Natrix rudabanyaensis Szyndlar, 2005

Natrix rudabanyaensis Szyndlar, 2005 Natrix aff. rudabanyaensis

Figures 49 View Fig , 50 View Fig , 51 View Fig , 52 View Fig

Material: Spilia 0: 12 trunk vertebrae ( UU SP0 153– UU SP0 164) and one caudal vertebra ( UU SP0 165); Spilia 1: one caudal vertebra ( UU SP1 1012); Spilia 4: 19 trunk vertebrae [ UU SP4 565, UU SP4 566, and UU SP4 568 (17 vertebrae)]; Vevi: Four anterior trunk vertebrae ( UU VE 603– UU VE 606), 10 mid-trunk vertebrae ( UU VE 607– UU VE 616), three posterior trunk vertebrae ( UU VE 617– UU VE 619), and nine caudal vertebrae ( UU VE 620– UU VE 628).

Description.

Te description of the trunk vertebrae is mainly based on the specimens from Vevi, which are more complete

( Fig. 49 View Fig ). Te vertebrae are lightly built. All specimens are at least partially fragmentary with the neural spine broken off close to its base (but see Fig. 51g View Fig for a perfectly preserved neural spine of a single specimen from Spilia 0). In lateral view ( Fig. 49a, f, k, n View Fig ), the anterior margin of the neural spine of the best-preserved mid-trunk vertebra ( UU VE 607 ) extends anteriorly to the level of the posterior margin of the zygosphenal facet. Te zygosphenal facet is markedly large and rhomboid. Tere is a distinct blunt ridge developed at the posterior margin of the zygosphenal facet which extends from the base of the anterior neural spine base. Te well-developed interzygapophyseal ridges are usually sharp. Te lateral foramen is situated close below the interzygapophyseal ridge. Te dorsally arched subcentral ridges are prominent. Te diapophyses are well-separated from the equally sized parapophyses. Te anteriorly directed parapophyseal processes are moderately long and they are well-separated from the parapophyseal facets. Te only preserved complete hypapophysis of one specimen ( UU VE 609 ) is sigmoid with blunt distal tip situated slightly anterior to the posterior margin of the condyle

( Fig. 49k View Fig ). Te condyle is developed on a rather short condylar neck. In dorsal view ( Fig. 49b, g, o View Fig ), the zygosphene has pointed lateral lobes and a rather wide medial lobe. Te prezygapophyseal articular facets are widely oval; however, prezygapophyseal accessory processes are broken off close to their base. Te epizygapophyseal spines are moderately developed but sometimes they are indistinct as a result of surface abrasion. Te posterior median notch of the neural arch is rather deep. Te diapophyses are directed posterolaterally. In ventral view ( Fig. 49c, l, p View Fig ), the hypapophysis extends anteriorly to form the triangular anterior keel with small subcotylar tubercles developed at the base of the cotylar rim. Teir distal tip is directed posterolaterally. Te converging subcentral ridges are straight and wide subcentral grooves occur between those ridges and narrow (almost sharp) hypapophysis. In posterior trunk vertebrae (UU VE 617; Fig. 49p View Fig ), the sharp subcentral ridges are markedly developed and the subcentral grooves are rather deep. Subcentral foramina are very small. Te postzygapophyseal articular facets are irregularly shaped. In anterior view ( Fig. 49d, i, m View Fig ), the thin zygosphenal roof is straight with a ventrally bent medial lobe. Te zygosphenal facets are slightly uplifted above the zygosphenal roof. Te neural canal is sub-squared with rather small lateral sinuses. Paracotylar foramina are situated in depressions on either side of the rounded cotylar rims. In posterior view ( Fig. 49e, j View Fig ), the neural arch is moderately vaulted, with a vaulting ratio (sensu Georgalis et al., 2021b) ranging between 0.32 and 0.39. Te zygantrum is wide. Te number of small parazygantral foramina is variable from 1 to 3 on either side. Te small condyle is almost orbicular with its ventral margin slightly depressed.

Trunk vertebrae from Spilia ( Figs. 51 View Fig , 52a–e View Fig ) are in most cases more fragmentary than those from Vevi. Nevertheless, they still afford some anatomical observations. In one specimen ( UU SP4 565; Fig. 52a–c View Fig ) from Spilia 4, the hypapophysis is complete, projecting ventrally and its termination does not extend posteriorly from the condyle. Some variation exists among the shape and direction of the neural spine: in one specimen ( UU SP4 566; Fig. 52d, e View Fig ) from Spilia 4, the posterior margin of the neural spine strongly overhangs posteriorly, whereas in a vertebra from Spilia 0 ( UU SP0 154; Fig. 51g View Fig ), the neural spine has its anterior margin straight to slightly anteriorly inclined and its posterior margin posteriorly inclined, and in another vertebra from the latter locality ( UU SP0 158; Fig. 51a View Fig ) it seems that both anterior and posterior margins of the neural spine are almost straight. Te neural arch of the Spilia trunk vertebrae is moderately depressed, with a vaulting ratio (sensu Georgalis et al., 2021b) ranging between 0.34 and 0.39 .

Te available caudal vertebrae from Vevi ( Fig. 50 View Fig ), Spilia 0, and Spilia 1 ( Fig. 52f View Fig ) are fragmentary with broken off pleurapophyses and haemapophyses. In lateral view ( Fig. 50d, i View Fig ), the neural spine is about twice longer than high in more anteriorly located caudal vertebrae whereas in posterior caudal vertebrae the neural spine is about three to four times longer than high. In the single caudal vertebra (UU SP1 1012) from Spilia 1, the neural spine has its anterodorsal margin strongly inclined anteriorly ( Fig. 52f View Fig ). In dorsal view ( Fig. 50b, e View Fig ), the zygosphene has distinct lateral lobes and a wide medial lobe. Prezygapophyseal articular facets are oval with their axis elongated anterolaterally. Prezygapophyseal accessory processes are pointed distally and about half of the length of the prezygapophyseal articular facets or they are shorter. In ventral view ( Fig. 50c, f View Fig ), pleurapophyses of anterior caudal vertebrae have narrow base and the preserved portions of pleurapophyses indicate that they were laterally rather than antero-laterally directed. In posterior caudal vertebrae the pleurapophyses with wide base are directed anteriorly. Tere is a distinct, posteriorly directed spur developed on the posterior margin of the pleurapophysis base.

Remarks. Te hypapophysis-bearing trunk vertebrae with triangular anterior keel, elongated centrum and well-developed epizygapophyseal spines correspond to a typical natricid morphology (Ivanov, 2002; Szyndlar, 1984, 1991b, 2005; Szyndlar & Schleich, 1993). Te referral to the genus Natrix is based on the following combination of features in mid-trunk vertebrae: 1, the neural spine is high; 2, the vertebrae with elongated centrum are cylindrical in shape; 3, the prezygapophyseal accessory processes are well developed; 4, the parapophyseal processes are moderately long and directed anteriorly rather than anteroventrally; 5, the hypapophysis is sigmoid with rounded distal tip. Tere are four extinct valid species of Natrix in the European Neogene: Natrix merkurensis Ivanov, 2002 (MN 3a–?MN 4; Ivanov, 2002; Rage & Bailon, 2005), Natrix sansaniensis (Lartet, 1851) (MN 3a–MN 4 and MN 6; Augé & Rage, 2000; Ivanov, 2002; Szyndlar & Schleich, 1993), Natrix rudabanyaensis (MN 9; Szyndlar, 2005), and Natrix longivertebrata Szyndlar, 1984 (widespread from the Early Miocene up to the Late Pliocene; Ivanov, 2022; Rage & Szyndlar, 1986; Szyndlar, 1984, 1991b; Vasilyan et al., 2022). A further species, Neonatrix natricoides Augé & Rage, 2000 , from the Early and Middle Miocene (MN 4 and MN 5) of France (Augé & Rage, 2000; Rage & Bailon, 2005), was considered a member of the genus Natrix by Szyndlar (2005, 2012); however, its rather short hypapophysis is unusual for Natrix , and therefore, even generic allocation of that species is uncertain (Ivanov, 2022). Te Natrix vertebrae from Vevi and Spilia particularly resemble those of N. rudabanyaensis by the following combination of features (see Szyndlar, 2005): 1, relatively small dimensions; 2, moderately elongated centrum; 3, elongated prezygapophyseal articular facets; 4, prezygapophyseal accessory processes long and moderately flattened dorsoventrally. However, the parapophyseal processes of N. aff. rudabanyaensis from Vevi and Spilia are shorter and the epizygapophyseal spines are less distinct, compared to those of N. rudabanyaensis from the Late Miocene of Rudabanya ( Szyndlar, 2005). Admittedly, several vertebral features that are used to differentiate Neogene Natrix spp. are subjected to intracolumnar and intraspecific variation or are anyway widespread among natricids. A proper taxonomic referal of this Greek form can only be made once the taxonomy and diagnosis, and intracolumnar variation of the Neogene European species of Natrix is better assessed and revised, something that is well beyond the scope of the present study. For these reasons, we only tentatively refer the Greek material as Natrix aff. rudabanyaensis , as is the case with the material from Maramena that was recently described by Georgalis et. al. (2019b).

? Natricidae indet.

Figures 53 View Fig , 54 View Fig , 55 View Fig

Material. Chalicorrema: three trunk vertebrae ( UU RA 408– UU RA 410); Spilia 0: two trunk vertebrae ( UU SP0 151 and UU SP0 152); Spilia 2b: one trunk vertebra ( UU SP2b 501); Vevi: one anterior trunk vertebra ( UU VE 601).

Description. All hypapophysis-bearing trunk vertebrae from Chalicorrema are rather fragmentary ( Fig. 53 View Fig ). In the best-preserved anterior trunk vertebra (UU RA 408; Fig. 53a–c View Fig ), only the centrum with broken off distal tip of the hypapophysis and incomplete neural arch is present. In lateral view ( Fig. 53a View Fig ), the short interzygapophyseal ridge is well developed. A small lateral foramen is situated in a shallow depression close below the interzygapophyseal ridge. Te subcentral ridges are arched dorsally and extend from the base of a non-preserved parapophysis up to the vicinity of the base of the short condylar neck. In dorsal view

( Fig. 53d View Fig ), the only preserved left prezygapophyseal articular facet of one fragment ( UU RA 409 ) is irregularly oval to subtriangular in outline. Te prezygapophyseal accessory processes, broken off at their wide base, were most probably well developed in life. In ventral view ( Fig. 53b, e View Fig ), the subcentral grooves are narrow. Subcentral ridges extend parallel along their entire length. Te hypapophysis extends to the close vicinity of the cotylar rim but moderately developed triangular expansion of its base occurs anterior to minute subcentral foramina. Small subcotylar tubercles are developed close behind the base of the cotylar rim. Te subcentral foramina are situated in the middle of the centrum length, the left one is doubled in UU RA 408 ( Fig. 53b View Fig ) but multiple foramina (three on the right side plus two on the left side) occur in UU RA 409 ( Fig. 53e View Fig ). Te condyle is relatively small. In anterior view ( Fig. 53c, f View Fig ), the neural canal is rounded with wide lateral sinuses. Te paracotylar foramina, situated in narrow depressions on either side of the circular cotylar rim, are either doubled with upper foramen larger than the lower one ( UU RA 408 ; Fig. 53c View Fig ). However, only one large single left paracotylar foramen is present in one specimen ( UU RA 409 ; Fig. 53f View Fig ). Te ventral border of the cotylar rim is flat in this specimen ( Fig. 53f View Fig ) .

Te few vertebrae from Spilia 0 and Spilia 2 are rather fragmentary ( Fig. 54 View Fig ). Tey all possess hypapophyses, which are, however, much incomplete in all specimens. Neural spines, paradiapophyses, and parts of the prezygapophyses are much damaged in all specimens.

Te single specimen from Vevi (UU VE 601) represents an anterior trunk vertebra ( Fig. 55 View Fig ). Its right side is damaged with broken off right postzygapophysis, incomplete prezygapophyses, and the right paradiapophysis eroded. In lateral view ( Fig. 55a View Fig ), the neural spine rises at the level of the posterior margin of the zygosphenal facets. Te neural spine is high with its basal anterior margin inclined slightly posteriorly whereas its posterior margin is inclined anteriorly. Te distal termination of the neural a spine is not preserved. Te long axis of the strongly elongated zygosphenal facet is directed anteriorly rather than anterodorsally. Te anteroventrally directed lamina, situated below the interzygapophyseal ridge, forms the dorsal limitation of the wide depression ventrally limited by a straight subcentral ridge. A large lateral foramen is situated close to the dorsal margin of this depression. Te diapophysis is well separated from the parapophysis. Te parapophyseal process is short but its anterior termination is slightly eroded. Te condyle is separated from the centrum by a wide groove. Te anterior keel of the hypapophysis is only moderately inclined in ventral direction but this inclination is well developed in the middle of the centrum length indicating most probably posteroventral inclination of the distal tip of the hypapophysis. In anterior view ( Fig. 55d View Fig ), the neural arch bears no epizygapophyseal spines. Te neural canal is rounded with shallow lateral sinuses. Te zygosphenal lip is slightly arched dorsally with straight medial part. Te prezygapophyses are horizontal with broken off prezygapophyseal accessory processes. Paracotylar foramina are situated in depressions on either side of the cotyle. Te cotyle is rounded with slightly depressed ventral margin. Te only complete right subcotylar tubercle occurs at the base of the cotyle. In posterior view ( Fig. 55e View Fig ), the neural arch is strongly vaulted, with a vaulting ratio (sensu Georgalis et al., 2021b) equal to 0.52. A very large parazygantral foramen is situated near the edge of the postzygapophysis.

Remarks. All poorly preserved fragments of trunk vertebrae from Chalicorrema possess hypapophyses. Te well-developed subcentral grooves and ridges in the best-preserved vertebra indicate that this vertebra did not belong to the anterior trunk region. Although all hypapophyses are broken off close to their base, the anterior keel of the hypapophysis is triangular (UU RA 408, UU RA 409) with small subcotylar tubercles which frequently occurs in Natricidae (e.g., Szyndlar & Schleich, 1993; Szyndlar, 1984, 1991b, 2005). Te only preserved left prezygapophysis of UU RA 409 is horizontal in anterior view. Although the anterior keel of the hypapophysis is reminiscent of that of Natrix aff. rudabanyaensis described above from Spilia and Vevi (see above), even an assignation of the Chalicorrema snakes to natricids is not safe and it should be eventually confirmed solely by better preserved material.

As for the few specimens from Spilia 0 and Spilia 2, all preserved vertebrae are too fragmentary with broken off hypapophyses, neural spines and paradiapophyses ( Fig. 54 View Fig ). Te elongated centrum, the presence of hypapophysis with distinct triangular anterior keel, as well as the presence of short epizygapophyseal ridges enable identification of these fragmentary vertebrae as possibly belonging to natricids (Head, 2005; Ivanov, 2002; Szyndlar, 1984, 1991b). Although an assignation of this material to the genus Natrix , already identified in Spilia 0 on the basis of several more complete specimens, seems probable, the absence of important diagnostic structures hinders even an exact family-level identification.

As for the Vevi specimen, this anterior trunk vertebra (UU VE 601) possesses a triangular anterior keel with distinct subcotylar tubercles and almost straight subcentral ridges in lateral view ( Fig. 55 View Fig ). Te first two features typically occur in large specimens of Natrix -like snakes. Tus, we tentatively assign UU VE 601 to? Natricidae indet.

Colubroidea indet.

Figures 56 View Fig , 57 View Fig , 58 View Fig Material. Spilia 0: Two anterior trunk vertebrae (UU SP0 166 and UU SP0 167); Spilia 4: an anterior trunk vertebra (UU SP4 507) and one trunk vertebra (UU SP4 618); Vevi: a mid-trunk vertebra (UU VE 602).