AsianScientist (May 16, 2017) – An international team of palaeontologists co-led by Dr. Michael Pittman of the University of Hong Kong has reported a new species of bird-like dinosaur in Nature Communications.
The new species Jianianhualong tengi is part of a family of bird-like dinosaurs called troodontids, which together with dromaeosaurids (Velociraptor and its kin) are the closest relatives to birds.
“Troodontids and dromaeosaurids are bird-like dinosaur groups that share their closest common ancestor with birds. This is like chimpanzees and bonobos sharing their closest common ancestor with humans,” Pittman explained.
J. tengi looked like a long-tailed one meter long chicken and weighed around 2.5 kilograms. It lived around 125 million years ago in a temperate environment. The J. tengi fossil was found in Northeastern China in Baicai Gou, Liaoning Province, a field site of the Jehol Biota, an ancient ecosystem famous for its feathered dinosaurs.
Large feathers adorned the forelimbs, hindlimbs and tail of J. tengi. Those on the tail show a frond-like arrangement just like the iconic early long-tailed bird Archaeopteryx, suggesting this was a relatively common feature in early birds and closely related bird-like dinosaurs.
Pittman said the importance of the discovery is that J. tengi possessed asymmetrical feathers, a feature commonly associated with flight. The tail feathers of J. tengi are asymmetrically vanned, which means that one side of the feather is wider than the other, just like in living birds and the ‘four-winged’ gliding dromaeosaurid Microraptor that lived around 120 million years ago.
“The asymmetrical feathers that we reported on the tail of J. tengi is the first record of these aerodynamically associated feathers in troodontid dinosaurs,” Pittman said.
“Now that we know birds, dromaeosaurids and troodontids all have representatives with asymmetrical feathers; we reconstructed these feathers at their closest common ancestor (the closest common ancestor of birds). This means that this feature (asymmetrical feathers) evolved earlier than previously thought—at least 160 million years ago—because a common ancestor is always older than its descendant groups.”
Birds have asymmetrical feathers that have been associated with flight capability, but they are also found in species that do not fly. We therefore cannot say that J. tengi glided or flew based on these feathers alone.
“However, we can say that the aerodynamic capabilities conferred by these feathers would have benefited its locomotion, be it ground-based or through the air (gliding and flying). This study makes important steps towards reconstructing the early evolution and function of asymmetrical feathers,” Pittman added.
The J. tengi fossil is currently housed in the Dalian Xinghai Museum in Liaoning Province, China and its specific name tengi honours its curator Teng Fang Fang who secured the specimen for scientific study.
The article can be found at: Xu et al. (2017) Mosaic Evolution in an Asymmetrically Feathered Troodontid Dinosaur with Transitional Features.
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Source: University of Hong Kong.
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