Natricinae

Ivanov, Martin, 2000, Snakes of the lower / middle Miocene transition at Vieux Collonges (Rhône, France), with comments on the colonisation of western Europe by colubroids, Geodiversitas 22 (4), pp. 559-588 : 575-576

Natricinae D

Natricinae D – Ivanov 1997a: 122, fig. 55.

MATERIAL EXAMINED. — 4 trunk vertebrae ( FSL 368892- FSL 368895).

DESCRIPTION

Trunk vertebrae ( Fig. 10 )

In lateral view, the neural spine is about four times longer than high; its cranial margin overhangs anteriorly, the caudal margin is broken off in all vertebrae. The interzygapophyseal ridges are slightly developed; the small lateral foramina do not open in depressions. The subcentral ridges are straight to weakly arched dorsally. The relatively straight and short hypapophysis is directed caudally; its distal termination is pointed or slightly rounded. The synapophyses are very damaged, the para- and diapophyses were most likely well-separated from each other. The anteriorly directed parapophyseal processes are short. The condyle is situ- ated on a short neck. In dorsal view, the zygosphenal lip generally possesses distinct lateral lobes and the wide median lobe is slightly developed. The prezygapophyseal articular surfaces are obovate to subtriangular, the prezygapophyseal processes are relatively short, heavily built and pointed. The epizygapophyseal spines are underdeveloped. In ventral view, the hypapophysis is sharp, its anterior keel expands anteriorly. The blunt subcentral ridges are well developed; the subcentral grooves are wide and more distinct in the cranial part of vertebrae. The subcotylar tubercles are absent or very slightly developed. The subcentral foramina are very small. In cranial view, the neural arch is slightly vaulted, the neural canal is subcircular and the zygosphenal lip is convex. The parapophyseal processes are separated from the cotyle by relatively deep furrows. The conspicuous paracotylar foramina are situated on both sides of the rounded to dorso-ventrally slightly flattened cotyle. The measurements of vertebrae are as follows (n = 4): cl: or = 3.33-4.37; naw: or = 2.32-2.80; cl/naw: or = 1.42-1.56, mean 1.48 + 0.06.

DISCUSSION

The vertebrae of the morphotype Natricinae D are characterised by both the relatively high neural spine and straight as well as short hypapophysis. The Natricinae D resembles especially some representatives of the genus Neonatrix . The Natricinae D differs from the morphotypes Natricinae A, B & C in the straight and short hypapophysis. A more precise determination was not possible because of damaged neural spines, synapophyses and broken off prezygapophyseal processes.

Figures

FIG. 10. — Natricinae D from the lower/middle (MN 4/5) Miocene of Vieux Collonges, trunk vertebra (FSL 368894); A, lateral view; B, dorsal view; C, ventral view; D, cranial view. Scale bar: 2 mm.