One of the oldest ever Jurassic dinosaurs has been discovered after it fell out of a cliff at Lavernock Point in South Wales, back in 2014. Now described in the journal PLOS ONE, this 201-million-year-old dinosaur fills in a key moment in dinosaur evolution.
The age of the dinosaurs is divided into three geological periods. The Triassic began 252 million years ago; it was marked by the world’s most extreme mass extinction event known as the Great Dying. The Jurassic began 201 million years ago, another time period delineated by another, and somewhat less severe extinction event, the Triassic-Jurassic mass extinction. The Cretaceous began 145 million years ago, and was the time period that contained both the famous T. rex and Velociraptor.
There is a lot that paleontologists do not know about the boundary between the Triassic and the Jurassic, as the fossil record is relatively sparse. The Early Jurassic, in particular, has plenty of unknowns in terms of how the dinosaurs began to evolve and dominate the land after the Triassic-Jurassic extinction, which killed off nearly half of the world’s species. This new species, Dracoraptor hanigani, or "dragon thief," will help to address this evolutionary gap.
Dated to be 201.3 million years old, it sits right on the boundary between these two periods, right at the point where scientists believe a massive diversification in dinosaur species began to occur. The researchers can be confident of their very precise dating, as the fossilized raptor was sandwiched between ammonite fossils and eel-like ancient creatures called conodonts, whose ages are very well constrained.
It is one of the oldest known Jurassic dinosaurs ever discovered, and represents one of the types of dinosaurs that immediately preceded the emergence of the most powerful beasts of the Jurassic and Cretaceous, and eventually avian dinosaurs – modern-day birds.
The skeleton outline of D. hanigani. Bones shaded green were excavated, those shaded orange were made from external molds, and blue were bones tentatively but not confidently identified. The white bones are those that have been inferred from symmetry. Martill et al./PLOS ONE
“It's not until the Middle Jurassic that we get all the diversity and forms that you know from children's books,” coauthor Steven Vidovic told BBC News. “So, everyone's been hunting for these really early Jurassic specimens, going to exotic places… and then a couple of brothers stumble across something on a beach near Cardiff.”
Remarkably, 40 percent of its skeleton was discovered, including seven of its teeth, its claws, feet and most importantly its skull. This rare level of preservation means that many of the missing fragments can be accurately filled in by the paleontologists because of the symmetry inherent in the skeleton.
At 2 meters (6.6 feet) in length, this juvenile dinosaur was clearly a meat-eater, having serrated, needle-sharp teeth designed to slice and pick up pieces of other animals or insects. The “thief” reference comes from the fact that this shoreline predator was also likely a scavenger. Its gracile form suggests that, much like the raptor dinosaurs that evolved later, it was an agile beast, able to steal bits of meat from deceased prey that may have been felled by larger predators.
The cliff it was found in was composed of marine rocks, indicating that it was washed out to sea as it died. Ancient sea urchins crawled all over it, jumbling up the bones and creating a jigsaw-like fossil that needed to be reassembled.