Coluber pouchetii ( Rochebrune, 1880 )

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 : 428-429

Coluber pouchetii ( Rochebrune, 1880)

pars Coluber sansaniensis Lartet, 1851: 40 .

Tamnophis Pouchetii – Rochebrune 1880: 281, pl. 12, fig. 9.

Sansanosaurus pouchetii – Kuhn 1939: 21.

Coluber pouchetii – Rage 1981: 540, 541, fig. 1B. — Augé & Rage 2000: 296-298, figs 26-28.

MATERIAL EXAMINED. — 12 trunk vertebrae (Béon 2004 LT 61).

COMMENTS

Coluber pouchetii , a large species, was revised and redescribed by Rage (1981) and Augé & Rage (2000) on the basis of material from Sansan (MN 6). In Europe, other extinct large species referred to Coluber are C. dolnicensis Szyndlar, 1987 , from the early Miocene of Merkur-North (MN 3) and Dolnice (MN 4), Czech Republic ( Szyndlar 1987; Ivanov 2002), C. caspioides Szyndlar & Schleich, 1993 , from the early Miocene of Merkur-North (MN 3), Petersbuch 2 (MN 4, Germany) and perhaps Oberdorf (MN 4, Austria) ( Szyndlar & Schleich 1993; Szyndlar 1998; Ivanov 2002), and C. suevicus (Fraas, 1870) from Steinheim (MN 7+8, Germany) and apparently Merkur-North ( Szyndlar & Böhme 1993; Ivanov 2002).

In addition to their large size, these four species share some other traits: anterior border of zygosphene more or less straight between the lateral lobes, with sometimes a small median notch; neural arch weakly depressed to weakly vaulted (except in the overgrown C. suevicus ); posterior borders of neural arch nearly straight or even straight in posterior view; neural spine not low. Moreover, two peculiar characters suggest that C. pouchetii and C. dolnicensis might be closely related. In both species, the diapophysis is shifted posteriorly with regard to the parapophysis and the haemal keel forms a step in the anterior part of the centrum. However, the step is present in all vertebrae of C. dolnicensis whereas it clearly occurs only in the posterior trunk region of C. pouchetii ; in the mid- and anterior trunk regions of the latter species it is weak or absent. C. pouchetii further differs from C. dolnicensis in having slightly shorter vertebrae and longer prezygapophyseal processes. In C. caspioides and C. suevicus , the diapophysis is not clearly shifted posteriorly and the step of the haemal keel is lacking. C. pouchetii further differs from C. caspioides in having a lower neural spine and from C. suevicus in having longer prezygapophyseal processes.

It should be noted that the Pliocene of Punta Nati (Balearic Islands) has yielded a species of Coluber that displays the two characters that are common to both C. dolnicensis and C. pouchetii . Moreover, as in the latter species, in the Balearic form the step of the haemal keel is restricted to the posterior trunk region (Bailon et al. in press). But because of some differences, Bailon et al. (in press) did not assign this snake to C. pouchetii ; they only referred it to the “ C. dolnicensis- C. pouchetii group”.

Coluber pouchetii is known only from Béon 1 (MN 4) and Sansan (MN 6).