The earliest birds had theropod dinosaur-like feet, according to a new study released on Thursday based on the best reserved Archaeopteryx fossil.

These findings support the arguable theory that Archaeopteryx, the first known bird, was a closest relative of the theropod dinosaur, and that modern birds arose from the dinosaurs, German and US researchers said in the Dec. 2 issue of the journal Science.

The nearly complete skeleton of the magpie-sized specimen, which lived about 150 million years ago during the late Jurassic period, was discovered in the Solnhofen limestone deposits of Bavaria, Germany. The fossil was recently acquired by the Wyoming Dinosaur Center, the United States.

Preserved in "undeniably worldclass", it provides important details about the feet and skull of the earliest birds, said Gerald Mayr of the Senckenberg Natural History Museum in Frankfurt, Germany, and Burkhard Pohl of the Wyoming Dinosaur Center.

It reveals that the bird could hyperextend its second toe, providing an additional similarity with the theropod dinosaurs proposed to be its closest relatives, the "deinonychosaurs." Parts of the new specimen's exceptionally well-preserved skull also share notable similarities with those of theropods.

Unlike modern birds, the first toe in this early bird was not reversed, the researchers found. Instead, the first toe pointed inward, similarly to the human thumb, indicating that the bird did not have a "perching foot."

This detail shows that Archaeopteryx was less similar to modern birds than previously thought, according to the researchers.

"The new specimen confirms the presence of a hyperextendible second toe as in dromaeosaurs and troodontids. Archaeopteryx had a plesiomorphic tetraradiate palatine bone and no fully reversed first toe. These observations provide further evidence for the theropod ancestry of birds," they wrote in the paper.

In addition to providing further evidence for the theropod ancestry of birds, these observations blur the distinction between archaeopterygids (the family that includes this early bird) and basal deinonychosaurs, a group of theropods with "fearsome claws," which includes Velociraptors, noted the authors.

They indicated that some feather-bearing dinosaurs should actually belong to a bigger family which also includes Archaeopteryx and modern birds.

"Aves, if defined as the clade including Archaeopteryx and modern birds, may actually include taxa hitherto referred to as ' beinonychosaurs,' some of which had fully developed avian-type wing feathers," the paper said.

Source: Xinhua