Synaphodus is an extinct genus of artiodactyls belonging to the basal family Dichobunidae. It was endemic to western Europe and lived during the Oligocene, although its specific temporal range is uncertain. Despite having only one recognized species S. brachygnathus, it has had a complicated taxonomic history due to the genus name, established by the French palaeontologist Auguste Pomel in 1848, being applied early on for a species that was eventually reclassified under the suoid genus Propalaeochoerus. It was a large-sized member of the Dichobuninae similar to Metriotherium but differed from it by its more bunodont (round and low cusps) dentition among other differences. As one of the few dichobunines of the Oligocene, it would have coexisted with immigrant faunas after the Grande Coupure extinction event and surviving faunas within western Europe.
Taxonomy In 1848, the secretary of French palaeontologist Jean-Louis Hardouin Michelin de Choisy, named Mr. Bayle, wrote about a presentation given by French palaeontologist Auguste Pomel, who gave mention to an artiodactyl genus named Synaphodus, assigning Anthracotherium gergovianum (originally named by French palaeontologist Jean-Baptiste Croizet) to it without further explanation. The same year, Pomel also erected the genus name Brachygnatus for the same species. He also wrote about the species Synaphodus brachygnathus, explaining that its dentition was similar to that of Anoplotherium and had continuous dentition meaning short diastemata. The etymology of Synaphodus derives from the Ancient Greek words σύναψη (union) and ὀδούς (tooth) in reference to the continuous dentition on the holotype mandible. In 1848–1852, French palaeontologist Paul Gervais tentatively listed A? gergovianum, explaining that he thought that its molars were more similar to those of Dichobune than Anthracotherium. He noted that the species was listed under three genus names, namely Cyclognathus, Brachygnathus, and Synaphodus. In 1853, Pomel listed the species name Synaphodus gergovianus based on a mandible with dentition, of which Anthracotherium gergovianus and Sinaphodus brachygnathus (the latter name created by him as well) are synonyms. He also defined Cyclognathus as being synonymous with Cainotherium. In 1899, Swiss palaeontologist Hans Georg Stehlin suggested that the synonymous names Synaphodus brachygnathus and Synaphodus gergovianus are invalid and that their specimens can be classified under Palaeochoerus. After Stehlin erected Propalaeochoerus the same year, P. gergovianus as originally named by Croizet has since been assigned to it. The taxonomic status of Synaphodus had often been overlooked by taxonomists of the 20th century, as noted by Jean Sudre. In 1951, French palaeontologist René Lavocat revived Synaphodus brachygnathus as a valid genus and species belonging to the Dichobunidae based on the mandible studied in 1853 by Pomel. The validity of Synaphodus was followed by Sudre in 1978, who stated that it was distinct enough from its close relative Metriotherium.
Classification
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