New species of early dinosaur described from South Africa

At the dawn of the Jurassic, having just weathered their first major extinction event, a relatively new group of animals - the dinosaurs - finally had their chance to reign. 

One of the first species to seize upon this opportunity was Massospondylus. Known from hundreds of specimens collected throughout southern Africa, the creature belonged to a group called the sauropodomorphs. These would eventually give rise to the sauropods, which include Diplodocus, along with some of the largest animals ever to have lived. 

It was long thought that Massospondylus was a disaster taxon, a species that rapidly became common after mass extinction events and took advantage of the empty landscape. But researchers have been looking closer at many of these supposed Massospondylus specimens, and things may not have been so straightforward.

Prof Paul Barrett, a dinosaur researcher at the Museum, is part of a team that has reassessed one of these specimens, which is held at the University of Witwatersrand, Johannesburg.

Along with his colleagues in South Africa, and led by Paul's PhD student Kimberley Chapelle, they recognised it not only as a new species of sauropodomorph but an entirely new genus. It has now been named Ngwevu intloko and announced in the journal PeerJ. 

'This is a new dinosaur that has been hiding in plain sight,' explains Paul. 'The specimen has been in the collections in Johannesburg for about 30 years, and lots of other scientists have already looked at it. But they all thought that it was simply an odd example of Massospondylus.'

A fresh look at an old fossil

The new dinosaur is known from a single fairly complete specimen whose skull and much of its skeleton are remarkably well preserved.

N. intloko was bipedal and had a fairly chunky body, with a long slender neck and a small, boxy head. It would have been a relatively small dinosaur, measuring perhaps three metres from the tip of its snout to the end of its tail. 

While it likely ate some plants, it may also have taken any small animals that were unable to escape its path. It would have been quite different from the large, plant-munching sauropods that came much later in the Jurassic.

'Other researchers have looked at the specimen and largely ignored it,' says Paul. 'Some thought that perhaps it might have been a young Massospondylus and that maybe some of the differences in the specimen were a result of growth patterns.

'But the most common explanation was that the skull had been deformed in some way during fossilisation and that was why it looked so different.'

Kimberley, Paul and their colleagues compared the specimen with those from definitive Massospondylus fossils that ranged from tiny animals with skulls measuring 10 centimetres to fully grown adults with skulls about 30 centimetres long. Kimberley applied CT scanning to each specimen to get as much detail as possible. 

'Studying how dinosaurs grew is a very important step in better understanding why some dinosaurs look different,' explains Kimberly. 'This is a difficult task to accomplish with fossils because it is rare to have a complete age series of fossils from a single species.

'Luckily, the most common South African dinosaur Massospondylus has specimens ranging from embryo to adult.'

None of the changes in growth patterns in these Massospondylus specimens reflected the differences observed in N. intloko. This meant that they were able to rule out the fact that the differences may have been down to age.

'The final clincher was that the skull is clearly not deformed,' says Paul. 'It's not obviously been twisted in any particular way and you can't see any breaks in the skull to suggest it had been broken. So we could rule that out as well.'

The team also considered whether sexual dimorphism might explain the differences in size and proportions. But while the size and structure of horns and antlers may vary between males and females in mammals, the general proportions of their skulls do not. This means that sexual differences are also unlikely to explain things.  

'All of these aspects combine to mean that we can be confident that this is genuinely something new,' explains Paul.

Surviving an extinction

The findings help to shed some light on what the environment was like at the transition between the Triassic and Jurassic periods, around 200 million years ago.

It is thought that at this time, massive volcanic activity in what is now the central Atlantic precipitated a mass extinction event, marking the end of the Triassic. In the oceans, around 30% of all marine genera went extinct, while on land, whole groups of animals died out. 

It seems that there may have been a much more complex ecosystem flourishing in the earliest Jurassic, not long after this extinction took place.  

'This new species is interesting,' says Paul, 'because previously we thought that there was really only one type of sauropodomorph living in South Africa at this time.

'Recent work has now shown that there were actually lots of different types of dinosaurs back then. While we used to think that there was maybe one type of dinosaur, we now know there were actually six or seven sauropodomorph dinosaurs in this area, as well as variety of dinosaurs from other, less common groups.

'Some of these other sauropodomorphs were very much like Massospondylus, but a few were incredibly close to the origins of true sauropods, if not true sauropods themselves.'

The high degree of diversity and varied appearance of these dinosaurs not only questions whether Massospondylus is indeed a disaster taxon, but also how groups of animals responded to large extinction events in the past.

Paul and his colleagues expect that many specimens previously identified as Massospondylus may well end up being either N. intloko or even some other new species in their own right.