Taxa named by John Ostrom

Deinonychus ( ; ) is a genus of dromaeosaurid theropod dinosaur with one described species, Deinonychus antirrhopus. This species, which could grow up to long, lived during the Early and Late Cretaceous Period, about 115–93.9 million years ago (from the mid-Aptian to Cenomanian stages). Fossils have been recovered from the U.S. states of Montana, Utah, Wyoming, and Oklahoma, in rocks of the Cloverly Formation and Antlers Formation, though teeth that may belong to Deinonychus have been found much farther east in Maryland.

Tenontosaurus ( ; ) is a genus of iguanodontian ornithopod dinosaur. It had an unusually long, broad tail, which like its back was stiffened with a network of bony tendons. The genus is known from the late Aptian to Albian ages of the Early Cretaceous period sediments of western North America, dating between 115 and 108 million years ago. It contains two species, Tenontosaurus tilletti (described by John Ostrom in 1970) and Tenontosaurus dossi (described by Winkler, Murry, and Jacobs in 1997). Many specimens of T. tilletti have been collected from several geological formations throughout

Sauropelta ( ; meaning 'lizard shield') is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species (S. edwardsorum) has been named. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of Wyoming, Montana, and possibly Utah. It is also the earliest known genus of nodosaurine; most of its remains are found in a section of the Cloverly Formation dated to 108.5 million years ago.

Bambiraptor is a genus of bird-like dromaeosaurid theropod dinosaur that lived during the Late Cretaceous (about 72 million years ago) of Montana. It was described by scientists at the University of Kansas, Yale University, and the University of New Orleans. The holotype fossil is less than long, although this specimen appears to be a juvenile, and it is possible that Bambiraptor is a juvenile Saurornitholestes. It is even suspected that the type specimen is a chimera, based on the fact that "there are elements of three different similarly sized lower legs included in the holotype." Because of

Microvenator (meaning "small hunter") is a genus of oviraptorosaurian theropod dinosaur from the Early Cretaceous Cloverly Formation in what is now south central Montana. The holotype fossil is an incomplete skeleton, most likely a juvenile with a length of , and consequently, the adult size remains uncertain. Microvenator is primitive and may be the "sister taxon to all other oviraptorosaurs."