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June 19, 2009

Dino Fingers

In the realms of paleontology, one of the great debates has been if birds are directly descended from dinosaurs. A new fossil discovery out of China points yet another finger of evidence to support this theory.

Xu Xing, of the Chinese Academy of Sciences (CAS) Institute
of Vertebrate Paleontology and Paleoanthropology, and his team recently uncovered two specimens of a beaked, herbivorous dinosaur named Limusaurus. This creature has 4 fingers, equivalent to our thumb, index, middle, and ring fingers. The thumb, however, was severely shrunken, while the index finger was elongated.

Previously, paleontologists had been puzzled by bird wings compared to dinosaur hands. The wings of birds contain 3 fingers, correlating to our index, middle, and ring fingers. But most theropods (the group of dinosaurs including Velociraptor and other similar creatures) had either 5 fingers, or had lost their pinky and ring fingers. Limusaurus is unique in that it shows the loss of the thumb, rather than the ring figure.

Critics of the dinosaur-to-bird theory still claim that these new fossils are not definitive. It is still the only dinosaur to show this particular digit pattern. However, it certainly gives a "hand" to the theory. This piece of evidence files in with many others, including comparisons of dinosaurs to flightless birds and specimens like Archaeopteryx. The theory is becoming widely accepted, redefining our view of the past.

One of the two Limusaurus specimens, from the Junggar Basin in China

Credit: People's Daily Online
Image Credit: People's Daily Online