Dinosaurs like tyrannosaurs and velociraptors famously walked on two legs. But they weren’t the only bipedal prehistoric creatures to exist. In a study published in June, paleontologists shared the discovery of a new bipedal shuvosaurid, an ancient, distant relative of crocodiles, that lived 212 million years ago in what is now the U.S. state of New Mexico.
Unlike modern-day crocs, the newly described Labrujasuchus expectatus was beaked, toothless, had two tiny arms, and walked on two legs.
Researchers found fossilized bones of L. expectatus alongside those of bipedal dinosaurs at the Hayden Quarry at the Ghost Ranch site, famous for its well-preserved fossils. They were found in sediments dated to the Late Triassic period.
The generic name of the species Labrujasuchus comes from “Ranchos de los Brujos,” or Ranch of the Witches, an old Spanish name for the Ghost Ranch area. The Greek word Σοῦχος (suchus) means crocodile.
The species name expectatus references the idea that researchers expected to find a shuvosaurid fossil at the Hayden Quarry. In an email interview with Mongabay, Nathan Smith, study co-author, paleontologist and director of the Dinosaur Institute, Natural History Museum of Los Angeles County, U.S., said the first shuvosaurid described, which was originally misclassified as a dinosaur, was named Shuvosaurus inexpectatus, as a way to point out that such a bizarre-looking creature was not “expected” in Late Triassic rocks.
“So, the ‘expectatus’ name is a cheeky nod to the original Shuvosaurus discovery, and the fact that we definitely expected to come across some shuvosaurid fossils at the Hayden Quarry,” Smith said.
Why shuvosaurids and dinosaurs evolved bipedal lifestyles is a biological mystery, but it could have offered several evolutionary advantages, he said, including faster locomotion and a higher line of sight for seeing prey or predators. It also likely freed up forelimbs for other activities such as grasping prey, he added.
Although L. expectatus fossils were found in what is now the New Mexican desert, the area was a very different habitat 212 million years ago. “It would have been a broad, low floodplain that would have seen a lot of seasonal fluctuation in rainfall, and also experienced shifts in plant communities and resources,” Smith said. “We also know that the region was marked by intermittent large-scale wildfires from fossil charcoal evidence.”
What L. expectatus ate is, however, a mystery. Some studies examining the skulls and jaws of other shuvosaurids suggest they consumed both plants and animals, Smith said. “[I]t’s worth noting that plenty of animals with toothless beaks are still carnivores,” he added. “Given the fact that these animals evolved from other terrestrial carnivores, I would wager that it was at least omnivorous if not solely carnivorous.”
L. expectatus could also have been prey. Long-snouted phytosaurs and the distant crocodile relative Vivaron, the largest predators of the time, may have eaten shuvosaurids, Smith said.
Banner image: Reconstruction of Labrujasuchus expectatus. Image © Jorge Gonzalez/NHMLAC Dinosaur Institute.
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