From Teeth to Beak

By Carl Zimmer|Monday, January 01, 1996
RELATED TAGS: DINOSAURS
For 135 years, the earliest known bird, Archaeopteryx, led a lonely life. A couple of ambiguous fossils aside, no avian specimen anywhere near as old as this 147-million-year-old creature had been found. As China opens up to fossil hunting, however, it is giving Archaeopteryx some company. Three years ago researchers reported finding a 135-million- year-old bird, Sinornis, in China. And this past year Lian-hai Hou of the Chinese Academy of Sciences in Beijing and his co-workers reported the discovery of an equally remarkable bird, possibly dating back as far as 142 million years.

Found in northeastern China, this new bird, called Confuciusornis sanctus, died in a forest lake. It retained many reptilian traits, as did Archaeopteryx, with a long, bony tail and wings that ended in exposed, needle-sharp claws. But in one way it was profoundly different: while Archaeopteryx had a mouth full of teeth, Confuciusornis had a toothless beak.

That doesn’t mean that Confuciusornis was the ancestor of today’s birds (which are universally beaked). Instead a number of features in its head, arms, and legs put it in a large group of birds called enantiornithines, or opposite birds, which vanished with the dinosaurs 65 million years ago. Meanwhile, the ancestors of modern birds held on to their teeth until 75 million years ago. Beaks, the Chinese fossil now suggests, arose independently in two very different groups of birds, which probably reflects the beak’s advantages for the avian life-style. All the different feeding types are based on modifications of the beak, from hawks to flamingos, says Alan Feduccia, an ornithologist at the University of North Carolina who coauthored Hou’s report. The beak really opened up a new era of possibilities that were not present before. At the same time, for a flying organism it is tremendously advantageous to have a light beak instead of bony teeth.

The dating of the rocks where Confuciusornis was found is unfortunately mushy--it’s possible that the bird could be as young as 132 million years old. But the emergence of birds in China not long after Archaeopteryx appeared thousands of miles away in Germany is striking in any case. It forces paleontologists to choose between two equally interesting possibilities: either Archaeopteryx appeared at the beginning of a swift, global burst of bird diversification, or it was just a small side branch in an already long course of evolution. In my opinion, this shows that the adaptive radiation of birds was under way long before Archaeopteryx, says Feduccia. Archaeopteryx may not have been so lonely in its day.
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