The fossil mammal genus Lophiodon has a complex taxonomic history, which records the likes of many valid species, synonymous species names, and species that were eventually reclassified to other mammal genera. Its taxonomic history dates back as early as 1804 when the French naturalist Georges Cuvier referred to some of its first studied fossils as belonging to tapirs before eventually being assigned to new species of Palaeotherium by him in 1812. Although first recognized as a distinct genus by French zoologist Henri Marie Ducrotay de Blainville, who gave it the name Tapirotherium, the name Lophiodon, deriving from the hill-like cusps somewhat like in tapirs, as given by Cuvier in 1822 became more widely used without its validity being overridden by the preexisting genus name at any point. Although Cuvier recognized many potential species of Lophiodon, later palaeontologists like the French zoologist Johann Baptist Fischer assigned them to formal species names. Many species in Europe and North America were assigned to Lophiodon in the 19th century but were eventually classified to various other mammal genera like other members of the Lophiodontidae as well as to other members of the Perissodactyla and to Coryphodon. There are fourteen species presently assigned to Lophiodon in total, although L. glandicus remains not as well-defined while "L." sardus is pending revisions to another genus and is not considered to be a Paralophiodon species despite having been previously reassigned there.
Early taxonomy
Cuvier's documentations and early taxonomy
Fossils of Lophiodon have first been studied in 1804 by the French palaeontologist Georges Cuvier, who originally referred to some of them as belonging to a small-sized tapir (with some close relatives also being studied by him before 1822). In 1812, he erected within the extinct genus Palaeotherium the species P. giganteum, P. tapiroïdes, P. buxovillanum, and P. occitanicum, describing them as being the size of rhinoceroses, oxes, pigs, and sheep, respectively. As early as 1817, French zoologist Henri Marie Ducrotay de Blainville suggested that some species classified to Palaeotherium by Cuvier like P. tapiroïdes should be classified under the new genus Tapirotherium. He suggested that it would have been intermediate in morphology between Tapirus and Palaeotherium. He said that he did not know of any upper jaw belonging to Tapirotherium but suggested that it would be similar to that of Palaeotherium. He noted a lower half of a jaw from a collection belonging to an individual named Mr. de Drée, which he said contained three incisors, a strong canine, and six molars, the last three of the latter of which he said were similar to those of tapirs and Palaeotherium. In 1822, Cuvier dedicated an entire chapter to "tapir-like" mammal fossils found in various European localities. In the chapter's first section, he described various tapir-like teeth from several localities that he did not assign any name to and referenced several other localities that he would then describe in the next section. Among them were dental material from the French city of Orléans that he assigned to the informal name "tapir gigantesques", or "gigantic tapirs." In the second section, Cuvier erected the genus name Lophiodon, stating that its name references the transverse hill-like cusps of the molars like in modern tapirs. He also stated that like tapirs, Lophiodon had six incisors and two canines on each side of its mouth (or three incisors and one canine in each jaw's side). Cuvier argued that it differed from tapirs in having more oblique cusps in each molar, there being one rather than two cusps in each of the first molars, and the bases of the molars being less rectangular (especially the last ones). Furthermore, he said that some species of Lophiodon had different tooth morphologies more reminiscent of hyraxes and rhinoceroses and thus form a diverse range of forms by species like Palaeotherium. The genus name Lophiodon means "crested tooth", which is a compound of the Greek prefix λόφος ('lóphos') meaning 'crest' and the suffix ὀδούς ('odoús') meaning 'tooth'.
… excerpt ends here. Continue reading the full article.
