This timeline of stegosaur research is a chronological listing of events in the history of paleontology focused on the stegosaurs, the iconic plate-backed, spike-tailed herbivorous eurypod dinosaurs that predominated during the Jurassic period. The first scientifically documented stegosaur remains were recovered from Early Cretaceous strata in England during the mid-19th century. However, they would not be recognized as a distinct group of dinosaurs until Othniel Charles Marsh described the new genus and species Stegosaurus armatus in 1877, which he regarded as the founding member of the Stegosauria. This new taxon originally included all armored dinosaurs. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs.

From the time of their earliest description, the chief mystery surrounding stegosaurs was the function of their distinctive back plates. Marsh originally interpreted them as being plates of armor that would protect against predators. In 1910, Richard Swann Lull would agree with this hypothesis. Charles Whitney Gilmore disagreed in 1914 and argued that the only protection a stegosaur could gain from its plates was to appear intimidatingly larger to potential predators. Nearly forty years later, Davitashvili argued that the plates were too fragile to be used for defense and instead used to attract mates and signal the stegosaur's rank in a social hierarchy.

In the late 1970s, James O. Farlow and others would propose that the thin, blood vessel-rich plates helped absorb or lose body heat, depending on the animal's own physiological requirements. This hypothesis was put forth in a broader context of scientists considering the possibility that dinosaurs may have maintained body temperatures and activity levels similar to those of modern birds and mammals, in which case the plates may have served primarily to shed heat rather than gain it. In the late 1980s Buffrenil and others revived the idea that stegosaur plates were display structures, an interpretation that would continue to find favor from researchers like Main and colleagues into the 21st century.

19th century

1840s

1841 Gideon Mantell described the new genus and species Regnosaurus northamptoni.

1870s

1874 Harry Govier Seeley described the new genus and species Craterosaurus pottonensis.

1875 Sir Richard Owen described the new genus and species Omosaurus armatus.

1876 Owen described the new species Anthodon serrarius.

1877 Othniel Charles Marsh described the new genus and species Stegosaurus armatus. Marsh named the Stegosauria. Owen described the new species Omosaurus hastiger.

1878 Edward Drinker Cope described the new genus and species Hypsirhophus discurus.

1879 Cope described the new species Hypsirhophus seeleyanus.

1880s

1880 Marsh named the Stegosauridae. Marsh interpreted the plates of Stegosaurus as an armored covering and its spines as natural weapons. Marsh described the new species Stegosaurus affinis.

1881 Marsh described the new genus and species Diracodon laticeps.

1884 Hulke reported a Cretaceous stegosaur pubis from England.

1887 Hulke described the new species Omosaurus durobrivensis. Marsh described the new species Stegosaurus sulcatus. Marsh described the new species Stegosaurus duplex. Marsh described the new species Stegosaurus stenops.

1890s

1891 Marsh provided an illustrated description of Stegosaurus ungulatus, with a row of erect plates running along the centre of its back.

1893 Harry Govier Seeley described the new species Omosaurus phillipsi.

20th century

1900s

1901 Seeley described the new species Omosaurus leedsi.

1902 Frederick Augustus Lucas described the new genus Dacentrurus to house the species Omosaurus armatus.

1905 Loomis argued that the plates adorning the backs of stegosaurs were maladaptive traits that sapped their vigor and signaled their impending extinction. Similar arguments would later be extended to the extinction of the dinosaurs overall by Woodward in 1910.

1910s

1910 Von Huene described the species Omosaurus vetustus. Richard Swann Lull followed Marsh's interpretation of Stegosaurus plates as armor and its tail spines as "defensive" weapons.

1911 Franz Nopcsa described the new species Omosaurus lennieri. He also described the new species Stegosaurus priscus.

1912 Robert Broom described the new species Palaeoscincus africanus.

1914

Charles Whitney Gilmore described Stegosaurus longispinus. He agreed with previous workers that Stegosaurus used its spines to protect itself, but dismissed the idea that its plates functioned as armor. However, Gilmore conceded that the plates may have helped protect it by making it appear intimidatingly large to predators.

1915 Edwin Hennig described the new genus and species Kentrosaurus aethiopicus.

1916 Nopcsa renamed Kentrosaurus into Doryphorosaurus. Hennig renamed Kentrosaurus into Kentrurosaurus. Both new names were unnecessary.

1920s

1924 Hennig described the distribution of Kentrosaurus bones in Quarry St at Tendaguru, Tanzania. He observed that at one place in the quarry multiple sacra were found near each other, while another area of the quarry contained limb bones, and yet another preserved vertebrae.

1927 Alfred Sherwood Romer observed that the anatomy of the stegosaur pelvis and hindlimb as well as their primarily Jurassic age distinguished them from the mainly Cretaceous ankylosaurs. As the Stegosauria originally included all armored dinosaurs, Romer's distinction marked the beginning of the modern use of the name to refer to the plate-backed and spike-tailed dinosaurs.

1929 Nopcsa erected the new taxon Paranthodon oweni for the same material as Palaeoscincus africanus.

1940s

1944 Yang Zhongjian ("C. C. Young") reported indeterminate stegosaur remains from the Kuangyuan Series. They are among the oldest known stegosaur bones.

1950s

1951 Young (Yang) described the new genus and species Chialingosaurus kuani.

1957 De Lapparent and Georges Zbyszewski described the new species Astrodon pusillus. De Lapparent and Zbyszewski reported a possible stegosaur egg associated with a Dacentrurus skeleton from Portugal. However, as the mysterious object lacks a shell, it is now considered to be a nodule of geologic rather than biological origin. Hoffstetter described the new genus Lexovisaurus to house the species Omosaurus durobrivensis.

1960s

1961 Davitashvili marshalled further evidence against the hypothesis that stegosaur plates functioned as armor. He observed that the plates would be ineffective as armor because they were thin, only shallowly embedded in the skin, and left most of the animal's sides exposed. He felt they were used as display structures to attract mates and signal an individual's position within a social hierarchy.

1963 Nicholas Hotton III proposed that stegosaur plates could be moved by flexing muscles in the skin, allowing the plates to function defensively, discouraging attacks from either above or the side depending on the plates' position at any given time.

1966 Dorothy Hill and others reported a possible Early Jurassic stegosaur footprint from Australia. John Ostrom and John Stanton McIntosh reported that Stegosaurus remains were unusually common in Quarry 13 at Como Bluff, Wyoming.

1970s

1973 Dong Zhiming described the new genus and species Wuerhosaurus homheni.

1976

James O. Farlow and others proposed that stegosaur plates were used to help regulate the animal's body temperature. Their alternating placement along its spine would allow them to dissipate its body heat by acting as forced-convection fins, the researchers argued.

1977 Dong and others described the new genus and species Tuojiangosaurus multispinus.

1978 Robert T. Bakker proposed that contrary to the prevailing interpretation of stegosaurs as low browsers, they were actually high browsers who fed on high foliage by rearing up on their hind limbs and propping themselves up in this position with their tail. Walter Coombs argued based on their limb anatomy that stegosaurs were graviportal animals.

1979 P. M. Yadagiri and Krishnan Ayyasami described the new genus and species Dravidosaurus blanfordi based on fragmentary material assumed to include a skull and plates. Since it was dated to the Coniacian it would have been the most recent known surviving stegosaur taxon. The authors also reported the existence of Maastrichtian stegosaur remains, but they did not describe these fossils. Michael Seidel argued that while the plates of Stegosaurus were used to help regulate its body temperature, they were actually used to absorb heat rather than lose it as argued by Farlow and others in 1976.

1980s

1980 Dale Russell and others reconstructed the ancient environment of Tendaguru, Tanzania as a warm coastal area that sometimes experienced droughts. The stegosaur Kentrosaurus was present there, although not especially common. Its local fossil record consists largely of "medium-sized" members of the species.

1981

Peter Malcolm Galton observed that stegosaurs were uncommon during the Cretaceous period.

1982 Dong, Tang Zilu, and Zhou Shiwu described the new genus and species Huayangosaurus taibaii as well as the Huayangosauridae. Nikolaï Spassov argued that the plates of stegosaurs were used as display structures in competitions over mates. Their orientation made them best suited to being viewed from the side. Galton studied the growth and development of Stegosaurus. Galton found that Kentrosaurus came in two varieties, one with an extra sacral rib. He speculated that this morph with the extra sacral rib was the female and the other morph lacking the rib was male.

Ralph Molnar published more research on the possible Early Jurassic stegosaur track from Australia. Jacques Jenny and Jean-Arsène Jossen reported a possible Pliensbachian stegosaur trackway from Morocco.

1983 Dong, Zhou and Zhang Yihong described the new genus and species Chungkingosaurus jiangbeiensis. Galton and Harry Philip Powell reported stegosaur armor and vertebrae from the Early Bajocian of England. These are among the oldest known stegosaur bones. Comic Artist Gary Larson humorously suggests the tail spikes on a stegosaur be named the Thagomizer.

1984 Giuseppe Leonardi attributed Early Cretaceous footprints of the ichnogenus Caririchnium to stegosaurs. Zhou observed that the Bathonian to Callovian Huayangosaurus was among the oldest known stegosaur fossils. Vivian de Buffrénil and others studied the histology of a Stegosaurus plate. They concluded that since the Sharpey's fibers that anchored it within the animal's skin were symmetrical it could not be moved. They also argued that there was no physical evidence in the anatomy of the plate to suggest that it was covered by horn in life. The researchers dismissed the idea that the plates could function as armor on the grounds that they were too fragile. They also doubted that the plates were used as threat displays for intimidation because "they could not unfold suddenly". They found that the plates were more likely used as sexual displays to attract mates or help regulate the animal's body temperature. They proposed that the plates were covered by a skin dense with blood vessels that helped exchange heat by both convection and radiation. They argued that their hypothesis was compatible with both major competing interpretations of dinosaur thermophysiology since if Stegosaurus was cold-blooded the plates could be used to absorb heat while if it was warm-blooded the plates could shed the excess heat that its body produced.