New Permian ostracods from Greece (Hydra Island)

A new Permian (Late Asselian–Dorashamian) ostracod fauna (66 species belonging to 35 genera) from Hydra Island (Greece) is described. Twelve new species are described: Hollinella (P.) hydraensis Crasquin-Soleau n.sp, Bairdia episkopiensis Crasquin-Soleau n.sp., Bairdia rigasensis Crasquin-Soleau n.sp., Bairdia thikiaensis Crasquin-Soleau n.sp., Chamishaella marmariensis Crasquin-Soleau n.sp., Cypridina gussevaae Crasquin-Soleau n.sp., Cyathus barmariensis Crasquin-Soleau n.sp., Cyathus klimakiensis Crasquin-Soleau n.sp., Bairdiacypris bistiensis Crasquin-Soleau n.sp., Shishaella hellenensis Crasquin-Soleau n.sp., Bairdia ishizakii Crasquin-Soleau n.sp., Petasobairdia kozuri Crasquin-Soleau n.sp. Forty-four other species are figured. This assemblage is characteristic of a shallow water platform. The palaeobiogeographic relationships are presented and represent significant additions to the Permian Palaeo-Tethyan ostracod faunas.

The Klimaki Group is subdivided into three formations: Riga, Cape Bisti and Marmari. Only the last one contains ostracods and is of Late Murgabian age. It consists of two calcarodolomitic cycles, 50 and lOOm thick, respectively (Grant et nl., 1991).
The Barmari Group is subdivided into two formations, the Episkopi Formation which fits below the Miras Formation above. They are separated by an unconformity from the underlying Klimaki Group. We will focus our analysis on the Episkopi Formation. The thickness of the formation varies from 10 m (tectonically reduced) at Agios Nikolaos (Eastern part) to lOOm at Lehusis, and 120m at Episkopi section in the West.
The lower part is mainly composed of conglomerate lenses with dolomitic pebbles from the underlying Marmari Formation, or of thin bedded dolomicrite. The lower 90m of the Episkopi Formation are thickly bedded and consist of high energy bioclastic lime packstone-grainstones with silicification, rich in calcareous algae, small foraminifers and fragments of brachiopods, bryozoans and corals. The following 55 m of stratified limestones are characterized by flat to round chert *In Sohn (1978): USNM locality 9260: southern side of the Island of Hydra, just off the Argolian coast, Greece (see Grant, 1972, pp. 214, 215, for description), about 0.5 km south of the village of Episkopi. Weathered limestone blocks containing silicified fossils on stratigraphically of two benches. USNM locality 9262: same Island as above, about 3 km north-northeast of Episkopi. Limestone blocks and pieces from a bed about 1.2m thick. pebbles in fine bioclastic lime packstone with sponge spicules, crinoids, calcareous algae and foraminifers. The cherty limestone is overlain by 10m of grey nodular lime wackestone followed by 30 m of well bedded lime packstone-wackestone with marly interbeds. Sponges, crinoids, bryozoans, foraminifers and ostracods are associated with this facies which also contains the famous brachiopods localities of Grant (1995).
The shallow carbonate Episkopi Formation ends abruptly with algal limestones. The overlying Miras Formation is c. 3 G lOOm thick, and consists of brown to dark red shales with various carbonate lenses or blocks. This terrigenous unit still contains Permian brachiopods and forams.
The ostracods described here occur in three main sections from the NE to the SW: Cape Rigas, Episkopi and Cape Bisti sections (Fig. 1). One sample of the Lehusis section (sample 4863 1) provides two species.
From 183 samples processed by hot acetolysis (Lethiers & Crasquin-Soleau, 1988) belonging to the four sections, only 39 samples contained ostracods. All the studied levels are well agecalibrated by foraminifera from the Late Asselian to Dorashamian (Grant et al., 1991). The distribution of the 66 ostracod species (34 genera) is given on a general statigraphic section of the Permian of Hydra (Fig. 3).  Description. Carapace long, with anterior and posterior borders laterally flattened; left valve slightly overlaps the right one all around the carapace; dorsal border straight at the two valves; anterodorsal border straight to gently concave; anterior border with small radius of curvature, laterally flattened, maximum convexity located above mid-height, anteroventral border straight; ventral border gently concave, presence of a straight ventral ridge on each valve; posteroventral margin straight and long; posterior border tapering, strongly flattened laterally, maximum convexity located below lower third of height; posterodorsal border straight; angle between posterodorsal border and dorsal border (of right valve) 130°, between dorsal border and anterodorsal border 140°; maximum height located at 57% of length; carapace smooth. Dimensions. L = 0.62-1.10 mm, H = 0.25-0.58 mm Discussion. This species has a general outline close to that of Buirdiu vyasovkensis Khivintseva, 1969 from the Kazanian of SW Urals, but that species has no ridge. This species has similar ventral ridges as in Buirdiu prueuliger Tkatscheva, 1975(in Ivanova et ul., 1975 from the Upper Carboniferous of Russian Platform, but here the ridges are straight and the valve overlap is less obvious.
(Pl. 2, figs 7-10) Remark. Guan (1978)  convexity of the carapace, orientation is difficult to ascertain. Kozur (1991~) published a long and very interesting discussion (pp. 16-17) about this problem and its systematic implications. The Chinese authors regard the strongly convex margin as being the ventral one. Kozur (1991~) considered that the convex margin is, in fact, the dorsal margin. After substantial observation of the specimens found here, the authors follow the Chinese procedure. Prof. F. Lethiers (Universite P. et M. Curie, Paris, pers. comm.) thinks that these two genera are the same (Cyathus). In accordance with him, we consider that the lateral ornamentation is an insufficient character with which to separate the two genera because the lack of ridges is often the result of fossilization, and the velate structure is low and its observation is not always possible. The genus Sinocoelonella is a junior synomym of Cyathus. Description. Dorsal border convex in central part and gently concave at its two extremities; cardinal angles very obtuse; anterior border with great radius of curvature, maximum convexity located at 4 2 4 % of height; ventral border regulary convex with maximum height located at mid-length or slightly in front of mid-height; posterior border with small radius of curvature, maximum convexity located at 3540% of height; carapace flattened laterally at anterior and posterior parts; in largest forms flattening also in ventral part; dorsal borders overhang hinge line on both valves but more strongly for the right one, right valve slightly overlaps the left one on free margins; surface with a very fine punctation, which seems to be organized along lines parallel to dorsal and ventral borders. Dimensions. L=0.55-0.76mm: H=0.36-0.45 mm. Derivation of name. From Hydra Island. Kozur, 1985. fig fig. 8: left lateral view,holotype, MGL74322, x80. fig. 9: left lateral view, paratype, MGL74323, x100. fig. 10. Indivisia symmetrica Kozur, 1985, right lateral view, MGL74324, x 100, sample 50146. fig. 11. Shzvaellacf. brazoensis (Coryell & Sample, 1932) Discussion. Our species is closed to Hollinella (P.) emaciata (Ulrich & Bassler, 1906) from the Lower Permian of Kansas, USA. In our species, the cardinal angles are less obtuse which tend to affect the lateral outline of the carapace.

PALAEOECOLOGY
The general composition of this marine ostracod assemblages for the entire composite section is typical of a shallow platform under tropical conditions, so characteristic of the Palaeotethys realm at this time.  (Melnyk & Maddocks, 1988) and Kansas (Peterson & Kaesler, 1980;Costenzo & Kaesler, 1987). For example, the Bairdiacypris group belongs to a nearshore group of species. Large Hollinella, with developed adventral structure, can characterize an environment such as an interdistributary bay prodelta and interdeltaic embayment lagoons (lowermost level of the section). The Bairdia group characterizes carbonate, open-marine environments. Carapaces are often broken and most of the well-represented species show only adults and last-larval stages (except for Hollinella hydraensis Crasquin-Soleau n.sp. which yields larval stages). This is a consequence of a high-energy biocenosis or a thanatocoenosis (Whatley, 1983(Whatley, , 1988Brouwers, 1988). However, transportation was limited since most individuals are represented by closed carapaces, indicating a soft substratum and a relatively high sedimentation rate (Oertli, 1971). However, some small variations are identifiable within these general characteristics along the section. The general ecological changes are summarized in Fig. 5. At the top of the Lehusis Formation, the percentage of Bairdiacea is low (45%) and the Kloedenellacea, characteristic of very shallow environments where salinity conditions can be very variable, abound together with the Hollinacea (the only level of the section). At the base of the Cape Rigas formation, the percentage of Bairdiacea increases very significant (70% of species), with less Kloedenellacea, and without Hollinacea: this environment is deeper, with more stable living conditions. After a gap (no ostracods found in the studied samples) along Cape Rigas, Riga, Cape Bisti and lower Marmari formations, we have in the Marmari a relatively homogeneous composition with low percentages of Bairdiacea, Paraparchitacea, Kloedenellacea: this represents a typical shallow platform environment. Nevertheless, a small event occurs at the boundary of the Marmari and Episkopi formations where the percentage of Bairdiacea increases together with the progressive disappearance of Kloedenellacea. This indicates a rapid deepening of the sea and the optimum marine environment for the construction of the last Permian carbonate platform. This event is correlated with the C event of Baud et al. (1991). Microchelinelluperoiperoi Kozur, 1985 (sample 90-59). fig. 11: right lateral view, MGL74354, x80; fig. 12: right lateral view, MGL74355, x70. fig.  13: right lateral view, MGL74356, x100. fig. 14. Fubulicypris obsoleru (Schneider, 1966), left lateral view, MGL74357, x100, sample 90-58. fig. 15. Acrariu sp.1, right lateral view, MGL74358, x60, sample 90-58. fig. 16. Microcheilinellu sp., right lateral view, MGL74359, x 100, sample 50148. fig.  17: Busslerellu cf. ucuru Kotschetkova, 1972, right lateral view, MGL74417, x 175, sample 48531. species, which is not surprising as there have been few published studies on the Permian ostracods from this area. In contrast, Permian ostracods are relatively well known in the USA and Russia (see exhaustive bibliography in . Available data on the Permian Tethys domain s.I., besides Greece (Kornicker & Sohn, 1976;Sohn, 1978) come from Hungary (Zalanyi, 1974;Kozur, 1985a, b,), Sicily (Kozur, 1991a, b), Tunisia (Lethiers et a[., 1989;Said-Benzarti & Crasquin-Soleau, 1997), Israel (Gerry et al., 1987), and South China (Chen, 1958;Wang, 1978;Chen & Bao, 1986;Chen & Shi, 1982). Some punctual studies were carried out in Japan by Ishizaki (1964). Figure 6 establishes the relationships between the Hydra Island ostracod fauna and the other ones from known Permian localities. The last line presents the number of common species and the number of species compared to forms belonging to other Permian localities. For clarity, we can use the 'provincialism index' (Johnson, 1971) PI (PI= C/2Ei), where Cis the number of common species between two areas and Ei the number of endemic species in the area where they are a t their lowest number. We observe that the relationships of the Hydra taxa are close to those of Hungary (PZ=O.14 and 0.17 with the affine species); this was expected as Hungary is the nearest site to Hydra palaeogeographically. After that, in decreasing order, we note the relations with South China (PZ= 0.08-O.14), the Russian Platform (PI= 0.054. lo), Tunisia (PZ= 0.02), Israel (0.02) and the USA (PZ= 0.01-0.05). The most interesting aspect is the significant palaeobiogeographic relationships between Hydra Island and South China during Permian time. This could be explained by the importance of surface palaeocurrents from East to West in the Palaeotethys realm  that would have dispersed the taxa.