Dinosaur enthusiasts like me will find a new discovery fascinating - especially because the Stegosaurus is one of the most well known dinosaurs of the Jurassic Period.
(Image: A Stegosaur drawing - by Posted by u/AramRex on REDDIT)
New stegosaur dinosaur could be the oldest ever discovered
By James Ashworth UK Natural History Museum 4 March 2022
One of the earliest stegosaurs has been uncovered in China.
The new species, Bashanosaurus primitivus, dates to the Middle Jurassic and could be a close relative of the ancestor of all stegosaurs that followed.
The origin of all stegosaurs could lie in Asia after what could be the oldest member of the group has been unearthed in China.
The description of a new species of early stegosaur, Bashanosaurus primitivus, suggests that the dinosaurs may have emerged in what was then the supercontinent of Laurasia over 165 million years ago.
The group then rapidly spread across large areas of the world, giving rise to many species including Stegosaurus, which gives the group of dinosaurs their name, before vanishing in the Late Cretaceous.
Bashanosaurus primitivus supplants the previous oldest known definitive stegosaur, Adratiklit boulahfa, which was discovered in Morocco in 2019.
Dr Susannah Maidment, a Principal Researcher at the Museum, was involved in the description of both these species. She says, 'The discovery of this stegosaur adds to an increasing body of evidence that the group evolved in the early Middle Jurassic, or perhaps even in the Early Jurassic, and as such represent some of the earliest known bird-hipped dinosaurs.
'China seems to have been a hotspot for stegosaur diversity, with numerous species now known from the Middle Jurassic right the way through until the end of the Early Cretaceous Period.'
The description of the species, led by Chinese researchers, was published in the Journal of Vertebrate Palaeontology.
What are stegosaurs? The stegosaurs were an iconic group of armoured dinosaurs with distinctive bony plates which ran along their back.
The first stegosaur ever discovered, Dacentrurus, was unearthed in Swindon, UK, in 1874 and was described by Richard Owen, the scientist who coined the term dinosaur.
Three years later, in 1877, Othniel Charles Marsh unearthed Stegosaurus armatus, which gives the group their name, in the Rocky Mountains, USA. At first, it was believed that the plates lay flat along the back as armour, until additional specimens with the plates preserved upright were found.
But this group of dinosaurs has caused a lot of confusion. Many fossils initially named as different Stegosaurus species are now considered to be the same species or from a completely different genus. Even Stegosaurus armatus has been replaced as the representative of its genus by Stegosaurus stenops due to concerns about it being difficult to identify.
All this reflects the difficulty palaeontologists have had in deciphering the group's family tree. Fossils of these dinosaurs are 'surprisingly rare', according to Susannah, and can often consist of only a few bones which make attempts to compare species difficult.
For instance, Isaberrysaura mollensis, was originally classed as an entirely different type of dinosaur before new analysis suggested it as a candidate for one of the earliest stegosaurs. More recently, early stegosaurs from Africa and China have also helped to clarify the origins of the group somewhat. Bashanosaurus primitivus may be older still than these dinosaurs, and is currently the earliest stegosaur to be described.
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