BBC Homepage World Service Education
BBC Homepagelow graphics version | feedback | help
BBC News Online
 You are in: Sci/Tech
Front Page 
UK Politics 
Talking Point 
In Depth 

Wednesday, 2 August, 2000, 13:39 GMT 14:39 UK
Sudden end for dinosaurs
Dino BBC
The finds suggest dinos flourished right to the end
By BBC News Online science editor Dr David Whitehouse

Dinosaurs were not gradually becoming extinct before they were wiped out by a meteor impact, as some scientists have suggested.

This is the conclusion reached by a team of North American scientists who have analysed fossils from the last dinosaurs who ever lived.

Many think that a massive, climate-changing impact merely finished what nature had already started and that the dinosaurs would have died out fairly soon anyway.

But this new analysis, published in the journal Geology, suggests that the dinosaurs were flourishing before they were suddenly wiped from the face of the Earth.

Dominant lifeform

Some researchers believe that even before the massive impact occurred dinosaurs were slowly becoming extinct and could not have lived more than a few more million years.

Being the Earth's dominant lifeform for over 150 million years was beginning to take its toll, it has been said.

This assertion is based on the lack of dinosaur fossils seen in certain layers of rocks at certain sites formed just before the mass extinction of dinosaurs around 65 million years ago.

That a massive impact killed off the dinosaurs is now widely accepted. Rocks laid down at the time show an abundance of rare elements that could only have been part of a massive meteor that struck the Earth and disrupted the global climate.

K-T boundary

The best example of such a site is probably the Hell Creek Formation. It lies to the east of the Rocky Mountains in the region known as the Badlands. It is a layer of rock that was formed at the very end of the age of the dinosaurs, between 65 and 67 million years ago.

The formation is found in Montana and North and South Dakota. It consists of about 175 metres (575 feet) of greyish sandstones and shales with interbedded lignites. Fossils such as those from the mighty Tyrannosaurus rex can be unearthed here.

Hell Creek is the only known stratum of rock that crosses what is known as the K-T boundary, the layer where dinosaurs vanish from the geological record.

In a new analysis of the abundance of dinosaur fossils in the Hell Creek deposits, Dr Peter Sheehan, of the Department of Geology of Milwaukee Public Museum, and colleagues, conclude that dinosaurs were not gradually becoming extinct before the impact.

Pivotal analysis

Using 200 volunteers to scour the Badlands, they found a minimum of 38 individual dinosaurs, represented by 113 separate bones, in the upper three metres (10 feet) of the Hell Creek Formation and in another formation in Montana and North Dakota.

By comparing the distribution of these fossils with those found in other layers, they are able to show that there is no decline in the numbers of dinosaur fossils in the few million years leading up to their ultimate extinction.

The researchers say that their analysis is pivotal to the understanding of dinosaur extinction.

Because they have shown there is no evidence of a barren zone just before the K-T boundary, the researchers believe they can demonstrate that dinosaurs were still flourishing when they were wiped out by a giant impact.

Search BBC News Online

Advanced search options
Launch console
See also:

22 Jun 00 | Sci/Tech
Earliest feathers fan controversy
18 May 00 | Sci/Tech
Dino fever grips Chicago
20 Apr 00 | Sci/Tech
Dinosaur heart found
18 Dec 98 | Sci/Tech
Some like it hot
13 Nov 98 | Sci/Tech
Fish-eating dinosaur found
Internet links:

The BBC is not responsible for the content of external internet sites

Links to more Sci/Tech stories are at the foot of the page.

E-mail this story to a friend

Links to more Sci/Tech stories