Sydney, July 16 - 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.