"Swimmer with large penis" first male animal Thu Dec 4, 3:55 PM ET
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - A fossil crustacean whose scientific name is "swimmer with a large penis" is the earliest clear example of a male animal, British researchers have reported.
The 425 million-year-old ancestor of modern water fleas, found in rocks in Britain, is unusually well-preserved, allowing scientists to see it had gills and an advanced circulatory system.
It shows that ostracodes -- extremely common water-dwelling creatures -- have evolved little in hundreds of millions of years, said David Siveter of the University of Leicester.
He and colleagues named it Colymbosathon ecplecticos, which means "swimmer with a large penis."
Siveter, in a telephone interview, said the 0.2-inch (5-millimeter-long) creature probably lived on marine shelves, about 500 to 650 feet (150 to 200 metres) deep.
"This crustacean clearly could swim," said Siveter.
And there was another striking feature, he added.
"It is certainly the oldest penis in the world, that's for certain."
He said fossils as old as 520 million years show dimorphism -- differences in anatomy seen between males and females. But there has been contention over which examples may be female and which male.
"In this case we clearly have a male," he said.
The fossil, preserved in volcanic ash, is so intact that the gut and even the anus can be clearly seen.
"It was probably a ... scavenger and predator," the researchers wrote in Friday's issue of the journal Science.
Other clues suggest the crustacean also had a heart and an integrated circulatory system, they said, with the first firm evidence of gills in such an old species.
Siveter said thousands of species of ostracods, the most common arthropod in the fossil record, exist around the world today. They are shrimplike animals with a two-part protective shell and can be found in ponds, lakes, rivers and seas.
The 425 million-year-old animal lived in what is called the Silurian period, when the first land plants appeared but when algae still dominated the seas. Fish were beginning to evolve. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
