Kerberos langebadreae
Kerberos is an extinct genus of large-bodied carnivorous mammal belonging to the order Hyaenodonta. The genus includes a single species, Kerberos langebadreae, from the Eocene of France. It represents one of the oldest members of the hyaenodont subfamily Hyainailourinae that have been recorded in Europe. Montespieu, the locality where "Kerberos" was found, is part of the “Castrais” fauna which is thought to be of Bartonian age. Many hyaenodont species are known only from fragments of the jaw or a few teeth. "Kerberos" represents the first instance where cranial, dental and postcranial material of an early hyainailourine have  been found associated with each other. Etymology. The genus name "Kerberos" comes from Cerberus, the hound of Hades, a multi-headed dog that guards the entrance to the Underworld in Greek mythology. The species name, "langebadreae", is dedicated to the French palaeontologist Dr. Brigitte Lange-Badré, who contributed extensively to the knowledge of Eocene carnivorous mammals. Description. The material that has been referred to "Kerberos" includes a nearly complete cranium, left and right halves of the lower jaw, a fibula and several foot bones including the astragalus, calcaneus, metatarsals 1-3 and two middle phalanxes. "Kerberos" displays both primitive and  derived features. Among the former is the anteriorly narrow jaw and the small space between the first and second lower premolars. The derived features include a premaxilla that is narrow along is full length as well as several dental characteristics. The skull of "Kerberos" is about 35 cm long, similar in size to that of a female brown bear. The snout is very short. The shape of the skull indicates large jaw muscles, suggesting that "Kerberos" had a powerful bite. The molars of "Kerberos" were cutting whereas the premolars display a shape and wear pattern more consistent with crushing action . Body mass. "Kerberos" was a large hyaenodont and is thought to have weighed around 140 kg based on measurements of the teeth, skull and astragalus. This makes Kerberos one of the largest carnivores known from the Eocene of Europe. Ecology. Both "Kerberos" and "Paroxyaena" were much larger than the proviverrine hyaenodonts that lived in Europe at the same time and are therefore unlikely to have been in direct competition with them. The small proviverrines may have even been their prey. Based on the neck vertebrae of closely related hyaenodonts, it is thought that "Kerberos" and its relatives had powerful necks  which allowed them to restrain struggling prey. This, together with the powerful jaw muscles and crushing premolars, suggests that Kerberos was capable of both hunting and scavenging similarly to the modern spotted hyena. Unlike the modern hyena, however, the foot bones of "Kerberos" indicate that it had a plantigrade posture and was not an efficient runner. "Kerberos" likely preyed on animals which were larger than itself, such as ungulates like "Choeropotamus", "Lophiodon" and "Palaeotherium". Because of its large size it would have been an important apex predator. Classification and phylogeny. The species "Kerberos langebadreae" was created along with the genus  in 2015 by Solé and colleagues based on a fossil skull, lower jaw and a number of associated hindlimb elements. The fossils were discovered in 1981 by Dominique Vidalenc at Montespieu, near the city of Lautrec in the department of Tarn in southern France. They were shown to come from a hyaenodont and were referred to a new genus and species. The original study placed "Kerberos" within the subfamily Hyainailourinae as more derived than "Paroxyaena", "Pterodon dasyuroides", "Parapterodon" and "Pterodon africanus". This and later studies all agree that "Kerberos" is less derived than "Pterodon phiomensis", "Akhnatenavus", "Leakitherium", "Isohyaenodon" and "Hyainailouros , but disagree on its position among the other hyainailourine species. More recent studies, using Bayesian tip dating, placed Kerberos" as the sister group to "Pterodon dasyuroides", but basally of the other above-mentioned taxa. Below is a cladogram showing the relationships of Hyaenodonta by Borths & Stevens (2019).