Dinosaurs dominated the earth completely by luck

Dinosaurs are often considered unfortunate creatures, because they are swept away from the ground by a meteorite. However, they have dominated the Earth for more than 160 million years, evolving into a variety of sizes and bodies suitable for different ecosystems.

Scientists previously thought that evolutionary diversity was the basis for dinosaur dynasties, allowing them to outperform similar reptile groups, but a new study, detailed above Science magazine, September 11, shows that luck is the root cause.

'For a long time, many argued that there was something special in the dinosaurs that helped them become powerful in the Triassic period, the first 30 million years in the history of this giant animal, but that It's not true , 'said Steve Brusatte, author of the study, who is now a Ph.D. student at Columbia University and a member of the American Museum of Natural History in New York.

The most formidable opponent of the dinosaurs in the Triassic period (about 251 to 199 million years ago) is the crurotarsans , the ancestor of crocodiles today.

The skull of some crurotarsan archosaurs, 'crocodile family' archosaurs is the main competitor of the dinosaurs in the late Triassic (230-200 million years ago).Above (1-r): Rauisuchians Batrachotomus and Postosuchus;between: Phytosaur Nicrosaurus and Aetosaur Aetosaurus;below: Lotosaurus Poposauroid and Ornithosuchid Riojasuchus.(Photo: Stephen Brusatte, Columbia University)

Both dinosaurs and crurotarsans evolved and occupied similar ecosystems after a mass extinction event in the late Pecmi period 250 million years ago. After that, both animals survived through another widespread extinction event about 228 million years ago.

However, only dinosaurs and crocodiles overcame the period when the Earth warmed rapidly in the late Triassic period 200 million years ago. And flying dinosaurs still exist with us today in the form of modern birds, evolving from theropod dinosaurs (two-legged dinosaurs), surviving another extinction event at the end of the Middle Kingdom. .

Special or lucky?

To verify if there is anything 'special' about dinosaurs that allows them to outperform crurotarsans, Brusatte and colleagues compare the rate of evolution and the morphological differences of the two reptiles. The team used data including 437 features from 64 skeletons, and also based on the Archosauria family tree, including flying dinosaurs and crurotarsans, as well as flying lizards, modern birds and fish sets. crocodile

The Marshall Scholarship and the Paleontology Society funded the study.

Morphospace spatial chart of dinosaurs, crurotarsans ('crocodile family' archosaurs), and pterosaurs in Triassic period.Morphospace is a graph showing the range of body types, food ingredients, and lifestyle in a group of organisms.In this case, crurotarsans have more morphospace than dinosaurs, meaning that they are 'more successful' in exploiting the diverse state of life.(Photo: Simon Powell, Bristol University)

The researchers found no difference in the rate of evolution between the two species. If the dinosaurs developed superior to crurotarsans, they should have evolved faster.

Crurotarsans also have a higher morphological disparity - or in other words, they are more diverse in terms of body form, food composition and lifestyle. This should have given them an advantage over dinosaurs.

Brusatte said: 'If we go back to the Triassic period and ask which animals will rule the world for the next 130 million years, the answer will be crurotarsans, not dinosaurs.'

Dinosaurs only crossed the crurotarsans when the crurotarsans died slowly in the late Triassic period , so dinosaurs no longer had to compete with them.

So why do dinosaurs survive the mass extinction event for the second time, while the crurotarsans (except for a few crocodile-like lines) disappear?

Brusatte said: 'We do not know the answer yet, but we think it is purely lucky, simple and easy to understand'.