The first Ptychodus mortoni teeth were originally found in Late Santonian beds of Alabama in 1833 by famous Philadelphia conchologist (he studied modern and fossil mollusk shells) Timothy Abbott Conrad (1803-1877), on his first trip to collect fossils in the South. There has been some argument about the age and type locality of the specimens, as it was later reported (Morton, 1842, p. 215) that they were from the well-known type locality of the Late Maastrichtian Prairie Bluff Formation, along the Alabama River in Wilcox County. As Meyer (1974, p. 70) has noted, there is no established record of P. mortoni above the [Late Santonian] phosphatic zone at the base of the Mooreville Formation. More likely, Conrad's specimens came from that bed at Erie Bluff, in what is now western Hale County, another of Conrad's 1833 Alabama collecting sites. On his return, Conrad gave the teeth to his friend Dr. Samuel George Morton (1795-1851 - Father of American Invertebrate Paleontology and Physical Anthropology), to include in his 1834 review of all then-known Cretaceous fossils of the United States (you could do that sort of thing then). In his over-broad definition of Cretaceous (then only recently used in America for the first time, by Morton, 1833), Morton also included Late Paleocene, Late Eocene, and Early Oligocene fossils in his "Cretaceous".
In 1834, Morton included poor drawings of a P. mortoni tooth (Morton, 1834, p. 30, pl. 18, figs. 1-2; see the accompanying Fig. , left) as "palate bones of a fish?" (ibid., fig. caption) in his important review of American Cretaceous fossils (the first paper in which American Cretaceous sharks were reported, from Ala., N.J., and Del.) Morton sent a similar tooth (not the same one) to Dr. Gideon Algernon Mantell (1790-1852 - who'd named the dinosaur Iguanodon in 1825) in England, asking if he could identify it.
In an early volume of his huge five-volume 1833-1844 monograph 'Research on Fossil Fish', Louis Agassiz (1807-1873 - oddly, Father of both Paleoichthyology and Glaciology) (Agassiz, 1835, p. 54) mentioned the name Ptychodus, but the illustrations were to be published in a later volume of plates. Agassiz had looked at fossil fish all over Europe, and evidently went to see those of Mantell. In a book on the fossils of Sussex, England, which included related species, Mantell (1836, p. 27) mentioned the name "Ptychodus mortoni", but included no figures of the tooth. Mantell could see that the American tooth differed from all of those he'd seen from the English Chalk, in that the occlusal ridges radiated from a central point, rather than being transverse, in parallel rows. The plates relating to Agassiz's Ptychodus were finally published in 1839 (the dates each section was published have been recorded in Brown, 1890), and the figures of Morton's tooth (Agassiz, 1839, pl. 25, figs. 1-3 - see the accompanying Fig. ) were labeled Ptychodus mortoni Mantell, apparently because Agassiz assumed that Mantell had published the name in 1836. Mantell later mailed Morton a letter, including excellent drawings of the tooth Morton had sent, calling it "Ptychodus mortoni", but not mentioning that he'd given it the name in 1836, Agassiz had had his artist do the drawings, and that Agassiz expected to publish it the coming years.
In a later addition to his 1834 review, and adding some new taxa, Morton (1842, p. 215, pl. 11, figs. 7) published the figures Mantell had sent him (see Fig. , right), and identified them as Ptychodus mortoni (Mantell), thinking that Mantell had already published (ibid., p. 215) on the new species - when, in fact, Agassiz intended to publish it in the coming year. By the time Agassiz (1843, p. 158) was published, with the formal description of Ptychodus mortoni, the name had been used in print three times before - by Mantell (1836), Agassiz (1839), and Morton (1842). Most authors today incorrectly accept Agassiz (1843) as author and date of P. mortoni. The International Code of Zoologic Nomenclature, the arbiter on scientific names, says that, in a species named before 1931, the new name must be cited and a recognizable illustration or description must be published (ICZN, 1999, chap. 4, art. 12.2.7). Because Mantell (1836) only cited the name, and included no figure or description, the name there was a nomen nudum (one invalid to formally establish a name). Because the name was cited and recognizable figues were published when his plates were published (printed and distributed), the authorship is thus Ptychodus mortoni Agassiz, 1839, and not Ag., 1843, when he formally described the species (and the date usually thought to be the valid one). Several of Agassiz's other species of Ptychodus (P. mammillaris [the type species], P. concentricus, P. decurrens, P. marginalis, and P. polygyrus) were also valid as of 1839. Had the figures been published in 1843, with the description, the authorship would have gone to Morton (1842), even though he thought Mantell had already named the species, and didn't intend to name it.
The moral of the story is that, in those days at least, a new scientific name was considered published if the new name is used, and a recognizable figure or description of the type specimen was included in the publication (names in unpublished manuscripts, theses, or dissertations don't count). It makes no difference if the naming was intentional or not, the species was published.
As with most paleo-related topics, others were critical in reconstructing this story. My dissertation advisor, Emily Vokes, pointed out to me that Morton (1842) has priority over Agassiz (1843) for the name P. mortoni. David Ward helpfully noted that Agassiz (1839), in turn, has priority over Morton (1842), cited the Mantell (1836) publication, and provided the Agassiz (1843) figures. I have learned much in both corresponding with Mike Everhart, his P. mortoni webpage and his fine Oceans of Kansas website. Mike Everhart kindly permitted this webpage to link to the fine P. mortoni webpages in his Oceans of Kansas website. René Kindlimann supplied the obscure Giebel reference. Andy Rindsberg, then of the Alabama Geological Survey, discussed with me Conrad's Alabama collecting sites in 1833, including Erie Bluff. Above all, Jim Bourdon provided the opportunity to put the story online.
Agassiz, L., 1839. Recherches sur les Poissons fossiles [Research on fossil fish]. Atlas vol. 3, 83 pls. Petitpierre, Neuchâtel and Soleure, Switzerland.
Agassiz, J. L. R., 1843. Recherches sur les Poissons fossiles [Research on fossil fish]. Vol. 3 text, viii+390 p. Neuchâtel and Soleure, Switzerland.
Brown, W. H., 1890. Dates of publication of 'Recherches sur les Poissons fossiles,' par L. Agassiz, with a note on Owen's 'Odontography', in Woodward, A. S. and C. D. Sherborn, Catalog of British Fossil Vertebrates. Dulau & Co., London.
Giebel, C. G., 1847.. Fauna der Vorwelt mit steter Berücksichtigung der lebenden Thiere [Fauna of the early world, with a full consideration of the living animals]. First volume, third section: fish. F.U Brockhaus, Leipzig (1848).
International Comission on Zoological Nomenclature, 1999. International code of zoologic nomenclature. 4th ed. International Trust for Zoological Nomenclature, London, 335 p. [online at: http://www.iczn.org/iczn/index.jsp].
Mantell, G. A., 1836. A descriptive catalogue of the objects of geology, natural history, and antiquity (chiefly discovered in Sussex) in the museum attached to the Sussex Scientific and Literary Institution at Brighton. 4th ed. Relfe & Fletcher, London, 44 p.
Meyer, R. L., 1974. Late Cretaceous elasmobranchs from the Mississippi and East Texas Embayments of the Gulf Coastal Plain. Unpublished PhD dissertation, Southern Methodist University, Dallas, xiv+419 p.
Morton, S. G., 1833. Supplement to the "Synopsis of the Organic Remains of the Ferruginous Sand Formation of the United States". American Journal of Science, vol. 24, no. 1, pp. 128-132, pls. 9 and 10.
Morton, S. G.,1834. Synopsis of the organic remains of the Cretaceous group of the United States. Key & Biddle, Philadelphia, 104 pp., 19 pls.
Morton, S. G.,1842. Description of some new species of organic remains of the Cretaceous Group of the United States: with a tabular view of the fossils hitherto discovered in this formation. Journal of the Academy of Natural Sciences of Philadelphia,, ser. 3, vol. 8, pt. 2, pp. 207-227, pls. 10 and 11.
Reuss, A. 1844. Geonostische skizzen aus Bohmen [Geographic sketches of Bohemia]: Prague, 304pp.
Reuss, A. 1845a. Die Versteinerungen der böhmischen Kreideformation [The fossils of the Bohemian chalk beds]: First section, Stuttgart, 58 pp.