NATRICINAE, Bonaparte, 1838

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, Geodiversitas 42 (20), pp. 343-376 : 365

“ NATRICINAE ” indet.

( Fig. 12 F-I)

cf. Neonatrix sp. – Ivanov et al. 2006: 229, table 2.

MATERIAL. — MWQ, early Miocene, Burdigalian, Orleanian, MN 4: 1/2001 Turtle Joint: One trunk vertebra (Pal. 1483). 2/2003 Reptile Joint: Four trunk vertebrae (Pal. 1970-1973).

DESCRIPTION

Trunk vertebrae

The most complete vertebra (Pal. 1483) has strongly damaged prezygapophyses and the zygosphene, and the neural spine is broken-off close to its base.In lateral view,the interzygapophyseal ridges are moderately developed and lateral foramina are situated within deep depressions.The subcentral ridges are nearly straight. The distal termination of sigmoid hypapophysis does not reach posterior to the caudal border of condyle. In dorsal view, the vertebra is cylindrical, the damaged zygosphene was wide relative to the neural arch width. Epizygapophyseal ridges are absent. In ventral view, the subcentral grooves are very shallow and short and the subcentral foramina are rather small and situated just posterior to the base of the hypapophysis. The subcotylar tubercles are missing.The damaged postzygapophyseal articular facets have a subrectangular outline and are not elongated laterally. In cranial view, the neural arch is slightly vaulted, and the large neural canal has developed conspicuously large and wide lateral sinuses.The cranial margin of the zygosphene was arched dorsally.The small paracotylar foramina are situated within wide depressions on either side of the rounded cotyle. The vertebral dimensions of the best-preserved specimen (Pal. 1483) are: cl = 3.51 mm; naw = 2.24 mm; cl/naw = 1.57.

REMARKS

The sigmoid shape of the hypapophysis, with an anterior keel sloping towards the cotylar rim is reminiscent of precaudal vertebrae of the genus Palaeonatrix Szyndlar, 1982 (seeMłynarski et al. 1982) reported from the early Miocene (MN 4) of Dolnice, Czech Republic ( Rage & Roček 1983; Szyndlar 1987), Petersbuch 2 and Langenau, Germany ( Szyndlar & Schleich 1993), Oberdorf, Austria ( Szyndlar 1998) and the middle Miocene of Sansan, France (MN 6; Augé & Rage 2000) and Opole, Poland (MN 7+8; Młynarski et al. 1982). However, a generic allocation is impossible because the relatively low neural spine which characterizes the genus Palaeonatrix ( Szyndlar 1987, 1991b) is not preserved in studied specimens from MWQ. Although the very strongly developed subcentral ridges are typical for the genus Palaeonatrix ( Szyndlar 1987) we cannot exclude the possibility that the subcentral ridges were shorter and less distinct in vertebrae situated anterior to the preserved vertebra. Because of the limited fossil material and lack of information on intracolumnar variability, a more precise assignment is not possible.

Figures

FIG. 12. — Natrix sp. and “Natricinae” indet. from the early Miocene (MN 4) of MWQ. Natrix sp.: trunk vertebra Pal. 1968 (2/2003 Reptile Joint) in left lateral (A), dorsal (B), ventral (C), cranial (D) and caudal (E) views.“Natricinae” indet.:trunk vertebra Pal. 1483 (1/2001 Turtle Joint) with preserved hypapophysis in left lateral (F), dorsal (G), ventral (H) and caudal (I) views. Abbreviations: ak, anterior keel; cd, condyle; ct, cotyle; es, epizypapophyseal spine; hy, hypapophysis; lf, lateral foramen;nc, neural canal;ns, neural spine;pctf, paracotylar foramen;po, postzygapophysis;pof, postzygapophyseal articular facet;prf, prezygapophyseal articular facet; prp, prezygapophyseal process;scf, subcentral foramen;scg, subcentral groove;scr, subcentral ridge;zy, zygosphene;zyg, zygantrum.Scale bars:2 mm.