Genus: Avisaurus BRETT-SURMAN & PAUL, 1985
Etymology: Latin, avis, "bird" and Greek, sauros, "lizard": Literally “bird-lizard” (a deliberate mixture of Latin and Greek to emphasize the archosaurian-avian nature of this genus).

Species: archibaldi BRETT-SURMAN & PAUL, 1985
Etymology: In honor of David Archibald, its discoverer.

Holotype: University of California (Berkeley) Museum of Paleontology, UCMP 117600

Location: University of California (Berkeley) Museum of Paleontology, UCMP Locality V73097, Garfield County, Montana.

Horizon: Hell Creek Formation.

Biostratigraphy:

Age: Lancian age, upper Maastrichtian Stage, uppermost Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Left Metatarsus.

Paratype:

YPM 17324: Isolated right metatarsus.

Referred material:

STIDHAM & HUTCHISON, 2001

Locality: Montana.

Horizon: Hell Creek Formation.

Biostratigraphy:

Age: Lancian age, upper Maastrichtian Stage, uppermost Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material:

Number: Not given: A large distal tibiotarsus.

= cf. Avisaurus archibaldi LONGRICH, TOKARYK & FIELD, 2011

YPM 57235: Large coracoid.

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Species: darwini CLARKE, ATTERHOLT, SCANNELLA, CARROLL & O’CONNOR, 2024
Etymology: In honor of Charles Darwin, whose momentous research and publications helped define the field of evolutinoary biology: Darwin's bird lizard.

Holotype: DDM 1577.730

Locality: Madison Shark Spine Locality (DDM-18-234,!n 55E 11), Carter County, Montana.

Horizon: Hell Creek Formation.

Biostratigraphy:

Age: Maastrichtian Stage, Late Senonian subepoch, Late Gulf epoch, Late Cretaceous.

Material: Right tarsometatarsus.