Paleontologists have identified a new species of avialan (a member of the group that contains modern birds and bird-like dinosaurs) from a fossilized partial skeleton found in China. This dinosaur exhibits an unusual set of morphological features that are shared with other early avialans as well as troodontid and dromaeosaurid dinosaurs.
Life reconstruction of Fujianvenator prodigiosus. Image credit: Chuang Zhao.
“Our understanding of the earliest evolutionary history of the Avialae, the most inclusive clade that contains all modern birds but not Deinonychus or Troodon, has been hampered by the limited diversity of fossils from the Jurassic period, when avialans diverged from the main line of theropods,” said Dr. Min Wang, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, and colleagues.
“Specifically, few avialans have been reported from localities other than the Middle-Late Jurassic Yanliao Biota in northeast China (166-159 million years ago) and the slightly younger Solnhofen Limestones in Germany, leaving a gap of approximately 30 million years until the oldest known record of Cretaceous avialans.”
“The earliest diverging avialans are key to deciphering the evolutionary origin of the characteristic avialan morphologies that contributed to their first global-scale diversification in the Cretaceous and, more importantly, to revealing the increasingly complex evolutionary history of stem avialans.”
The newly-identified avialan species roamed our planet around 150 million years ago (Late Jurassic epoch).
Dubbed Fujianvenator prodigiosus, it may be the youngest known member of the Jurassic avialans.
“Fujianvenator prodigiosus was a pheasant-sized avialan with a lower hindlimb (tibia) that is twice as long as the thigh (femur), a previously unknown condition for non-avian dinosaurs,” the researchers said.
“This finding contrasts with other early avialans, which are thought to have been more arboreal and aerial in nature.”
According to the team, Fujianvenator prodigiosus lived in a swamp-like environment and was a high-speed runner or a long-legged wader.
“Our comparative analyses show that marked changes in body plan occurred along the early avialan line, which is largely driven by the forelimb, eventually giving rise to the typical bird limb proportion,” Dr. Wang said.
“However, Fujianvenator prodigiosus is an odd species that diverged from this main trajectory and evolved bizarre hindlimb architecture.”
The partial skeleton of Fujianvenator prodigiosus was unearthed in Zhenghe County in China’s Fujian province.
The dinosaur was part of the newly-discovered Zhenghe Fauna, a diverse collection of vertebrate fossils dominated by aquatic and semiaquatic species, including turtles and ray-finned fish, which are indicative of a swampy ecosystem.
“The extraordinary diversity, unique vertebrate composition, and paleoenvironment strongly indicate that this locality documents a terrestrial fauna, which we named the Zhenghe Fauna,” said Dr. Zhonghe Zhou, also from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.
A paper on the findings appears today in the journal Nature.
_____
L. Xu et al. A new avialan theropod from an emerging Jurassic terrestrial fauna. Nature, published online September 6, 2023; doi: 10.1038/s41586-023-06513-7
