Late Miocene bony fishes from Pocşeşti (Republic of Moldova)

Isolated pharyngeal and jaw teeth of bony fishes, as well as numerous bones of other vertebrates dated by Late Miocene (middle late Sarmatian s.l. = early Tortonian, 9.8 Ma), were found in the alluvial sediments of Pocşeşti site (Republic of Moldova). Six fish taxa were identified and described in the paper; the majority of them (4 species) are representatives of Cyprinidae family. Taxonomic list also includes sturgeons (Acipenseridae gen. et sp. indet.) and pikes (Esox sp.). Mixed character of fauna, joint presence of freshwater and marine species suggests that the burial of remnants took place in close proximity to large marine basin in river avandelta. Fish assemblage of Pocşeşti shows an affinity to other early Tortonian localities in Europe and reflects paleobiogeographic changes on the territory of Paratethys during the Late Miocene.


INTRODUCTION
European bony fish fauna began to be formed in the second half of the Paleogene. This process was continued in the Neogene, accompanied by a large-scale restructuring of ecosystems on the background of significant climatic changes. Numerous remnants of freshwater and marine bony fishes from the Late Miocene of Eastern Europe need careful handling and detailed study.
Pocşeşti (Pokshesht) site was discovered by G.M. Bilinskis in 1975 [11] and is dated to Balta suite. It is located near eponymous village on the border of Orgeevskyi and Strashenskyi districts in the Republic of Moldova (Fig. 1). Fossil bones are concentrated on the right side of Ikel River valley at the attitude of 195-200 m. According to palaeomagnetic analysis, provided by I.A. Pevzner with colleagues [18], fosilliferous horizon of Pocşeşti has right magnetization and dated to the 9 th epoch of magnetic polarity (between 10 and 9 Ma).

MATERIAL AND METHODS
The present article is based on the study of 12 fish bones, 8 of which are determinable to species or at least to genus level. The investigated material was collected by A.N. Lungu in 1980s and also V.A. Marareskul and T.F. Obada during the 2011-2013.
A direct determination of fossil remnants was provided by authors using diagnostic features. For comparative purposes bones from the osteological collections of the National Museum of Natural History NAS of Ukraine were used. Ichthyologic systematics in this paper follows Yu.V. Movchan [15].

GEOLOGICAL SETTING
The following layers were identified by A.N. Lungu in 1979 [11] in the geological section of Pocşeşti: 1) Top soil, 0.2-0.3 m; 2) Brown loam, 0.2-0.4 m; 3) Lumpy non-laminated greenish-gray clay with nodules of carbonates and charred plant remnants, 1.8 m; 4) Sandy gray clay with calcareous concretions, gradually moving up in dark green lumpy clay with bones of terrestrial vertebrates, 0.5 m; 5) Lumpy non-laminated gray clay with charred plant remnants and fragments of vertebrate bones, 0.5-1.0 m; 6) Sandy gray clay, contain with clay nodules and bones of terrestrial vertebrates, 1.0-2.5 m; 7) Fine clay, slightly cross-bedded sand with gravel lenses, 0.5-2.5 m; 8) Sandy shaly gray clay with rusty spots, 1.5-2.0 m. Khersonian deposits on the Moldavian plate are composed by clastic sediments [20]. On the described territory only lower horizon is clearly identified and represented by marine greenish-gray clays interbedded with siltstone and fine-grained quartz sand.
Upper horizon is composed by alluvial sediments and is not separated from younger lithologically similar Balta suite formations. Balta sandy-clay deposits are widespread within the central and southern part of the Dniester-Prut interfluve and between Dniester -Southern Bug. Formation time of these sediments is associated with the end of the middle Sarmatian to Pontian. They are represented by lake-marsh, river, and deltaic facies. Their stratigraphic division is not clear [8]. Description: Pharyngeal tooth is slender, with relatively low rounded crown, broken at the base. Tooth back is straight, top of the tooth is elongated in the blunt robust hook. Its edge is targeted forward and upward. Grinding surface has two small jags. Tooth belly is slightly convex. Height of the crown is 2.3, width is 1.4 mm. Tooth belongs to small (juvenile?) specimen.

Rutilus Rafinesque, 1820
Rutilus frisii (Nordmann, 1840) Referred specimen: pharyngeal tooth (IZ Poc/02) (Fig. 3, 2). Description: Tooth is rough, with fungiform, laterally compressed crown. Tooth back is convex and arcuate, top without hook. Grinding surface is narrow, slightly convex, with weekly marked longitudinal furrow and has traces of intravital obliteration. Tooth belly is convex and hangs over the neck. Pedicle is partly broken, oval in the crosssection. Crown is coarcted to neck and a little larger than its width. Height of the tooth is 3.2, width of the crown is 3.1 mm.

Scardinius Bonaparte, 1837
Scardinius sp. Referred specimen: pharyngeal tooth (IZ Poc/03) (Fig. 3, 3). Description: Small pharyngeal tooth on the long pedicle has high laterally slender cylindrical crown with broad base. Tooth back is straight, with robust hook at the top. Grinding surface is narrow with a higher edge that has 3 robust pointed jags and a lower edge without jags. Tooth belly is rounded and compressed, without keel. Height of the tooth is 3.2, width of the crown is 1.5 mm.
Tinca Cuvier, 1816 Tinca sp. Referred specimen: pharyngeal tooth (IZ Poc/04) (Fig. 3, 4). Description: Flattened pharyngeal tooth has low crown. Pedicle is rounded and slightly deflexed. Neck is expressed well, tooth back is convex and arcuate. Tooth belly is also slightly convex. Grinding surface is narrow, laterally compressed, having a deep longitudinal wrinkle with slightly convex roller edges. Wrinkle on the lower edge of the grinding surface is jagged by transverse corrugations and forms a fin scroll on the posterior surface of the crown. Height of the tooth is 5.6, width of the crown is 5.8 mm.

ESOCIFORMES Bleeker, 1858
Family ESOCIDAE Cuvier, 1816 Esox Linnaeus, 1758 Esox sp. Referred specimen: jaw tooth, 2 vertebrae (IZ Poc/05-07) (Fig. 3, 5). Description: The long, slender, pointed tooth has two sharp edges. Its conical crown with slightly worn apex is partly broken. Cross-section is interiorly smooth and exteriorly convex. Height of the tooth is 5.5 mm, width of the crown is 2.1 mm. The attribution of vertebrae to pike was based on morphological similarities and remains more unclear.

DISCUSSION
All the above-mentioned bony fish species from Pocşeşti were identified based on single disarticulated specimens. Nevertheless, it is possible to provide a view on composition fish community in the late Sarmatian of that area. It includes reophiles (Leuciscus, Rutilus) and limnophiles (Scardinius, Tinca, Esox). Fishes from Pocşeşti are presented by four different trophic groups (herbivorous, malacophagous, piscivorous and omnivorous).
The majority of identified fish taxa (4 species) are representatives of the family Cyprinidae. Other families (Acipenseridae, Esocidae) are presented by single species. It must be noted that all identified genera are still available in the recent Dniester River delta fish community [4,23].
Taxonomic composition of terrestrial oriktokomplex from Pocşeşti indicates its archaic appearance and brings it with hipparion fauna from Varnitsa, as well as hipparion assemblages from Eldar in Transcaucasia, Berislav and Grebeniki in Ukraine [10]. Terrestrial fauna of Pocşeşti occupies an intermediate position between the earliest and late hipparion faunas on the Northern Black Sea Coast and stands as an independent faunal complex [12]. Most of its representatives inhabited savanna landscapes of the steppe type, as well as wetlands, forested floodplains and riparian forests [10,12]. This community suggests be related to the first half of the late Sarmatian s.l. (9.8 Ma, MN10). Ізольовані глоткові та щелепні зуби костистих риб, а також численні кістки інших хребетних тварин, датовані пізнім міоценом (серединою пізнього сармату = раннім