Science

Dinosauromorph research sheds light on dinosaur evolution

Dinosaurs evolved much faster than previously thought, a new study looking at dinosaurs' predecessors, dinosauromorphs, has found. Science columnist Torah Kachur discusses the findings.

Dinosauromorphs roamed the Earth almost 10 million years earlier than previous estimates: study

Animals escape from an erupting volcano 235 million years ago in northwestern Argentina, including early mammal relatives (the dicynodont Dinodontosaurus in the left background, and the cynodont Massetognathus in the left foreground) and early dinosaur precursors (Lewisuchus in the right background, and Lagerpeton in the right foreground). (Victor Leshyk)
Dinosaurs evolved much faster than previously thought, a new study looking at dinosaurs' predecessors, dinosauromorphs, has found.

Science columnist Torah Kachur discusses the findings:

What are dinosauromorphs?

They are a large class of creatures that were dinosaurs' ancestors.

Even though they may be new to most of us, they have been known for a long time. Some of the more important fossils and even footprints have been discovered in places like Argentina, Poland and Texas.  You can consider them primitive dinosaurs.

What did these creatures look like?

Like dinosaurs, but in a way, more lizard-like. 

But with some important distinguishing characteristics. They moved with more of a swayed gait, like the way a crocodile moves, because they didn't have ball and socket hip joints that are found in dinosaurs. 

Some of them were bipedal, walking on two legs, while others were quadrapedal.

They tended to be smaller than the giants that dinosaurs were and also were weaker. They just didn't have the bulk that we associate with dinosaurs. So basically they were wimpy dinosaurs.

What are the main findings of this new research? 

A new study was published in the Proceedings of the National Academy of Sciences where researchers went to Argentina to look at the timeline of the dinosauromorphs

There is an area in Argentina called the Chaneres formation where a treasure trove of fossils have been found. One layer of the rock there has given rise to dinosaur bones, while a deeper layer has revealed dinosauromorph fossils as well.

Co-author Adriana Mancuso (far left) investigates badlands of the Chañares Formation, deposited 236 to 234 million years ago in what is now Talampaya National Park, Argentina. (Randall Irmis)

The researchers used zircon crystals taken from the layer of sediment where the dinosauromorph fossils were found and used radioactivity to date the rocks. They found that the dinosauromorphs existed around 236 to 234 million years ago. That is quite a bit later than was previously thought, which was that dinosauromorphs went extinct by 240 million years ago. 

Now, this new data suggests dinosauromorphs roamed the Earth more recently, by almost 10 million years, than previous estimates.​

What are the implications of this research?

There are two big shifts in thought that this paper has created.

First, this means that dinosaurs evolved a lot faster than previously thought. The transition from dinosauromorph-dominated landscape to a dinosaur world was thought to have taken over 15 million years. That was simply the difference in the age of the most recent dinosauromorph ever dated and the earliest true dinosaur dated.

But now, the idea that it was only five million years is significant this means that dinosaurs really did hit the ground running. They obviously made a rapid rise to dominate the Earth as much, and for as long as they did.

The biggest change that palaeontologists think allowed dinosaurs to catapult to the top of the food chain was the evolution of much more powerful hind limbs. This made them scary, fast and powerful. So all of sudden they were better hunters than anything else on the planet at the time. And, voila, the dinosaur age. 

It also changes what and how palaeontologists think about the origins of the dinosauromorphs.

See, for as long as dinosauromorphs were dated, it was thought that they rose to prominence after the great Permian extinction event. The biggest die-off in Earth's history happened 252 million years ago. Ninety per cent of sea life and 70 per cent of terrestrial life was wiped out. This created a vacuum that it was assumed that dinosauromorphs and their ancestors were primed to fill. 

Co-author Adriana Mancuso (right) and Juan Martn Leardi (left) excavate the skeleton of the early mammal relative Massetognathus. This was also the site of one of the dated samples in the study. (Randall Irmis)

But now, if you shift all the dates we have of the dinosauromorphs with more accurate dating — as was done just recently — then all of a sudden we have a 15-million-year gap in the fossil record between the Permian extinction and the evolution of the dinosauromorphs.

Does anyone have any idea what would have filled this gap?

No, that's the fun part now.  We know what came before dinosaurs and when they came about. 

Now what came before the dinosauromorphs?  I guess we need to (literally) keep digging.

ABOUT THE AUTHOR

Torah Kachur

Science Columnist

Torah Kachur has been the syndicated science columnist for CBC Radio One since 2013. Torah received her PhD in molecular genetics from the University of Alberta and studied how worm gonads develop. She now teaches at the University of Alberta as a contract lecturer in cell biology and genetics.

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