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Tiny, long-armed dinosaur leads to rethink of dinosaur miniaturization

March 9, 2026
•Ars technica
Tiny, long-armed dinosaur leads to rethink of dinosaur miniaturization

Here's something that caught my attention — scientists recently uncovered a tiny dinosaur with long arms, but it’s shaking up our whole idea of miniaturization in dinosaurs. Usually, Alvarezsaurids, those small, bird-like predators from the Late Cretaceous, were thought to have shrunk down specifically to specialize in eating ants and termites. That made sense, right? Smaller bodies, better at sneaking into termite mounds. But now, Jacek Krywko reports that the discovery of a new fossil, called Alnashetri cerropoliciensis, suggests otherwise. According to paleontologist Peter Makovicky, this little guy probably didn’t feed on social insects at all. Instead, it was a pursuit predator hunting insects and tiny mammals. So what does this mean? It turns out, mini dinosaurs might not have evolved in such a straightforward way — sometimes, their sizes and diets were more complex than we imagined. Honestly, this finding makes us rethink how evolution actually works in these tiny, long-armed dinosaurs.

Alvarezsaurids were mostly small-bodied theropods that paleontologists originally misinterpreted as early flightless birds, only to later recognize them as an ant-eating lineage of non-avian dinosaurs. For years, we suspected that Alvarezsaurids underwent a rare process of evolutionary miniaturization directly coupled to a diet of social insects like ants and termites. It was a tidy hypothesis: They got smaller to become more efficient at catching ants.

Now, a recently discovered fossil of one of the smallest alvarezsaurids ever found suggests that the evolution of miniature dinosaurs likely wasn’t as neat and linear as we thought. This new species, called Alnashetri cerropoliciensis, probably did not feed on ants at all. “It was a pursuit predator actively hunting insects and small mammals,” said Peter Makovicky, a paleontologist at the University of Minnesota.

The oddball

Alverezsaurids, found mostly in the Late Cretaceous rocks of Asia and South America, had short forelimbs tipped with a single oversized thumb claw built for digging. They also had minute teeth and sensory adaptations akin to those in modern nocturnal birds—everything necessary to work on termite mounds. “The explanation of their small body size has been tied to this specialization,” Makovicky explained.

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Audio Transcript

Alvarezsaurids were mostly small-bodied theropods that paleontologists originally misinterpreted as early flightless birds, only to later recognize them as an ant-eating lineage of non-avian dinosaurs. For years, we suspected that Alvarezsaurids underwent a rare process of evolutionary miniaturization directly coupled to a diet of social insects like ants and termites. It was a tidy hypothesis: They got smaller to become more efficient at catching ants.

Now, a recently discovered fossil of one of the smallest alvarezsaurids ever found suggests that the evolution of miniature dinosaurs likely wasn’t as neat and linear as we thought. This new species, called Alnashetri cerropoliciensis, probably did not feed on ants at all. “It was a pursuit predator actively hunting insects and small mammals,” said Peter Makovicky, a paleontologist at the University of Minnesota.

The oddball

Alverezsaurids, found mostly in the Late Cretaceous rocks of Asia and South America, had short forelimbs tipped with a single oversized thumb claw built for digging. They also had minute teeth and sensory adaptations akin to those in modern nocturnal birds—everything necessary to work on termite mounds. “The explanation of their small body size has been tied to this specialization,” Makovicky explained.

Read full article

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