known from the humid low-lying swamps, lakes, and river basins of the western shore of the Western Interior Seaway, Hell Creek Formation, and from the much more arid uplands between that area and the Cordilleran Overthrust Belt which eventually formed the Rocky Mountains. In those flooded coastal wooded plains with predominantly coniferous trees and flowering bush Avisaurus were hunting. A strong tarsus of Avisaurus with inwardly curved claws resembles that of eudromaeosaurs. With these claws, they could grab and hold prey, presumably having a resemblance to modern raptors. References Further reading Brett-Surman, Michael K. & Paul, Gregory S. (1985): A new family of bird-like dinosaurs linking Laurasia and Gondwanaland. J. Vertebr. Paleontol. 5(2): 133–138. Cambra-Moo, Oscar; Delgado Buscalioni, Ángela; Cubo, Jorge; Castanet, Jacques; Loth, Marie-Madeleine; de Margerie, Emmanuel & de Ricqlès, Armand (2006): Histological observations of Enantiornithine bone (Saurischia, Aves) from the Lower Cretaceous of Las Hoyas (Spain). C. R. Palevol 5(5): 685–691. PDF fulltext Chiappe, Luis M. (1993): Enantiornithine (Aves) Tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates 3083: 1-27. [English with Spanish abstract] PDF fulltext Avisaurids Bird genera Maastrichtian life Cretaceous birds of North America Prehistoric birds of North America Late Cretaceous dinosaurs of North America Hell Creek fauna Fossil taxa described in 1985 Taxa named by Gregory S. Paul