Azilestes ("Mas-d'Azil robber") is a genus of probable zhelestid eutherian mammal, a family consisting of small herbivores, that was discovered in the early Maastrichtian Grès de Labarre Formation of France.[2] It is a monotypic genus, with only type species A. ragei being known. Only one specimen, the holotype described in 2021, is known. It consists of a partial dentary with teeth.[2]
Certain aspects of Azilestes's dental anatomy are convergent with later groups of herbivorous mammals, including Glires, though phylogenetic analysis strongly suggests a position within the Zhelestidae.[2] It possesses bunodont molars, enlarged postfossids and hypoconids, an interradicular crest and radicular grooves, a unique combination among Cretaceous eutherians.[2]
The sole specimen and holotype of Azilestes, a partial dentary with teeth, was discovered in the Grès de Labarre Formation of the northern Pyrenees, near the Mas-d’Azil of the Ariège department in Occitanie region, France.[2] The specimen was found in the northeastern outcrops of the Grès de Labarre levels, northeast of the Mas-d’Azil, by surface prospecting in the area. The vertebrate-bearing level where it was found is a fossiliferous hard limestone, belonging to the upper unit of the Grès de Labarre which overlies the Marnes d’En locality.[2] Together with the overlying "Marnes Rouges Inférieures" formation, an eastern lateral equivalent of the Marnes d'Auzas, it comprises the last Cretaceous deposits of the Sub-Pyrenean zone.[2]
Azilestes was described by Emmanuel Gheerbrant and Dominique Teodori in 2021, and much of its anatomy was mapped using CT scanning.[2] It was named for Mas-d'Azil, the type locality, and the Greek λῃστήσ, or lestes ("robber"). The specific epithet is after Jean-Claude Rage, in tribute to his major contribution to the study of Cretaceous microvertebrates from Europe.[2]
Though damaged and fragmentary, the sole specimen of Azilestes, dated to the early Maastrichtian,[2] is one of the most complete jaw remains of a eutherian reported from the Late Cretaceous of Europe. It preserves only part of the mandibular corpus, including the posterior part of the mandibular symphysis.[2] The symphysis extends far posteriorly, close to the level of the alveolus of the fourth upper molar, and is very compact. The mandibular corpus is dorso-ventrally high, and labially inflated.[2] It is convex below the molars, but below the premolars and the symphysis, it is concave. Its dorso-ventral depth decreases drastically at the length of the symphysis.[2]
The posterior mental foramen is rather large and located ventro-labially below and between the two roots of the fifth upper molar, as in most Cretaceous eutherians.[2] The dentary preserves two damaged molars and four well-developed empty anterior alveoli, interpreted as corresponding to two-rooted fifth upper molar, and a single-rooted fourth upper molar and canine.[2] Among Cretaceous eutherians, the molar morphology of the holotype most closely resembles the family Zhelestidae, to which it is tentatively assigned.[2] Zhelestids were non-placental eutherians, and were specialized for a herbivorous diet.[3]