90-Million-Year-Old Fossil Reveals a Fully Grown Dinosaur That Weighed Less Than 2 Pounds (Discovermagazine) [View all]

Written by Anastasia Scott
Feb 25, 2026, 4:00 PM | 3 min read

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That’s the story of Alnashetri cerropoliciensis, a 90-million-year-old dinosaur that may unlock the mysteries of Alvarezsaurid{s}, a group of bird-like dinosaurs so strange they almost look like cartoon caricatures, with tiny teeth and stubby arms ending in a single large thumb claw.

“Going from fragmentary skeletons that are hard to interpret, to having a near complete and articulated animal is like finding a paleontological Rosetta Stone,” said Peter Makovicky, lead author in a press release. “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.”


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This Tiny Dinosaur Was Small Before It Specialized

Microscopic analysis shows that this individual was fully grown, at least four years old, yet weighed less than two pounds. That alone makes Alnashetri one of the smallest dinosaurs known from South America.

Most later Alvarezsaurids had compact bodies and stubby forelimbs, features many researchers assumed evolved early as adaptations for digging into insect nests. But Alnashetri had relatively long arms and larger teeth. Instead of a creature specialized from the start, this dinosaur was more generalized. It hadn’t yet evolved the extreme body plan of its later cousins.
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more: https://www.discovermagazine.com/90-million-year-old-fossil-reveals-a-fully-grown-dinosaur-that-weighed-less-than-2-pounds-48735

Although this article is a month old, I hadn't seen the news elsewhere. It is apparently a Very Big Deal to paleontologists, as a Google search reveals numerous hits on major sites.

Alvarez is a common surname -- one of the scientists involved in this discovery is Gregorio Alvarez-Herrara, not the Alvarez after whom this group of dinosaurs is named. Nor is it named after either of the father-son physicists Luis or Walter Alvarez, of K-T Boundary Layer and Chicxulub impact crater fame. Rather, the Argentinian paleontologist José Bonaparte named it after the Argentinian physician, historian, and author Gregorio Alvarez.

(BTW, there is a much deeper history of paleontology in Argentina, incl. Patagonia, than most English-only readers are aware. It really deserves a comprehensive history translated into English, or made into a documentary program (subtitles OK). Post if you know of one ...)




Probably best they didn't let me name it -- I might have called it Roadrunnersaurus looneytoonsie .