Dinosaur fish had sex 380 million years ago

July 16th, 2009 - 2:12 pm ICT by IANS  

Sydney, July 16 (IANS) The male members of an ancient fish species known as sea dinosaurs impregnated females with penis like organs 380 million years ago, just like modern day sharks.
Some fish species engaged in penetrative sex and gave birth to young ones, according to a study conducted by Curtin University of Technology (CUT).

“The findings throw light on the evolution of vertebrates on earth, including our own species. This discovery provides a link in the chain of evolution,” Kate Trinajstic, a researcher in CUT, said.

The research involves the identification of claspers in the fossil of a male Incisoscutum, exceed the oldest known date for vertebrates by approximately 200 million years. The Incisoscutum is an extinct species of placoderm, a primitive, shark-like armoured fish.

Placoderms dominated the oceans for around 70 million years, until their extinction about 360 million years ago.

“Another interesting discovery was that vertebrates have been giving birth to young ones since much longer than previously thought, and that some species of placoderms had shark-like claspers,” said Trinajstic.

Claspers are modifications of the pelvic fins that form the penis-like organ found in sharks. These organs are used to deposit sperms into the genital duct of sexually receptive females.

It is also possible to consider the mating habits of modern-day sharks to understand how ancient placoderms reproduced.

When most species of shark mate, the male holds the female in position by biting onto her fins, before arching the body so that the pelvic fins are brought close to the mating partner.

“This is quite an advanced mating behaviour. It gives the first evidence of complex foreplay,” Trinajstic said.

For researchers, this sort of finding has broad implications in the study of the evolution of complex vertebrates, including humans.

These findings were published in Nature.

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