Gobiconodon, Trofimov, 1978

Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique & Bailly, Gilles, 2022, Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J / K boundary, Geodiversitas 44 (25), pp. 683-752 : 728

Gobiconodon ? sp.

( Fig. 32A, B )

DESCRIPTION

Within the eutriconodontan material from Angeac-Charente, the specimen ANG M-21 ( Fig. 32A, B ) consists of an isolated tooth crown, the main central cusp a being surrounded by two unequal cusps b and c (see figures 4.7 and 7.2 by Crompton & Jenkins [1968] and Kielan-Jaworowska et al. [2004] respectively for an explanation of the cusp-numbering system). The root is missing but the tooth was probably uniradiculate. The crown is labiolingually compressed and the lingual face appears almost planar in occlusal view, while the labial face is convex at its base ( Fig. 32A ). There is no trace of either a labial or lingual cingulid. Cusp a dominates the crown and is triangular in lateral profile ( Fig. 32B ). Its mesial surface is rounded, but its distal edge shows a well-defined crest ( Fig. 32A ). An oval wear facet can be observed on the labiodistal surface of cusp a ( Fig. 32A ). Cups b is smaller than cusp c; it is also placed higher relatively to cusp a and less separated from it than cusp c. The apex of cusp c appears to be slightly flexed labially. Both cusps b and c bear small labially oriented wear facets. The presence of a probably single root indicates a tooth from the anterior dentition, but the well-developed accessory cusps show that it is a distal premolar and not a more mesial tooth. Among Laurasian Early Cretaceous mammals, single-rooted distal premolars are only seen within the Gobiconodontidae family ( Sweetman 2006). Moreover, the specimen ANG M-21 closely resembles the gobiconodontid distal premolar (possibly right p4) described by Sweetman (2006) in the Early Cretaceous Wessex Formation of the Isle of Wight, southern England, and tentatively referred to Gobiconodon . Considering this, and the general morphology of ANG M-21 (tricuspid tooth with mesiodistally aligned cusps; dominant cusp a and small but well-developed accessory cusps; labial inflation of the crown; lack of cingulid), the specimen is identified as a left distal premolar, probably a p3 (as the accessory cusps are less developed than in the possible p4 described by Sweetman [2006]), of a gobiconodontid mammal, and is tentatively referred to Gobiconodon .

Figures

FIG. 32. — Mammal teeth from Angeac-Charente: A, B, premolariform or molariform tooth of Gobiconodon? sp. (ANG M-21) in occlusal (A) and labial (B) views; C, D, premolariform tooth of Mammalia indet. (ANG M-34) in lingual (C) and labial (D) views; E, F, left lower molar of Triconodon sp. (ANG M-02) in lingual (E) and occlusal (F) views; G-I, left upper molar of Thereuodon cf. taraktes (ANG M-23) in labial (G), lingual (H) and occlusal (I) views. Scale bar: 500 µm.