الخميس، 16 سبتمبر 2021

Prehistoric Winged Lizard Unearthed in Chilean Desert

Rhamphorhynchus phyllurus. (Image: Ryan Somma/FunkMonk, CC BY-SA 2.0)
Pterosaurs are an interesting bunch. They are the first vertebrates that took flight, and they share a number of traits with birds despite not being directly related to them. Pterosaurs aren’t actually dinosaurs, despite the fact that dinosaurs and pterosaurs had a large temporal overlap. Both they and dinosaurs descend from an ancient clade of reptiles and birdlike things, known as archosaurs, and pterosaurs are more closely related to dinosaurs and birds than to other reptiles.

Our understanding of the range and lifestyle of these ancient creatures is still evolving because pterosaurs fossilize poorly compared with dinosaurs. Nevertheless, there are some places more hospitable than others to preserving even the fragile bones of flying creatures. One of them is the Atacama, where it basically never rains, so there’s little movement of the salty, alkaline sediment. A remarkable trove of fossils was unearthed there in 2009 but immediately snatched by the illegal fossil trade and sold on the black market. Having recovered and identified the fossil, Chilean scientists have now revealed that it represents a palaeontology first: the skeleton is of a winged reptile called a rhamporhynchine pterosaur, the first of its kind known to live outside Gondwana.

Some reports are calling it a “dragon,” which I think is pretty appropriate, given the physiology of its species: flying lizards with pointed snouts and sharp teeth, four limbs, membranous wings, and long tails with a “peculiar rhombus-shaped ending.” Personally, I think it resembles the ikran from Avatar (although we don’t know yet whether it would have had the same Technicolor skin). With featherlight bones and a wingspan of around two meters, it would have been a capable flyer. And because its full name is a “rhamphorhynchine pterosaur,” which is a tongue-twister, I’m going to call it Ringo.

The fossil is beautifully preserved. This is a rarity; usually, the skeletons of flying things get crushed flat over the eons, shattering the birdlike bones. But Ringo was discovered in the Atacama, which is a place of extremes. It’s the driest place on Earth, a cool and coastal desert so sere and alien that we use it for filming Mars scenes, with a colossal upwelling of cold water right off the coast called the Humboldt Current. The Humboldt Current is also wildly productive in terms of aquatic life. Ringo would have swooped over the rocky coastal shallows and snatched prey out of the water with his slender jaw and forward-pointing teeth. When he died, his bones were gently covered with sand and sediment, resulting in the remarkable 3D preservation we see. When the seas receded to form the Atacama desert, Ringo’s rock was finally exposed.

Another thing that makes our ikran buddy notable is his location. The fossil was located in the late Jurassic strata of the Atacama and dated to be 160 million years old. (Pterosaurs were already the twilight of their many millions of years when the asteroid hit.) And the Atacama is in Chile, in the Southern hemisphere. Up until now, with a few exceptions from Argentina, we’ve mostly found pterosaur fossils on ground that used to be part of Laurasia — the supercontinent that broke up to form North America, Europe, and much of Asia. Finding a fossil of Ringo’s vintage in Chile backs up the idea of the pterosaurs’ migration and distribution throughout Laurasia’s supercontinent companion Gondwana, which eventually formed most of the South American landmasses.

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