Rare Intermediate Fossils Give Researchers Insight Into Evolution of Bird-Like Dinosaur
Xiyunykus and Bannykus are both alvarezsaurs, an enigmatic group of dinosaurs that share many characteristics with birds. Their bodies are slender, with a bird-like skull and many small teeth instead of the usual large, sharp cutting teeth of their meat-eating relatives.
Artist’s reconstruction of important alvarezsaur species from left to right, Haplocheirus, Xiyunykus, Bannykus, and Shuvuuia. Note the lengthening of the jaws, reduction of the teeth and changes in the hand and arm.
“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,” James Clark, the Ronald Weintraub Professor of Biology at the GW Columbian College of Arts and Sciences, said.
However, alvarezsaurs did not always look this way. Early members of the group had relatively long arms with strong-clawed hands and typical meat-eating teeth. Over time, the alvarezsaurs evolved into dinosaurs with mole-like arms and a single claw. The discovery of the new specimens allowed the researchers to uncover an important shift in how the specialized features of the alvarezsaurs evolved.
“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,” Jonah Choiniere, an associate professor at Wits University and member of the research team, said.
The fossils were discovered during an expedition co-led by Dr. Clark and Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences. Xiyunykus pengi is the ninth species of dinosaur identified by the partnership between GW and the academy.
“Our international field teams have been tremendously productive over the years,” Dr. Xu said. “This research showcases just some of our incredible discoveries.”
The fieldwork and research were supported by U.S. National Science Foundation grant EAR 0922187.
Contacts and sources:
Timothy Pierce:
George Washington University
Citation: Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution.
Xing Xu, Jonah Choiniere, Qingwei Tan, Roger B.J. Benson, James Clark, Corwin Sullivan, Qi Zhao, Fenglu Han, Qingyu Ma, Yiming He, Shuo Wang, Hai Xing, Lin Tan. Current Biology, 2018; DOI: 10.1016/j.cub.2018.07.057
Source: http://www.ineffableisland.com/2018/08/rare-intermediate-fossils-give.html
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Yet more drivel designed to mislead. “intermediate” fossils LOL. Adaptation within species exists throughout nature. There is ZERO proof that these fossils are in transition to a separate species.
Best definition of an ‘evolutionist’ I’ve read yet: One who attempts to hurt God’s feelings by denying His existence.
Fossils studying Fossils, gripping research you have there.
https://www.youtube.com/watch?v=Q8DDIe_2cHM
Wow.