Timeline of ceratopsian research
This timeline of ceratopsian research is a chronological listing of events in the history of paleontology focused on the ceratopsians, a group of herbivorous marginocephalian dinosaurs that evolved parrot-like beaks, bony frills, and, later, spectacular horns. The first scientifically documented ceratopsian fossils were described by Edward Drinker Cope starting in the ; however, the remains were poorly preserved and their true nature was not recognized. Over the next several decades, Cope named several such genera and species. Cope's hated rival, Othniel Charles Marsh, also described ceratopsian remains. In 1887, Marsh mistook a "Triceratops" horn for  one belonging to a new species of prehistoric "Bison". Marsh also named the eponymous genus "Ceratops" in 1888. The next year, he named the most famous ceratopsian, "Triceratops horridus". It was the discovery of "Triceratops" that illuminated the ceratopsian body plan, and he formally named the Ceratopsia in 1890. The early 20th century was a fruitful time for ceratopsian research. In 1907, Hatcher and others published a monograph on ceratopsid anatomy that is still considered the single most significant publication on the topic to date. Many new species were being described, including "Centrosaurus", "Styracosaurus", and "Chasmosaurus". Not long after, the  Central Asiatic Expedition led by Roy Chapman Andrews of the American Museum of Natural History discovered the primitive ceratopsians "Psittacosaurus" and "Protoceratops" in Mongolia. "Protoceratops" gained notoriety as the supposed parent of the first fossil dinosaur eggs known to science. One of these supposed "Protoceratops" nests preserved the skeleton of a new kind of theropod dinosaur, "Oviraptor". It was thought to have been preserved after being killed in the act of raiding the "Protoceratops" nest. This narrative would last until the , when the ""Protoceratops"" eggs were determined to belong to "Oviraptor" itself. Throughout the rest of the century, paleontologists would  be occupied with several controversies regarding ceratopsian paleobiology. One concerned the stance of the ceratopsid forelimbs. When Marsh first reconstructed the ceratopsid forelimb, he portrayed it in an erect posture. However, when later researchers like Sternberg and Osborn tried to mount the skeletons, they found that the forelimb bones apparently sprawled despite the hindlimbs standing straight up and down. Later researchers like Robert T. Bakker and Gregory S. Paul attempted to revive the erect reconstruction, but continuing research in the 1990s by researchers like John Ostrom, Peter Dodson, and James Farlow found an intermediate value to be better supported. The  original use of the ceratopsids' horns and frills was another long-running controversy in ceratopsian paleontology. Early researchers like Richard Swann Lull thought that bony frills served as the attachment site for enlarged jaw muscles. This explanation was followed by researchers like Russell, Haas, and Ostrom. Sternberg thought the horns of ceratopsians helped defend against predators. In 1961, Davitashvili proposed that ceratopsids used their horns and frills to compete over mates. Farlow and Dodson arrived at the same conclusion in the , and were followed by Ralph Molnar. Ostrom, who had previously followed the jaw musculature interpretation, came to support this  view in 1986. The idea gained further support in the 1990s from researchers like Forster and Sampson. 19th century. 1870s. 1872 1876 1878 1880s. 1887 1888 1889 1890s. 1890 1891 1896 1898 20th century. 1900s. 1901 1902 1904 1905 1907 1908 1910s. 1910 1913 1914 1915 1917 1918 1920s. 1922 1923 1924 1925 1928 1927 1929 1930s. 1930 1931 1933 1935 1937 1940s. 1940 1942 1946 1947 1949 1950s. 1950 1951 1953 1955 1958 1959 1960s. 1960 1961 1962 1964: 1966 1967 1969 1970s. 1971 1972 1975 1976 1977 1978 1979 1980s. 1981 1983 1984 1985 1986 1987 1988 1989  1990s. 1990 1991 1992 1993 1994 1995 1996 1997 Sampson and others studied centrosaurine bonebeds and found that the individuals preserved therein could be categorized into three broad phases of developments; juveniles, subadults, and adults. The researchers defined these age groups based on specimens' body size, the surface texture of their bones, and how completely closed the sutures between their bones were. They observed that the juveniles and subadults of different centrosaurine species are practically indistinguishable and can only be told apart upon reaching adulthood when their horns and frills were fully developed. Sampson and the other researchers interpreted the  delay of ceratopsid horn and frill development to sexual maturity as further evidence for the hypothesis that these traits evolved primarily for competition over mates. They disagreed with more functional explanations for these structures, like the idea that the frills served as attachment points for enlarged jaw muscles. The researchers also marshalled support from the fact that the horns and frills of ceratopsids are the primary source of variation between species within the family and observations of modern animals, whose horns are also primarily used to acquire mates. Nevertheless, they argued that there was still no evidence for sexual dimorphism  in ceratopsids. The researchers argued that the anatomical variation in horns and frills and their delayed development had taxonomic implications. They concluded that species based on immature type specimens like "Brachyceratops montanensis" and "Monoclonius crassus" were dubious because immature individuals would not yet have developed the primary traits paleontologists rely on to distinguish one kind of ceratopsid from another. Likewise, they dismissed "Avaceratops" as just a juvenile rather than a small adult from a distinct taxon. Sampson and the other researchers noted that bonebeds differing in location and age all preserved ""Monoclonius"-like" fossils left behind by immature animals, which is  consistent with the idea that these remains are actually the juveniles of a variety of species from different times and places rather than a unique kind of animal in their own right. 1998 1999 21st century. 2000s. 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010s. 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020s. 2020 2022