Some 113 million years ago, a little turkey-sized dinosaur that stalked the dense forests that once covered Australia and Antarctica came to an unfortunate end, after it was caught in a log-jam on an ancient river.

The astonishing partial fossil of the dinosaur has been identified as a new species named Diluvicursor pickeringi, and its unfortunate end is helping researchers piece together an incredible picture of what this part of the world was like back when the dinosaurs were thriving and Antarctica was covered in forests. From the tail and hind leg, they have identified the poor beastie as a bipedal herbivorous dinosaur known as an ornithopod, but it was unlike many examples already uncovered, they report in PeerJ.

The fact that the remains of the dinosaur were seemingly caught up in a log-jam on a river can tell us a lot about the environment at the time, and from this, we can begin to build up an image of the ecology of the dinosaurs themselves.

“The carcass of the Diluvicursor pickeringi holotype appears to have become entangled in a log-jam at the bottom of this river,” explained Dr Matt Herne, who led the study. “The sizes of some of the logs in the deposit and the abundance of wood suggest the river traversed a well-forested floodplain.”

The researchers were able to deduce that the dinosaur was living in the rift valley ecosystem that straddled the two southern continents, which was lush, green, and brimming with life. The logs found show that the sides of the valleys were blanketed in conifer forests made up of trees from families that are still found in parts of Australia today, while deep fast rivers flowed across the valley floors. As trees died and fell over they were washed away and collected in bends in the rivers, not unlike what is seen today in large forested areas.

But in addition to the unusual way in which the dinosaur was preserved, and what this can tell us about the ecology of the animal itself and the environment it roamed through at the time, the fossil remains are also helping palaeontologists better understand the diversity of the group of dinosaurs to which it belonged.

“Diluvicursor shows for the first time that there were at least two distinct body-types among closely related ornithopods in this part of Australia,” said Dr Herne. “One was lightly built with an extraordinarily long tail, while the other, Diluvicursor, was more solidly built, with a far shorter tail. Our preliminary reconstruction of the tail musculature of Diluvicursor suggests this dinosaur was a good runner, with powerful leg retracting muscles.”