Scientists in Argentina's Patagonia have discovered an almost complete skeleton of Alnashetri cerropoliciensis, a small theropod from 95 million years ago. Weighing less than a kilogram and comparable in size to a chicken, this predator challenges existing hypotheses about the evolution of alvarezsaurs. The discovery suggests that miniaturization in this group occurred much earlier than assumed, and that specific anatomical features evolved independently of body mass reduction, forcing a revision of paleontology textbooks.

Breakthrough in evolutionary theory

The find challenges the theory that the miniaturization of alvarezsaurs was a late process linked solely to a shift to an insectivorous diet.

Exceptional state of preservation

The discovered skeleton is nearly complete, which is rare for such small and fragile fossils from 95 million years ago.

Featherweight of the Mesozoic

The dinosaur weighed less than 1 kg and measured about 70 cm in length, most of which was a tail that facilitated fast running.

In the Río Negro province in northern Patagonia, researchers have made an extraordinary find that sheds new light on the diversity of Mesozoic ecosystems. Alnashetri cerropoliciensis is a creature weighing less than one kilogram that shared its environment with giants like the 70-ton Argentinosaurus. Although the first description of this genus appeared in 2012 based on fragmentary remains, the newly found skeleton is nearly complete and exceptionally well-preserved, allowing for detailed phylogenetic analyses. The discovered individual belonged to the group of alvarezsaurs, enigmatic relatives of the famous Tyrannosaurus rex. For years, the scientific community held the belief that this group evolved linearly: from larger ancestors to increasingly smaller forms specialized in myrmecophagy, or the eating of ants and termites. Alnashetri, possessing evolutionarily advanced features while appearing very early in the fossil record, proves that this process was far more complex. This suggests that small size was not the result of a late adaptation but a feature already present in alvarezsaurs during the period when continents formed the supercontinent Pangaea. The Candeleros Formation, where the discovery was made, is one of the world's most important paleontological sites from the Cretaceous period, known for the excellent preservation of small vertebrates in the sediments of the ancient Kokorkom desert.Research published in the prestigious journal „Nature” indicates that this dinosaur, weighing about 700–800 grams, most likely possessed feathers, although direct feather impressions were not preserved in the sandstone. Its anatomical structure—long legs, small hands ending in a strong claw, and numerous small teeth—suggests a diet consisting of insects and small vertebrates such as lizards or snakes. The international team led by Peter Makovicky and Sebastián Apesteguía emphasizes that Alnashetri constitutes a missing link in understanding how small theropods survived in the shadow of the largest land predators of all time.

Mentioned People

  • Peter Makovicky — Paleontologist from the University of Minnesota, co-author of the research on Alnashetri.
  • Sebastián Apesteguía — Argentine paleontologist from Maimónides University, head of the work at La Buitrera.