Extinct dinosaurs are not just meteorites

A new study shows that some dinosaurs died out in the last 12 million years of the Cretaceous (about 150 million years ago), long before meteorites attacked the earth.

The unexpected 'mass destruction' of the meteorite 'visit ' of 65.5 million years ago may be just one of many factors leading to the extinction of dinosaurs.

'I think our research clarifies the fact that we still have a long way to go before we can fully understand the dinosaur extinction , ' said University researcher Stephen Brusatte. Columbia (USA) told Discovery news site.

According to Mr. Brusatte, there are some things we know for sure about dinosaurs: a meteorite or comet hit Earth about 65.5 million years ago, even when the dinosaurs completely disappeared from the data. jelly.

Tyrant dinosaur

We also know that there is strong volcanic activity and major changes in sea level at that time. At least some dinosaur groups are undergoing long-term decline in biodiversity in the last 12 million years of the Cretaceous, at least in North America.

The new study provides a first look at dinosaur extinction based on morphological disparities, meaning the variation of body structure in a certain dinosaur group. The greater the variation in a species, the healthier its population is.

Previous studies have always been based on estimates of changes in dinosaur numbers over time, but that could be affected by irregular sampling in fossil data. For example, some geological structures tend to preserve dinosaurs better than others.

In his study, Brusatte and colleagues calculated the body size differences of seven large dinosaur groups using databases that include extensive structural features. bones of nearly 150 different species.

They found that large plant-eating species die a long time before natural disasters 65.5 million years ago. These animals are duck-billed dinosaurs (hadrosaur) and herbivores (ceratopsid).

In contrast, smaller herbivores such as dinosaurs bordering the mace tail (ankylosaur) and dragon head dinosaurs (pachycephalosaur); carnivorous species like tyrant dinosaurs (tyrannosaur), small head dinosaurs (coelurosaur); and large plant-eating dinosaurs with no high-level chewing ability like sauropods remained stable during the same period.

While the extinction of large dinosaurs is still a mystery to researchers, Mr. Brusatte believes that a 'certain event' happened to the large herbivorous dinosaurs at the end of the Cretaceous. , at least in North America. He said: 'Perhaps it is the local environments that are fluctuating due to changes in sea level and mountain formation during that time'.

This expert explained that herbivores can be affected by a changing land area first because they stand at the end of the food chain. According to this logic, the dinosaur groups standing higher in the food chain would begin to die a few million years later.

Brusatte agrees that his findings and his colleagues are not undisputed, but at least one can imagine the end of the Cretaceous period not a sudden 'lost world'. destroyed by a tremor caused by meteors.

'Instead, live dinosaurs during this time are undergoing major changes before being attacked by meteorites , ' he stressed.