C. R. Acad. Sei. Paris, t. 311, Série II, p. 1267-1272, 1990 1267 Paléontologie/ Paleontology Les plus anciens Serpents (Reptilia, Squamata) connus. Mise au point sur l'âge géologique des Serpents de la partie moyenne du Crétacé Gilles CuNY, Jean-Jacques JAEGER, Mohamed MAHBOUBI et Jean-Claude RAGE Résumé - Jusqu'à présent, Lapparentophis defrennei trouvé à In Akhamil, en Algérie, était consi- déré comme le plus ancien Serpent. Son âge supposé, Crétacé inférieur, n'était connu qu'avec une certaine imprécision. En fait ce fossile peut maintenant être attribué à I' Al bien supérieur ou au Cénomanien. D'autre part, deux Serpents ont été trouvés récemment dans l'Albien supérieur d'EI Kohol (Algérie). Il s'agit d'un possible Lapparentopheidé et d'un Serpent incertae sedis. Ces deux fossiles, ainsi peut-être que Lapparentophis, sont maintenant les plus anciens Serpents connus. The oldest known snakes (Reptilia, Squamata). Update on the geological age of the snakes from the middle part of the Cretaceous Abstract - Up to now il has been held that the oldest known snake is Lapparentophis defrennei /rom ln Akhamil (Algeria), the geological age of which was considered early Cretaceous. lt is now possible to indicate that the age of this snake is either late Albian or Cenomanian. On the other hand, two snakes have beenfound in the upper Albian of El Kohol (Algeria). They are referred to as (?) Lapparentopheidae and Serpentes incertae sedis. These Iwo fossils are now the oldest known snakes with perhaps Lapparentophis; however, the latter might be slightly younger than the fossi/s /rom El Kohol. Abridged Eng/ish Version - Up to now, it has been held that Lapparentophis defrennei from the lower Cretaceous of In Akhamil (Algeria) ts the oldest known snake ((l], [3]). However, its geologic age was not precisely known within the early Creta- ceous. lt is now possible to reduce this uncertainty. The precise bed that has yielded Lapparentophis remains unidentified. However, it is established that this bed is a part of a series of strata which is located above the Taouratine sandstones and below clays that would be of Cenomanian age. According to Busson [8] and G. Philippe (pers. comm.), this stratigraphie location indicates a late Albian or Cenomanian age for the fossiliferous bed. This age is corroborated by the presence, in this bed, of the elasmobranch Onchopristis numidus the stratigraphical range of which ts precisely late Albian and Ceno- manian [9]. Therefore, Lapparentophis cornes either from the upper Albian or from the Cenomanian, that is from the latest early Cretaceous or from the earliest late Cretaceous. On the other hand, two snakes have been discovered in the upper Albian of El Kohol (Algeria); they are referred to as (?) Lapparentopheidae and Serpentes incertae sedis. The possible Lapparentopheid from El Kohol (Fig. 1) is known only by a very fragmentary vertebra, a centrum whose morphology is reminiscent of Lapparentophis; moreover, the uncommon ratio width of neural canal/diameter of cotyle (i.e., small neural canal/large cotyle) is consistent with that of this latter snake. However, the incompleteness of this specimen prevents an ascertained systematic assignment. The other fossil from El Kohol (Fig. 2) is known by a rather complete vertebra which is more or less distorted. lt does not clearly correspond to a known type of vertebral morphology. lt is heavily built but elongate, and it lacks a posterior median notch in the neural arch which is a primitive feature. A hypapophysis was perhaps present. The paradiapophyses are situated low which corresponds to an adaptation Note présentée par Yves COPPENS. 0764-4450/90/03111267 $ 2.00 !Cl Académie des Sciences