(CN) – Archaeologists combing through dinosaur fossil sites in Japan have discovered a previously unknown bird species that soared through the skies over 120 million years ago. The pigeon-sized bird holds clues to the evolution of modern birds, according to a study released Thursday.
Scientists consider the archaeopteryx, or bird-like dinosaur, to be the first known bird on the planet.
The archaeopteryx, whose fossils were found in Germany, lived during the Late Jurassic period between 160 to 140 million years ago.
But the archaeopteryx did not develop the fundamental flight mechanism that modern birds have.
Birds flying over us today have a skeletal structure containing a pygostyle, a triangular plate located near the backbone that supports tail feathers, a key adaptation for flight.
The earliest known birds with pygostyle skeletal structures appeared in the Cretaceous period about 120 million years ago.
Cretaceous era bird fossils have been found only in northeastern China, Spain and Brazil, until now.
While digging at a fossil site in central Japan in 2013, Takuya Imai of Fukui Prefectural University discovered a three-dimensionally preserved fossil of what has since been named fukuipteryx prima. The light brown-colored bird had a wide wingspan and a short tail feather.
The primitive bird’s fossils are the first from the Cretaceous period to be found outside of China, according to the study published in Communications Biology.
Imai observed that the fukuipteryx prima had a fully formed pygostyle and shared several features with the archaeopteryx, including a wide wishbone, an unfused pelvis, and forelimbs.
But researchers advance the theory that fukuipteryx prima’s pygostyle is simply a byproduct of tail reduction during evolution and is unrelated to flight.
An early Cretaceous bird called the jeholorniformes lacked the pygostyle, for example, according to the study.