Rana sp.

Rage, Jean-Claude & Bailon, Salvador, 2005, Amphibians and squamate reptiles from the late early Miocene (MN 4) of Béon 1 (Montréal-du-Gers, southwestern France), Geodiversitas 27 (3), pp. 413-441 : 420

Rana sp. ( Fig. 3 A-C)

MATERIAL EXAMINED. — 2 angulosplenials (Béon 2004 LT 21), 6 presacral vertebrae (Béon 2004 LT 22), 6 sacral vertebrae (Béon 2004 LT 23), 6 humeri (Béon 2004 LT 24-26), and 1 ilium (Béon 2004 LT 27).

DESCRIPTION

The specimens clearly show the characteristics of the genus Rana . More specifically, several features are typical of species belonging to the “green frogs group”, or “water frogs” (i.e. synklepton Rana esculenta sensu Dubois & Günther 1982 ). The processus coronoideus of the angulosplenial forms a well developed vertical lamina whose dorsal edge is convex; its extent is similar to that of green frogs. Moreover, the lateral surface of the angulosplenial that is located below the sulcus Meckeli, at the level of the processus coronoideus, is nearly vertical and limited ventrally by an elongate external mandibular ridge as in green frogs ( Bailon 1999). The vertebrae and humeri show all of the characteristics of the genus Rana . All available humeri are small, they likely belonged to juvenile individuals ( Fig. 3A, B ). The only available ilium is damaged ( Fig. 3C ), but the depth of the supracetabular fossa and the thickness of the ilio-ischiatic face also point to green frogs ( Bailon 1991, 1999).

COMMENTS

Green frogs are comparatively frequent in Tertiary localities. The earliest fossils were report- ed from the early Oligocene ( Sanchiz et al. 1993), perhaps the late Eocene ( Rage 1984a; Holman & Harrison 1999). Several species from the Miocene of Europe likely belong to this assemblage ( Rage & Roček 2003), but Sanchiz (1998b) regarded all of them as nomina dubia.

Today, the green frogs group includes true species and hybridogenetic “species” that form a complex assemblage. Dubois & Günther (1982) named this assemblage “Synklepton Rana esculenta ”. The morphology of these frogs is very homogeneous and the osteology of several recently recognized living species is unknown. Consequently, it is practically impossible to distinguish extinct species within this complex.

Figures

FIG. 3. — A-C, Rana sp. synkl. R. esculenta Linnaeus, 1758; A, left humerus of a female (Béon 2004 LT 24); B, right humerus of a female (Béon 2004 LT 25); C, right ilium (Béon 2004 LT 27); D, gekkonid lizard, right dentary (Béon 2004 LT 28); E, lacertid lizard, unidentified genus and species 1, left dentary (Béon 2004 LT 30); F, lacertid lizard, unidentified genus and species 2, right dentary (Béon 2004 LT 32). Medial (m), posterior (p), right lateral (r), and ventral (v) views. Scale bars: 2 mm.