Natrix sansaniensis ( Lartet, 1851 )

Ivanov, Martin, 2002, The oldest known Miocene snake fauna from Central Europe: Merkur-North locality, Czech Republic, Acta Palaeontologica Polonica 47 (3), pp. 513-534 : 523-525

Natrix sansaniensis ( Lartet, 1851)

(part) Coluber Sansaniensis ; Lartet 1851: 40.

Pylmophis sansaniensis Lartet ; Rochebrune1880:282–283,pl.XII:11. Pilemophis sansaniensis Rochebrune ; Lydekker 1888: 251. Pylmophis sansaniensis Rochebrune nec Lartet; Młynarski 1961: 33. Pylmophis sansaniensis Rochebrune ; Kuhn 1963: 29.

Natrix sansaniensis (Lartet) ; Rage 1981: 538–540, fig. 1A.

Natrix sansaniensis (Lartet) ; Rage 1984: 48–49, fig. 30A.

Material.—Six compound bones (3 left + 3 right) ( SGDB Ah−291–295;SGDBAh−620),1trunkvertebra( SGDB 7408/ MI−84), 19 trunk vertebrae ( SGDB Ah−296–311; SGDB Ah−621–623).

Compound bone ( Fig. 7A 1 –A 3 , B).—The left compound bone is fragmentary and its rostral part and the retroarticular processarebrokenoff.Thelabialflangeofthecomparatively deep mandibular fossa is almost as high as the lingual flange. The labial flange is concave through its entire length and is bordered ventrally by a distinct ridge that extends from distinct supraangular crest to the proximity of the large supraangular foramen. This foramen is situated far from the rostral end of the markedly enlarged mandibular fossa that is narrow in its rostral part. Adistinct groove continues anteriorly from the rostral termination of the mandibular fossa. This groove is formed by a connection of the labial and the lingual flange. Alow but obvious crest extending from the base of the retro − articular process to the proximity of the rostral end of the mandibular fossa occurs on the inner side of the lingual flange. This crest never reaches the dorsal margin of the lingual flange.

Trunk vertebrae ( Fig. 7C 1 –C 5 ).—In lateral view, the neural spine is about 2–3 times longer than high; its cranial margin overhangs anteriorly and the caudal margin overhangs posteriorly. The interzygapophyseal ridges are distinct. The lateral foramina are minute and hardly visible and occur in shallow depressions. The paradiapophyses are indistinctly divided and the diapophyses are directed postero−laterally. The parapophyseal processes are short. The subcentral ridges are prominent especially in posterior trunk vertebrae and they are straight and extend to the short neck on which the rounded condyle occurs. The hypapophysis has a distinct anterior keel, the border of which, slopes postero−ventrally. The distal tip of the hypapophysis is directed caudally. In dorsal view, the zygosphene has distinct lateral lobes and the median lobe is wide and rounded. The enlarged prezygapophyseal articular facets are oval to subtriangular and the slen− der prezygapophyseal processes are obtuse and may be as long or shorter than the prezygapophyseal facets. The epizygapophyseal spines are well developed. In ventral view, the anterior keel of the hypapophysis is triangular anteriorly and the small but distinct subcotylar tubercles are situated at the base of the cotyle. The tiny and hardly visible subcentral foramina occur at the base of the hypapophysis. The laterally slightly enlarged and irregularly shaped postzygapophyseal articular facets are damaged in most vertebrae. In cranial view, the neural arch is moderately vaulted and the neural canal is rounded with distinct lateral sinuses. The cotyle is rounded and distinct paracotylar foramina occur on either side of the cotyle in conspicuous (but sometimes also shallow) depressions. Measurements are as follow (n = 12): cl: or = 4.21–5.82 mm; naw: or = 2.52–3.58 mm; cl/naw: or = 1.39–1.80, mean 1.64±0.11.

Comments.— Natrix sansaniensis ( Lartet, 1851) represents an extinct species of a small natricine snake. Adiagnosis of this taxon including precise description of vertebrae was proposed by Augé and Rage (2000). Extinct species of the genus Natrix have not been defined on the basis of cranial bones but only by the structure of vertebrae (with the exception of Natrix longivertebrata Szyndlar, 1984 and now also of N. sansaniensis and N. merkurensis sp. nov.). The compound bone resembles especially that of N. natrix but there are several differences: 1, the rostral part of the bone is flattened unlike N. natrix ; 2, the mandibular fossa of N. sansaniensis is comparatively longer, narrower and deeper than it is in N. natrix ; moreover, it markedly narrows in anterior direction in N. sansaniensis ; 3, the labial flange is higher in N. sansaniensis than it is in N. natrix ; 4, a distinct groove extends from the rostral termination of the mandibular fossa in N. sansaniensis ; this groove is absent in all living and fossil representatives of N. natrix .

The vertebrae (one vertebra was originally assigned to Natricinae C, Ivanov 1997a: 120, fig. 54) are very similar to those of the recent representatives of the genus Natrix . The vertebral centra are elongated and the neural spines are very highandoverhanginginbothanteriorandposteriordirections. N. sansaniensis resembles the recent species N. tessellata in having the sigmoid hypapophysis with a pointed distal tip but the prezygapophyseal articular facets are not elongated in N. sansaniensis . Vertebrae of N. sansaniensis differ from those of the extinct species N. merkurensis sp. nov. in having a pointed distalterminationofthehypapophysiswhilein N. merkurensis sp. nov. this termination is obtuse. Vertebrae of the extinct species N. longivertebrata are more elongated, the parapophyseal processes are longer and the hypapophysis extends behind the caudal margin of the condyle. It is possible that N. sansaniensis is closely related to the living species N. natrix . This is documented not only by the vertebral structure but also by the very similar structure of the compound bone.

Figures

Fig. 7. Natrix sansaniensis (Lartet, 1851) from the Early Miocene (MN 3a) of Merkur−North. A1–A3. Left compound bone (SGDB Ah−291). B. Right compound bone (SGDB Ah−620). C1–C5. Precaudal vertebra (SGDB Ah−296). In labial (A1, B), lingual (A2), dorsal (A3, C4), lateral (C1), cranial (C2), ventral (C3), and caudal (C5) views. Scale bar 2 mm.

Fig. 1. The distribution of some Early and Middle Miocene ophidian localities in the areas of Germany, Czech Republic, Slovak Republic, Poland and Austria. 1, Weisenau (MN 1); 2, Hessler (MN 1); 3, Ulm−Westtangente (MN 2); 4, Stubersheim 3 (MN 3); 5, Merkur−North (MN 3a); 6, Dolnice (MN 4); 7, Petersbuch 2 (MN 4); 8, Langenau (MN 4); 9, Oberdorf (MN 4); 10, Randecker Maar (MN 5); 11, Eichstätt (MN 4–6); 12, Ivančice (MN?4–6); 13, Oggenhausen (MN 5/6); 14, Przeworno (MN 5–6); 15, Devínska Nová Ves (MN 6); 16, Vösendorf; 17, Sandelzhausen (MN 6); 18, Rothenstein 13 (MN 6); 19, Opole (MN 7); 20, Öhningen (MN 7+8); 21, Steinheim am Albuch (MN 7+8).

Fig. 3. Coluber dolnicensis Szyndlar, 1987 from the Early Miocene (MN 3a) of Merkur−North. A1, A2. Left dentary (SGDB Ah−12). B1, B2. Right compound bone (SGDB Ah−l 4). C. Left compound bone (SGDB 7408/MI−9). D1–D4. Cervical vertebra (SGDB 7408/MI−5). E1–E5. Trunk vertebra (SGDB 7408/MI−7). F1–F3. Caudal vertebra. In labial (A1, B1), lingual (A2, B2, C), lateral (D1, E1), dorsal (D2, E2, F1), ventral (D3, E3, F2), cranial (D4, E4, F3), and caudal (E5) views. Scale bar 2 mm.

Fig. 5. Coluber caspioides Szyndlar and Schleich, 1993 from the Early Miocene (MN 3a) of Merkur−North. A1, A2. Left frontal (SGDB Ah−44). B. Right palatine (SGDB Ah−46). C1, C2. Right pterygoid (SGDB Ah−45). D. Right quadrate (SGDB Ah−l 1). E. Left dentary (SGDB Ah−48). F1, F2. Right compound bone (SGDB Ah−49). G1–G5. Cervical vertebra (SGDB Ah−51). H1, H2. Mid−trunk vertebra (SGDB Ah−615). I1–I5. Posterior trunk vertebra (SGDB 7408/MI−37). In dorsal (A1, C1, G2, H2, I2), ventral (A2, B, C2, G3, I3), postero−lateral (D), labial (E, F1), lingual (F2), lateral (G1, H1, I1), cranial (G4, I4), and caudal (G5, I5) views. Scale bar 2 mm.