Particle.news

Tiny Argentine Dinosaur Fossil Reshapes Alvarezsaur Evolution and Global Spread

The Nature paper finds miniaturization preceded the clade’s later ant‑eating adaptations.

Overview

  • A near-complete adult skeleton of Alnashetri cerropoliciensis, published Feb. 25 in Nature, weighed roughly 0.7–0.9 kg and was at least four years old.
  • The specimen preserves long, slender hindlimbs, relatively long three‑fingered forelimbs, and larger teeth, contrasting with the reduced arms and tiny teeth of later relatives.
  • Analyses infer an early Pangean distribution for Alvarezsauroidea, with continental breakup driving their presence on multiple continents rather than improbable ocean crossings.
  • Unearthed at La Buitrera in 2014, the fossil underwent more than a decade of preparation at a site famed for exquisitely preserved small Cretaceous vertebrates.
  • Researchers describe the find as a paleontological “Rosetta Stone” enabling reidentification of fragmentary museum specimens, with further material from the same valley already under study.