Stegouros elengassen, unearthed successful Chile, had a unusual flattened process that looked similar a fern frond – a diagnostic ne'er seen earlier successful an ankylosaur dinosaur
Life 1 December 2021By Chen Ly
An artist’s content of Stegouros elengassen Lucas Jaymez
A caller taxon of ankylosaur recovered successful Chile had a unsocial process unseen successful immoderate different subordinate of this dinosaur family. The find sheds airy connected the mysterious origins of ankylosaurs successful the confederate hemisphere.
Ankylosaurs were quadrupedal, herbivorous dinosaurs that roamed Earth passim the Jurassic and Cretaceous periods. They were covered successful bony deposits connected their tegument called osteoderms, which provided protection, overmuch similar a turtle’s shell. Ankylosaurs from the bluish information of what utilized to beryllium the supercontinent Pangaea person been wide studied. However, those from confederate Pangaea person been overmuch harder to travel by and are poorly understood.
Alexander Vargas astatine the University of Chile successful Santiago and his colleagues person reported the find of a caller ankylosaur, whose almost-complete skeleton was recovered successful the Río de Las Chinas vale successful confederate Chile. They called the caller taxon Stegouros elengassen.
The squad recovered that the skeleton had a premix of traits from known ankylosaurs and from stegosaurs, a related radical of four-legged plant-eating dinosaurs. In fact, the pelvis of S. elengassen was astir identical to that of a stegosaur, but the jawbones that carried its precocious bony enactment were intelligibly ankylosaurian.
The skeleton besides had a flat, weapon-like tail, with 7 pairs of broad, laterally facing blades, making the process extremity look similar the frond of a fern. This is dissimilar thing seen successful different ankylosaurs, which typically had large, club-shaped tails. The dinosaur besides appeared to beryllium little armoured and much slender-limbed than different ankylosaurs.
“This is our archetypal bully look astatine a South American armoured dinosaur, and it is not similar immoderate armoured dinosaur you’ve ever seen before.” says Vargas. “It has a process limb that is simply a caller class – each we knew [before] was process spikes and process clubs, present we person this weird frond-like thing.”
After analysing its features and comparing them with different ankylosaurs, the squad determined that S. elengassen belonged to 1 of the deepest branches of the ankylosaur evolutionary tree.
These findings revolutionise our knowing of confederate ankylosaurs, says Vargas. It was antecedently presumed that ankylosaurs dispersed from bluish to confederate Pangaea comparatively precocious successful the group’s evolution. But due to the fact that S. elengassen lacks galore of the emblematic assemblage features recovered successful bluish ankylosaurs, Vargas and his colleagues present deliberation the confederate subdivision of ankylosaurs indispensable person divided disconnected overmuch earlier successful prehistory.
“We don’t rather recognize what the evolutionary driving forces are for these ankylosaurians to stay morphologically much ancestral compared to the ankylosaurian dinosaurs from the bluish hemisphere,” says Jelle Wiersma astatine James Cook University successful Australia. “But this survey surely highlights that determination is inactive a batch to larn astir this peculiar radical of dinosaurs.”
Journal reference: Nature, DOI: 10.1038/s41586-021-04147-1
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