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Tiny, Near-Complete Dinosaur From Patagonia Refines Alvarezsaur Evolution

New Nature research uses exceptional preservation to infer age, size, and ecology from microscopic bone evidence.

Overview

  • Researchers describe Alnashetri cerropoliciensis, one of the smallest known non‑avian dinosaurs, at roughly 0.7 kg and 70 cm in length.
  • The nearly complete skeleton, found at La Buitrera in Río Negro, Argentina, was preserved in life position after rapid burial by a sand dune about 95 million years ago.
  • Bone histology indicates a near‑adult female about four years old, allowing precise growth and maturation assessments.
  • Features include numerous pointed teeth and forelimbs lacking the extreme single‑claw specialization of later alvarezsaurs, suggesting hunting small vertebrates rather than insect digging.
  • The study challenges a simple miniaturization trend in alvarezsaurs, pointing to repeated size reductions and ecological diversity; earlier finds were partial legs in 2004, with this complete specimen discovered in 2014 and prepared over 12 years.