On the line from dinosaurs to birds.

Scientists who support the idea that birds evolved from dinosaurs are clucking over newfound fossils from Madagascar and Mongolia. These extremely primitive birds date from about 70 million years ago, in the Cretaceous period, and retain many characteristics of their dinosaurian ancestors, researchers say.

The Madagascan fossil, Rahona ostromi, has a mosaic of features belonging to birds and theropod dinosaurs, according to Catherine A. Forster of the State University of New York at Stony Brook and her colleagues. Although they had discussed their find at meetings (SN: 8/23/97, p. 121), the researchers named the species in the March 20 Science.

The raven-sized Rahona specimen has a perching-style first toe resembling that of other birds. Moreover, its arm bone has knobs where feathers were attached in life. Yet the animal also displays a large sickle-shaped second toe--a weapon that certain dinosaurs used for slashing their prey.

"This is clearly one of the most important documents of the transition from dinosaurs to conventional birds," says Lawrence M. Witmer of Ohio University in Athens.

The Mongolian bird, Shuvuuia desert), was described in the March 19 Nature by Luis M. Chiappe of the American Museum of Natural History in New York and his colleagues. They identify the animal as a close relative of the Mongolian creature Mononykus, which has aroused debate among researchers. Chiappe and his colleagues consider the dinosaurlike Mononykus a primitive bird, whereas opponents of the bird-dinosaur link identify it as a dinosaur wholly unrelated to birds.

Shuvuuia has a well-preserved skull, something missing from the known Mononykus fossils. The skull lends support to the theory that Mononykus is a primitive bird because it has many avian features, including a hingelike joint on its snout just in front of its eyes, report Chiappe and his colleagues.