Natrix, Laurenti, 1768

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 : 430-431

Natrix aff. N. merkurensis Ivanov, 2002 ( Fig. 6B)

MATERIAL EXAMINED. — 24 trunk vertebrae (Béon 2004 LT 70, 71).

COMMENTS

N. merkurensis is based on vertebrae and skull bones from Merkur-North (MN 3; Czech Republic). The vertebrae are mainly characterized by the peculiar combination of an elongate and narrow centrum that is reminiscent of N. longivertebrata and a neural spine as high as that of N. sansaniensis ( Ivanov 2002) .

The species might be present also at Petersbuch 2 (MN 4; Germany). A natricine from the latter locality was first regarded as a possible variant of N. sansaniensis by Szyndlar & Schleich (1993) who reported it as Natrix aff. N. sansaniensis . But, after having described Natrix merkurensis, Ivanov (2002) suggested that the snake from Petersbuch 2 belongs to the latter species. However, Szyndlar & Schleich (1993) noted that the main characteristic of the natricine from Petersbuch 2 is verteb r a l p o l y m o r p h i s m a n d t h e y h i n t e d a t t h e possible presence of more than a single species. Therefore, it may be entertained whether all vertebrae from Petersbuch 2 or only a part of them belong to N. merkurensis . Both N. sansaniensis

A(d) A(l) A(v)

a n d N. m e r k u r e n s i s a r e p e r h a p s p r e s e n t a t Petersbuch 2.

At Béon 1, all vertebral characters, but one, are consistent with N. merkurensis : centrum elongate and narrow; subcentral ridges prominent; hypapophysis prolonged anteriorly by a prominent keel; neural spine high; dorsal edge of neural spine slightly forked anteriorly and posteriorly; tip of hypapophysis rounded; prezygapophyseal facets rather broad for typical Natrix ; subcotylar tubercles present; parapophyseal processes directed anteriorly (rarely anteroventrally); epizygapophyseal spines present. The only difference is that, at Béon 1, the prezygapophyseal processes are shorter than those of N. merkurensis from Merkur-North; consequently, this natricine from Béon 1 is referred to as Natrix aff. N. merkurensis .