. Understanding how creatures coped with such conditions will aid our understanding of how modern-day animals will respond to future climate change, the researchers added.