Pterror of the Skyes

Pterosaurs reached large sizes much earlier in their evolutionary history than we thought, as revealed by an exquisitely-preserved skeleton of a new species from the Isle of Skye in Scotland. Meet Dearc sgiathanach (pronounced “Jark ski-an-ack”).

Study authors Natalia Jagielska, Steve Brusatte, and Greg Funston tell the story of the new Scottish pterosaur, Dearc sgiathanach.

Pterosaurs are the famed ‘pterodactyls’. They were closely related to dinosaurs (new discoveries are pinpointing just how close), but they were not dinosaurs, contrary to popular belief (although see here for one ‘pterosaur’ that ended up being a dinosaur…). They were the largest flying animals of all time, some reaching the size of small planes.

But these plane-sized giants only existed towards the end of the reign of pterosaurs, in the Cretaceous Period (145–66 million years ago). For a long time, we thought that earlier pterosaurs, which originated in the Triassic Period (252–201 million years ago), were restricted to smaller sizes, until they refined their wings and became more efficient fliers.

The ‘main block’ of the pterosaur skeleton from the Isle of Skye. Visible to the left is the skull, attached to the neck vertebrae. The arms, including a pristine hand, are preserved in the main block.

Now, Dearc is challenging that idea. This immaculate skeleton, discovered in 2017 on the majestic Isle of Skye, in northwest Scotland, preserves an almost-complete skull alongside most of the body, including much of the wings, torso, and hind leg. The skeleton comes from rocks that are Middle Jurassic in age, about 170 million years old, filling a major gap in the pterosaur fossil record. But even better, the bones of Dearc are preserved in three dimensions, rather than being squashed down to a single plane like most Jurassic pterosaurs, giving an unprecedented view into its anatomy.

The skull of Dearc sgiathanach, the first part of the skeleton to be found. The 3-dimensional preservation of the skull gives new insight into the palates, brains, and evolution of early pterosaurs.

But the biggest surprise is the SIZE of Dearc. Compared to the dainty pterosaurs of the Triassic and early Jurassic, Dearc‘s >2.5 metre wingspan would have cast a terrifying shadow over the subtropical seas of ancient Scotland. Perhaps more frightening for the fishes and squids it ate: this skeleton is only from a subadult, that still had room to grow. It was the largest animal to have ever taken to the skies at that point in time. But it wasn’t alone: by developing a new method to predict wingspan in pterosaurs, project leads Natalia Jagielska and Michael O’Sullivan revealed that other isolated pterosaur bones were from equally large animals. Together, these finds paint a new picture of the way pterosaur body sizes evolved.

The incredible skeleton of Dearc also gives hope that other superb fossils are lurking nearby. The find comes as part of reinvigorated efforts to search for fossils in the isles of Scotland, a venture that has also turned up amazing trackways and highlighted fossil riches in some of the less-prospected Small Isles. Although isolated bones have been known for centuries by the locals, an articulated skeleton–much less of so delicate an animal–was completely unexpected. Who knows what else is waiting to be found?

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