First Discovery of American Dinosaurs, 1856
This is a very short, two-page paper, with no illustrations to arrest the eye, but if one takes the time to read the text, or even just the headings, a remarkable document comes alive. Ferdinand V. Hayden, in 1855, had conducted a geological survey along the Judith River in the Nebraska Territory, and he had found a number of large fossilized teeth belonging to some unknown animals. Hayden sent the specimens to Joseph Leidy, a physician and eminent naturalist of Philadelphia. Leidy recognized that some of these were the teeth of very large reptiles, and in this paper he identified and named eight genera, of which three turned out to be dinosaurs: Trachodon, Troodon, and Deinodon. This paper is the first published description of dinosaur remains in the United States. Leidy truly understood what he had found; although his Trachodon was classified primarily on the basis of one tooth, Leidy observed that it was an animal similar to Iguanodon, and he commented that the Deinodon teeth, although fragmentary, resembled those of Megalosaurus.
Leidy's article is unillustrated; we produced the first page of the two-page paper, which announces the three dinosaur genera. In an article published in 1860, Leidy included a plate with an illustration of the Trachodon tooth.
The Trachodon Tooth, 1860
In this article of 1860, Joseph Leidy described in more detail the fossils that he first mentioned in his seminal paper of 1856. He also included large lithograph plates that illustrated all the fossils. In particular, he provided twenty figures of his Trachodon teeth. Apparently many of these are incorrectly identified, but figures 1-3 do indeed show a genuine hadrosaur-like tooth. The name Trachodon means "rough-tooth," and the roughness certainly shows in the figures. The illustration shown here is a greatly enlarged detail of the upper-left of the plate, which contains sixty-one figures in all.