Alvarezsaurus

Say it like this: “AHL-vahr-ez-SAWR-us”

Alvarezsaurus calvoi

Alvarezsaurus ate meat and walked on two legs. It lived in the Late Cretaceous. Bones have been found in Argentina.

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When: Late Cretaceous (Santonian) · roughly 85.7 to 83.6 million years ago
Named in: 1991 · Bonaparte, J. F.
Hip height: 0.4 m · 1 ft
Length: 1–1.4 m · 3–5 ft
Weight: 3 kg · 7 lb
Found in: Argentina · Bajo de la Carpa
Food and walking: Carnivore · Two legs
Kind: sharp-clawed runner · Theropod
Family branch: Alvarezsauridae

The story in short

In 1991, J. F. Bonaparte published the name Alvarezsaurus. The name means “don Gregorio Alvarez.”

Fossils referred to Alvarezsaurus date to the Late Cretaceous (Santonian), roughly 85.7 to 83.6 million years ago. Finds come from Argentina, including the Bajo de la Carpa Formation. It was a carnivore and walked on two legs.

Published estimates put Alvarezsaurus at a length near 1–1.4 m, hips about 0.4 m high, and a body mass around 3 kg.

On the family tree it sits in Alvarezsauridae, among the theropod dinosaurs.

Close relatives

Achillesaurus

Achillesaurus manazzonei

Late Cretaceous (Santonian) · roughly 85.7 to 83.6 million years ago

Albertonykus

Albertonykus borealis

Late Cretaceous (Maastrichtian) · roughly 72.2 to 66 million years ago

Heptasteornis

Heptasteornis andrewsi

Late Cretaceous (Maastrichtian) · roughly 72.2 to 66 million years ago