As an Amazon Associate I earn from qualifying purchases.
An extremely total skeleton of the alvarezsauroid dinosaur types Alnashetri cerropoliciensis from Patagonia, Argentina, along with 2 alvarezsauroid specimens from the northern hemisphere expose how the once-mysterious family tree of theropod dinosaurs progressed and spread out in the past continents wandered apart, challenging long-held presumptions about their origins.
Alnashetri cerropoliciensisImage credit: Gabriel Díaz Yantén, Universidad Nacional de Río Negro.
Alnashetri cerropoliciensis resided in what is now Argentina throughout the Cenomanian age of Late Cretaceous date, some 90 million years earlier.
Explained in 2012 from fragmentary remains, the types belongs to a group of bird-like dinosaurs called the Alvarezsauroidea.
These little dinosaurs are well-known for their small teeth and stubby arms ending in a single big thumb claw.
“Alvarezsauroids are an enigmatic clade of mainly small-bodied theropod dinosaurs that are understood generally from the Jurassic to Cretaceous durations of Asia and South America,” stated University of Minnesota Twin Cities paleontologist Peter Makovicky and his coworkers.
“Late Cretaceous alvarezsauroids have specialized forelimbs adjusted for digging, minute supernumerary teeth and increased sensory capabilities, and are analyzed as myrmecophagous (feeding mostly on ants).”
“They are assumed to show evolutionary miniaturization paired to their dietary expertise.”
The brand-new, nearly total skeleton of Alnashetri cerropoliciensis was found in the La Buitrera fossil location in Río Negro province, northern Patagonia.
Tiny analysis of the specimen verified the animal was undoubtedly a grownup of a minimum of 4 years of ages.
It weighed less than 0.9 kg (2 pounds), making it among the tiniest dinosaurs understood from South America.
Unlike its later family members, Alnashetri cerropoliciensis had long arms and bigger teeth.
According to the paleontologists, this shows that some alvarezsauroids developed to be small long before they established these specialized functions believed to be adjustments for their ant-eating diet plan.
By determining formerly discovered alvarezsauroid fossils in museum collections from North America and Europe, the scientists likewise showed these dinosaurs stemmed much earlier than anticipated when the continents were still linked as the supercontinent Pangea.
Their circulation was brought on by the break up of the Earth’s landmasses, possible treks throughout oceans.
“Our biogeographical analyses presume a Pangean ancestral circulation for Alvarezsauroidea, with vicariance controling the early history of the clade,” the researchers stated.
Their paper was released today in the journal Nature
_____
P.J. Makovicky et alArgentine fossil rewords evolutionary history of a complicated dinosaur clade. Naturereleased online February 25, 2026; doi: 10.1038/ s41586-026-10194-3
Find out more
As an Amazon Associate I earn from qualifying purchases.
