Oldest Male Fossil Found in United Kingdom

Scientists have discovered a very well preserved, ocean dwelling creature from 425-million-year-old rocks in the United Kingdom that may be the world’s oldest fossil animal that is definitively male, according to a study published this week in Science.

The fossil record is packed with shells from this group of arthropods. The “ostracodes,” fossilized soft parts such as those discovered by a group of researchers, including Derek Briggs, professor of geology and geophysics at Yale, are extremely rare.

“The ostracodes are important for two reasons,” said Briggs, one of the principal investigators of the study. “They give us insights about crustacean evolution, and they’re widely used to work out the age of rock sequences.”

The finding pushes back the earliest described evidence for soft-tissue anatomy of this important group of living crustaceans by nearly 200 million years. Ostracode appendages, soft parts that protrude from the gap between its two hinged shells, suggest that it swam and scavenged for food along the ocean floor.

The authors cracked open the rock with the embedded creature and embarked on a shave-and-photograph technique that yielded a virtual fossil with extraordinarily preserved three-dimensional details. The five-millimeter long fossil is remarkably similar to some modern ostracodes. This past and present likeness suggests an extremely low rate of evolutionary change over the last 425 million years.

The researchers have called the new species “Colymbosathon ecplecticos.”

“It’s a nice example of very slow evolutionary change, reflected in a very conservative morphology over a long period of time,” Briggs said.

Co-authors included David Siveter of Leicester and Mark Sutton and Derek Siveter, both of Oxford.

Citation: Science, Vol. 302: (December 5, 2003)