Thursday, December 4, 2014

Rival Species Recast Significance of ‘First Bird’

The first Archaeopteryx fossil specimens turned up in limestone quarries in Bavaria, southern Germany, in the early 1860s. Until recently, they were the only fossil specimens found to mix bird- and dinosaur-like features. On the one hand, they are small — the fossils show juvenile creatures about the size of a magpie, which as adults may have been raven-sized — and have broad feathered wings that look good for gliding; on the other, they have a jaw with sharp teeth, dinosaur-like claws and a bony tail. These features led to the idea of the first bird, and generations of scientists have treated the 145-million-year-old animal as a ‘transitional species’ — the key piece of evidence linking birds and dinosaurs (Archaeopteryx is Greek for ‘ancient feather’, whereas its German name, Urvogel, means ‘first bird’).

But starting in the 1990s, the unique status of Archaeopteryx faced a challenge from the discovery in China of other potential transitional species. Fossils of Anchiornis huxleyi and Microraptor gui reveal small-bodied creatures like Archaeopteryx, and they may have used their four wings to glide. Another, Aurornis xui, has legs, claws and a tail similar to those of Archaeopteryx, yet lived about 10 million years earlier, leading some to propose it as a better candidate for first bird (see ‘The fight for first bird’).

Many scientists now believe that Archaeopteryx is just another dinosaur. Others find this hard to swallow. “To some ornithologists this is a really big deal — Archaeopteryx is the first bird,” says Gareth Dyke, a vertebrate palaeontologist at the University of Southampton, UK. “They’d rather cut off one of their legs than admit it has nothing to do with bird origins.”

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