http://www.theage.com.au/national/ancient-art-of-fishy-sex-20090226-8i6y.html
Ancient art of fishy sex a.. Bridie Smith b.. February 26, 2009 - 7:27AM c.. FOSSILISED fish have revealed that sex is more ancient and common than scientists thought. The 380-million-year-old fish fossils also carry evidence of the oldest "penises" yet discovered, with the males boasting "pelvic claspers" similar to the ones sharks use today to insert sperm into females. The findings, to be published today in Nature, are significant because they prove the existence of internal fertilisation in fish and shift the evolutionary origin of sex further back in time. The fossilised fish were placoderms, an extinct group of jawed fish that were the dominant vertebrates in the Middle Palaeozoic era, meaning that sex was going on underwater as far back as 420million years ago. Museum Victoria's John Long, along with Kate Trinajstic from the University of Western Australia and Zerina Johanson of London's Nat ural History Museum, made the discovery. Dr Long said the pelvic fin that hosts the clasper was the equivalent to the hind leg in land mammals. "We humans say we like to get a leg over, but for these invertebrates, they like to get a leg in," he said. "It's quite amazing that these ancient fishes could have had such advanced reproductive and social behaviour." Dr Long discovered the world's oldest mother - a 375-million-year-old fossilised fish with an embryo inside it - last year. The next question, in Dr Long's words, was "how the hell were they doing it"? The answer lay in the structure of the fish's pelvis, and with it came the proof that these ancient creatures were reproducing via an early form of sex. "These primitive placoderms had the same type of mating structure as modern sharks," Dr Long said. However, most modern fish spawn in the water, leaving scientists with establishing if this internal fertilisation was unique to certain orders of placoderms or if reproduction in fish evolved more recently. Some of the fossil fish will be on display at Museum Victoria from today.
