New light on dinosaur evolution
AN INTERNATIONAL research team has announced the discovery of two new Chinese insect-eating dinosaurs, shedding light on their evolution.
Bannykus and Xiyunykus were discovered in North China during collaborative international fieldwork.
Xiyunykus was discovered in 2005 in Xinjiang, northwestern China, while Bannykus was discovered in 2009 in Inner Mongolia, north-central China.
Both research trips were joint expeditions co-led by Professors Xu Xing (Institute for Vertebrate Palaeontology and Palaeoanthropology, Beijing) and James Clark (George Washington University, Washington DC).
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.
South African Professor Jonah Choiniere, from the University of the Witwatersrand, was a leading member of the team and is a co-author on the research.
The dinosaurs are both alvarezsaurs, an enigmatic group of theropod (meat-eating) dinosaurs that have many similarities with birds, and which show adaptations thought to be related to eating insects that live in colonies.
“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,” said Choiniere.
But 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.
“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 to what happens in tyrannosaurs, which have short arms and giant size,” said co-author Professor Roger Benson of Oxford University.
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. These dinosaurs show us how a lineage can make a major shift in its ecology over time,” said Clark.
Choiniere added: “China and South Africa have a great deal of overlap in palaeontology, and it has been a privilege to cross-train students there over the last two years.”