Viperinae Oppel, 1811b

Viperinae Oppel, 1811b

Viperinae (“Oriental Vipers”) indet.

Figure 60 View Fig

Material. Spilia 3: one fang ( UU SP3 601), two trunk vertebrae ( UU SP3 674 and UU SP3 675), and six fragments of trunk vertebrae ( UU SP3 676).

Description.

Te isolated fang (UU SP3 601) from Spilia 3 is relatively complete ( Fig. 60a–e View Fig ). Te specimen is relatively large. Te apical termination is slightly curved, with a wide pulpal cavity and the venom canal situated anteriorly in central position. In dorsal view ( Fig. 59e View Fig ), the base of the entrance orifice, which is situated in the anteriormost proximal part of the element, is indicated by the separation of the dentine folds which form the anterior closure of the venom canal. In anterior view ( Fig. 60c, d View Fig ), there is a distinct suture close to the distal termination of the element. Tis suture turns proximally into a narrow groove, which diminishes in front of the entrance orifice base where the fang surface is completely smooth. Te discharge orifice is preserved. A wide groove occurs on both lateral sides of the fang along its entire length.

Te few available vertebrae from Spilia 3 are rather fragmentary, missing in fact, most parts of the vertebral body ( Fig. 60f, g View Fig ). Despite their fragmentary nature, they are characterized by a large overall size, massive cotyle and condyle, and the presence of hypapophysis.

Remarks. Te fang can be referred to Viperidae based on the presence of a closed venom canal (Edmund, 1969; Kardong, 1979; Zahradnicek et al., 2008). Te large size of the fang suggests a probable referal to the “Oriental Vipers” complex. In fact, the fang looks very similar with the fang of “Oriental vipers” described by Georgalis et. al. (2019b, fig. 38.6–10) from the nearby (and slightly older; MN 13/14) locality of Maramena. Te fragmentary vertebrae can be referred to Viperidae based on their massive nature, the relatively short centrum, the presence of hypapophysis, and the dorsal inclination of the prezygapophyses in anterior view (Georgalis et al., 2016a; Szyndlar, 1984, 1991b; Zaher et al., 2019). Unfortunately, important viperid features, such as the anteroventral inclination of the parapophyses, the shape and inclination of the hypapophysis, the height of the neural spine, and the strongly depressed neural arch, are not preserved in the available vertebrae from Spilia, precluding thus a more precise identification. Nevertheless, as in the case of the fang above, the large size of the vertebrae suggests a probable referral to the “Oriental Vipers” complex.

Colubriformes incertae sedis

Periergophis Georgalis, Villa, Ivanov, Vasilyan & Delfino, 2019b

Periergophis micros Georgalis, Villa, Ivanov, Vasilyan & Delfino, 2019b

Figures 61 View Fig , 62 View Fig

Material. Spilia 1: one posterior mid- or posterior trunk vertebra ( UU SP1 1011); Spilia 4: one anterior trunk vertebra ( UU SP4 550), three trunk vertebrae ( UU SP4 539, UU SP4 619, and UU SP4 623), and eight caudal vertebrae ( UU SP4 542– UU SP4 545, UU SP4 547, UU SP4 548, UU SP4 620, and UU SP4 658).

Description.

A few trunk vertebrae were available in our sample from Spilia 1 and Spilia 4 ( Fig. 61 View Fig ). UU SP4 550 is an anterior trunk vertebra, judging from the presence of a hypapophysis ( Fig. 61a–c View Fig ). Te specimen has small dimensions, blunt subcentral ridges, and the anterior margin of the neural spine is inclined posteriorly. Te zygosphene in this specimen is distinctly trilobed and the posterior median notch of the neural arch is rather deep. Te hypapophysis is not fully preserved, but it seems that it was somehow posteroventrally inclined in lateral view; in ventral view, this structure crosses the whole midline of the ventral surface of the centrum.

Te remaining trunk vertebrae from Spilia 4 ( UU SP4 539, UU SP4 619, and UU SP4 623) and the single vertebra from Spilia 1 ( UU SP1 1011) are all posterior mid- or posterior trunk vertebrae, judging from the wide haemal keel and the deep subcentral grooves ( Fig. 61d–m View Fig ). However, they all lack the characteristic haemal keel tubercles that are known for the posterior trunk vertebrae of this species from the type locality of Maramena. In these small vertebrae, the haemal keel is considerably wide, running throughout the midline of the centrum. Te haemal keel possesses a distinctive constriction, situated posteriorly from the level of the synapophyses; the degree of this constriction varies, being apparently dependent on the vertebral position on the column, and is particularly prominent in UU SP4 619 ( Fig. 61k View Fig ). Te neural spine is dorsoventrally short; when fully preserved, its anterior margin is straight to posteriorly inclined. Te neural arch is much depressed, with a vaulting ratio sensu Georgalis et. al, (2021b) ranging between 0.22 and 0.28. Te zygosphene is trilobed, with the two lateral lobes being considerably prominent. Te prezygapophyseal accessory processes are relatively long and acute. Te synapophyses are clearly separated into diapophysis and parapophysis. Cotyles and condyles are small and almost circular .

All available caudal vertebrae from Spilia 4 are incomplete, with their haemapophyses being mostly damaged

( Fig. 62 View Fig ). Because of this incompleteness, in most specimens it is not possible to assess whether or not the, presumably autapomorphic, haemapophyseal tubercles were indeed present in these vertebrae, as in the case of most caudal vertebrae from the type locality of Maramena. Te only two caudal vertebrae that do possess more or less complete haemapophyses ( Fig. 62h, n View Fig ) do not show any evidence of haemapophyseal tubercles, but as it was already suggested by Georgalis et. al. (2019b), this presence/absence across the column might be subjected to intracolumnar variation. Te caudal vertebrae possess large subcentral foramina and unusual “lateral wings”, situated close to the base of the broken off pleurapophyses. Tese distinctive “lateral wings” are actually present in all available caudal vertebrae. Te pleurapophyses are elongated, pointed, and face anteroventrally. Te neural spine is dorsoventrally rather short; its posterior margin is either almost vertical or inclined anteriorly ( Fig. 62h, k, m, n, r View Fig ). Large lateral foramina are present below the interzygapophyseal ridges. Cotyles and condyles are small and almost circular. Paracotylar foramina are present. Te more elongated vertebra UU SP4 543 represents a more posterior caudal vertebra than the other specimens ( Fig. 62f–i View Fig ) .

Remarks. Te material from Spilia 1 and Spilia 4 resembles Periergophis micros , otherwise known from the nearby Maramena, in regards to the following features: trunk vertebrae with anterior margin of the neural spine being posteriorly inclined, rather wide haemal keel with a constriction present posteriorly to the synapophyses, zygosphene with distinct lateral lobes, a depressed neural arch, large parapophyses, and a small size with an overall light structure (see Georgalis et al., 2019b). However, the most prominent diagnostic feature (the presumed autapomorphy) of this species is not evident in the Spilia sample: the distinct paired anteroventrally directed tubercles or short processes developed on the wide haemal keel of posterior mid- and posterior trunk vertebrae and the haemapophyseal tubercles separated from the remaining part of haemapophyses in caudal vertebrae, at least in a portion of the caudal series (Georgalis et al., 2019b). We here interprete this absence of this feature as:

i) intracolumnar variation: the few available Spilia trunk vertebrae pertain to a part of the posterior mid- or anterior posterior trunk portion of the vertebral column that was genuinely not characterized by the presence of haemal keel tubercles. Similarly, the available caudal vertebrae from Spilia originate from a portion of the caudal vertebral column that was genuinely not characterized by the presence of haemapophyseal tubercles. As also suggested by Georgalis et. al. (2019b, p. 45), “an alternative explanation would be that in some portion of the caudal series, the haemapophyseal tubercles are substituted by strongly ventrally exposed anterior thickenings of the haemapophyses”.

ii) chronospecific variation: Spilia is younger than Maramena and eventually this structure disappeared from this lineage. In this case, perhaps the Spilia sample would pertain to a different species within the genus Periergophis .

iii) taphonomy: these structures were originally present in (certain of) the Spilia specimens but have been eroded/faded out due to preservational/taphonomical issues.

Worth mentioning is that in our sample there are more available caudal vertebrae compared to trunk ones; Smith (2013) had proposed that in fossil localities, such high percentages of caudal versus trunk vertebrae could be indicative of snakes with long tails. However, based on such limited sample from Spilia, it is premature to assume anything about the tail proportions of the Spilia Periergophis . Moreover, the original material of Periergophis micros from the type locality of Maramena consisted of much more trunk vertebrae compared to caudal ones.

Paraxenophis Georgalis, Villa, Ivanov, Vasilyan &