Photography in the United States
In spring 1839, the daguerreotype was introduced into the United States by an Englishman named D.W. Seager, who took the first photograph of a view of St. Paul’s Church and a corner of the Astor House in Lower Manhattan in New York City. Painter and inventor Samuel Finley Breese Morse had met Louis Daguerre in Paris in the spring of 1839, becoming the first American to see his photographic process and becoming enamored with it as a result. When he returned to the United States later that year, he enthusiastically promoted the daguerreotype while hailing Seager's prototypical image. Morse had painted "The Gallery of the Louvre" in 1833, and the appeal of the medium of the daguerreotype was an obvious one to him: it was a means of making faithful copies of artworks, in addition to anything else that would be still in front of the slow eye of the camera.
Dacentrurus
The holotype, BMNH 46013, was found in a layer of the Kimmeridge Clay Formation dating from the late Kimmeridgian. The main nodule fragment contains the pelvis; a series of six posterior dorsal vertebrae, all sacrals and eight anterior caudal vertebrae; a right femur and some loose vertebrae. In all, thirteen detached vertebrae are present in the material. Also an almost complete left forelimb was contained by another loam clump. Additional elements include a partial fibula with calcaneum, a partial tibia, a right neck plate and a left tail spike.
Several other species would be named within the genus "Omosaurus". Part of the British Museum of Natural History collection was specimen BMNH 46321, a pair of spike bases found in the Kimmeridge Clay by William Cunnington near the Great Western Railway cutting near Wootton Bassett. These Owen in 1877 named "Omosaurus hastiger", the epithet meaning "spike-bearer" or "lance-wielder", the spikes by him seen as placed on the wrist of the animal. In 1887, John Whitaker Hulke named "Omosaurus durobrivensis" based on specimen BMNH R1989 found at Tanholt, close to Eye, Cambridgeshire, the specific name being derived from Durobrivae. (That specimen is sometimes mistakenly said to have been found at Fletton, Peterborough, Cambridgeshire, which is where Alfred Nicholson Leeds made most of his finds.) This in 1956 became the separate genus "Lexovisaurus". In 1893, Harry Govier Seeley named "Omosaurus phillipsii", based on a femur, specimen YM 498, the epithet honouring the late John Phillips. Seeley suggested this may be the same taxon as "Priodontognathus phillipsii" Seeley 1869, which has led to the misunderstanding, due to its having the same specific name, that "Priodontognathus" was simply subsumed by him under "Omosaurus". This interpretation however, is incorrect as both species have different holotypes. "Omosaurus leedsi" is a "nomen nudum" used by Seeley on a label for CAMSM J.46874, a plate found in Cambridgeshire, the epithet honouring Alfred Nicholson Leeds. In 1910 Friedrich von Huene named "Omosaurus vetustus", based on specimen OUM J.14000, a femur found in the west bank of Cherwell River, the epithet meaning "the ancient one". In 1911 Franz Nopcsa named "Omosaurus lennieri", the epithet honouring Gustave Lennier, based on a partial skeleton in 1899 found in the Kimmeridgian "Argiles d'Octeville" near in Normandy, France. The specimen would be destroyed during the allied bombing of Caen in 1944.
Even as the last two "Omosaurus" species were named, it had become known that the name "Omosaurus" had been preoccupied by a "crocodilian" (in fact a phytosaur), "Omosaurus perplexus" Leidy 1856. In 1902 Frederick Augustus Lucas renamed the genus into "Dacentrurus". The name is derived from Greek δα~, "da~", "very" or "full of", κέντρον, "kentron", "point", and οὐρά, "oura", "tail". Lucas only gave a new combination name for the type species "Omosaurus armatus": "Decentrurus armatus", but in 1915 Edwin Hennig moved most "Omosaurus" species to "Dacentrurus", resulting in a "Dacentrurus hastiger", "Dacentrurus durobrivensis", "Dacentrurus phillipsi" and a "Dacentrurus lennieri". Nevertheless, it would be common for researchers to use the name "Omosaurus" instead until the middle of the twentieth century. "D. vetustus", earlier indicated as "Omosaurus" ("Dacentrurus") "vetustus" by von Huene, was included with "Lexovisaurus" as a "Lexovisaurus vetustus" in 1983, but that assignment was rejected with both editions of the "Dinosauria", and "O. vetustus" is now the type species of "Eoplophysis".