Organisms that have barely changed from their earliest fossil

The Ostracode

Scientists have identified the oldest male fossil animal yet discovered. It is an ocean-dwelling creature from 425-million-year-old rocks in the UK called an Ostracode.

Unusually, its soft parts are well preserved as well as its hard shell. It has limbs for swimming and feeding. Researchers are puzzled as to why the ancient creature appears so similar to its modern relatives. Their research is to be found in the journal Science.

"It pushes back our knowledge about the palaeo-biology of an important group of animals by more than 200 million years," Professor Siveter told the BBC. "The whole animal is amazing," Professor Siveter added. "We have got something we could only dream about."

The ostracode's appendages suggest that it swam and scavenged for food along the ocean floor. It was also definitely male as it has the oldest known example of a penis.

The scientists say that the five-millimetre-long fossil is remarkably similar to some modern ostracodes, suggesting an extremely low rate of evolutionary change over the last 425 million years.

"This is a demonstration of unbelievable stability," said Dr Tom Cronin, of the US Geological Survey.