Two sauropod dinosaurs

This is the first time diplodpocoids have been found in Asia. © Zhang Zongda

Herd of sauropod dinosaurs become the oldest diplodocoids ever discovered

A newly discovered sauropod species from China has become the oldest of its kind ever to be unearthed. It's changing how we think these dinosaurs evolved, as well as making us rethink how entire continents were linked 174 million years ago. 

A relatively unexplored site near the city of Lingwu in northern China has revealed a striking series of dinosaur fossils.

Palaeontologists have uncovered the partial skeletons of seven to 10 sauropods ranging in age from juveniles to adults. This was likely a family herd that met their unfortunate end during the Middle Jurassic (174-163 million years ago).

The dinosaurs belong to a group of sauropods known as diplodocoids. Until now it was thought that the lineage was entirely absent from China.

It was believed that by the time these dinosaurs evolved, eastern Asia had already split from the rest of Pangaea, the supercontinent that existed about 280 million years ago. This split isolated those animals that were already on the land mass, preventing the diplodocoids from getting there.      

But these fossils show that eastern Asia was not cut off as previously thought and that these dinosaurs may have dispersed into the region long before any isolation occurred.

This has remarkable implications not only for how dinosaurs may have evolved and dispersed during this period, but also for other groups such as early mammals and birds.

Prof Xu Xing, from the Chinese Academy of Sciences, Beijing, and lead author of the study published in Nature Communications, says, 'I suspect that when we go back to some old collections we may find some dinosaurs or other animal groups that normally we wouldn't expect to be present in China at this time.

'So this particular discovery will really push us to look at other possibilities.'

Reconstruction of sauropod

Piecing together the fossils reveals what the sauropod once looked like. © Shi Aijuan

 

The origins of Dippy

The new species of sauropod has been named Lingwulong shenqi ('amazing dragon from Lingwu'), and is thought to be the earliest diplodocoid discovered to date. This group of dinosaurs includes some of the largest animals ever to have walked the Earth, as well as more well-known sauropods such as Diplodocus and Apatosaurus.

Some sauropods reached lengths of 20 or 30 metres. This new species wasn't quite that big, but still measured on average an impressive 15 metres long.

The study, which included Museum scientist Prof Paul Barrett and was supported by the National Geographic Society, has described fossils from multiple individuals, including partial skulls, vertebrae and ribs. From the remains they are able to create a composite image of what the animal would have looked like in life, revealing a short-necked sauropod.   

Crossing continents

While Asia was home to its own unique group of sauropods, until now fossils of diplodocoids have most frequently been associated with North America and the southern continents.

This was thought to be down to how Pangaea was breaking up at the time that these animals were evolving. It has long been believed that eastern Asia became the first notable land mass to fully separate from the rest of the continents when the divide began about 200 million years ago.

Known as the 'East Asian isolation hypothesis', it explained why some groups of animals were only found within China during this period, and why others were absent.

'That hypothesis was supported by many endemic species found in Asia, for example mamenchisaur sauropods and some other animals that were unique to China and eastern Asia,' says Prof Xu.

The discovery of L. shenqi therefore calls into question this hypothesis.

Prof Xu says, 'If you have a connection between eastern Asian animals and those on other continents, then the question is how they dispersed. So far we don't have a good answer, but it is very likely that there was a land bridge or something like that connecting eastern Asia to other continents.'

Researchers measure dinosaur bone

The bones belong to a species of short-necked sauropod. © Xu Xing

 

Back to the start

The age of the fossils is also highly significant. As the earliest diplodocoid found so far, it could mean that not only did these dinosaurs cross from one land mass to the other, but that they might even have originated in China.

'This type of dinosaur is from the Middle Jurassic and at that age it is unexpected, as for this lineage of sauropods we only have fossils from later deposits,' says Professor Xu. 'That means a whole group of different sauropod lineages must have appeared on the planet earlier than we thought.

'L. shenqi opens up the possibility that this particular group has an Asian origin, though our currently reconstructed evolutionary tree suggests that the group was dispersed to Asia from elsewhere.'

A new era

Over the past few decades some extraordinary Mesozoic (252-66 million years ago) fossils have been unearthed in China, which has emerged as something of a hub for these finds. From birds, mammals and non-avian dinosaurs, the sheer number and superb preservation of fossils from this region has radically transformed our understanding of this period of history.

This particular site near Lingwu, and the surrounding Ningxia province, is no exception and promises to hold even more discoveries. 

'We hope in the future we can organise more expeditions to this particular site,' says Professor Xu. 'We'd also like to expand our digs to look at other sites nearby and hopefully make more exciting discoveries in the future.

'I hope that this is a new beginning for a totally new area. Ningxia as a province is kind of blank in China for dinosaur research, so there is lots of potential.' 

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