John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s.Ostrom showed that dinosaurs were more like big non-flying birds than they were like lizards (or "saurians") as first proposed by Thomas Henry Huxley in the 1860s.The first of Ostrom's broad-based reviews of the osteology and phylogeny of the primitive bird Archaeopteryx appeared in 1976.