Two newly discovered dinosaurs may be missing links in an unusual lineage of predators that lived between 160 million and 90 million years ago, a study suggests.
The two species, Xiyunykus and Bannykus, were theropods -- a group of bipedal, largely carnivorous dinosaurs -- researchers from the University of Alberta in Canada told PTI.
What happened to these theropods?
Some theropods eventually gave rise to birds, while another branch, the alvarezsauroids, evolved into strange-looking insectivores with short arms and hands with an enlarged finger for digging into nests.
However, until now, little was understood about how this change happened because of the 70-million-year evolutionary gap separating the insect-eating alvarezsauroids from the earliest known member of the group, Haplocheirus.
Significance and findings of these 2 theropods
"The significance of Xiyunykus and Bannykus is that they fall within that gap and shed light on patterns of evolution within Alvarezsauroidea," said Corwin Sullivan, a paleontologist at the University of Alberta.
"These specimens greatly improve the scientific community's understanding of the early stages of alvarezsauroid evolution and give us a better idea of what early alvarezsauroids were like," Sullivan said.
The new specimens reveal clues about how the creatures' diet shifted from meat to insects, Sullivan noted.
The forelimbs show some adaptations for digging, which would later become more exaggerated, and some features of their skulls also resemble those of insectivorous alvarezsauroids.
"The hindlimbs are less modified, suggesting the arms and head of alvarezsauroids underwent significant change before the legs did," said Sullivan.
Check out this supercool paleoart of the two newly-discovered dinosaurs by an illustrator!
#Paleoart of the two new alvarezsauroid #dinosaurs Bannykus & Xiyunykus. These two nicely illustrate the transition between a general coelurosaur bodyplan and the bizarre tiny-armed alvarezsaurids. #scicomm #palaeontology pic.twitter.com/kCQxoLaDWITom Parker (@Tomozaurus) August 28, 2018
Scientists still need more fossils to be sure
"Xiyunykus and Bannykus are currently represented by one incomplete specimen apiece. Those specimens provide a good deal of intriguing information, but we'll need many more fossils before we can be confident that we have a clear understanding of how alvarezsauroids, to put it bluntly, got so weird," Sullivan said.
When the missing link in the evolution of 'Frankenstein dinosaur' came out
An analysis in 2017 on the Chilesaurus dinosaur discovered in 2015 revealed a missing link between plant-eating dinosaurs and members of the theropod group, including carnivores like Tyrannosaurus Rex and Velociraptor.
According to study researchers, the finding was very crucial to understanding the evolution of dinosaurs.
At the time, Matthew Baron from the University of Cambridge said, "There was a split in the dinosaur family tree, and the two branches took different evolutionary directions. This seems to have happened because of change in diet for Chilesaurus. It seems it became more advantageous for some of the meat-eating dinosaurs to start eating plants, possibly even out of necessity. Chilesaurus almost looks like it was stitched together from different animals, which is why it baffled everybody."
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