In the last two days, scientists have announced two new findings about the connection of birds to dinosaurs. Both discoveries date to a similar age — 118-120 million years ago, or the Early Cretaceous period — a time when bird-like animals “were highly successful and became widely diversified.”
First feathered polar dinosaurs and birds
In the first discovery, announced yesterday in the journal Gondwana Research, scientists analyzed a collection of 10 fossil feathers found in Australia that reveal an unexpected diversity of tufted hair-like “proto-feathers” from meat-eating dinosaurs, together with downy body feathers and wing feathers from primitive birds that would have been used for flight.
Uniquely, the fossil feathers from Australia were all entombed in fine muddy sediments that accumulated at the bottom of a shallow lake close to the South Pole during the Age of Dinosaurs.
“Dinosaur skeletons and even the fragile bones of early birds have been found at ancient high-latitudes before,” says Benjamin Kear from Uppsala University in Sweden, an author of the study. “Yet, to date, no directly attributable integumentary remains have been discovered to show that dinosaurs used feathers to survive in extreme polar habitats.
“These Australian fossil feathers are therefore highly significant because they came from dinosaurs and small birds that were living in a seasonally very cold environment with months of polar darkness every year.”
The well-preserved fossil dinosaur and bird feathers have “tiny filament-like structures that would have ‘zipped’ the feather vanes together, just as in the flight feathers of modern birds,” says fossil bird expert Patricia Vickers-Rich of Monash University and the Swinburne University of Technology in Melbourne.
However, unlike the structurally complex feathers of birds today, which are characterized by interlocking branches called barbs and barbules, different kinds of small dinosaurs had coverings that comprised much simpler hair-like “proto-feathers.”
The “proto-feathers” would have been used for insulation, suggesting that they “might have helped small dinosaurs keep warm in ancient polar habitats,” says Martin Kundrát, of Pavol Jozef Safarik University in Slovakia.
Newly discovered extinct bird from Japan
The second discovery is of a fossil of a previously unknown species of bird from Japan.
The earliest known Cretaceous bird fossils are two-dimensional specimens found in northeastern China. These birds 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.
Takuya Imai and colleagues describe a three-dimensionally preserved pigeon-sized bird fossil in central Japan that dates to the Early Cretaceous. This specimen, named Fukuipteryx prima, is the first species of primitive bird from this time period found outside China.
The authors suggest that F. prima may have shared several features with the so-called first bird, Archaeopteryx, including a robust wishbone, unfused pelvis, and forelimbs, but F. prima also has a fully formed pygostyle.
Previous research has suggested that 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 byproduct of tail reduction and unrelated to flight adaptation.
The authors of the study, published in Communications Biology, say more explorations of Early Cretaceous sediments are needed to improve our understanding of the period’s birds.
Thanks to Uppsala University and Nature Research for providing this news.