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Fish out of water: The evolutionary crawl from sea to land
2008-06-25
PARIS (AFP) - A 370-million-year-old skull and shoulder bone from a walking fish have shed light on when and how our distant ancestors slithered out of the sea to begin a new life on terra firma. The fossilised remains belong to a beast which had the head of a tetrapod -- among the first animals more adapted to land than water -- and a body and fins resembling its fish-like predecessor, Panderichthys, scientists say. Their study, released Wednesday, says the creature, known as Ventastega curonica, had an ample jaw and razor-like teeth, suggesting a ferocious predator the size of an adult crocodile. It also had primitive flippers, allowing it to explore shallow marshes for prey. The fossil suggests early amphibious animals of the Late Devonian period did not evolve in a simple linear fashion, as once thought, but in fact diversified along differing branches. "It is tempting to interpret Ventastega as a straightforward evolutionary intermediate," the Swedish-led authors say. "However, this simple picture should be approached with a degree of caution." Per Ahlberg of Uppsala University in Sweden and a team of palaeontologists uncovered Ventastega's remains at a site in western Latvia, once part of a swampy, semi-tropical continent straddling the equator. Other fossil specimens of this strange species exist, but none is as complete or intact, according to the study, published in the British journal Nature. The discovery comes two years after the unveiling in 2006 of a previously unknown species -- dubbed Tiktaalik roseae -- also described as a "missing link" between its ocean-dwelling precedessors and full-fledged tetrapods. The Latvia find falls into the morphological gap between Tiktaalik and the first of the tetrapods, Acanthostega, the authors conclude.
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