Reconstruction of Alnashetri cerropoliciensis
Gabriel Díaz Yantén, Universidad Nacional de Río Negro.
An extraordinary discovery has shed light on the evolution of alvarezsaurs, one of the smallest dinosaurs to have ever roamed the Earth. The fossil of Alnashetri cerropoliciensis, which dates back 95 million years, was unearthed at the La Buitrera site in northern Patagonia, Argentina, in 2014.
Originally, only a set of incomplete hindlimb bones of Alnashetri was found in 2012, leaving researchers uncertain about its classification. However, with the discovery of a nearly complete skeleton, scientists were able to gain valuable insights into the anatomy and characteristics of this tiny dinosaur.
Weighing a mere 700 grams during its lifetime, Alnashetri was smaller than a chicken. Contrary to previous beliefs that alvarezsaurs were early ancestors of birds, further analysis revealed that they were non-avian theropods. The unique features of Alnashetri, such as its long hind limbs and well-developed fingers, challenge previous assumptions about the evolution of alvarezsaurs.
Unlike other alvarezsaurs, Alnashetri did not exhibit the typical characteristics of short forelimbs and tiny teeth associated with ant-eating behavior. This suggests a different evolutionary path for this species, indicating a broader prey range than just ants and termites.
Researchers are still puzzled by the miniature size of alvarezsaurs and the reasons behind their evolution into such small predators. While Alnashetri provides valuable information about the early branches of the alvarezsaur evolutionary tree, the exact factors driving their size reduction remain a topic of ongoing investigation.
