Avisaurus

Avisaurus archibaldi was discovered in the Late Cretaceous Hell Creek Formation of North America (Maastrichtian, from c.70.6–66 million years ago), making it one of the last enantiornithines. It was collected in 1975 in the UCMP locality V73097, in Garfield County, Montana, USA. The holotype is represented by a single fossil of a tarsometatarsus in the collection of the University of California Museum of Paleontology. It has the catalog number UCMP 117600. The species name honors J. David Archibald, its discoverer, from The University of California, Berkeley. It was initially described as the left tarsometatarsus of a non-avian theropod by Brett-Surman and Paul in 1985. It was later redescribed as the right tarsometatarsus of an enantiornithine bird by Chiappe in 1992. Avisaurus gloriae Varricchio and Chiappe 1995, In 2024, another species of Avisaurus from the Hell Creek Formation was named as Avisaurus darwini, with the specific name in honor of Charles Darwin. ==Description==

, and a human Avisaurus was a large enantiornithine, with A. darwini weighing up to and A. archibaldi weighing up to . ==Classification==

This genus belongs to the enantiornithine family Avisauridae, which also contains similar animals from South America such as Soroavisaurus, Neuquenornis and Intiornis. Further discoveries and further study by Chiappe showed that all of the material belonged to enantiornithine birds, and PVL 4690 was given its own genus Soroavisaurus. ==Paleoenvironment and paleobiology==

Avisaurus remains fossilized in the humid low-lying swamps, lakes, and river basins of the western shore of the Western Interior Seaway, Hell Creek Formation. File:Avisaurus and Brachychampsa by tomozsaurus.jpg|Reconstruction of Avisaurus and Brachychampsa File:Reconstruction of an avisaurid (e.g., A. darwini).png|Reconstruction of Avisaurus darwini with prey ==References==