Timeline of plesiosaur research

This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished during the Mesozoic Era. The first scientifically documented plesiosaur fossils were discovered during the early by Mary Anning. Plesiosaurs were actually discovered and described before dinosaurs. They were also among the first animals to be featured in artistic reconstructions of the ancient world, and therefore among the earliest prehistoric creatures to attract the attention of the lay public. Plesiosaurs were originally thought to be a kind of primitive transitional form between marine life and terrestrial reptiles. However, now plesiosaurs are recognized as highly derived marine reptiles descended from terrestrial ancestors.
Early researchers thought that plesiosaurs laid eggs like most reptiles. They commonly imagined plesiosaurs crawling up beaches and burying eggs like turtles. However, later opinion shifted towards the idea that plesiosaurs gave live birth and never went on dry land. Plesiosaur locomotion has been a source of continuous controversy among paleontologists. The earliest speculations on the subject during the 19th century saw plesiosaur swimming as analogous to the paddling of modern sea turtles. During the 1920s opinion shifted to the idea that plesiosaurs swam with a rowing motion. However, a paper published in 1975 that once more found support for sea turtle-like swimming in plesiosaurs. This conclusion reignited the controversy regarding plesiosaur locomotion through the late 20th century. In 2011, F. Robin O'Keefe and Luis M. Chiappe concluded the debate on plesiosaur reproduction, reporting the discovery of a gravid female plesiosaur with a single large embryo preserved inside her.
Prescientific.
Associated remains of plesiosaurs and animals like the diving bird "Hesperornis" or the pterosaur "Pteranodon" may have inspired legends about conflict between Thunder Birds and Water Monsters told by the Native Americans of Kansas and Nebraska.
18th century.
1719
19th century.
1810s.
1811
1820s.
1821
1822
1823
"December"
"c. December"
1824
1829
1830s.
1837
1839
1840s.
1840
1841
1842
1846
1848
1860s.
1863
1864
1865
1867
"March, mid"
"March 24"
1868
"September"
1869
"August"
1870s.
1870
"March 8"
"November"
1871
1872
1873
1874
1875
1876
1877
1879
1880s.
1880
1881
1882
1884
"Spring"
1888
1890s.
1890
1892
1893
1894
1895
1897
1898
1899
20th century.
1900s.
1900
1902
1903
1904
1906
1907
1909
1910s.
1910
1911
1913
1914
1919
1920s.
1922
1923
1924
1926
1929
1930s.
1930
1931
1931-1932
1934
c. 1935
1935
1936
1938
1940s.
1940
1941
1942
1943
1944
1948
1949
1950s.
1950
"October"
1952
1954
1960s.
1960
1962
1967
1970s.
1971
1975
1976
1977
1980s.
1980
1981
1982
1984
1985
1986
1987
1988
1989
1990s.
1990
"May"
"October"
1991
1992
1993
1994
1996
In his remarks on short-necked plesiosaur evolution, Carpenter argued that polycotylids were more closely related to long-necked plesiosaurs than pliosaurs. He observed that "Trinacromerum bentonianum" seems to have existed from the late Cenomanian to the Turonian. This represents a span of time approximating 3.3 million years. He found "Dolichorhynchops osborni" to have had an even longer lifespan, from the middle Turonian to the early Campanian., or roughly 4 million years. His research also suggested that there was a span of time during the life of the Western Interior Seaway in which it was not inhabited by polycotylids.
He also reported that the "Dolichorhynchops" specimen KUVP 40001 from the Pierre Shale of South Dakota may have achieved the extraordinary length of 23 feet. The large size of the Pierre Shale "Dolichorhynchops" compared to those of the earlier Smoky Hill Chalk suggested to Carpenter that these plesiosaurs were evolving larger body sizes over time. In fact the Pierre Shale specimens of "Dolichorhynchops" were nearly as large as "Brachauchenius lucasi". Carpenter described a particularly large specimen of that latter taxon in this paper as well, specifically FHSM VP-321. His study of "Brachauchenius" led him to concur with Williston that it was closely related to "Liopleurodon ferox".
1997
1998
1999
21st century.
2000s.
2000
"November"
2001
They also noted that some of NJSM 15435's gastroliths were scarred by rounded chips and arc-shaped marks. These were likely inflicted by contact with other gastroliths during the churning of the animal's stomach, and constituted physical evidence that plesiosaurs used their gastroliths to help break down their food during digestion. Cicimurri and Everhart disputed the hypothesis that plesiosaurs used their gastroliths for ballast on the grounds that swallowing and vomiting such stones would be relatively difficult for the long-necked forms and their feeding grounds may have been hundreds of miles from sources of stones.
"September"
"September 11"
"November"
2001–2002
2002
"December 30"
2003
2004
2005
2006
2007
2008
2009
2010s.
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020