Coronella miocaenica Venczel, 1998

Venczel, Márton & Stiuc, Emanoil, 2008, Late middle Miocene amphibians and squamate reptiles from Taut ,, Romania, Geodiversitas 30 (4), pp. 731-763 : 755-756

Coronella miocaenica Venczel, 1998 ( Fig. 14 )

MATERIAL EXAMINED. — Four fragmentary trunk vertebrae ( ISER Tt-0490/1-4).

DESCRIPTION

All the vertebrae are of minute size. The centrum length of the largest specimen is 3.45 mm, while the centrum width is 2.38 mm (centrum length/ centrum width ratio = 1.45). The centrum is elongated; the neural arch is moderately vaulted and provided with a longer than high neural spine. The dorsal margin of the latter structure is not thickened and both the anterior and posterior margins are overhanging. The posterior margin of the neural arch lacks epizygapophyseal spines. The zygosphene lacks a medial lobe, or it is provided with a rather indistinct medial and two small lateral lobes. The anterior portion of the haemal keel is rather promi-

nent and thin, while the posterior part diminishes in

Venczel M. & Ştiucă E.

height and becomes spatulate-shaped. Tiny paired tubercles are present on the subcotylar lips. The subcentral ridges are weakly defined.The prezygapophyseal articular facets are of oval shape, while the prezygapophyseal processes are extremely short and with obtuse extremities. The paradiapophyses are evidently differentiated into diapophyses and parapophyses. The latter structures are noticeably longer than the diapophyses.

REMARKS

The vertebral morphology of the above fossils closely resembles that of Coronella miocaenica , known from the late Miocene (MN 13) of Polgárdi 4, Hungary (see Venczel 1998: fig. 6a-e). The centrum length/ centrum width ratio approaches also the intraspecific variation of this species (1.02-1.42 in specimens coming from Polgárdi 4U). The neural arch in the extant C. austriaca Laurenti, 1768 is more flattened and provided with a somewhat lower neural spine.

The genus Coronella is considered closely related to Old World rat snakes ( Dowling & Duellman 1978; Utiger et al. 2002; Nagy et al. 2004). There is some evidences that the ancestry of the above groups could have differentiated in tropical Asia during late Eocene and afterward dispersed among others to the western Palearctic during Oligocene times ( Burbrink & Lawson 2007). As a result the genus Coronella could have reached the European continent at an earlier date than considered before ( Venczel 1998). Unfortunately, remains of Coronella ,

except those from a number of Quaternary localities ( Szyndlar 1991), were rarely reported from Europe. Nevertheless, small sized colubrids, reminiscent of Coronella , were described from a number of European Tertiary localities but referred to other genera (e.g., Texasophis Holman, 1977 and Hispanophis Szyndlar, 1985 ) ( Rage & Holman 1984; Szyndlar 1985, 1987, 1991, 1994; Gál et al. 1999; Ivanov 2000). Conceivably, a detailed revision of all these remains should indicate (at least in some cases) a putatively early presence of the genus Coronella in the European Tertiary.

Figures

FIG. 14. — Coronella miocaenica Venczel 1998, presacral vertebra (ISER Tt-0490/1): A, dorsal view; B, right lateral view; C, ventral view. Scale bar: 2 mm.