Meet Labrujasuchus: The toothless, beaked crocodile cousin that walked on two legs

Crocodiles are one of evolution's great success stories. They have survived largely unchanged for over 200 million years, outlasting the dinosaurs, enduring multiple mass extinctions, and arriving in the modern world with the same basic formula: armoured, low-slung, toothy, and exceptionally patient, which made them lethal in the Triassic, which makes it all the more startling that a newly identified relative of the crocodile lineage was none of those things. It had no teeth. It had a beak. It walked upright on its hind legs, with tiny arms it almost certainly did not use much. It lived 212 million years ago in what is now New Mexico during the Late Triassic, when the supercontinent Pangaea was beginning to break apart, and the first true dinosaurs were just establishing themselves. The creature is called Labrujasuchus expectatus, and according to a new study published in the Journal of Vertebrate Palaeontology, it is one of the most unusual animals to emerge from a fossil site already famous for producing extraordinary finds.The remains of L. expectatus were originally excavated in 2006 from a quarry at Ghost Ranch in New Mexico, a site that has been central to palaeontology for decades and is particularly renowned for its rich trove of Triassic-era fossils. The bones sat in collections for years before researchers took a closer look and realised something was different.The specimen closely resembled the two recognised North American species of Shuvosauridae, a family of ancient bipedal reptiles that lived through the Late Triassic but was not quite either of them. The bones were dated to around 212 million years ago, placing them between the two known North American Shuvosauridae species in time. There were also subtle but consistent physiological differences, including in the shape of the humerus, that distinguished the specimen from its closest relatives.Alan Turner, professor of anatomical sciences at Stony Brook University and leader of the discovery team, explained why those fine details matter: "We look at those fine details because those are the things that the evolutionary processes are shaping, and that lets us get at their family tree that way." Labrujasuchus expectatus was bipedal it walked exclusively on its two hind legs, with small forelimbs that were largely vestigial in function. This alone makes it deeply counterintuitive as a crocodile relative. Every living crocodilian moves on four legs, pressing itself close to the ground. L. expectatus stood upright, in a posture more reminiscent of a small theropod dinosaur than anything in the modern crocodile family tree.It also had no teeth whatsoever. In place of them, it had a beak with the same basic structure seen in birds today. This presents an obvious question about diet, since the absence of teeth is not, by itself, evidence of herbivory. Birds have beaks and no teeth, and that does not prevent an eagle from being a committed carnivore. Turner believes L. expectatus was most likely a meat eater, and possibly a scavenger, though he notes it is not possible to say definitively. What can be said with confidence is that fruit was not on the menu, flowering plants had not yet evolved 212 million years ago, and the landscape of the Late Triassic offered nothing resembling modern fruit. The relationship between L. expectatus and modern crocodiles is one that requires some careful framing. Turner is explicit that this animal is "definitely not a direct ancestor to modern alligators and crocodiles." The relationship is better understood as an extremely distant branch of the same broader family tree, one that split from the line eventually leading to crocodilians hundreds of millions of years ago and went off in an entirely different evolutionary direction.The Shuvosauridae family to which L. expectatus belongs sat within Archosauria, the same broad group that includes both crocodilians and dinosaurs. But the Shuvosauridae lineage was its own experiment, and a striking one: bipedal, beaked, toothless, apparently carnivorous, and ultimately extinct. It did not survive into the Jurassic. The crocodile line, which took the opposite approach in almost every respect, is still with us today. Beyond the intrinsic interest of finding a bipedal beaked crocodile relative, which is considerable L. expectatus adds a significant data point to the science of convergent evolution, the process by which unrelated or distantly related animals independently evolve similar traits in response to similar pressures.L. expectatus was not a dinosaur. It was not even closely related to dinosaurs. And yet it walked like one, was roughly the same size as many small theropods of the same period, and almost certainly occupied a similar ecological niche as an upright, bipedal, likely carnivorous animal moving through the same Late Triassic landscapes at the same time. The resemblance was not inherited. It was arrived at independently, through a completely separate evolutionary lineage responding to similar environmental conditions."That's the thing I think I find the most interesting about an animal like L. expectatus," Turner said. "It's one more data point that we have in furthering these models about that important evolutionary process."Convergent evolution is one of the most compelling arguments against the idea that evolution is purely random. When unrelated lineages, separated by vast stretches of evolutionary time, keep arriving at the same solutions, bipedalism, beaks, and body size, it suggests that certain designs are not accidents but optimal responses to particular conditions. L. expectatus, walking upright through the Triassic alongside the earliest dinosaurs and bearing no close relationship to them, is a vivid illustration of that principle.What makes the Ghost Ranch specimen especially valuable is that it sat unrecognised in a collection for nearly two decades. It is a reminder that some of the most significant discoveries are not made in the field, but at a desk, looking more carefully at what was already there.