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Last Updated: Tuesday, 10 February, 2004, 13:37 GMT
Many dino species 'undiscovered'
T Rex     BBC
The study combines data on evolution patterns with fossil ages
Up to 500 dinosaur groups may remain undiscovered, yet our knowledge of the creatures and how they were related is relatively complete, a scientist says.

The figure of 500 may seem a lot, but this is a maximum possible value.

The expert behind the study actually thinks the dinosaur fossil record is between one-half and two-thirds complete, which is comparatively good.

The data comes from an analysis of more than 250 dinosaur groups and their family tree branches.

Julia Heathcote, a graduate student at Washington University in St Louis, US, used statistical analysis to determine how much missing data there might be on dinosaur groups to how much researchers actually have.

She also calculated how well proposed splits in the dinosaur family tree matched the fossil evidence over time.

Good record

The research was carried out in collaboration with researchers from the Natural History Museum in London.

"The whole Dinosauria fossil record I would say is moderately good, which was a surprise, becuase I thought it would be much worse," said Ms Heathcote.

Although there had been previous attempts to analyse evolutionary patterns with the dinosaur fossil record, she added, these patterns could only be interpreted in a useful way when the ages of fossils were taken into account.

Ms Heathcote claimed that her work could be added to by other researchers as new dinosaur specimens are discovered and see where the new discovery fits in with previous ones.

Another calculation gave how much missing data there is to the minimum missing data possible if all dinosaur groups were arranged in a family tree in order of age.

"[The analysis] draws together all of the data of the past 150 years," said Ms Heathcote. "You can see how far back these dinosaurs go, see their relationships with each other."

Previous studies have attempted to provide complete dinosaur family trees. Researchers at the University of Bristol have combined 150 previously published evolutionary trees to form one supertree of 277 dinosaur groups.

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