In the field of paleontology, Ostrom is responsible for the following key discoveries:
Hadrosaurs Ostrom's work first achieved international attention with his studies of the unique hadrosaur nasal apparatus, which had not been convincingly explained by the early 1960s. By examining the
olfactory apparatuses of modern
reptiles and drawing comparisons via
comparative morphology, Ostrom concluded that hadrosaurs likely developed an acute sense of smell by a lengthening of the nasal passages into long chambers that wound around the skull and were protected by bony crests. He speculated in a subsequent paper that hadrosaurs had need for such an acute sense of smell as a defense against larger carnivorous dinosaurs, of which the hadrosaur body plan had little in the way of armor and speed. This hypothesis led Ostrom to further conclude that ecology of hadrosaurs was more likely to be that of dry ground such as conifer forests, rather than swampy, aquatic environments, thought to be the case at the time. This idea was further justified by a 1922 paper that Ostrom rediscovered in 1964, which described the stomach contents of a mummified specimen of the hadrosaur
Anatosaurus, which included conifer needles, twigs, fruit and seeds, plant matter that would be consumed in a terrestrial environment.
Deinonychus Ostrom worked in the Cloverly Formation Site in Montana and Wyoming from 1962 to 1966. Late in 1964, he detected unfamiliar fossils in the Bridger Fossil Area, near the town of Bridger, Montana. In subsequent seasons, his team unearthed four specimens of a small bipedal carnivorous
theropod, and parts of a larger plant-eating dinosaur. The discovery of the
Deinonychus fossils is considered one of the most important fossil finds in history.
Deinonychus was an active predator that clearly killed its prey by leaping and slashing or stabbing with its "terrible claw", the meaning of the animal's genus name. Ostrom also suggested that it had hunted in packs. He concluded that at least some dinosaurs had a high
metabolism and were in some cases
warm-blooded. This position was further popularized by Ostrom's student
Robert T. Bakker. The implications of
Deinonychus changed depictions of dinosaurs both by professional illustrators and as perceived by the public eye. Museums worldwide changed their dinosaur bone displays. The altered view of dinosaurs inspired a new generation of dinosaur movies such as
Jurassic Park, which based its murderous "Velociraptors" on
Deinonychus. Ostrom's work on
Deinonychus is credited with triggering the "
dinosaur renaissance",
Energy and climate Due in large part to his earlier research on hadrosaurs—and his conclusion that they were likely upright, terrestrial animals rather than sluggish, swamp-bound lizards—Ostrom was one of the first paleontologists to grasp the implications of the amount of energy it would take such large animals (and their still larger predators, such as
Tyrannosaurus rex) to stand and move erect. At the first North American Paleontological Convention, held at the
Chicago Field Museum in 1969, Ostrom spoke out against the accepted wisdom that
Mesozoic climates were universally tropical and that such warm climates would be necessary to sustain large animals with lizard-like
metabolisms. Ostrom supported this view by noting the correlation of erect posture and locomotion with high metabolism and body temperature in modern mammals and birds, stating that this relationship cannot be accidental. Ostrom's reappraisal of dinosaurs as
endothermic was considered radical at the time, but its ability to resolve outstanding contradictions in
dinosaur physiology immediately drew many followers, and would be supported by many future discoveries. In his 1973 paper in
Nature, "The Ancestry of Birds", Ostrom argued for a coelurosaurian (Theropoda) ancestry of birds, based on the skeletal anatomy of
Archaeopteryx. He suggested that dinosaurs, far from becoming extinct, had evolved into a wide variety of descendants in the form of birds. Ostrom's work led to a revolution in the classification of fossils and the understanding of dinosaur-bird lineages. In considering the possible evolution of flight, Ostrom theorized that birds might have evolved the ability for powered flight as a result of cursorial, or ground-upward movement such as leaping up to capture prey. This position was opposed to the arboreal hypothesis in which activities such as gliding down from trees were suggested to have been a precursor to flight. ==Awards and honors==