Validate ontology for Dinodon horridus
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Leidy (1856) described Deinodon horridus (Fig. 3) based on a series of twelve teeth and tooth fragments, which he thought resembled Megalosaurus, a large theropod dinosaur known from Jurassic deposits in England. The teeth were originally in the collection of the Philadelphia Academy. Leidy (1860) discussed similarities among the animal communities across space and time. For example, the presence of a hadrosaur herbivorous dinosaur, a theropod carnivorous dinosaur, as well as crocodiles and a ray-finned fish called Lepidotes in both Jurassic England and Cretaceous North America. Leidy (1860) provided the first illustrations of Deinodon horridus (https://zenodo.org/record/1068922#.XWU58-MzZp8), and clarified that only some of the associated teeth resembled Megalosaurus in having a broadly elliptical cross section (Leidy 1860: figs. 21-34, plate 9) while several other teeth were more peculiar with a somewhat U-shaped cross section (Leidy 1860: figs. 35-48, plate 9). But since the complete dentation of Megalosaurus was not yet known, Leidy (1860) deferred his conclusions pending further discovery. The teeth described as Deinodon horridus were collected from a part of the Nebraska Territory that in 1864 would become the Montana Territory, and later (1889) the US state of Montana.
Cope (1866) described Laelaps aquilunguis, a large therapod from Cretaceous deposits in New Jersey comparable to Megalosaurus or Deinodon. This specimen provided an opportunity to assess the dental anatomy, and to generalize anatomical characteristics typical of this group of dinosaurs. Cope (1866) went on to define the genus Laelaps as having Megalosaurus-like teeth, distinguishing it from the U-shaped teeth of Deinodon (which misspelled as “Dinodon”).
Based in part on characteristics of the teeth revealed by the Laelaps aquilunguis specimen, Leidy (1868) became more convinced that the series of teeth he had previously described as Deinodon horridus were in fact from two distinct species. He restricted “Dinodon” to the Megalosaurus-like teeth, and proposed the new name Aublysodon mirandus to refer to the distinctive U-shaped teeth illustrated in figs. 35-48, plate 9 of Leidy (1860).
Cope (1868, 1869) agreed with Leidy (1868) that the series of teeth originally described as Deinodon horridus represented two species. But he disagreed about the most appropriate nomenclature, and had already distinguished Laelaps from Deinodon based on tooth shape (Cope 1866). Leidy’s (1868) concept of Deinodon was in direct conflict with Cope’s. Cope (1868) argued that because the Megalosaurus-like teeth included in the description of Deinodon horridus (misspelled Dinodon) were not particularly novel, that Deinodon should apply to the distinctive teeth and Laelaps to the Megalosaurus-like teeth. However, Cope (1868, 1869) determined that the genus name Deinodon (misspelled Dinodon) was preoccupied by the snake genus Dinodus Dumeril & Bibron. In zoological nomenclature, two different taxa cannot share the same name. Because taxonomic nomenclature is based on classical languages, determining whether two taxonomic names are the same (in the special sense of taxonomic nomenclature) can involve more than simply comparing patterns of letters. Cope (1868, 1869) synonymized Aublysodon mirandus with Dinodon horridus. But since Cope (1868, 1869) had determined that D(e)inodon was not available, he referred to this species as Aublysodon horridus. Hay (1899) determined that Cope had indeed misinterpreted the intermingled rules of taxonomic nomenclature and classical languages, and that Deinodon Leidy, 1856 was not preoccupied (see below).