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John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized the modern understanding of . Ostrom's work inspired what his pupil Robert T. Bakker has termed a "dinosaur renaissance".
Beginning with the discovery of Deinonychus in 1964, Ostrom challenged the widespread belief that dinosaurs were slow-moving (or "saurians"). He argued that Deinonychus, a small two-legged carnivore, would have been fast-moving and warm-blooded.
Further, Ostrom's work made zoologists question whether birds should be considered an order of Reptilia instead of their own class, Aves. The idea that dinosaurs were similar to birds was first proposed by Thomas Henry Huxley in the 1860s, but was dismissed by Gerhard Heilmann in his influential book The Origin of Birds (1926). Prior to Ostrom's work, the development of birds was generally believed to have split off early on from that of dinosaurs.
Ostrom showed more bird-like traits common in dinosaurs and proved that birds themselves are theropod dinosaurs. (2025). 9781862393110, Geological Society of London. ISBN 9781862393110
The first of Ostrom's broad-based reviews of the osteology and phylogeny of the primitive bird Archaeopteryx appeared in 1976. Ostrom lived to see the eventual discovery of feathered dinosaurs in northeastern China, confirming his theories about dinosaurs being progenitors of birds, and the existence of dinosaurs with feathered plumage.
Ostrom enrolled at Columbia University as a graduate student with Ned Colbert as his advisor. In 1951 Simpson invited Ostrom to spend the summer as a field assistant in the San Juan Basin of New Mexico. Ostrom also worked as a research assistant with Colbert, who was the Curator of Vertebrate Paleontology at the American Museum of Natural History (AMNH), Ostrom earned his doctorate in geology (vertebrate paleontology) in 1960 with a thesis on North American hadrosaurs that was based on the skull collection housed at the AMNH. (1997). 9780080494746, Elsevier Science. ISBN 9780080494746
In 1952 Ostrom married Nancy Grace Hartman (d. 2003). They had two daughters, Karen and Alicia.
Throughout his career, Ostrom led and organized fossil-hunting expeditions to Wyoming and Montana. He worked in the Cloverly Formation Site in Montana and Wyoming from 1962 to 1966. By 1964, he had made 10 expeditions to the Big Horn Basin, in Wyoming, east of Yellowstone National Park. Late in 1964, he discovered Deinonychus fossils near the town of Bridger, Montana. He also discovered and named Tenontosaurus fossils from the Cloverly Formation. In 1966 John H. Ostrom helped to establish Dinosaur State Park in Rocky Hill, Connecticut ("because the governor was besieged by letters from schoolchildren swayed into dino-mania by Ostrom".).
Ostrom edited the American Journal of Science, published over a dozen books for both scientific and lay audiences. He was the recipient of numerous awards and honors. In the 1960s, Ostrom wrote a paleontology themed guide for the National Park Service's National Natural Landmarks (NNLs) Program. He recommended 20 sites for designation and protection as NNLs, of which 13 became designated landmarks.
Others sites such as the Charles O. Wolcott Quarry near Manchester, Connecticut have since been destroyed. As early as October 20, 1884, stones from the Wolcott Quarry, reportedly containing fossils, were used to build a local bridge. In 1969, Ostrom surveyed over 60 bridges to find the missing blocks. They were part of a bridge over Hop Creek at Bridge Street which was scheduled for replacement. The highway department allowed Ostrom and his team to examine 400 sandstone blocks to find dinosaur fossils. Despite lobbying to preserve it, a shopping mall was built on the site of the Charles O. Wolcott Quarry in 2000.
Ostrom officially retired from Yale in 1992, but continued to write and research as a professor emeritus until his health failed. Ostrom died from complications of Alzheimer's disease in July 2005 at the age of 77 in Litchfield, Connecticut.
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.
In the 1970s, Ostrom examined Fossil trackway at the Dinosaur Footprints Reservation in Holyoke, Massachusetts. He mapped the site, identifying preserved dinosaur tracks in the sandstone beds of various sizes and species. Ostrom's reading of fossilized Hadrosaurus trackways led him to the conclusion that these duckbilled dinosaurs were gregarious and traveled in herds.
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. John Ostrom's work on the functional morphology of dinosaurs found that the claws and tendon scars in the tail would indicate a running position. Evidence of a truly active lifestyle included long strings of muscle running along the tail, providing a stiff counterbalance for jumping and running. This changed the posture of bipedal dinosaurs to one of agile, fast-running, fearsome predators. 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.
This helped to change the impression of dinosaurs as sluggish, slow, Poikilotherm lizards, which had prevailed since the turn of the century. 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", a term coined in a 1975 issue of Scientific American by Bakker to describe increased interest in paleontology. The "dinosaur renaissance" continues, with scientists describing new species of dinosaurs every year and expanding the understanding of dinosaur biology.
The observation that dinosaurs, thought to be uniformly cold-blooded at the time, could not be used as indicators of paleoclimatology was further validated in 1973 with the discovery of hadrosaur fossils above the Cretaceous Canadian Arctic Circle by the Canadian paleontologist Dale Russell. Ostrom's reappraisal of dinosaurs as endothermy 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.
As a result of subsequent research and comparison with more recently found specimens from the Tiaojushan Formation of China, it was suggested in 2017 that the Haarlem Archaeopteryx actually represents a separate taxon. The genus has been given the generic name Ostromia, after John Ostrom. The Haarlem fossil is now considered to be of the species Ostromia crassipes. It is the first representative of the basal avialian clade Anchiornithidae to be found outside eastern Asia.
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.
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