Natrix sp. Laurenti 1768

Natrix sp. (Fig. 12 A-E) Natrix sp. – Ivanov & Musil 2004: 229. Natrix sp., type I – Ivanov et al. 2006: 229, table 2 (in part). MATERIAL. — MWQ, early Miocene, Burdigalian, Orleanian, MN 4: 1/2001 Turtle Joint:Two trunk vertebrae (Pal. 1481-1482); 2/2003 Reptile Joint: Two trunk vertebrae (Pal. 1968-1969). DESCRIPTION Trunk vertebrae The most complete specimen, Pal. 1968, is fragmentary with the hypapophysis and right prezygapophyseal process broken off, and strongly damaged paradiapophyses (Fig. 12 A-E). The vertebral centrum is cylindrical. In lateral view, the interzygapophyseal ridges are moderately developed. The completely preserved neural spine is about twice as long as high. Its cranial margin is inclined anteriorly whereas the caudal margin is inclined posteriorly. The small lateral foramina are situated in shallow depressions. The well-developed subcentral ridges are arched dorsally. In dorsal view, the prezygapophyseal articular facets are almost oval.The prezygapophyseal processes are about two thirds of the prezygapophyseal facets length. The cranial margin of the mostly damaged zygosphene has developed a wide medial lobe and small lateral lobes. The epizygapophyseal spines are absent. In ventral view, the hypapophysis expands laterally in a cranial direction to form a triangular anterior keel. The very small subcentral foramina are situated on both sides of the hypapophysis.In cranial view, the neural arch is slightly vaulted, and the neural canal is rounded with short lateral sinuses. The parapophyseal processes are separated from the rounded cotyle by deep furrows.The paracotylar foramina are situated on both sides of the cotyle. The left paracotylar foramen is doubled in Pal. 1968. The small paracotylar tubercles occur at the ventral margin of the cotyle. The vertebral dimensions of the figured specimen (Pal. 1968) are as follows: cl = 4.60 mm; naw = 2.72 mm; cl/naw = 1.69. The largest specimen (Pal.1481) measures as follows: cl = 4.93 mm; naw = 2.85 mm; cl/naw = 1.73. REMARKS Assignment to the “natricine” snakes is based on the presence of hypapophyses in precloacal vertebrae, the vaulted neural arch, the high neural spine, and the presence of paracotylar foramina on either side of the cotyle. The most complete vertebra with laterally directed prezygapophyses, an elongated centrum with a triangular anterior keel on the hypapophysis, and a neural spine inclined both anteriorly and posteriorly permit identification of the preserved vertebrae to the genus Natrix whose fossil remains are abundant in Central Europe as early as the early Miocene (Ivanov 2002a; Čerňanský et al. 2015). Natrix sp. differs from early Miocene N. merkurensis Ivanov, 2002 (MN 3a-?MN 4; Ivanov 2002a; Rage & Bailon 2005) in its smaller dimensions, elongated prezygapophyseal facets, shorter prezygapophyseal processes, and more distinct lateral lobes of the zygosphene. It differs from N. sansaniensis (Lartet, 1851), reported from the early and middle Miocene (MN 3-?MN 7+8; Augé & Rage 2000; Ivanov 2000, 2002a, b), in the less vaulted neural arch and flattened prezygapophyseal processes (Szyndlar 2005). N. longivertebrata Szyndlar, 1984 reported from the late Miocene (MN 9, MN 10/11; Ivanov 1997; Tempfer 2005) and Pliocene (MN 14-MN 16; Szyndlar 1984, 1991b; Venczel 2001), and doubtfully as early as the middle Miocene (?MN 6-?MN 7+8; Rage & Szyndlar 1986; Szyndlar 1991c), has more elongated vertebrae and a much lower neural spine. Natrix sp. closely resembles the extinct N. rudabanyaensis Szyndlar, 2005 reported from the early late Miocene of Rudabánya, Hungary (MN 9a; Szyndlar 2005) and perhaps the middle Miocene of Tauţ, Romania (MN 7+8; Venczel & Ştiucă 2008) in: 1) the same height and shape of the neural spine; 2) moderately developed subcentral ridges; 3) elongated prezygapophyseal facets; and 4) flattened prezygapophyseal processes (Szyndlar 2005). However, the absence of the hypapophysis and paradiapophyses prevents alpha taxonomy.
Published as part of Ivanov, Martin, Čerňanský, Andrej, Bonilla-Salomón, Isaac & Luján, Àngel Hernández, 2020, Early Miocene squamate assemblage from the Mokrá-Western Quarry (Czech Republic) and its palaeobiogeographical and palaeoenvironmental implications, pp. 343-376 in Geodiversitas 42 (20) on page 363, DOI: 10.5252/geodiversitas2020v42a20, http://zenodo.org/record/4447563
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