This timeline of hadrosaur research is a chronological listing of events in the history of paleontology focused on the hadrosauroids, a group of herbivorous ornithopod dinosaurs popularly known as the duck-billed dinosaurs. Scientific research on hadrosaurs began in the 1850s, when Joseph Leidy described the genera Thespesius and Trachodon based on scrappy fossils discovered in the western United States. Just two years later he published a description of the much better-preserved remains of an animal from New Jersey that he named Hadrosaurus.

The early 20th century saw such a boom in hadrosaur discoveries and research that paleontologists' knowledge of these dinosaurs "increased by virtually an order of magnitude" according to a 2004 review by Horner, Weishampel, and Forster. This period is known as the great North American Dinosaur rush because of the research and excavation efforts of paleontologists like Brown, Gilmore, Lambe, Parks, and the Sternbergs. Major discoveries included the variety of cranial ornamentation among hadrosaurs as scientist came to characterize uncrested, solid crested, and hollow crested species. Notable new taxa included Saurolophus, Corythosaurus, Edmontosaurus, and Lambeosaurus. In 1942 Richard Swann Lull and Wright published what Horner, Weishampel, and Forster characterized as the "first important synthesis of hadrosaurid anatomy and phylogeny".

More recent discoveries include gigantic hadrosaurs like Shantungosaurus giganteus from China. At 15 meters in length and nearly 16 metric tons in weight it is the largest known hadrosaur and is known from a nearly complete skeleton.

Hadrosaur research has continued to remain active even into the new millennium. In 2000, Horner and others found that hatchling Maiasaura grew to adult body sizes at a rate more like a mammal's than a reptile. That same year, Case and others reported the discovery of hadrosaur bones in Vega Island, Antarctica. After decades of such dedicated research, hadrosaurs have become one of the best understood group of dinosaurs. 19th century

1850s

1856 Joseph Leidy described the new genus and species Thespesius occidentalis. He also described the new genus and species Trachodon mirabilis. Although both species were based on poorly preserved material, this paper was the first to be published on hadrosaurid dinosaurs.

1858 Leidy described the new genus and species Hadrosaurus foulkii. He thought it was an amphibious animal.

1860s

1868 Leidy collaborated with artist Benjamin Waterhouse Hawkins to mount Hadrosaurus foulkii for the Academy of Natural Sciences of Philadelphia. This became both the first mounted dinosaur skeleton ever mounted for public display and also one of the most popular exhibits in the history of the academy. Estimates have the Hadrosaurus exhibit as increasing the number of visitors by up to 50%.

1869 Edward Drinker Cope described the new genus and species Hypsibema crassicauda. Cope named the Hadrosauridae. He observed that the primary distinguishing trait of the group was their dental battery. Cope described the new genus and species Ornithotarsus immanis.

1870s

1870 Othniel Charles Marsh described the new species Hadrosaurus minor.

1871 Cope described the new species Hadrosaurus cavatus.

1872 Marsh described the new species Hadrosaurus agilis.

1874 Cope described the new species Agathaumas milo. He also described the new genus and species Cionodon arctatus.

1875 Cope described the new species Cionodon stenopsis.

1876 Cope described the new genus and species Diclonius calamarius. He also described the new species Diclonius pentagonus, Diclonius perangulatus, and Dysganus encaustus.

1880s

1883 Harry Govier Seeley described the new genus and species Orthomerus dolloi. Cope still regarded hadrosaurs as amphibious.

1888 Richard Lydekker described the new species Trachodon cantabrigiensis.

1889 Marsh described the new species Hadrosaurus breviceps. He also described the new species Hadrosaurus paucidens. Cope described the new genus and species Pteropelyx grallipes.

1890s

1890 Marsh erected the new genus Claosaurus to house the species Hadrosaurus agilis. He also described the new species Trachodon longiceps.

1892 Marsh described the new species Claosaurus annectens. Cope described the new genus and species Claorhynchus trihedrus. Newton described the new species Iguanodon hilli.

20th century

1900s

1900 Franz Nopcsa described the new genus and species Limnosaurus transsylvanicus.

1902 Lawrence Lambe described the new genus and species Trachodon altidens; in the same volume, he suggested the name Didanodon for the same species, but the validity of this name has been questioned.Lund, E.K. and Gates, T.A. (2006). "A historical and biogeographical examination of hadrosaurian dinosaurs." pp. 263 in Lucas, S.G. and Sullivan, R.M. (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35. He also described the new species Trachodon marginatus. He also described the new species Trachodon selwyni.

1903 Nopcsa erected the new genus Telmatosaurus to house the species Limnosaurus transsylvanicus, as the latter genus name was preoccupied . George Wieland described the new species Claosaurus affinis.

1910

1910 Barnum Brown described the new genus Hecatasaurus. He also described the new genus and species Kritosaurus navajovius.

1912 Brown described the new genus and species Saurolophus osborni.

1913 Brown described the new genus and species Hypacrosaurus altispinus. Cutler excavated a juvenile Gryposaurus now catalogued by the Canadian Museum of Nature as CMN 8784. The site of the excavation has since been designated "quarry 252". Winter: Cutler partly prepared the young Gryposaurus specimen, possibly in Calgary while working on dinosaurs for Euston Sisely.

1914 Brown described the new genus and species Corythosaurus casuarius. Lambe described the new genus and species Gryposaurus notabilis.

1915 Charles H. Sternberg's crew excavated a Corythosaurus from quarry 243 in Dinosaur Provincial Park, Alberta, Canada. The specimen would later be displayed at the Calgary Zoo. Matthew observed that fossils of hadrosaur eggs and hatchlings were absent in coastal areas and suggested that hadrosaurs may have preferred nesting grounds further inland. He believed that these inland nesting grounds were actually where hadrosaurs first evolved and therefore to breed, hadrosaurs retraced their ancestors route back to their place of origin. After hatching, the young hadrosaurs would spend some time inland maturing before migrating out to more coastal areas.

1916 Brown described the new genus and species Prosaurolophus maximus.

1917 Lambe described the new genus and species Edmontosaurus regalis. Lambe described the new genus and species Cheneosaurus tolmanensis.

1918 Lambe named the Hadrosaurinae.

1920s

1920 Matthew described the new genus Procheneosaurus. Parks described the new species Kritosaurus incurvimanus.

1922 William Parks described the new genus and species Parasaurolophus walkeri. Krausel reported fossil gut contents from an Edmontosaurus annectens mummy. He described the material as including conifer needles and branches, deciduous foliage, and possible small seeds or fruit. Abel argued that the plant material Krausel argues was the fossilized remains of the gut contents of an Edmontosaurus annectens was actually deposited by flowing water.

1923 Charles Whitney Gilmore described the new species Corythosaurus excavatus. Parks described the new species Corythosaurus intermedius. He also described the new genus and species Lambeosaurus lambei.

1924 Gilmore described the new species Thespesius edmontonensis.

1925 Riabinin described the new species Trachodon amurensis.

1926 Sternberg described the new species Thespesius saskatchewanensis.

1929 Wiman described the new genus and species Tanius sinensis.

1930s

1930 Riabinin described the new species Saurolophus kryschtofovici. Riabinin erected the new genus Mandschurosaurus to house the species Trachodon amurensis.

1931 Parks described the new genus and species Tetragonosaurus erectofrons. He also described the new species Tetragonosaurus praeceps. Wiman described the new species Parasaurolophus tubicen. Riabinin described the new genus and species Cionodon kysylkumensis.

1933 Gilmore described the new genus and species Bactrosaurus johnsoni. He also described the new species Mandschurosaurus mongoliensis. Parks described the new species Corythosaurus bicristatus and C. brevicristatus.

1935 Sternberg described the new species Tetragonosaurus cranibrevis. He also described the new species Lambeosaurus clavinitialis and L. magnicristatus. Parks described the new species Corythosaurus frontalis.

1936 Takumi Nagao described the new genus and species Nipponosaurus sachalinensis.

1939 Riabinin described the new genus and species Jaxartosaurus aralensis. He also described the new species Bactrosaurus prynadai.

1940s

1942 Richard Swann Lull and Wright described the new genus Anatosaurus for Claosaurus annectens. They also name the new species Anatosaurus copei.

1943 Hoffet described the new species Mandschurosaurus laosensis.

1945 Riabinin described the new species Orthomerus weberi. Gilmore and Stewart described the new genus and species Neosaurus missouriensis. Gilmore erected the new genus Parrosaurus to house the species Neosaurus missouriensis, as the name Neosaurus was occupied.

1946 Young described the new genus and species Sanpasaurus yaoi. Colbert redescribed the species Hadrosaurus minor.

1950s

1952 Rozhdestvensky described the new species Saurolophus angustirostris.

1953 Sternberg described the new genus and species Brachylophosaurus canadensis.

1958 Young described the new species Tanius chingkankouensis. Young described the new genus and species Tsintaosaurus spinorhinus.

1960s

1960 Langston described the new genus and species Lophorhothon atopus.

1961 Ostrom described the new species Parasaurolophus cyrtocristatus.

1964 Ostrom supported Krausel's 1922 claim that fossil plant material found associated with an Edmontosaurus annectens mummy was actually its gut contents.

1967 Russel and Chamney studied distribution of hadrosaur in Maastrichtian North America. The concluded that Edmontosaurus regalis lived near the coasts while Hypacrosaurus altispinus and Saurolophus osborni lived slightly more inland.

1968 Rozhdeventsky described the new genus and species Aralosaurus tubiferous. He also described the new species Procheneosaurus convincens.

1970s

1970 Galton argued that the anatomy of the hadrosaur pelvis was more consistent with a horizontal posture like that seen in modern flightless birds than with the "kangaroo" posture they were often reconstructed in.

1971 Dodson argued that hadrosaurs may not have fed exclusively on land.

1973 Hu described the new genus and species Shantungosaurus giganteus.

1975

Dodson found evidence for sexual and ontogenetic dimorphism in two different kinds of lambeosaurine using morphometrics.

1976 Zhen described the new species Tanius laiyengensis.

1979 Brett-Surman erected the new genus Gilmoreosaurus to house the species Mandschurosaurus mongoliensis. He also described the new genus and species Secernosaurus koerneri. Brett-Surman was unable to determine where hadrosaurs first evolved. Horner and Makela described the new genus and species Maiasaura peeblesorum. They argued that hadrosaurs cared for their young for an extended period after hatching. Horner argued that hadrosaur fossils found in marine deposited were simply the preserved remains of individuals that had washed out to sea from a terrestrial place of origin.