Eryx, Daudin, 1803

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 : 563-565

Eryx sp.

Bransateryx sp. – Hoffstetter & Rage 1972: 102, pl. II, fig. 11. — Ivanov 1997a: 36-37, fig. 19.

MATERIAL EXAMINED. — 4 trunk vertebrae ( FSL 368337- FSL 368340), 2 caudal vertebrae ( FSL 368341, FSL 368342).

DESCRIPTION

Trunk vertebrae ( Fig. 3 A-D)

In lateral view, the bases of broken off neural spines are shifted caudally. Short interzygapophyseal ridges are sharp. The caudal part of the neural arch is turned up dorsally. The slightly dorsally arched subcentral ridges extend from the distinctly cranially situated synapophyses to the basis of the condyle. The paradiapophyses are not distinctly divided, the diapophyseal area is larger than the parapophyseal one. The lateral foramina are relatively large and well-visible. In dorsal view, the cranial margin of the zygosphene has prominent lateral lobes and the median lobe is wide. The neural spine is narrow. The prezygapophyseal articular surfaces are subtriangular, well-visible prezygapophyseal processes are very short and pointed. In ventral view, the haemal keel is very wide. It extends from the base of the cotyle to the base of the condyle. In the cranial part of vertebrae the haemal keel can be strikingly expanded. The haemal keel is very distinct in posterior trunk vertebrae. In the case of anterior trunk vertebrae, the haemal keel is indistinct as well as the short subcentral ridges and the shallow subcentral grooves. In all vertebrae, both the subcentral grooves and ridges are more distinct in their cranial part. The subcentral foramina are very small and hardly perceptible. In cranial view, the neural arch is conspicuously flattened, the neural canal is approximately circular with distinct lateral sinuses. The cranial margin of the gracile zygosphene is straight. The prezygapophyses are distinctly tilted upward. The cotyle is flattened dorso-ventrally, the paracotylar foramina are lacking. Metrical measurements are as follows (n = 4): cl: or = 1.65-3.41; naw: or = 1.88-3.52; cl/naw: or = 0.74-0.97, mean 0.84 + 0.11.

Caudal vertebrae ( Fig. 3 E-G)

Both the zygosphene and the zygantrum are absent, which proves that these specimens are posterior caudal vertebrae. In lateral view, the vertebrae are high with short vertebral centrum. On the more complete vertebra the right pleurapophysis is broken off near its base (the left pleurapophysis is completely missing like the left prezygapophysis). The neural spine, broken off at the base, is accompanied laterally with prominent pterapophyses which project cranially into a distinct process. The caudal extension is less perceptible. The pleurapophysis projects distally into a process where the prezygapophysis of the subsequent vertebra is wedged between this process and the postzygapophysis. In dorsal view, the damaged right prezygapophyseal artic-

A B

C

ular surface is irregular, the pterapophyses are relatively wide. In cranial view, the neural arch is approximately rounded with lateral sinuses, the prezygapophyses are tilted upward and the prezygapophyseal processes are very short and obtuse. The cotyle is approximately rounded, its ventral margin is thickened. The haemapophyses are directed latero-ventrally, their distal ends are broken off.

DISCUSSION

The assignment to the subfamily Erycinae and to the genus Eryx is based on the presence of caudal vertebrae with complicated structure. The discovered vertebrae belong most probably to the genus Eryx – the remaining material of 25 caudal and 70 trunk vertebrae of this genus, discovered at Vieux Collonges, have recently been investigated by Szyndlar & Rage (in prep.). The morphology of the caudal vertebrae is very complicated in the subfamily Erycinae and the problems connected with the determination of such vertebrae will be widely discussed (Szyndlar & Rage in prep.).

Figures

FIG. 3. — Eryx sp. from the lower/middle (MN 4/5) Miocene of Vieux Collonges; A-D, trunk vertebra (FSL 368339); A, lateral view; B, dorsal view; C, ventral view; D, cranial view; E-G, posterior caudal vertebra (FSL 368341); E, lateral view; F, cranial view; G, dorsal view. Scale bars: 2 mm.