Japanese researchers have described what they say is the first species of bird from the Early Cretaceous period (around 146-100 million years ago) found outside China.
Takuya Imai and colleagues from Fukui Prefectural University analysed the three-dimensionally preserved fossil of a pigeon-sized species, now known as Fukuipteryx prima, discovered in central Japan. Their paper is published in the journal Communications Biology.
The Archaeopteryx from the Late Jurassic (160-140 million years ago), found in Germany, is generally considered the first known bird, but characteristics associated with modern birds didn’t begin to appear until the Cretaceous, the authors say.
The earliest known Cretaceous bird fossils are two-dimensional specimens found in north-eastern China. These lack a pygostyle, a triangular plate found at the end of the backbone to support tail feathers, which is a fundamental feature of modern birds.
Imai and colleagues suggest F. prima may have shared several features with Archaeopteryx, including a robust wishbone, unfused pelvis, and forelimbs. But F. prima also has a fully-formed pygostyle.
Previous research has suggested the pygostyle is one of the key flight adaptations in the early evolution of birds. However, the authors propose that the presence of the pygostyle with F. prima supports recent theories that it is merely a by-product of tail reduction and unrelated to flight adaptation.