A REVIEW OF NEOGENE AND QUATERNARY SNAKES OF CENTRAL AND EASTERN EUROPE. PART 11: NATRICINAE, ELAPIDAE, VIPERIDAE

Remains of Neogene and Quaternary "natricine" colubrids, elapids and viperids, including snakes previously described and those undescribed yet, coming from Poland, Ukraine, Moldavia, Czechoslovakia, Austria, Hungary, Romania, Bulgaria, and Greece are discussed. The following taxa, including 11 extinct species, were recognized: "Natricinae": Neonatrix nova, Neonatrix sp., Palaeonatrix silesiaca, Palaeonatrix lehmani, Natrix longivertebrata, Natrix cf. N. longivertebrata, Natrix natrix, Natrix tesselata, Natrix cf. N. tesselata, Natrix sp., "Natricinae" indet.; Elapidae: Naja romani, Naja sp., cf. Naja sp.; Viperidae: Vipera platyspondyla, Vipera sarmatica, Vipera burgenlandica, Vipera gedulyi, Vipera kuchurganica, Vipera antiqua, Vipera cf. V. ammodytes, Vipera berus, Vipera sp. ('Oriental vipers' group), Vipera sp. ('aspis' group), Vipera sp. ('berus' group), Vipera sp. (status unknown). Taxonomic status of two other extinct species, Natrix parva and Laophis crotaloides, is uncertain. Modern species appeared fírst in Central and East Europe in the middle Pliocene (MN 15). Older snakes belonged to extinct species of either extinct or extant genera; taxonomic distinction of most extinct genera is, however, not fully demonstrated. Best recognized oldest snakes from the area (Elapidae, Viperidae, and sorne Colubridae) are clearly referable to modern genera and intrageneric subdivisions occurring today are observed in oldest (Iower Miocene) remains; closest living relatives of these fossils are presently distributed in the Oriental Realm.


Introduction
Toe present paper, devoted to Neogene and Quaternary "natricine" colubrids, elapids and viperids from Central and Eastern Europe, supplements Szyndlar's (1991) review of fossil scolecophidians, boids and "colubrine" colubrids coming from the same area.Table 1 lists aH ophidian taxa described in both papers.
The arrangement of the information presented below in the chapter "Systematic account" foHows exactly the system employed in my previous paper; see chapters "Localities" and "Systematic account" in Szyndlar (1991) for details.
The chapter "History of snakes in Central and East Europe" is based on the data presented in both papers and summarizes information about the composition and past distribution of the extinct snake fauna in the area, against the background of the recent fauna.The last chapter of the present paper, containing a critica!review of methods used in ophidian paleontology, summarizes my ten-years experience with research on Neogene and Quaternary European snakes.
The basic feature differentiating natricine vertebrae from those of other members of the family Colubridae (s.l.) is the presence of hypapohyses throughout the precaudal region of the column; colubrines possess hypapophyses in the cervical region only, while in the remaining precaudal vertebrae this structure is replaced by the haemal keel.Natricine vertebrae can be easily distinguished Z. SZYNDLAR from those belonging to other hypapophysis-bearing snakes.They differ from the Viperidae in having usuaIly sigmoid (and not straight) hypapohyses, posteriorly vaulted (and not depressed) neural arches, shorter parapophyseal processes, and usuaIly much longer centra (Szyndlar 1984(Szyndlar , 1988)).They differ from the Elapidae in having lightly built vertebrae, provided with much longer centra and strong subcentral ridges.In addition, the modero genus Natrix has relatively much higher neural spines than those of elapids.
Natricine snakes presently inhabiting Europe belong exclusive-Iy to the genus Natrix (see below).There are two valid extinct genera known from Europe, Neonatrix and Palaeonatrix.
Genus Neonatrix Holman, 1973.Neonatrix is an extinct genus, widespread in the North American and European Miocene (Holman, 1979;Rage, 1984;Rage and Holman, 1984).The most important diagnostic feature of this genus are strongly reduced hypapophyses.One species was reported from East Europe.
Diagnostic vertebral characters: This extinct species, known only from the type locality, is most similar to its North American relative, N. elongata, but differs from the latter in much larger absolute size.The centrum length of the holotype vertebra is 4.33 mm and it is 1.54 times longer than wide.For detailed description see Szyndlar (1987a).
Remarks: The vertebrae, somewhat damaged, c10sely resemble those of N. nova, but differ from them by smaIler absolute size and by having strongly reduced neural spines.Genus Palaeonatrix Szyndlar, 1982.This extinct genus consists of two species, P. silesiaea and P. lehmani, both from the East European Miocene.These snakes are known exclusively by vertebrae.The most important diagnostic features, differentiating Palaeonatrix from the living genus Natrix and sorne other related genera, are a prominent anterior keel accompanying the hypapophysis and a vestigial neural spine (Szyndlar 1987a).
Diagnostic vertebral characters: This species, known only from the type locality, differs from P. lehmani in sorne minor features, among others, in lacking the epizygapophyseal process, in having postzygapohyses less expanded latera1ly, and a relatively larger condyle.The largest vertebra has the centrum length 5.77 mm.For detailed description see Szyndlar in Mlynarski et al. (1982) and Szyndlar (1984).
Diagnostic vertebral characters: Vertebrae of this species are somewhat smaller than those of P. silesiaea.For differences between both species see aboye (P. silesiaea).
Remarks: This species, known exclusively from the tUJe locality, was originally described by Rage and Rorek (1983) as the only member of the extinct genus DolnieeoJ!his; it was then synonymized with Palaeonatrix by Szyndlar (1987a).For detailed description see Rage and Rocek (1983) and Szyndlar (1987a).
Genus Natrix Laurenti, 1768.The genus Natrix consists of four living members presently inhabiting Europe and adjacent areas of the West Paleartic.In ad-dition, four fossil species are known from Europe; their geological age ranges from the Oligocene to Upper Pliocene (Rage 1988).The most important feature differentiating Natrix from the extinct natricine genera is a distinctly higher neural spine.
Diagnostic vertebral characters: Trunk vertebrae of this extinct snake differ from other members of the genus Natrix by having stout and dorsoventrally flattened prezygapophyseal processes; a narrow centrum with the hypapophyseal basis continuing anteriorly by a salient ridge (Rage and Szyndlar 1986).The most distinct feature is an extreme elongation of vertebrae.The centrum length of 27 vertebrae from the type locality ranges between 4.27 and 5.58 mm and the centrum length/width ratio is 1.76-2.22(mean 1.92 ± 0.12); in another vertebra it reaches 2.30.
Remarks: Most cranial bones of this snake closely resemble those of the living N. natrix.The maxilla, quadrate and parietal are practically identical in both snakes; the compound of N. lon- givertebrata differs from that of N. natrix by presence of a distinct concavity below the posterior end of the lateral flange.The main difference between both species is in the posteriormost area of the basiparasphenoid: in N. longivertebrata the posterior orifices of the Vidian canals are hidden inside bony recesses.This condition is also observable in basiparasphenoids from the French Miocene (described as Natrix afi.longivertebrata by Rage and Szyndlar 1986).In N. natrix, recesses housing the orifices are largely absent; of about 170 examined basiparasphenoids of (recent and Pleistocene) N. natrix, the pattern characteristic for N. longivertebrata occurred in three examples only.A, left lateral view; B, anterior view; C, posterior view; D, dorsal view; E, ventral view.Scale equals 2 mm (From Szyndlar 1984).
Remarks: The aboye listed materials do not differ essentially from the vertebrae of N. longivertebrata from the type locality.
Diagnostic vertebral characters: Trunk vertebrae of N. natrix differ from those of both N. tesselata and N. maura by having obtuse distal hypapophysis and parapophyseal processes.The homologous structures of the two latter species are characterized by pointed tips (Szyndlar 1984, fig. 7); it is to be noted, however, that these observations were based on few specimens.Skeletons of N. megalocephala were not available for study.The centrum length of the largest vertebrae of N. natrix rrom two Polish upper Pleistocene localities (90 bones altogether) was 3.81-5.90mm and 4.17-5.60mm; the centrum lengthlwidth ratio was 1.45-1.90(mean 1.63 ± 0.11) and 1.57-2.07(mean 1.74 ± 0.10), respectively (Szyndlar 1984).
Remarks: (9) (25) (56) (57) Vertebrae examined personally by me are usually well preserved and display clearly the diagnostic features characteristic for N. natrix. (35) No comment to his report of the presence of Natrix aff.natrix in the Moldavian Pliocene was given by Redkozubov (1987).
Diagnostic vertebral characters: For differences between vertebrae of N. tesselata and N. natrix see the diagnosis of N. natrix
(44) Regarding the presumed presence of N. tesselata in the Miocene of Polgárdi, no comments were given by Bolkay (1913) who first reported its presence in the aboye locality.Von Szunyoghy (1932) based his determination on parietals and compounds coming from Polgárdi.Although the parietals can be easily mistaken for those of N. natrix, there are clear differences between compounds belonging to the two species -N.tesselata is characterized by a much higher medial flange.Unfortunately, the fossils from Polgárdi were not figured by Bolkay (1913) nor by von Szunyoghy (1932).

Z. SZYNDLAR
Remarks: The vertebrae are perfectly preserved and they clearly display distally pointed hypapophyses and parapophyseal processes.Considering both the scarcity of the material and the fact that the aboye features also occur sometimes (although rarely) in Na- trix natrix, proper taxonomic allocation of the discussed fossils cannot be fully demonstrated.It should be noted that there are no significant differences between vertebrae of N. tesselata and N. maura from West Mediterranean; presence of the latter species in the Pleistocene of East Mediterranean is little probable.The two localities lie within the present range of both N. tesselata and N. natrix (Wettstein, 1953) Chkhikvadze and Lungu (1984: 82) as "Natrix, a small snake with well-developed hypapophyses on the trunk vertebrae (..,)"; unfortunately, this brief description is inadequate and does not demonstrate that the discussed fossil belonged indeed to the genus Natrix.
Vertebrae of cobras found in European fossil sites may be easily differentiated from those of other snakes; they closely resemble vertebrae of large-sized colubrine snakes, but contrary to the latter, they are provided with hypapophyses throughout the precloacal region of the column; moreover, they are characterized by very low neural spines.Apart from isolated vertebrae, elapid fossil finds also often offer numerous, well preserved cranial elements.On this account, diagnoses of the fossil species are based mainly on skull bones.
Morphological descriptions of skeletal elements of the genus Naja may be found in papers of Hoffstetter (1939), Bogert (1943), Rage (1976), Szyndlar (1985), and Szyndlar and Zerova (1990).The most comprehensive study, covering important diagnostic features found in braincases of most species of the genus Naja, is that of Szyndlar and Rage (1990).
1939 Palaeonaja Romani Hoffstetter, pp.57-65, PI. 1, PI. 11: 1-13.1939 Palaeonaja crassa Hoffstetter, pp. 65-66, PI. 11: 14, 15. 1963Palaeonaja romani Hoffstetter: Kuhn, p. 31. 1963Palaeonaja crassa Hoffstetter: Kuhn, p. 31. 1984Palaeonaja romani Hoffstetter: Rage, p. 54, fig. 32. 1984 Palaeonaja crassa Hoffstetter: Rage, p. 54. (40)  Diagnostic vertebral characters: Differences between vertebrae of particular species of the genus Naja are usually indistinct; the most informative element is the braincase, especially the basicranium and temporal region (cf.below).Trunk vertebrae of N. romani most resemble those of the living Asiatic species N. naja, but differ from them by having much longer prezygapophyseal processes; the processes of N. romani are almost as long as the prezygapophyseal facets.AIso the neural spine is relatively lower in N. romani; it is approximately three times longer than high.The zygosphene is provided with three distinct lobes in dorsal view; in very large specimens the median lobe disappears.There is a small difference between the populations from Gritsev and Kohfidisch, namely the parapophyseal processes of the former are directed anteriorly, while the processes of the latter face anteroventrally; the material from Gritsev is, however, very scarce; thus the variation within this population remains largely unrecognizable.Thirty of the largest trunk vertebrae from Kohfidisch have a centrum length ranging between 9.53 and 10.80 mm; the centrum lengthlwidth ratio is 0.82-0.99(mean 0.90 ± 0.04) (Bachmayer and Szyndlar 1985).The centrum of smaller vertebrae is more elongate and it is longer than wide.Trunk vertebrae of N. romani from Central and East Europe do not differ significantly from those coming from the type locality; the only slight difference can be observed in the shape of the zygosphene, but only in the largest vertebrae.More differences are visible in the anteriormost vertebrae, including the atlas.For detailed morphological description of the remains from Kohfidisch and Gritsev see Bachmayer andSzyndlar (1985, 1987) and Szyndlar and Zerova (1990).
Remarks: The fossil cobra from Kohfidisch was originally des-cribed as a new extinct species, N. austriaca, by Bachmayer and Szyndlar (1985).Szyndlar and Zerova (1990), after examination of some new material from Kohfidisch, synonymized N. austriaca with N. romani; moreover, they a1so identified the remains from the Ukrainian locality of Gritsev as N. romani.N. romani was originally described as a member of the extinct genus Palaeonaja from the French Middle Miocene by Hoffstetter (1939); Szyndlar and Rage (1990) made Palaeonaja a junior synonym of the living Naja.
Based on the morphology of its basisphenoid (especially considering Vidian canals opening extracranially), N. romani clearly displays features of the Asiatic complex of the genus; some conservative features of its skull (Le., a groove for the facial nerve not covered from outside, presence of 2 solid maxillary teeth) demonstrate, however, that the snake represented an early offshoot of the Asiatic lineage (Szyndlar and Zerova, 1990;Szyndlar and Rage, 1990).Remarks: In having relatively broad centra, relatively short and obtuse hypapophyses as well as a convex zygosphene in dorsal view the vertebrae differ significantly from those of N. romani; identification below the generic level, however, cannot be demonstrated (Szyndlar and Zerova, 1990).cf.Naja sp.
Remarks: Two centra coming from large trunk vertebrae were identified as belonging to a cobra-like snake on the basis of flat and broad subcentral portions.Most likely they represented, the genus Naja, but it cannot be fully demonstrated.
(?) Naja sp.Viperid vertebrae are provided with hypapophyses throughout the precloacal region as in elapids and natricines.Viperids differ from natricines in having straight (not sigmoid) hypapophyses, posteriorly depressed neural arches, distinctly longer and ventral-Iy oriented parapophyseal processes and shorter vertebral centra; they differ from elapids (at least from the genus Naja and its allies) in having bigher neural spines and longer hypapophyses, distinctly longer parapophyseal processes, posteriorly depressed neural arches and postzygapophyses strongly expanded laterally (Szyndlar, 1988).For differentiation between various viperine genera in vertebral morphology see also Szyndlar (1988).
1857 Laophis erotalordes Owen,p. 199 Remarks: Laophis crotaloides was described by Owen (1857) on the basis of thirteen vertebrae coming from the Uppermost Miocene or Lowermost Pliocene of Karabournu in the Thessalonica area (Greek Macedonia) (62).Owen bimself did not determine the exact taxanomic position of Laophis, although throughout the text he observed its close sirnilarity to the North American pit-viper genus Crota/us.It has been later generally believed that Owen assigned Laophis to the subfamily Crotalinae, but this opinion was constituted under the infiuence of the specific name rather than Owen's writing.
Comments on the material described by Owen (wbich is probably lost) are only occasionally found in the literature.In bis review of the fossil record of viperids, Hoffstetter (1955: 659) discussed Laophis in the section devoted to crotalines; nevertheless, he concluded that the available material was unfit for subfamilial Z. SZYNDLAR identification.In bis catalogue of fossil snakes, Kuhn (1939) placed Laophis within the farnily Crotalidae, but he used this name as a synonym of the Viperidae.However, in the second edition of the catalogue (Kuhn, 1963), Laophis is placed in the subfarnily Crotalinae.Rage (1984), following Hoffstetter (1955), recognized that distinguishing the Crotalinae from the Viperinae is impossible on the basis of vertebrae.In conclusion, because "the characters mentioned by Owen are characteristic of a number of viperid genera, the figures are inadequate (...) and the syntypes are probably lost", Rage (supra cit.: 58) considered Laophis a nomen dubium.
The differentiation between crotaline and viperine vertebrae may be problematic indeed in many cases, as suggested by Rage; however, I agree only in part with bis opinion.As an example, it may be very difficult or even impossible to distinguish vertebrae of smaller members of the genera Vipera and Asiatic Agkistrodon (= Gloydius) from each other, these difficulties, however, usually do not occur in the case of larger viperids.Considering Laophis, it most resembles largest members of the crotaline genera Crotalus and Agkistrodon from North America as well as Deinagkistrodon and Calloselasma from East Asia.Of the true vipers, the only snakes resembling Laophis in vertebral morphology is Bitis.Taking into consideration the absolute size of the vertebrae of Lao- phis, they undoubtedly come from the rniddle of the column.Midtrunk vertebrae of the above-mentioned snakes, including Lao- phis, are strongly elongate dorso-ventrally in lateral view, owing to exceptionally long hypapophyses and neural spines together with relatively short centra (fig.8).The vertebrae are more than twice the height (distance between the hypapophyseal tip and neural spine top) as long (centrum length).The same ratio observed in mid-trunk vertebrae of large viperines other than Bitis, Le., Vipera in part ('Oriental vipers'), is distinctly lower.(In fact, the largest member of the Asiatic crotaline genus Trimeresurus, namely T. flavoviridis, displays in its vertebral morphology "typical" conditions of the 'Oriental vipers').The aboye remarks are based exclusively on Owen's figures (1857, plate IV).The figures (according to Owen) display the lateral and anterior views of a single vertebra.The anterior view, as previously noticed by Rage (1984), is inaccurate.According to tbis figure, the zygosphenal roof is strongly convex, while in the lateral view its is distinctly concave.Moreover, the prezygapophyseal articular surfaces, as they are shown in the anterior view, have a thickness unparalleled in any snakes.It is to be noted that Laophis, according to the Owen's figure, was the largest viperid snake ever known; the centrum length of its vertebra is about 15 mm, while the same value for the largest reported pit viper is aboye 12 mm (Crotalus adamanteus : Christman, 1975, fig. 1) and for the largest true viper 12.37 mm (Vipera maxima from the Spanish Pliocene; Szyndlar, 1988: 700).Besides its absolute size, there are at least two distinct features distinguishing Laophis from other large viperids, namely very thin parapophyseal processes and, especially, a long condylar neck.It seems, however, that the latter as well as sorne other features, reflect fantasy of the lithographer rather than real morphology.
The problem of validity of this species remains then an open question.In light of current knowledgeof past viperid distribution in the area, Laophis may have been a Bitis-like snake rather than a pit viper.The latter genus is unknown from European fossil sites: the only report of presumed Bitis remains from eastem Europe (Kormos, 1911) is most likely erroneous (Szyndlar, 1984; see also below).
Identification of isolated vertebrae to particular complexes of the genus is usually an easy task.Vertebrae of the 'Oriental vipers' are characterized by much larger absolute size and less relative length (lower centrum length/width ratio) than those of the 'European vipers' (Szyndlar 1988).Of the latter group, the 'berus' group may be differentiated from the 'aspis' group on the ba-sis of greater elongation of vertebrae and distinctly relatively 10wer neural spines and shorter hypapophyses (Szydlar 1984).Reliable allocation of fossils in the 'aspis' group may, however, be problematic in the case of absence of cervical vertebrae; identification on the basis of mid-trunk vertebrae alone may be rnisleading because the latter are closely similar to those of the cervical region in the 'berus' group.Cranial elements of viperids, especial-Iy those of smaller species, are seldom found in the fossil state.
Although differences among the aboye mentioned groups of the genus Vipera are usually very clear, skeletal morphology within each complex is usually highly homogenous.For instance, though V. russelli of the 'Oriental vipers' displays, both in its axial and crania!elements, an extremely distinct morphology, sorne other members of the same complex, as V. lebetina, V. xanthina, and V. palestinae are very similar to each other.Proper classification of isolated bones belonging to these species is thus always a hazard.
Diagnostic vertebral characters: This extinct species, known from the type locality only, differs from most of its living relatives in sorne minor features, among others by having sharp laterallobes of the zygosphenal roof and elliptical shape of the prezygapophyseal articular facets.It most resembles the living Vipera xanthina but a close relationship between both species, considering scarcity of the fossil material, cannot be fully demonstrated.The centrum length of the holotype vertebra is 6.90 mm (Szyndlar 1987a); it is 1.18 times longer than wide.
Remarks: This is the oldest representative of the 'Oriental vipers' in East Europe.For more detailed morphological description see Szyndlar (1987a).
Diagnostie vertebral eharaeters: Tbis extinet species, known from the type locality only, displays all tbe eharaeteristie features of tbe 'Oriental vipers'.Comparisons of V. sarmatica with two living species of the 'Oriental vipers', provided by Chkhikvadze and Lungu (in Zerova et al. 1987), are not satisfaetory beeause they are concentrated on features subjected to allometric variation: V. sarmatica differs from V. xanthina «...by larger absolute dimensions of the vertebrae, by a thicker cotyle, by more strongly developed subcentral ridges and a groove between tbe hypapophysis and subcentral ridges»; it differs from V. lebetina « ... by a wider zygosphene the width of which is approximately equal to the eentrum width» (ibid., p. 94).Aecording to the figure of Chkhikvadze and Lungu (ibid.,fig. 2v), tbe latter statement is untrue.Tbe zygosphene is straight (or slightly concave or convex) in dorsal view.Tbe eentrum lengtb of the holotype vertebra is 9.4 mm; in tbe entire sample, tbe centrum lengtb/widtb ratio ranges between 1.25 and 1.62 (ibid., p. 94).(Tbe centrum lengtb/width ratio, original-Iy given in tbe paper of Zerova et al.,; the data presented here come from a corrected reprint provided by the autbors).For more detailed morphological description see Chkhikvadze and Lungu (in Zerova et al. 1987).
Vipera burgenlandica Bachmayer et Szyndlar, 1987 (figs. lO, 11) Diagnostie vertebral characters: Trunk vertebrae of this extinet snake, known exclusively from the type locality, closely resemble those of tbe living V. lebetina and V. palaestinae; differences be-Z.SZYNDLAR tween these three species are, however, clearly visible in eranial elements (see below).Tbe zygosphene is provided with two distinet outer lobes and an indistinct median lobe; the prezygapophyseal proeesses are extremely short; the neural spine of the midtrunk vertebrae is approximately as high as long; the parapophyseal processes are direeted downwards.Tbe centrum length of 11 trunk vertebrae is 5.59-7.18mm (mean 6.40 ± 0.49); the centrum lengtb/width ratio is 1.18-1.28(mean 1.22 ± 0.05) (Bachmayer and Szyndlar 1987).
Remarks: Tbis snake is at present the best documented fossil member of the 'Oriental vipers' group.Of several cranial bones available, the lower jaw elements are of lesser importanee because they display the same morphologieal pattem as in most 'Oriental vipers'.Tbe holotype basiparasphenoid was supposed to be closest to that of the living V. xanthina (Bachmayer and Szyndlar 1987); discovery of another basiparasphenoid (fig.11A,B), most similar to V. lebetina, indicates a broad spectrum of intraspecific variation of this bone.Another reeently discovered element, a maxilla (fig.11C, D), by having a distinct ridge on the antero-inner wall of its ascending process, closely resembles that of the extinct V. gedulyi from the Hungarian Miocene.Both species can be, however, well differentiated on the basis of morphology of the ba- ry compound bones, 33 fragmentary eetopterygoids (syntypes, MHGI Ob-4467Nt.74; not seen, fide Bolkay 1913 andvon Szunyoghy 1932).Remarks: This snake, known from the type loeality only, was deseribed exclusively on the basis of eranial bones.Bolkay (1913:225) pointed out «...the great degree of agreement whieh this species shows with Vipera ammodytes»; at the same time he observed that the most important differenee between both species is «...the considerably larger size of this Viper [i.e., of V. gedulyi]».Bolkay was largely correet in his statement beeause, in faet, most isolated cranial bones of both V. ammodytes and the 'Oriental vipers' display similar morphologieal patterns, apart from the difierent absolute size.Unfortunately, he neither descrlbed nor figured the bones of the temporal region, whieh have perhaps the greatest taxonornie importance in viperids; also, Bolkay did not consider vertebrae, whieh provide the best data in differentiating the 'Oriental vipers' from other members of the genus.Bolkay's opinion may have simply resulted from the faet that he did not have any skeletons of the 'Oriental vipers' at hand.Although von Szunyoghy (1932) observed some similarities between the Polgárdi fossil and the living V. lebetina, his observations were ignored by later students and V. gedulyi was then traditionally regarded a close relative of the living Vipera ammodytes.
Aetually, the skeletal elements figured by Bolkay (1913, PI.XII) clearly display features eharacteristic for the 'Oriental vipers' group; V. gedulyi seems closest to the living V. lebetina (Szyndlar 1987b(Szyndlar , 1988)), but differs clearly from the latter in having an extremely long basioccipital proeess and in the presenee of a strong ridge on the aseending process of the maxilla (ef.Bolkay 1913, PI. XlI:9,12).Perhaps one of most important features showing close relationships between V. gedulyi and lr.lebetina is the type of the eetopterygoid-maxillary artieulation.In both species (as well as in V. mauritanica) the internal (i.e., smaller) ramus of the eetopterygoid is well produeed anteriorly so that it protrudes distinetly outside the stem of the bone (ef.Bolkay 1913, PI. XII:10); on the eontrary, in V. xanthina (as well as in V. raddei) the ramus is shifted far posteriorly.Kormos (1911), who first deseribed briefly the Polgárdi herpetofauna, mentioned a fragmentary maxilla provided with a fang, supposedly belonging to a large venomous snake, perhaps of the genus Ritis.The supposition of Kormos was not commented on by Bolkay (1913) or von Szynyoghy (1932); most likely, the maxilla was included by Bolkay to the syntypes of V. gedulyi.Vipera kuchurganica Zerova, 1987 (fig. 12) Diagnostie vertebral eharaeters: According to Zerova (in Zerova et al. 1987), this extinet species, known exclusively from the type loeality, most closely resembles the living V. lebetina.It differs from V. lebetina «.. .in a wider and larger vertebral eentrum, more laterally projeeted pre-and postzygapophyses, less developed parapophyseal proeesses.»;it differs from V. xanthina « ...in the shape of the zygosphene (straight in V. kuchurganica (...) and un• dulating in V. xanthina), [and in] the degree of development of parapophyseal processes and subcentral ridges» (ibid., p. 96).The vertebrae of V. kuchurganica are also closely similar to those of V. burgenlandica from the Austrian Miocene (see aboye) and perhaps both snakes represented the same evolutionary lineage or even the same speeies; the only signifieant differenee is the presenee of two distinet outer lobes in the zygosphene of V. burgen- landica, struetures that are absent in V. kuchurganica.For detailed morphologieal deseription of V. kuchurganica see Zerova (in Zerova et al. 1987).Remarks: Considering absolute size and centrum length/width ratios of all the examined vertebrae, they undoubtedly belong to the 'Oriental vipers'; unfortunately, beeause of the poor preservation of the material, no more precise identification is possible.(DPFNSP 938, 1114(DPFNSP 938, , 1213, 4014, 4057), 4014, 4057).D!agnostic vertebral characters: Owing to the presence of both cervical and trunk vertebrae in the material, it is clearly referable to the 'aspis' group.It differs from the living members of the latter group in having vertebrae of the mid-trunk region characterized by relatively longer centra and a distinctly lower neural spine.The centrum length of the holotype vertebra is 3.75 mm; it is 1.54 times longer than wide.For more detailed morphological description see Szyndlar (1987a).
R~mar~s: This extinct species, known exclusively from the type locahty, IS the oldest known representative of the 'European vipers'.
Vipera cf.V. ammodytes (Linnaeus, 1758) (fig.15).Diagnostic vertebral characters: V. ammodytes can be easily differentiated from another living member of this complex, V. aspis, on the basis of cervical vertebrae, which in the former snake are provided with much longer hypapophyses and much higher neural spines (Szyndlar, 1984, fig. 8).It should be stressed, however, that trunk vertebrae immediately following the cervical region of the column in V. ammodytes, which have both reduced height of neural spines and reduced length of hypapophyses, can be easily mistaken for cervical vertebrae of V. aspis.In both V. ammodytes and V. aspis, the zygosphene is provided with three distinct lobes and the prezygapohyseal processes are extremely short.The centrum length of 60 trunk vertebrae of a large specimen of the living V. ammodytes (ZZSiD 292) ranges between 4.54 and 5.10 mm and it is 1.42-1.63(mean 1.53 ± 0.06) times longer than wide; the largest fossil vertebra from Wc;ie 1 has a centrum length of 4.22 mm (Szyndlar, 1984).For detailed morphological description of vertebrae of V. ammodytes see Szyndlar (1984).
Remarks: (4) (6) (7) The features characteristic for V. ammodytes are clearly visible in the material corning from three Polish Pliocene localities and this was the basis for identifying them as V. ammodytes without any reservation by Szyndlar (1984).There are no significant differences, however, in vertebral morphology between V. ammodytes and its close relative from Iberia and north-westem Africa, V. latastei.Considering that in the Pliocene the differences between both species may have been lesser than today and that their geographical ranges may have been closer to each other, the taxomonic syntax used in the present paper was completed by the qualifier "cf.".(55) (68) (56) The same syntax was employed in reference to the remains from the Pleistocene Greek and Bulgarian sites, in this case, however, regarding the poor preservation of the fossils rather than other reasons.
(44) One parietal from Polgárdi, referred originally by Bolkay to the extinct V. gedulyi, was then compared by von Szunyoghy (1932) with the living species V. ammodytes.The discussed bone perhaps belonged indeed to V. gedulyi, but von Szunyoghy did not consider intraspecific variation.The material needs re-exarnination.
Except for Poland, the remaining fossil sites are located within the present range of V. ammodytes.Remarks: Taxonomic allocation of the parietals from Polgárdi is doubtful for the same reasons as discussed above with reference to V. ammodytes from the same locality.Von Szunyoghy (1932) did not consider intraspecific variation; the bone probably belonged to V. gedulyi as previously recognized by Bolkay (1913).The present range of V. apis is restricted to West Europe; the only (uncertain) record from East Europe was reported by Buresch and Be §kov (1965).
Diagnostic vertebral characters: Precaudal vertebrae of two East European smallest vipers, V. berus and V. ursinii, are very similar to each other; sorne minor differentiating features were found in caudal vertebrae by Szyndlar (1984, fig. 8).The centrum length of 25 trunk vertebrae of a living example of V. berus (ZZSiD 22) is 3.40-3.95mm and it is 1.70-1.88(mean 1.80 ± 0.05) times longer than wide; the largest vertebra from the Polish Pleistocene has a centrum length oí 5.51 mm (Szyndlar, 1984).The absolute size and proportions of vertebrae of V. ursinii are similar.For detailed morphological description of vertebrae of V. berus see Szyndlar (1984).
Remarks: Regarding cranial bones occurring in fossil sites, sorne differences between V. berus and V. ursinii are visible in basiparasphenoids and maxillae.In V. berus, the anterior orifices of the Vidian canals are located on the dorsal side of the basiparasphenoid, while in V. ursinii they lie on the lateral margin of the bone; the maxilla of V. berus is relatively much higher than that of V. ursinii.(9) (43) The fossil remains from both Polish and Austrian Pleistocene, containing weU preserved cranial bones of taxonomic importance, are cleariy referred to V. berus.(53) Based on Bolkay's drawing (Bolkay, 1913, fig. 5), allocation of the figured basiparasphenoid to V. berus is not demonstrable.
Al the discussed fossil sites are situated withing the present range of the species.Redkozubov, 1987).

History oC snakes in Central and East Europe
A scenario of the distributional history of the European snake fauna, outlined by Szyndlar (1984), was mainly based on the present distribution of particular snake species rather than on the fossil record.This hypothesis is confronted below with paleontological evidence.Szyndlar (1984) pointed out that the recent European snakes (except for a few species of northernmost ranges) may be grouped into three separate geographical units, restricted to southeastern Europe, western Europe exclusive of Iberia, and the Iberian Peninsula.It was then supposed that these regions were settled by modern snakes as a result of migrations via three different corridors, Le., from western Asia through the Asia Minor, from western Asia through Central Europe, and from northwestern Africa through the Gibraltar Strait, respectively.Later studies (Szyndlar, 1985(Szyndlar, , 1988) ) confirmed the supposition that in the past Iberia was invaded by African snakes.At the same time, there is no evidence that African snakes entered the remaining parts of the European continent, at least with reference to post-Paleogene times; thus, the non-Iberian European snakes are supposed descendants of invaders from Asia.
Considering that the aboye supposition is demonstrable, traces of any faunal exchanges between Asia and West Europe are to be found in the area covered by the present study.Although this is largely true, unfortunately the Miocene history of East European snakes may be demonstrated in the northern part of the area only.Regarding the southernmost part of Eastern Europe, no snake fossils coming from localities older than uppermost Miocene were available for study.The oldest examined remains from the Greek locality of Pikermi 4 are so damaged that identification even to familiallevel was impossible; those from two other Greek Miocene localities (Maramena 1 and Ano Metochi 2) are also poorly preserved and (except for a presumed Naja from Maramena 1) they were not identified below the subfamiliallevel.

Scolecophidians
The oldest scolecophidians are known from the 10- wer Eocene of Belgium (Rage, 1984).In the Miocene, they occupied a considerable part of the European continent; a fuHlist of the fossil record reported from the entire Europe prior to 1985 can be found in Szyndlar (1985).In West Europe, scolecophidians survived until at least the Pliocene (S.Bailon, pers. comm., 1989).
In East Europe, scolecophidians probably occupied most of the area during almost entire Miocene; the youngest East European site yielding remains of these snakes and lying outside the present range of scolecophidians, Cherevichnoie (lower layer), is of upper Miocene age.Younger localities are located exclusively within the area occupied presently by Typhlops vermicularis.This species, the only representative of the family Typhlopidae in Europe, occurs in the south-eastern part of the continent.
As stated in the previous paper (Szyndlar, 1991), identification of scolecophidian vertebrae to the familial level is not possible.Therefore, it cannot be demonstrated whether the European fossils belong-Z.SZYNDLAR ed to the family Typhlopidae or to the Leptotyphlopidae: at present, members of the latter family live in the close vicinity of Europe, occupying among other areas the entire south Mediterranean coast and southwestern Asia.

Boidae
Except for a doubtful record of Python euboicus, non-erycine boids have never been reported from Eastern Europe.The subfamily Erycinae, recorded since the Paleocene, underwent a great radiation in West Europe and North America in the Eocene (Rage, 1987).Erycine snakes were also widespread in the end of the Paleogene and in the Neogene of Europe (Hoffstetter and Rage, 1972).They probably inhabited a considerable part of Western Europe until the end of the Pliocene (Szyndlar, 1985).AH pre-Miocene finds represent extinct genera; during the Miocene, they were being graduaHy replaced by members of the living genus Eryx.At present, species belonging to this genus occur in west and southern Asia and in a part of Africa; the only species presently inhabiting Europe, Eryx jaculus, occupies the southeastern part of the continent (fig.17).
The Miocene erycine fauna of East Europe is re- According to Rage (1977), the oldest European erycines were replaced by Bransateryx and Albaneryx in post-Eocene times, Le., after disappearance of the Turgai Strait, which separated Asia from Europe.Szyndlar (1987a) suggested an opposite direction of these migrations.Unfortunately, there is no direct evidence supporting either hypothesis.The only record of a presumed Bransateryx from Central Asia (Zaisan locality near the Kazakhstan-Chinese frontier) is of middle Oligocene age; middle Eocene and early Oligocene erycines from the same locality are represented by primitive Calamagras-like snakes and by " ... a small, apparently new genus of the Erycinae" (Chkhikvadze, 1985: 234).The pre-Oligocene presence of Bransateryx to the east of the Turgai Strait is thus not demonstrable; nevertheless, the Zaisan remains (if indeed they belonged to Bransateryx) indicate that the genus was widely distributed by the end of the Paleogene.Bransateryx is not found in post-Oligocene materials from Zaisan; since the early Miocene, the only erycine remains recorded from this locality are referable to the modero genus Eryx (Chkhikvadze, 1985).
As noted in the previous paper (Szyndlar, 1991), Bransateryx and Albaneryx closely resemble the living North American Charina and Lichanura, respectively, at least with reference to the axial skeleton (Rage, 1984;Szyndlar, 1987a).It is quite probable that the European extinct genera are synonymous with their American counterparts.
Bransateryx and Albaneryx disappeared in West Europe in the lower and middle Miocene, respectively (Rage, 1984).Finds of these genera in the late Miocene of Ukraine provide new evidence that extinction of archaic European snake faunas proceeded gradually from West to East.The available fossil record demonstrates that in the Miocene the Old World and New World ranges of Bransateryx-Charina and Albaneryx-Lichanura lineages were disjunct (only Charina is known from the North American Miocene; Holman, 1979).It is quite probable that Eastero Europe was a last refugium of these snakes in OId World.Ã similar phenomenon, Le., a gradual extinction from West to East, took place later in the case of the living genera, Gongylophis and Eryx.The oldest European find of Eryx comes from the Spanish lower Miocene (Szyndlar, 1987a); the oldest (and the only) European record of its close relative, Gongylophis from Czechoslovakia, represents the same age.In the Miocene, Eryx was widely distributed in the southero half of Europe; in West Europe it gradually disappeared during the Pliocene (Szyndlar, 1985).AIso, no post-Neogene find is available from the Black Sea area where Eryx was common until the end of the Pliocene (Zerova, 1987).The only Pleistocene records come from the area inhabited by this snake today, Le., southeasteromost Europe.

Colubridae
A few of the oldest European finds of the Colubridae come from the Oligocene of France and Germany; they are represented exclusively by vertebrae displaying morphology consistent with those characteristic for both modero "natricines" (Natrix) and "colubrines" (tentatively placed in the genus Coluber) (Rage, 1988).
Although most described extinct species represent only this family, perhaps an overwhelming majority of these descriptions does not reflect the true taxonomic position of the fossils.This situation derives from the fact that the family Colubridae ineludes an enormous number of species that are largely characterized by homogenous morphology of vertebrae.Since most ophidian paleontologists use a subdivision of the family Colubridae into Colubrinae and Natricinae, it generates widespread opinions that only members of these two subfamilies were found in fossil state in Europe (e.g., Cadle, 1987).However, this subdivision has only a symbolic meaning and is used for differentiating hypapophyses-bearing colubrids from those devoid of hypapophyses (d. the previous chapter).In fact, with reference to most fossil "colubrines", it is impossible to demonstrate whether they represented the Colubrinae (s.s.) or another subfamily.Regarding "natricines", neither all members of the Natricinae (s.s.) possess hypapohyses throughout the column nor are they the only colubrids having them.
It is symptomatic that the best recognized fossils of the family Colubridae are clearly referable to modero genera and the particular extinct species are in many aspects closely similar to their living relatives.On the other hand, all fossil genera reported from the area (including those originally described from remote regions) were erected on the basis of very scarce material.
No extinct colubrid genus was compared with all or even with a considerable part of living genera.Such a comparison seems to be physically impossible and that is why disregard of large scale comparisons is a normal practice among ophidian paIeontologists.
In particular, regarding widespread fossil genera, e.g., those described from the Miocene of North America and then recorded also from the European Miocene, their taxonomic status leaves much to be desired.Considering sympatric occurrence of these fossils along with other snakes presently distributed, for example, in the Oriental Realm (as in the case of Dolnice), it is possible that the presumed extinct genera may have actuaHy represented some modero genera with the present range of distribution remote from the fossil sites.
In conelusion, the taxonomic status of aH of the discussed fossil colubrid genera is then either doubtful or not fuHy demonstrated.
The taxonomíc status of extinct members of modero genera is usuaHy more credible but (in most cases) only when their descriptions are based on both cranial elements and vertebrae.It seems demonstrable that European Miocene colubrids did not belong to living species, thus proper taxonomic description of these snakes may be realized, but only on the condition (usuaHy) that cranial elements make satisfactory generic allocation possible.Regarding the Pliocene, when both extinct and extant species occurred, proper taxonomic aHocation of given fossils needs comparison with all related taxa presently inhabiting both the elose vicinity of the fossil site as well as some adjacent areas (in the case of Eastero Europe, more or less the West Palearctic).
The oldest unquestionable member of the genus Coluber in Eastero Europe is the lower Miocene C. dolnicensis, while the oldest member of Elaphe (still undescribed) comes from the late Miocene of Gritsev in the Ukraine; at the same time these taxa are also probably the oldest certain representatives of both genera in the whole of Europe.The oldest European remains of Natrix were recorded from the French (probably) lower Oligocene (Rage, 1988); the oldest (uncertain) record from East Europe comes from the late Miocene.

Elapidae
The entire available fossil record of these snakes from the West Palearctic was recently reviewed by Szyndlar and Rage (1990).All but one find from the area, coming from eighteen localities, belong to the modero genus Naja; the oldest European remains of Naja (at the same time the oldest known elapid remains) come from the lower French Miocene.In the Miocene, members of this genus occupied a major part of Europe.The last unquestionable members of the genus Naja survived in the Mediterranean area of the both West and East Europe at least until the upper Pliocene (Bailon, 1989;Szyndlar and Zerova, 1990).
At present, members of the genus Naja occur in most of Africa and southero Asia.Living members of the genus Naja represent two separate evolutionary lineages, confined to Asia and Africa respectively; it should be stressed that this subgeneric split can be observed in the oldest fossils.Most likely, aH fossil cobras from Central and East Europe belonged to the former group (Szyndlar and Rage, 1990).It demonstrates, along with the fossil record of large vipers, that in the Miocene the discussed area was inhabited by snake faunas similar to those occurring at present in the Middle East ami/or the Oriental Realm.It is also noteworthy that the oldest fossil cobras (at least those known from abundant remains), apart from some primitive features, are morphologi-caHy very similar to living species.

Viperidae
The oldest vipers were reported from the West European lowermost Miocene (Agenian) by Kinkelin (1892Kinkelin ( , 1896) ) and by Hoffstetter, (1962).The former find, an isolated fang named Provipera boettgeri by Kinkelin (1892), was then referred to the subfamily Crotalinae (Kinkelin, 1896).Taxonomic status of this fossil was rightly criticized by Cope (1892: 224) who stated that "neither species nor genus can be possibly described from the specimen in Dr. Kinkelin's possession"; Rage (1984) considered Provipera boettgeri as a nomem dubium.Hoffstetter (1962) only mentioned that the Viperidae appeared in Europe in the Aquitanian (= Agenian), unfortunately, no more lengthy information about his find has ever been published.Hoffstetter's report may have been based on a coHection presently housed at P. & M. Curie University in Paris; it comes from the lowermost French Miocene (Agenian) and consists ofvertebrae of small vipers (J.e.Rage, pers. comm., 1989).The same collection ineludes also numerous well preserved large vertebrae belonging apparently to the 'Oriental viper' group (pers.obs., 1989), coming from the lower Miocene (Orleanian) of France.
Fossil members of the family Viperidae found in Europe probably belonged exelusively (perhaps with exception of the enigmatic Laophis) to the modero genus Vipera (Szyndlar, 1987b).
As noted in the previous chapter, extant members of the genus Vipera form several separate complexes and this subgeneric diversity is usually also recognizable in fossil materials.The largest members of the genus, 'Oriental vipers' , presently inhabit southero Asia and northwestero Africa.The European distribution of the 'Oriental viper' group is restricted to the Cyclades (Vipera lebetina), easthernmost Greece, European Turkey, and Greek islands in the vicinity of west Anatolian coasts (V.xanthina).In the Miocene, 'Oriental vipers' were widely distributed in the entire southern half of the continent; in Western Europe, they survived until the end of the Pliocene in the Mediterranean area (Szyndlar, 1987b(Szyndlar, , 1988)).In Eastern Europe, they probably inhabited vast areas until at least the middle Pleistocene (fig.18).
Smaller members of the genus Vipera ('European vipers') presentIy inhabit the southern part of the West Palaearctic ('aspis' group) and the northern part of the Palaearctic ('berus' group).A representative of the 'European vipers', V. antiqua, is present in the oldest site of Central and Eastern Europe, Le., in the lower Miocene of Dolnice.It should be noted that all fossil species of Vipera, including the oldest forms, were closely similar to the living members of the genus.
Sympatric occurrence of two separate groups of Vi- pera was also reported from the early Miocene of Central Asia (Zaisan basin) by Chkhikvadze (1985: 234) who recorded " ... Pelias (a small species) [Le., a 'European viper'] and a much larger viper of size [comparable with] V. xanthina".
These facts suggest that the split of Vipera into the complexes characteristic for living members of the genus is an old phenomenon, undoubtedly antedating the early Miocene.According to Groombridge (1986), who based his supposition on morphological analysis, the 'European vipers' are members of early sidebranches, whereas the 'Oriental vipers' are regarded as recent radiations.On the contrary, Herrmann et al. (1987) considered that the 'xanthina' and 'lebetina' groups were early offsprings of the Vipera stem, whereas the 'European vipers' resulted from a comparatively modero radiation; the biochernically based reconstruction of the phylogeny of Vipera presented by the latter authors, which considers the first branching within the genus at ca. 17-18 million years ago (Herrmann et al. 1987, fig.3), cannot be accepted.Palaeontological evidence cannot support any of these opposing hypotheses; however, the available fossil record indicates that irrefutably the main split within the genus Vipera must have taken place much earlier than suggested by the latter authors.
It should be stressed once again that aH weH recognized fossil snakes from the Central and East European Miocene belonged exclusively to modern genera and were very similar to related living species.Regarding extinct genera, they are either closely related to modern genera (as in the case of Bransateryx-Charina and Albaneryx-Lichanura lineages), and perhaps they ought to be synonymized with the latter or their generic status is not demonstrated in a satisfactory manner, and therefore their distinction is uncertain.These facts suggest that the ophidian faunas (or at least the majority of snakes) inhabiting Central and East Europe since the beginning of the Miocene closely resembled those of living faunas, al-Z.SZYNDLAR though not necessarily those occurring presently in Europe.
It is quite probable that the modern pattern of European snake faunas was characteristic also for the times immediately preceding the Miocene; presence of colubrid remains resembling living species in the West European Oligocene (Rage, 1988) may support this opinion.Unfortunately, the Oligocene is characterized by impoverished faunas, both in West Europe and anywhere, which contrasts sharply with the rich assemblages of the Eocene; the European ophidian fauna of the latter epoch was represented exclusively by representatives of archaic snake families (Rage, 1987).
A considerable part of the Miocene snakes of Eastern and Central Europe represent modern genera the distribution of which is located in the Middle East and the Oriental Realm.Connections between Europe and North America are also weH demonstrated, at least with reference to erycine genera.Possible migrations between both continents seem, however, to antedate the Miocene; ranges of snake taxa, common for both Europe and North America, were perhaps disrupted in the Miocene.It is probable that at least a part of the colubrid snakes occurring in both the European and North American Miocene actuaHy re-Fig.19.---Cranial bones of Naja romani, in left lateral views.Not to scale.Black colour: elements identical with those of aH or majority of living species of the genus Naja; slanting lines: elements identical with those of Asiatic members of the genus; dots: element identical with those of African members of the genus; white colour: element differing from those of aH members of the genus.Abbreviations: Bü, basioccipital; BP, basiparasphenoid; e, compound; D, dentary; E, exoccipital; F, frontal; M, maxilla; PL, palatine; PR, prootic; Q, quadrate; S, squamosal.
presented living genera presently restricted to the Oriental Realm.
A striking feature observed in the European Miocene is the longevity of ophidian species; it was well documented with reference to two Miocene snakes, Natrix longivertebrata and Naja romani.The former survived for about ten million years and only slight morphological differences can be observed between the oldest and youngest records (Rage and Szyndlar, 1986).The latter persisted in invariable form for at least six million years (Szyndlar and Zerova, 1990;Szyndlar and Rage, 1990).These long spans, apparently correlated with prolonged favourite climatic conditions, sharply contrast with the short longevities characteristic of living ophidian species; perhaps they were typical for most Miocene snakes.Indirectly it can suggest that snake species inhabiting presently tropical zones may have been established in remote epochs, perhaps in the Miocene.
Lack of an appropriate fossil record hinders the recording of any possible changes in the character of snake faunas in the Mediterranean area of Eastero Europe during the time of the Messinian crisis.In the northero part of the discussed area, no sudden changes occurred at the turo of Miocene (MN 13).The following phase of the Neogene, namely the lower Pliocene (MN 14) seems to be of special importance as a "transitional epoch" preceding immediately first appearance of modero snake species.Unfortunately, except for viper remains, the entire fossil record from the lower Pliocene is very scarce.
First living species (Colubridae) were recorded from the middle Pliocene (MN 15); in the upper Pliocene (MN 16), living species predominate over the Central and East European snake assemblage.It is noteworthy that the upper Pliocene fauna, apart from sorne relicts (Elapidae, 'Oriental vipers'), does not differ significantly from that inhabiting the area presently.The only apparent difference in comparison with the recent fauna is that the ranges of particular living species were more northero in the past.
In conclusion, snakes inhabiting Europe since the beginning of the Miocene do not differ significantly from the living relatives occurring presently in various regions of Eurasia and, although to much lesser degree, of North America: close similarities can be observed in the morphology of particular species as well as in intrageneric diversification.Considering these facts, divergence of advanced snakes (for which pre-Miocene fossil record, except for the Colubridae, is unknown) must have taken place long before the Miocene.This assumption is not concordant with the opinions of many authors that most lineages of advanced snakes emerged around the Paleogene/Neogene boundary.For instance, Dowling et al. (1983) suggested the origin of most colubrine genera as late as the Miocene, while Herrmann et al. (1987) hinted a similar opinion with reference to the genus Vipera.These hypotheses, however, when confronted with the fossil record, are little probable because they would suggest an extremely transient radiation leading to modero genera and, then, a surprising long evolutionary stasis in post-Paleogene times.
Contrary to interpretations of the above cited authors, Cadle (1988: 48) postulated that " ... separation of the elapid and colubrid lineages was most likely a late Cretaceous-early Tertiary event, and the divergence of the viperids even earlier" and his opinion is clearly concordant with data provided by the available fossil record.These events, however, must have occurred in areas remote from Europe, presumably in tropical zones.

Methods in ophidian paleontology: a critique
Description of methods used in this study is brief and does not require additional comments.The fossil remains were identified on the basis of their similarity or dissimilarity with homologous skeletal elements of living snakes and of other fossils, while the use of numerical methods was of secondary utility.This essay is then intentionally placed at the end instead at the beginning of the present paper and aims at a critical appreciation of methodologies employed by students of snake fossils.
Writing the following remarks was inspired in part by recently published criticisms addressed to ophidian paleontology (e.g.McDowell, 1987;Cadle, 1987Cadle, , 1988;;Hecht and LaDuke, 1988).McDowell (1987) expressed the opinion that the fossil record of snakes is extremely difficult to interpret because it is based almost entirely on vertebrae, while considerable evolution may produce no detectable change in vertebrae; on the other hand, closely related forms may sornetimes have quite different vertebrae.Mc-Dowell concluded that no use was made of the fossil record in snake classification until the twentieth century.Cadle (1987) pointed out that a lack of adequate survey of vertebral morphology and variation of extant snake lineages has hindered fully effective use of the fossil record.Hecht and LaDuke (1988) demonstrated that vertebrae of two closely related genera can display divergent morphology, implying that allocation of extinct forms to family or subfamily based on isolated vertebrae may be questionable.Rage (1987) refuted a part of the above arguments, stating that the usefulness of vertebrae for purposes of identification is well established, but at the same time he observed that their significance in phyletic reconstruction is sometimes questioned on account of conservative vertebral morphology; this is awkward f::i;j¡ +Nr.  48: Nagyharsány-hegy .
The aboye opinions concern, however, rather 01der snake fossils that require somewhat different methodologies when studied.Perhaps it will be useful to summarize briefly sorne basic problems arising during examination of post-Paleogene snakes.Special attention is paid below to methods leading to false interpretations of studied snake fossils.

Main difficulties
It is largely true that examination of geologically relatively young snake fossils is a more complex task than in the case of older materials.As pointed out in the previous chapter, even early Miocene snakes closely resemble their living relatives; obviously, this resemblance is more striking in the case of Pliocene and, especially, Pleistocene fossils.Paleogene snakes resemble modern snakes to a lesser degree and therefore examination of their remains does not require such detailed comparisons with related living taxa as in the case of geologically younger fossils.Proper examination of the latter requires not only access to large skeletal collections including related living species, but it also requires a knowledge of intraspecific variability.Unfortunately, intraspecific variation in skeletons of living snakes is poorly recognized in reference to most ophidian taxa.It is noteworthy that in rare cases where the variation was recognized its spectrum may be unexpectedly broad (as in members of the genus Naja; cf.Szyndlar and Rage (1990».Problems concerning taxonomic validity of extinct genera were widely discussed in the previous chapter.I have stated that satisfactory pros or cons of distinction of any fossil genera do not exist, especially in regard to colubrids.On account of that I have temporarily retained these genera valido A possible fruit-fuI systematic revision of these extinct genera would be perhaps possible after assignment of patterns of vertebral morphology for basic lineages of living snakes, as suggested by Cadle (1987).Unfortunately, so far nobody has undertaken such a study.
Another important problem is the proper recognition of whether given fossils belonged to a living or extinct species.As pointed out in the previous chapter even early Miocene European snakes are very similar to their living relatives.It means that sorne bones display distinct morphology, but most skeletal elements (usually an overwhelming part!) are morphologically concordant with homologous elements of recent species.It was well demonstrated in reference to two Miocene species, known on the basis of abundant cranial elements, namely Natrix longivertebrata and Naja romani (Rage and Szyndlar, 1986; Szyndlar  and Rage, 1990; cf. also chapter "Systematic account").
For example, as shown on fig.19, there are no significant differences between most cranial bones (frontal, basioccipital, squamosal, quadrate, palatine, dentary, compound) of the Miocene Naja romani and homologous elements belonging to majority or even all living members of the genus Naja; two other kinds of bones of N. romani do not differ significantly from those belonging to the living Asiatic members of the genus, while maxillae of N. romani are identical with those characteristic for living African species.The only cranial element of N. romani clearly differing from those of other members of the genus Naja, is the prootic.
Regarding Natrix longivertebrata, a presumed ancestor of the living N. natrix, it differs from the latter in frequency of two patterns of the basisphenoid morphology, while remaining available cranial elements are very similar or identical in both species.These examples are shown here in order to indicate that isolated cranial bones found in fossil sites, although identical with homologous elements of sorne living species, did not necessarily belong to the same species.
A classical example of doubtful identification, resulting from treatment of particular fossil remains independently, are descriptions of presumed living species from the Miocene of Polgárdi by Bolkay (1913) and von Szunyoghy (1932).In order to avoid such errors (or at least to lessen the probability of the errors) it is usually necessary to "fit" cranial elements to vertebrae coming from the same locality (d.below).

Vertebrae
Most fossil snake collections consist exclusively of isolated vertebrae, therefore most fossil records are based exclusively (or mainly) just on these elements.Usefulness ofvertebrae (usually trunk vertebrae) for identifying snake taxa differs for various families.Identification of scolecophidians based on vertebrae alone is impossible even to familial level; regarding viperids, vertebrae make it possible to identify most genera and even subgeneric units but identifications to specific level are hazardous in most cases; vertebrae of colubrids may be a sufficient basis for identifying species, but on the other hand it is often difficult to recognize the generic allocation (see Szyndlar, 1991, for details).
Although somewhat surprising, vertebrae are of especially great importance in studying materials containing also cranial elements.In many cases, consi-deration of vertebrae alone enables proper estimation of the number and kind of taxa occurring in a given material.Szyndlar (1984) pointed out that disregard of vertebrae (often along with unawareness of intraspecific variation of skull bones) repeatedly has led to false identification of snake fossils.For example, particular isolated cranial bones that actually belonged to a single species may be identified as belonging to a few living species (if they are identical with comparative materials in hand).In such a case, proper number of species will be revealed when vertebrae are considered.
The basis of proper identification of snake vertebrae is mainly their morphology, while the use of numerical data is at most of secondary significance.Although presentation of measurements and ratios as a part of morphological description is desirable, satisfactory methods of identification based on numerical data have not been demonstrated yet (cf.Szyndlar, 1984).The difficulties result from the fact that ratios are strongIy distorted by at least three kinds of considerable variation, Le., intraspecific, allometric, and intracolumnar variations.It should be stressed that numerical differences, sometimes pointed out in differentiating diagnoses (especially in cases when morphological differences are unclear), are based both on limited fossil material and on limited comparative material.Such diagnoses are of doubtful value.Unfortunately, detailed studies of numerical variation of snake vertebrae, based on large number of specimens representing various age classes and considering all kinds of variation are not yet available in the literature.
It should be also stressed that vertebrae of Miocene and younger snakes cannot be a basis for any phylogenetic considerations.The only useful information available from vertebrae alone, apart from their systematic allocation, is the past distribution of the taxon considered.

Geographic and stratigraphic location
Difficulties connected with proper identification of snake fossils are closely correlated with latitudinal 10- cation of a given fossil site and with its geological age.In the case of localities of, let us say, middle Pleistocene age, containing exclusively modern snake species, the more northern locality the easier the identification of fossils.For example, northernmost sites (e.g., the Polish Pleistocene) always contain only a few snake species that are easily differentiated from each other even in the case when they are not abundant and strongly damaged.
The situation may change radically in reference to more southern and geologically older sites, e.g.Bad Deutsch Altenburg 20 in Austria (Szyndlar and Rabeder, in prep.).This upper Pliocene locality yielded exceptionally abundant snake material, consisting of thousands of vertebrae and hundreds of cranial bones, belonging to several ophidian species; an additional difficulty is the fact that upper Pliocene localities may contain both extant and extinct species.It perhaps seems paradoxical, but the remains from Bad Deutsch Altenburg 20 cannot be identified with full confidence, although they contain extremely abundant skull bones.On account of overlapping intraspecific variation of sorne cranial elements belonging to members of the genera Coluber and Elaphe, correct specific (and even generic) identification is impossible.Considering the high intraspecific variation of vertebrae coming from the same locality, proper taxonomic allocation of many fossil elements cannot be demonstrated.I suggest here that N. longivertebrata, morphologically closer to N. natrix than any other living members of the genus are (Rage and Szyndlar 1986), was a direct ancestor of N. natrix.The available skeletal material clearly demonstrates progressibe replacement of the sphenoid pattern characteristic for N. longivertebrata (supposed to be ancestral) by that prevailing in the living N. natrix.The few basiparasphenoids of Natrix natrix, displaying the ancestral pattern, are almost identical with all basiparasphenoids of N. longivertebrata coming from the French Miocene.The bones from France (including newly discovered materials, not yet described) are characterized by highly homogenous overall morphology unlike those from the type locality.The latter, although all possessing the 'typical' longivertebrata pattern in the posteriormost sphenoid area, differ much from one another in the shape of the basipterygoid processes and suborbital flanges (cf.Szyndlar 1984, Fig. 27:1-5).Such a broad spectrum of variation indicates high polymorphy in the hypothetical lineage leading to the recent N. natrix still in the Upper Pliocene; most features observed in the basiparasphenoid of the living N. natrix very little.
For more detailed description of skeletal elements of N. longivertebrata see Szyndlar (1984) and Rage and Szyndlar (1986).
The same author (Venczel, 1991) also mentioned sorne new colubrid and viperid materials coming from the early Pleistocene of Betfia and Subpiatra (Bihor county); these remains have not been described in detail yel.

Note 2
The remarks concerning Coluber podolicus (cf.Szyndlar, 1991: 115) are unprecise and erroneous in parl.The following explanation comes from Szyndlar and Bohme (in prep.): The proper name of the type locality of this snake is either Holuzubiniec (Pusch 1837: 168) or Hotozubince (Pusch 1842: 179), and not Bolurubince as given by Mlynarski (1961: 36) and Rage (1984: 52). .In the opinion of Pusch (1837: 168), who first reported and figured the discussed fossil, it was similar to vertebrae of sorne small lizards and also to those of the living North American salamander Siren lacertina.The illustration of this vertebra (ibid.: PI.XV: 5a-c) indicates with no doubt that it belonged to a member of the ophidian genus Natrix.The original erroneous systematic allocation of the vertebra was emended in a later paper of Pusch (1842. 180), who compared it correctly with Coluber natrix (i.e., Natrix natrix).
Then, in order to distinguish the vertebra from sorne related fossil snakes of the German Neogene, von Meyer (1844: 565) named it Coluber (Tropidonotus?) Podolicus.It should be noted that von Meyer considered the fossil a member of the genus Natrix (in the present sense of this name).The use of the nomenclatural combination 'Coluber (Tropidonotus?)' reflected only von Meyer's uncertainty what was the proper generic allocation of the snakes presently included in the genus Natrix.

Note 3
The following remarks concern the classical material from the Hungarian locality of Polgárdi (labelled number 44 in this paper), examined recently by the author.
Of the snake remains from Polgárdi described by Bolkay (1913) and von Szunyoghy (1932), only types of Coluber hungaricus, Elaphe kormosi and Vipera gedulyi are available, while the remaining material is lost.
Coluber hungaricus (Bolkay, 1913) (cf. remarks in Szyndlar, 1991: 115).The only element referred to this snake (right quadrate, holotype, MHGI Ob-4464) is most similar (but not identical with) to quadrates of the living Coluber gemonensis and to a lesser degree to those of C. najadum and C. rubriceps.1 maintain my previous opinion that a single quadrate is insufficient for establishing a new colubrine species; C. hungaricus is considered here a nomen dubium.
Elaphe kormosi (Bolkay, 1913) (cí. remarks in Szyndlar, 1991: 120).The syntypes of this snake (MHGI Ob-4465) actually belonged to several ophidian species.Of the two ectopterygoids, that figured by Bolkay (1913, pI. XII: 6) most resembles ectopterygoids of the living E. longissima, but the other bone, with a distinctly bent stem and a very short internal ramus, is similar to those of the living E. quatuorlineata; the difference may result, however, from intraspecific variation.The premaxilla, weakly pointed anteriorly and with indistinct processes on the lateral arms, is similar (but not identical with) to that of E. longissima.The basioccipital and the three quadrates display features found in both E. longissima and E. quatuorlineata.The anterior portion of a palatine, identified by Bolkay as a fragmentary maxilla, characterized by the maxillary process almost parallel to the stem of the bone, is clearly referable to Elaphe.Based on the above-mentioned elements, 1 recognize E. kormosi a valid taxon, although it cannot be demonstrated with confidence that all these elements belonged indeed to a single species.Generic allocation of the fragmentary palatine figured by Bolkay (1913, pI. XII: 5) is uncertain; it belonged either to Elaphe or to Natrix.The parasphenoid fragment provides no information.Of the four maxillary fragments, no one can be referred to the genus Elaphe; two posterior fragments, with relatively short ectopterygoid processes and well defined dorsal constrictions for reception of the ectopterygoid, are Z.SZYNDLAR clearly referable to Coluber; of two anterior fragments, one may have belonged to Natrix, while taxonomic allocation of the other cannot be demonstrated.
Vipera gedulyi Bolkay, 1913 (cf. remarks aboye, p. ).The syntypes (MHGI Ob-4467) are clearly referable to a single species, although in some kinds uf bones a broad spectrum of intraspecific variation can be observed.The ectopterygoids (30 anterior fragments), prefrontals (6 specimens), frontals (2 specimens, one left and one right), and compound bones (25 fragments) display, however, homogenous morphology; all these elements as well as a single left exoccipital do not differ from homologous bones of the living V. lebetina.Two small parietal fragments provide no usefui information.In one right prootic, the constrictor internus dorsalis (cid) nerve pierced the laterospheroid bar and continued antero-ventrally within a deep and narrow furrow, the condition not observed in several available specimens of V. lebetina; considering high polymorphy of this feature in the genus Vipera, the observation derived from a single bone cannot provide any decisive evidence of taxonomic distinction.The basiparasphenoids (16 fragments) differ slightly from one another in location of the posterior orifice of the Vidian canal (either it is distinctly separated off the cerebral foramen or both foramina are located together in a shallow common recess) and in the course o the palatine and cid nerves on the inner side of the bone; this variation is concordant with that observed within V. lebetina (Zerova and Chikin, in press).Of 8 basioccipitals, only one bone (figured by Bolkay, 1913, pI. XII: 12), apparently belonging to a very large snake, possesses an exceptionally long and broad basioccipital process; the remaining basioccipitals are usually provided with distinctly shortcr and thinner processes.The maxillae (16 specimens of various sizes) differ from one another in presence or absence of foramina at the top of the ascending process; all of them, ho• wever, are characterized jointly by a strong ridge on the inner side of the process, developed to the degree not observed in other «Oriental vipers».
(Wettstein 1953) likely represented different species, but neither this nor any other opinion can be fully demonstrated.(65):ThevertebralfragmentfromTourkobounia1, with the centrum length reaching 10.10 mm, represented the largest viper known from East European fossil sites.(70):ThevertebrafromChios,according to the figure given by Schneider (1975, fig.3C), displays clearly features characteristic for the 'Oriental vipers'.Nilson and Andrén  (1986:77), who re-examined this material, stated that the fossils « ... are very similar in size and form to vertebrae from large specimens of the recent V. lebetina from Cyprus.»No members of the genus Vipera presently occur on Chios(Wettstein 1953).
It should be noted that the finds of Bransateryx and Albaneryx from the Ukrainian locality of Gritsev are the youngest European records of these genera.On the other hand, first appearance of the living genera antedated disappearance of the archaic elements in the area.