The common image of a dinosaur in our mind is of a huge animal. But if the findings of a recent study by a group of Chinese researchers are to be believed, alvarezsaur dinosaurs were as small as a chicken. This study led by Zichuan Qin, a PhD student at the University of Bristol and Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, found that alvarezsaur dinosaurs rapidly shrunk in size after turning into specialized anteaters about 100 million years ago, reported phys.org.
Zichun analyzed dozens of specimens of the dinosaur species spanning over millions of years to track this change in the size. The alvarezsaurs lived in the late Jurassic to late Cretaceous age (160 to 70 million years ago) across many parts of the world including China, Mongolia, and South America. For the most part of their existence, the alvarezsaurs were slender, two-legged predators who ate lizards, early mammals, and baby dinosaurs astheir diet.
While analyzing the specimen, Zichun learned that the older specimen ranged in size from 10 - 70kgs or roughly about the size of a large turkey to the size of a small ostrich. However, towards the later part of the evolution, the specimen showed that the size of the alvarezsaurs had plumped down to size of a chicken and Zichun concluded that it was because they moved to ant-eating.
One of Zichuan’s supervisors, Professor Michael Benton from the University of Bristol, said that this drastic change in the diet of alvarezsaur could have been a result of the increased competition for food.
He tells that during the Cretaceous age, the ecosystem was rapidly evolving, and flowering plants were taking over the landscape. The dinosaurs did not feed on these flower plants but they led to the explosion of new types of insects, including ants and termites. The restructuring of the ecosystems has been called the Cretaceous Terrestrial Revolution and it marks the emergence of modern-style forests and woodlands.