John Ostrom

John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist.
In the 1960s, he showed that dinosaurs are more like big non-flying birds than they are like lizards (or "saurians"). Thomas Henry Huxley in the 1860s had thought birds evolved from dinosaurs, based on a comparison of "Archaeopteryx" with "Compsognathus". Huxley's idea was later discarded, mainly because Heilmann, in 1926, had different views.
The first of Ostrom's reviews of the osteology and phylogeny of the primitive bird "Archaeopteryx" appeared in 1976. After the modern discoveries of fossil dinobirds in China, the HuxleyOstrom theory was accepted by almost all palaeontologists.
Ostrom was a professor at Yale University. He was the Curator Emeritus of vertebrate paleontology at the Peabody Museum of Natural History, which has an impressive fossil collection started by Othniel Charles Marsh. He died from complications of Alzheimer's disease.
Discoveries.
His 1964 discovery of "Deinonychus" was 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". Evidence of a truly active lifestyle included long strings of tendons running along the tail, making it a stiff counterbalance for jumping and running. The conclusion that at least some dinosaurs had a high metabolism, and were therefore warm-blooded, was popularized by his student Robert Bakker. This helped to change the impression of dinosaurs as the sluggish, slow, cold-blooded lizards which had prevailed since the turn of the century.
This changed how dinosaurs are seen by both professional dinosaur illustrators, and by the public. The find is also credited with triggering the "dinosaur renaissance", a term coined in a 1975 issue of "Scientific American" by Bakker. It describes the renewed interest in paleontology, which has lasted from the 1970s to the present.
Ostrom's interest in the dinosaur-bird connection started with his study of what is now known as the Haarlem "Archaeopteryx". Discovered in 1855, it was actually the first specimen recovered but, incorrectly labeled as "Pterodactylus crassipes", it languished in the Teyler's Museum in the Netherlands until Ostrom's 1970 paper (and 1972 description) correctly identified it as one of only eight "first birds" (counting the solitary feather).
Ostrom also studied fossilized trackways of the duckbilled dinosaur "Hadrosaurus". He decided they traveled in herds. To this extent they were social animals like many birds and mammals, but unlike lizards.