86-million-year-old fossils lead to the discovery of two new species of bird-like dinosaurs

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As part of an expedition to Xinjiang, China, a joint team of researchers has identified a hitherto-unknown species of dinosaur, known as Xiyunykus pengi. Published recently in the Current Biology journal, the discovery was made by paleontologists from the George Washington University, in collaboration with the Chinese Academy of Sciences.

The study also entailed the identification of a second new intermediate species, Bannykus wulatensis. According to the scientists, both species are members of Alvarezsaurus, a genus of small alvarezsaurid dinosaur that existed during the Late Cretaceous period around 86 million to 83 million years ago.

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A representation of Xiyunykus

Measuring about 2 meters (6.5 feet) in length and weighing approximately 20 kilograms (45 pounds), these creatures – with their slender profile and narrow skull – bore multiple resemblances to the early birds. In fact, both of these dinosaurs possessed many small teeth, instead of the large, sharp teeth of their carnivorous counterparts. Speaking about the characteristics of alvarezsaurs, James Clark, a Professor of Biology at the GW Columbian College of Arts and Sciences, said –

When we described the first well-known alvarezsaur, Mononykus, in 1993, we were amazed at the contrast between its mole-like arms and its roadrunner-like body, but there were few fossils connecting it back to other theropod groups.

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A representation of Bannykus

As per Clark, alvarezsaurs originally had long arms with strong claws and sharp meat-eating teeth. However, over time, they evolved into smaller, bird-like dinosaurs with a single claw and short arms. Through the latest discovery, the team has been successful in tracing this evolution. Shedding light on the findings, Jonah Choiniere, an associate professor at Wits University and member of the research team, added –

It can be hard to pin down the relationships of highly specialized animals. But fossil species with transitional features, like Xiyunykus and Bannykus, are tremendously helpful because they link bizarre anatomical features to more typical ones.

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A representation of Alvarezsaurs

Xiyunykus pengi, Choiniere stated, is the ninth species of dinosaur identified by the international team of researchers from George Washington University and the Chinese Academy of Sciences. The project was co-led by Dr. Clark and Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences. Dr. Xu averred –

Our international field teams have been tremendously productive over the years. This research showcases just some of our incredible discoveries.

Earlier in 2014, paleontologists unearthed as many as 47 skeletal specimens belonging to a new species of pterosaurs, the ancient flying dinosaurs, from the southern part of Brazil. Christened as Caiuajara dobruskii, this breed of prehistoric airborne reptiles is believed to have inhabited a desert lake of the Cretaceous period, nearly 100 million to 60 million years ago.

More recently, in June 2016, researchers discovered two dinosaur wings so well preserved inside amber that they could even discern the feathers on their forms. Dating from around 99 million years ago, the organism in question belongs to the Enantiornithes, a group of extinct avialans (from the clade Dinosauria) who retained some features of their dinosaur cousins, like emerging teeth from inside their beaks and tiny clawed fingers on each wing.

However other than such ‘anachronistic’ features, the creatures resembled modern birds from the external perspective. Two such Enantiornithes wing specimens from the Mesozoic Era got trapped in some tree sap occurring in present-day Myanmar. The sap, in turn, morphed into amber over the long period of time by a process known as molecular polymerization, thus creating what is now believed to be the first ever almost ‘complete’ specimen of dinosaur plumage.

Source: George Washington University

Image Credits: Phys.org

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About the Author

Sukanya Mukherjee
With a master's degree in English Literature and several years of writing experience under her belt, Sukanya specializes in creating content particularly related to history, science, and technology. In the past, she worked as a business journalist at a reputable digital media company. Apart from being an avid fan of Victorian literature, she can found spending her free time baking and exploring the Great Himalayas!
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