The dinosaurs are both Alvarezsaurs, an enigmatic group of theropod dinosaurs, which have many similarities with birds.
An international research team has announced the discovery of two new Chinese dinosaurs - Bannykus and Xiyunykus.
The dinosaurs are both Alvarezsaurs, an enigmatic group of theropod [meat-eating] dinosaurs, which have many similarities with birds and show adaptations thought to be related to eating insects that live in colonies.
Co-author on the research, Professor Jonah Choiniere, said, "Alvarezsaurs are weird animals. With their strong, clawed hands and weak jaws, they appear to be the dinosaurian analogue to today's aardvarks and anteaters."
However, alvarezsaurs did not originally eat insects. The earliest members of the group had more typically meat-eating teeth and hands, useful for catching small prey. Only later-evolving members reduced their teeth and evolved a hand with a huge, single claw capable - perhaps - of tearing open rotting logs and anthills.
Co-author Professor Roger Benson said, "The new fossils have long arms, and so show that alvarezsaurs evolved short arms only later in their evolutionary history, in species with small body sizes. This is quite different from what happens in the classic example of tyrannosaurs, which have short arms and giant size."
Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new diets.
"The fossil record is the best source of information about how anatomical features evolve," said James Clark, co-author and an Honorary Professor at Wits University. "And like other classic examples of evolution such as the 'horse series', these dinosaurs show us how a lineage can make a major shift in its ecology over time."
Once the fossils were discovered, their further study was made possible by a joint South Africa/ China collaborative grant through South Africa's National Research Foundation, held by Choiniere and Xu.
The full findings are present in the journal- Current Biology.