Tiny Dinosaur Fossil Upends Prehistoric History

Newly discovered 90-million-year-old fossil provides "missing link" for mysterious group of bird-like dinosaurs

Published on Feb. 26, 2026

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A team of researchers co-led by University of Minnesota Twin Cities professor Peter Makovicky and Argentinean colleague Sebastian Apesteguía has identified a 90-million-year-old fossil that provides key insights into the evolution of a mysterious group of prehistoric animals known as alvarezsaurs. The nearly complete skeleton of the species Alnashetri cerropoliciensis, discovered in Patagonia, Argentina, reveals new details about the anatomy and distribution of these tiny, bird-like dinosaurs.

Why it matters

The discovery of the Alnashetri fossil helps fill a crucial gap in the evolutionary history of alvarezsaurs, a group of dinosaurs that have remained a mystery due to the scarcity of well-preserved fossils, especially from South America. This finding provides a "Rosetta Stone" for understanding the evolution and spread of these diminutive dinosaurs across the ancient supercontinent of Pangaea.

The details

The Alnashetri fossil, discovered in 2014 in northern Patagonia, is the most complete alvarezsaur skeleton ever found. The researchers spent a decade carefully preparing and piecing together the small bones to avoid damage. Analysis of the fossil revealed that unlike its later relatives, Alnashetri had longer arms and larger teeth, indicating the group evolved to be tiny long before developing the specialized "ant-eating" features. The fossil also confirmed Alnashetri was an adult weighing less than 2 lbs, making it one of the smallest dinosaurs known from South America.

  • The Alnashetri fossil was discovered in 2014 in northern Patagonia, Argentina.
  • The research team spent the last decade carefully preparing and piecing together the fossil.

The players

Peter Makovicky

A professor in the University of Minnesota Department of Earth and Environmental Sciences and the lead author on the paper.

Sebastian Apesteguía

A researcher at Universidad Maimónides in Buenos Aires, Argentina, and Makovicky's co-lead on the research.

Alnashetri cerropoliciensis

The newly identified species of tiny, bird-like dinosaur whose nearly complete fossil skeleton was discovered in Patagonia.

La Buitrera

The fossil site in northern Patagonia where the Alnashetri fossil was recovered, which has yielded other scientifically critical animal fossils.

Pangaea

The ancient supercontinent that broke apart, allowing the distribution of alvarezsaur dinosaurs across North America, Europe, and South America.

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What they’re saying

“Going from fragmentary skeletons that are hard to interpret, to having a near complete and articulated animal is like finding a paleontological Rosetta Stone. We now have a reference point that allows us to accurately identify more scrappy finds and map out evolutionary transitions in anatomy and body size.”

— Peter Makovicky, Lead author and professor (University of Minnesota)

“After more than 20 years of work, the La Buitrera fossil area has given us a unique insight into small dinosaurs and other vertebrates like no other site in South America.”

— Sebastian Apesteguía, Researcher (Universidad Maimónides)

What’s next

The researchers continue to discover and study additional fossils from the La Buitrera site, where they have already found the "next chapter of the alvarezsaurid story" that is currently being prepared in the lab.

The takeaway

The discovery of the Alnashetri fossil provides a critical missing link in understanding the evolution and distribution of the mysterious alvarezsaur dinosaurs, revealing that these tiny, bird-like creatures evolved to be diminutive much earlier than previously thought, long before developing their specialized "ant-eating" features.