Evrim Yazgin
Cosmos science journalist
In an important advance in palaeontology, researchers have uncovered a 149-million-year-old fossil in southeast China which could be the earliest “true bird”.
It is well understood that dinosaurs evolved into birds. Today, birds are the most diverse group of terrestrial vertebrates with at least 11,000 species. Macroevolutionary studies suggest that birds began to diversify after evolving about 165–150 million years ago during the Jurassic period (201–145 million years ago).
But evidence of where, when and how this feathery lineage started has remained elusive.
Archaeopteryx has long been described as a “missing link” between non-avian dinosaurs and birds. It was first discovered in the late 19th century and lived about 150 million years ago.
While Archaeopteryx has many bird-like traits including feathers and a wishbone, it also has reptilian features like a long, bony tail and sharp-clawed hands. For this reason, its historical title as the “first bird” has been subject to debate over the decades.
A 2011 paper describing an Archaeopteryx-like dinosaur from the late Jurassic found in China challenged the centrality of Archaeopteryx in the origin of birds. As a result, scientists have opted in recent literature to refer to Archaeopteryx not as a basal bird, but as a deinonychosaurian dinosaur – a sister group to birds.
Until now, this has thrown up question marks about whether any unambiguous birds from the Jurassic exist.
Now new fossils detailed in a paper published in Nature might represent the earliest “true bird”.
The specimens were uncovered in the Jurassic-era rocks in southeast China’s Fujian Province. Rocks in the region have previously revealed other significant dinosaur discoveries including one of the world’s largest raptor species, Fujianipus yingliangi.
The new study describes 2 species of feathered dinosaur dating to 149 million years ago – right at the end of the Jurassic.
One, Baminornis zhenghensis, displays a unique set of features. It has bird-like shoulder and pelvic girdles as well as a hand structure similar to non-avian dinosaurs.
Notably, B. zhenghensis has a short tail ending in a compound bone called pygostyle – a feature also observed in living birds.
“Previously, the oldest record of short-tailed birds is from the Early Cretaceous,” says corresponding author Wang Min from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) of the Chinese Academy of Sciences.
“Baminornis zhenghensis is the sole Jurassic and the oldest short-tailed bird yet discovered, pushing back the appearance of this derived bird feature by nearly 20 million years.”
Several lines of investigation into the position of B. zhenghensis in the evolutionary tree of birds show that the species represents one of the oldest birds, only just further along the line from Archaeopteryx.
“If we take a step back, and reconsider the phylogenetic uncertainty of Archaeopteryx, we do not doubt that Baminornis zhenghensis is the true Jurassic bird,” says co-author Zhou Zhonghe from IVPP.
The other specimen is known from a single, poorly preserved bone. It is probably related to a group of Cretaceous birds called ornithuromorpha, but the palaeontologists refrained from naming the new taxon before finding further fossil evidence.
