Reinterpretation and new denominationof Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)

Abstract

The holotype of Atacisaurus crassiproratus Astre, 1931 (Middle Eocene; Issel, France) is herein reinterpreted and attributed to cf. Iberosuchus. The holotype of A. crassiproratus consists of a fragment of a mandible that Astre (1931) assigned to an eusuchian crocodile. However, the combination of characters that we have recognized in this mandible allows to consider it as a member of the Metasuchia clade ( sensu Benton & Clark 1988). Furthermore, the specimen from Issel shows a similar morphology and the same combination of character states than those of several specimens from the middle Eocene site of Caenes (Duero basin, Salamanca province, Spain). We consider that both the Issel and Caenes mandibles belong to the same taxon. The mandibles of all these specimens, attributed to cf. Iberosuchus, share with other metasuchians the following combination of apomorphic traits: a dorsal prolongation of the dentary ascending behind the tooth row; the presence of a lateral depression on the dentary; robust splenials; the presence of a big slot-like foramen intramandibularis oralis;; and an anteroposteriorly elongated glenoid fossa of the articular. These specimens are also compared with the Eocene African species Eremosuchus elkoholicus Buffetaut, 1989 . The phylogenetic relationships, based on mandibular characters, of cf. Iberosuchus with other taxa previously associated to this genus, such as the Sebecosuchia Simpson 1937 ( sensu Gasparini et al. 1991 ) and the Trematochampsidae Buffetaut, 1974 ( sensu Buffetaut 1986, 1988, 1989), as well as with other members of the Metasuchia and Neosuchia clade, are discussed.