Pterodon (Ancient Greek: (wing) + (tooth) meaning "wing tooth") is an extinct genus of hyaenodont in the family Hyainailouridae, containing two species. The type species Pterodon dasyuroides is known exclusively from the late Eocene to the earliest Oligocene of western Europe. The genus was first erected by the French zoologist Henri Marie Ducrotay de Blainville in 1839, who said that Georges Cuvier presented one of its fossils to a conference in 1828 but died before he could make a formal description of it. It was the second hyaenodont genus with taxonomic validity after Hyaenodon, but this resulted in taxonomic confusion over the validities of the two genera by other taxonomists. Although the taxonomic status of Pterodon was revised during the late 19th and early 20th centuries, it became a wastebasket taxon for other hyaenodont species found in Africa and Asia. Today, only the type species is recognized as belonging to the genus while just one is pending reassessment to another genus.
P. dasyuroides had cranial and dental characteristics typical of the Hyainailouridae such as an elongated, narrow, and proportionally large skull which measures ~ in length and dentition for hypercarnivorous diets and bone-crushing similar to modern hyenas. Due to the scarcely known postcranial materials of the species, its overall anatomy is unknown, although it likely weighed and may have been similar to another Eocene-aged European hyainailourine Kerberos.
The hyainailourine made its appearance in western Europe back when it was a semi-isolated archipelago, likely originating from a ghost lineage from Afro-Arabia. It was one of the larger-sized carnivores of the continent, a typical trait of hyainailourines. It coexisted largely with faunas that were adapted to tropical to subtropical environments and grew strong levels of endemism, becoming a regular component based on fossil evidence from multiple localities. Pterodon went extinct by the Grande Coupure extinction and faunal turnover event in the earliest Oligocene of Europe, which was caused by shifts towards seasonality plus glaciation as well as closing seaway barriers that allowed for large faunal dispersals from Asia. Its extinction causes are uncertain but may have been the result of rapid habitat turnover, competition with immigrant faunas, or some combination of the two. However, competition has been questioned as experts found no evidence of carnivorans competitively replacing hyaenodonts in Europe.
Taxonomy Research history Early history
In 1838, French zoologist Henri Marie Ducrotay de Blainville made a review of palaeontological history and taxonomy as built upon from previous decades. Blainville recognized the importance of dentition in determining the affinities of fossil animals but criticized the overreliance of dental systems as automatically indicating taxonomic affinities. He then went on to examine reported fossil "didelphids" (the taxonomic group now known as "marsupials") in European land. He conducted reviews of fossils as previously described by Laizer and Parieu, concluding that Hyaenodon is a valid genus based on its dentition but rejected the idea of it being a didelph based on its dental system and its molars being closer in affinity to modern carnivorans.
Blainville also mentioned a fossil of an upper jaw that the late Georges Cuvier found and previously thought was close in affinity to the Tasmanian devil (Sarcophilus harrisii) of New Holland (Australia). Previously, Cuvier presented the fossil to the French Academy of Sciences in 1828 and thought that it was a large species of thylacine (Thylacinus cynocephalus) but died before he could make a formal description of it. Of note is that although the article of Hyaenodon by Blainville was first written and published in 1838, it was not until a year later in 1839 when it was republished that Blainville added a footnote to the paragraph about the upper jaw. In it, he said that he restudied that fossil from the Paris Basin and again was certain that it was a "monodelphian" (today placental) predator, which he named Pterodon dasyuroides. The genus name means "wing tooth" and is a combination of the Ancient Greek words "" (wing) and "" (tooth). The etymology of the type species name derives from the Australian marsupial genus Dasyurus and the Greek suffix "" meaning "like" due to apparent initial confusion of the genus affinity by Blainville.
In 1841-1842, Blainville mentioned the genus Pterodon but replaced the previous species name with P. parisiensis. He also stated that despite thinking that the mammal did not have close affinities with Dasyurus, he did not have sufficient skull material to prove what mammal group it was closest to. The species name is in reference to Paris where its first fossil was found.
Taxonomic disputes
The taxonomic positions of Pterodon and Hyaenodon for much of the 19th century were disputed by many palaeontologists. In 1846, Auguste Pomel argued that he was unsure if Pterodon belonged to the didelph clade based on its dentition being apparently similar to thylacines but having different skull structures from them and other marsupials. However, he rejected the position that Pterodon was more closely related to the monodelphs due to thinking that the skull did not closely resemble its members. Additionally, he said that it, Taxotherium, and Hyaenodon are functionally the same genus if not the same species, therefore stating that the latter two genera are synonymous with Pterodon. Pomel defined four species for the genus Pterodon: P. parisiensis, P. cuvieri (erected previously for Taxotherium as T. parisiense by Blainville), P. leptorhynchus (erected for Hyaenodon by Lazier and Parieu), and P. brachyrhynchus (previously named for Hyaenodon by Blainville).
In 1846, Paul Gervais recognized the species P. requieni, having named the species in honor of French naturalist Esprit Requien, the founder and director of the Musee d' Avignon (now the Musée Requien) who allowed him and Marcel de Serres to study local fossil mammal specimens. In 1848-1852, however, he reclassified the species as Hyaenodon requieni (having recognized the validity of the genus) and listed P. dasyuroides as the only species of Pterodon.
In 1853, Pomel changed his position by recognizing the validity of Hyaenodon, restoring the taxonomic affinities of species previously classified as belonging to it and therefore establishing that they no are no longer classified under Pterodon (H. leptorhynchus and H. brachyrhynchus). He also reclassified Taxotherium as a junior synonym of Hyaenodon instead of Pterodon. Within the genus Pterodon, he recognized the species name P. dasyuroides instead of P. parisiensis and created two additional species based on dentition shapes and sizes: P. cuvieri and P. coquandi.
European hyaenodont revisions
Gervais erected the species P. exiguum in 1873 based on dentition with some similarities to both Pterodon and Hyaenodon but noted that it may constitute a new genus once he has more fossil material. The palaeontologist then corrected himself in 1876 by stating that the species belongs to Hyaenodon as H. exiguum, not Pterodon.
In 1876, Filhol recognized only P. dasyuroides among all species previously erected for the genus and named a new species P. biincisivus from the phosphorite deposits of Escamps, France. He, in addition to confirming the taxonomic validities of the two species, erected a third named P. quercyi in 1882. The French naturalist named a new species Oxyaena galliæ based on dental remains being apparently similar to that of species of Oxyaena previously described by Edward Drinker Cope in the Eocene deposits of New Mexico, United States. in The same year, Filhol also reported that an individual whose last name was Pradines recently discovered anterior portions of the skull of P. dasyuroides from the phosphate deposits of Limogne-en-Quercy.
English naturalist Richard Lydekker made a review of known pan-carnivoran genera in 1884, classifying them within the order Carnivora and rejecting Cope's classification of the members into the suborder Creodonta within the order Bunotheria. While Cope originally assigned Hyaenodon as the sole member of Hyaenodontidae and Pterodon plus Oxyaena into Oxyaenidae, Lydekker felt that Pterodon was close in affinity to Hyaenodon and therefore belonged in Hyaenodontidae. For H. brachyhynchus, he listed P. brachyhynchus, P. requieni, and H. requieni as junior synonyms. He also listed P. leptorhynchus as a junior synonym of H. leptorhynchus as well as H. exiguus and P. exiguus as synonyms of H. vulpinus. For Pterodon, he recognized P. dasyuroides as the main valid species of the genus and listed P. parisiensis as a definite synonym as well as P. cuvieri and P. coquandi as possible synonyms, although he did not invalidate P. biincisivus. He also listed the species Oxyæna galliæ but thought that the genus could be merged into Pterodon due to minor dental differences and similarities to P. biincisivus.
Swiss palaeontologist Ludwig Rütimeyer erected another species named P. magnus in 1891 based on the larger dentition sizes compared to typical species of Pterodon. However, in 1906, German scientist Rudolf Martin said that he wanted to synonymize P. magnum and the questionable P. quercyi with P. dasyuroides. He also listed P. biincisivus as a synonym of P. dasyuroides and stated that only one species is valid within Pterodon. Additionally, he revalidated the species O. galliæ but created the genus Paroxyaena for it, arguing that because oxyaenids are very weakly represented in Europe compared to North America and that therefore the species' similarities to oxyaenids may have an instance of convergent evolution.
In 1979, Brigitte Lange-Badré made a systematic review of known hyaenodonts from Europe including Pterodon. She listed P. parisiensis, P. cuvieri, P. coquandi, P. biincisivus, and P. quercyi as synonyms of the only European species P. dasyuroides. In addition, she listed P. magnum as a synonym of Paroxyaena galliae and listed Hyaenodon exiguus as taking taxonomic priority over H. vulpinus, therefore making the latter name and P. exiguum synonyms.
Wastebasket history For much of its history, Pterodon was a wastebasket taxon for middle to late Paleogene and Miocene hyainailourines that lacked unique or advanced dental traits that Hyaenodon had. Many of the species classified or formerly classified to Pterodon were of African or Asian origins. Within the 20th century, the species formerly classified to the genus Pterodon were Apterodon macrognathus, Akhnatenavus leptognathus, "Hyainailouros" bugtiensis, Orienspterodon dahkoensis, and Neoparapterodon rechetovi. Several species names previously assigned to Pterodon were later considered to be synonyms of Hyaenodon species, namely "P. exploratus" (= H. incertus), "P. californicus" (= H. vetus), and "P. mongoliensis" (= H. mongoliensis). Also, both "Pterodon nyanzae" and "Hyainailouros nyanzae" were synonymized with Hyainailouros napakensis. Additionally, Hemipsalodon was made a synonym of Pterodon by Robert Joseph Gay Savage in 1965 while Metapterodon was synonymized with it by Leigh M. Van Valen in 1967, but the synonymies were unsupported by later authors.
In 2025, the three African species previously assigned to Pterodon, P. africanus; P. phiomensis; and P. syrtos; were reassigned to newer genera. Shorouq F. Al-Ashqar et al. erected Sekhmetops for the former two species and Bastetodon for the latter. As a result of the synonymies, only one species assigned to Pterodon remains pending reassessment to another genus: P. hyaenoides, which is classified as belonging to the Hyaenodontinae and is located in Asia.