Genus
Valid Extinct

Alvarezsaurus

Bonaparte 1991

Alvarezsaurus is a genus of alvarezsaurid dinosaur from the Late Cretaceous, living in Argentina approximately 86 - 83 million years ago. It was a small dinosaur, measuring 1–1.4 m (3.3–4.6 ft) long and weighing approximately 3 kg (6.6 lb). It was found in the Bajo de la Carpa Formation and was named by paleontologist José Bonaparte in 1991 after the historian Don Gregorio Alvarez. The type species is A. calvoi.

Temporal range
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
252 201 145 66 0 Ma
PBDB occurrences
1
Group
Dinosaures
Carnivore Ground dwelling, solitary Terrestrial
Alvarezsaurus
click to enlarge
Alvarezsaurus skeleton restoration, Copenhagen. © FunkMonk · CC BY 3.0 · Wikimedia
PBDB ↗ Wikipedia ↗
Classification
Dinosauria Unranked clade
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Theropoda Unranked clade
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Neotheropoda Unranked clade
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Averostra Unranked clade
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Tetanurae Unranked clade
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Coelurosauria Unranked clade
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Alvarezsauria Infraorder
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Alvarezsauroidea Unranked clade
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Alvarezsauridae Family
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Alvarezsaurus Genus
Fossil sites 1 geolocated sites
Distribution
Top countries
🇦🇷 Argentina
1
Geological formations
Bajo de la Carpa
1
Temporal distribution
Santonian (85.7–83.6 Ma)
1
Species (1)
Alvarezsaurus calvoi 86 Ma
News 1
This 2-pound dinosaur is rewriting what scientists know about evolution
fossil Alnashetri Alvarezsaurus Dinosaurus bird +2
A nearly complete dinosaur skeleton discovered in Patagonia is helping scientists crack the mystery of alvarezsaurs, a bizarre group of bird-like dinosaurs. The fossil of Alnashetri cerropoliciensis reveals that these animals became tiny before developing their later specialized features, such as stubby arms and ant-eating adaptations. Weighing under two pounds, the dinosaur is one of the smallest known from South America.
10/03/2026 sciencedaily
Images 1
Bibliography
Original description
J. F. Bonaparte. 1991. Los vertebrados fósiles de la Formación Rio Colorado, de la Ciudad de Neuquén y Cercanías, Cretácico Superior, Argentina [The vertebrate fossils of the Rio Colorado Formation, from the city of Neuquén and surrounding areas, Upper Cretaceous, Argentina]. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" e Instituto Nacional de Investigación de las Ciencias Naturales: Paleontología 4(3):17-123
Bibliography (1)
J. F. Bonaparte. 1991. Los vertebrados fósiles de la Formación Rio Colorado, de la Ciudad de Neuquén y Cercanías, Cretácico Superior, Argentina [The vertebrate fossils of the Rio Colorado Formation, from the city of Neuquén and surrounding areas, Upper Cretaceous, Argentina]. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" e Instituto Nacional de Investigación de las Ciencias Naturales: Paleontología 4(3):17-123