Long-legged dinosaur as a link to the birds

Fujianvenator

This is what the dinosaur Fujianvenator prodigiosus might have looked like around 150 million years ago. © Chuang Zhao

The fossil of a previously unknown dinosaur from the Late Jurassic provides new insights into the evolution of birds. The roughly pheasant-sized Fujianvenator prodigiosus had exceptionally long legs and probably resembled later ratites or wading birds. This distinguishes it from other ancestors of birds, which were adapted to a life in trees and in the air. Additional fossils from the same site indicate that it was a swampy ecosystem that was home to both terrestrial and aquatic species.

During the Jurassic period, around 201 to 145 million years ago, birds evolved from two-legged dinosaurs called theropods. In addition to the famous ancient bird Archeopteryx, which lived in the middle to late Jurassic, only a few other similarly old fossils of bird ancestors have been preserved. Most specimens date from the Cretaceous period, leaving a gap of 30 million years in the fossil record.

Exceptional mosaic of features

A team led by Liming Xu from the Fujian Institute for Geological Investigations in China has now described a new fossil that also lived in the late Jurassic period and provides new insights into the early days of birds: Fujianvenator prodigiosus comes from the eastern Chinese province of Fujian and was founded dated to be 148 to 150 million years old. The name means “bizarre hunter from Fujian” and refers to the unusual physique of the pheasant-sized dinosaur.

“Fujianvenator is distinguished from all other bird-like dinosaurs by its combination of features,” the team reports. “Among other things, the tibia is about twice as long as the femur.” The proportions of the hand bones, on the other hand, are typical of bird-like dinosaurs and are similar to those of Archeopteryx. At the same time, the tank has features of other theropods. “The unique combination of skeletal features that Fujianvenator shares with early avian dinosaurs shows how much the evolutionary history of birds was influenced by evolutionary mosaicism,” the team writes.

No adaptation to life in the air

Unlike other bird ancestors, Fujianvenator, with its long legs, was apparently not adapted to life in the air or in trees. Instead, it was probably a fast runner or some kind of ancient wading bird stalking through swampy terrain. Other fossils from the same site also suggest that Fujianvenator lived in a moist ecosystem. “In addition to Fujianvenator, we found numerous other vertebrates, including bony fish, turtles and crocodile-like reptiles,” reports Liming. The mixture of land and aquatic animals suggests that it was essentially a terrestrial ecosystem, although large parts of it were under water.

“During the Late Jurassic and Early Cretaceous, there was strong tectonic activity in southeast China,” explains the research team. This also created the fault basin in which Fujianvenator and the other fossils were found. Because the site is in the Zhenghe region of Fujian Province, the team named the fossil collection Zhenghe Fauna. “The exceptional fossil diversity and distinctive paleoenvironment, coupled with the precise dating of the fossil-bearing horizons to 148 to 150 million years, demonstrate the great potential of Zhenghe as an emerging Jurassic vertebrate fauna, filling an important temporal and geological gap in our understanding of the ecosystems of Northeast Asia Late Jurassic closes,” the researchers write. In future studies, they want to further investigate the Zhenghe fauna.

Source: Liming Xu (Fujian Institute of Geological Survey, Fuzhou, China) et al., Nature, doi: 10.1038/s41586-023-06513-7

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