Naja romani ( Hoffstetter, 1939 )

Syromyatnikova, Elena, Tesakov, Alexey & Titov, Vadim, 2021, Naja romani (Hoffstetter, 1939) (Serpentes: Elapidae) from the late Miocene of the Northern Caucasus: the last East European large cobra, Geodiversitas 43 (19), pp. 683-689 : 685-686

Naja romani ( Hoffstetter, 1939)

( Fig. 2 )

MATERIAL EXAMINED. — One precloacal vertebra GIN 1145/305, Solnechnodolsk locality, Northern Caucasus, Russia; late Turolian, MN 13 .

DESCRIPTION

The vertebra is large and robust with a centrum length of 9.2 mm and width of 9.7 mm.The CL/NAW (centrum length/ width of interzygapophyseal constriction) ratio is 0.95. The constriction between the pre- and postzygapophyses is weakly developed. From the ventral view, the subcentral ridges are well developed and relatively straight. The subcentral grooves are deep. The hypapophysis is very long and laterally compressed. It is directed ventrally and slightly posteriorly, with its posterior tip being obtuse and protruding posteriorly to the level of the condyle. The neural spine is relatively long and low, and incomplete in its mid length. The neural arch is markedly vaulted. The synapophyses are broken, but the left parapophyseal process is partly preserved and projected anteriorly and slightly ventrally. The zygosphenal roof is concave in dorsal view, presenting a small prominence in the middle of its width that can be considered as minute median lobe. In anterior view, the zygosphenal roof is straight. The prezygapophyseal articular facets are nearly circular.The prezygapophyseal process is missing on the left side, but completely present on the right side where it is well developed and relatively long (about half as long as the prezygapophyseal articular facet). It is obtuse distally. The postzygapophyseal articular facets are nearly rounded. The cotyle is slightly dorsoventrally compressed whereas the condyle is circular. The subcentral, lateral, and paracotylar foramina are clearly visible. The lateral and paracotylar foramina are situated in deep and wide depressions.

COMPARISON AND REMARKS

The presence of hypapophysis is a typical distinctive feature for snakes of the families Natricidae , Viperidae , and Elapidae ( Szyndlar 1991) . Thus, the vertebra GIN 1145/305 can be assigned to one of these groups. The large size, robustness, and inclination of hypapophysis (directed ventrally rather than postero-ventrally) preclude the attribution of GIN 1145/305 to Natricidae . The shape and inclination of hypapophysis in GIN 1145/305 correspond to that of the vertebrae of Viperidae , however the vertebrae of the latter group have a dorso-ventrally depressed neural arch and larger cotyle and condyle. The laterally compressed hypapophysis and the very low neural spine observed in GIN 1145/305 are characteristic of Elapidae and “ Naja group” ( Szyndlar 1991). Elapid fossil finds often offer, well preserved cranial elements, which are useful keys for determining the fossil species. Accordingly, isolated elapid vertebrae are not very informative. Naja romani is currently the only recognized species of Naja in Central and Eastern Europe (a possible alternative opinion was announced by Quadros et al. 2019). The material herein can be assigned to N. romani based on long prezygapophyseal processes and presence of the concave zygosphene with minute median lobe. The vertebra likely comes from the anterior precloacal region of the vertebral column based upon the relatively vaulted neural arch and the morphology of the hypapophysis, which is directed rather ventrally than postero-ventrally.

The precloacal vertebrae of N. romani are well described from Kohfidisch, Petersbuch 2 and Vieux-Collonges. In contrast to the precloacal vertebrae of N. romani from Kohfidisch (originally described as N. austriaca Bachmayer & Szyndlar, 1985 and synonymized with N. romani by Szyndlar & Zerova in 1990), in the vertebra from Solnechnodolsk the neural arch is vaulted and the hypapophysis is narrower and more ventrally directed. The vertebra from Solnechnodolsk is more similar to the vertebra of N. romani described as cervical ( Szyndlar 1985: fig. 5.9) in direction of the hypapophysis, but the latter one is widely rounded distally in lateral view.

The material attributed to N. romani from Petersbuch 2 presents several precloacal vertebrae ( Szyndlar & Schleich 1993). Among them, the vertebra from Solnechnodolsk is most similar to those described as anterior cervical vertebrae ( Szyndlar & Schleich 1993: fig. 7C-D) in presenting a slender hypapophysis. However, the vertebra from Solnechnodolsk differs from the anterior cervical from Petersbuch 2 in retaining a more anteriorly directed parapophyseal process. The vertebra from Solnechnodolsk is also similar to the anterior precloacal vertebra of Naja cf. romani from Vieux-Collonges ( Ivanov 2000: fig. 12A-D). However, the vertebra from Solnechnodolsk clearly differs from all known precloacal vertebrae of Naja romani in having less developed interzygapophyseal constriction. The only exception is the vertebra with poorly developed interzygapophyseal constriction from Kohfidisch figured by Tempfer (2005: pl. 10a-d). In having the poorly developed interzygapophyseal constriction the vertebra from Solnechnodolsk is more reminiscent of Naja from the late Pliocene of Tourkobounia 1 ( Greece; Szyndlar & Zerova 1990). Among the other species of Naja , precloacal vertebrae were described for N. iberica ( Szyndlar 1985) . The vertebra from Solnechnodolsk differs from anterior precloacal vertebrae of N. iberica in having a distally pointed hypapophysis and from posterior precloacal vertebrae in having a more obtuse prezygapophyseal processes.

It is worth noting that intracolumnar variation of some precloacal vertebrae of Naja romani was mentioned by Szyndlar & Zerova (1990) and Szyndlar (2005). There is no doubt that intracolumnar variation is also present in the anterior precloacal region, though it is not described due to the scarcity of the material. Until new material from different vertebral regions are discovered for N. romani , we consider the abovementioned variations of Naja from Solnechnodolsk (poorly developed interzygapophyseal constriction and morphology of the hypapophysis) to be intracolumnar variations.

Figures

FIG. 2. — The precloacal vertebra of Naja romani (Hoffstetter, 1939) from Solnechnodolsk locality in dorsal (A), ventral (B), left lateral (C), right lateral (D), anterior (E) and posterior (F) views. Scale bar: 5 mm.