Phlyctocythere sicula, Sciuto & Pugliese, 2013

Sciuto, Francesco & Pugliese, Nevio, 2013, Description of two new species of ostracods from the Strait of Messina (central Mediterranean), Zoosystema 35 (1), pp. 35-44 : 40-42

Phlyctocythere sicula n. sp.

( Fig. 3 )

TYPE MATERIAL. — Holotype: Strait of Messina , central Mediterranean , R / V Universitatis, cruise MERC, Sampling station MERC 10 (38°07’14’’N, 15°32’55”E; 545 m depth), terrigenous mud, 10.XII.2005, right valve (L 0.670 mm, H 0.365 mm), MNHN PMC. O8 H. 1.10.2012 ( Fig. 3A ).

Paratypes: same data as holotype, 2 left valves, MNHN PMC.O 28P. 1.10.2012 ( Fig. 3B ), O 29P. 1.10.2012 ( Fig. 3C ).

OTHER MATERIAL EXAMINED. — One left valve found in the Pleistocene (Calabrian) sedimentary succession cropping out at Scoppo (ME) ( Fig. 1 ) along the sicilian side of the Strait of Messina.

STRATIGRAPHIC RANGE.— Early Pleistocene (Calabrian) to Recent.

ETIMOLOGY. — Named from the Sicily Island.

DIAGNOSIS. — Phlyctocythere sicula n. sp. is characterised by a suboval, inflated carapace with swollen posteroventral area and a short caudal process in postero-central area.

DESCRIPTION

Carapace medium to large sized, suboval in lateral view.Anterior margin rounded and slightly pointed, dorsal margin regularly arched and convex, gently passing to the caudal process of the posterior area ( Fig. 3A, B ). Caudal process short and obtuse. Ventral margin slightly sinuous, regularly and steeply bending to the posterior margin towards the caudal process.

Carapace inflated and oval in dorsal view.

Outer surface lightly ornamented by a very weak reticulum particularly evident in the ventrolateral area ( Fig. 3I ). Few normal pore-canals, simple and evenly distributed, widely spaced, on the surface of the valve ( Fig. 3C, G, H ).

Inner lamella anteriorly wide, narrower posteriorly, reduced to the minimum ventrally ( Fig. 3C ). Vestibula large anteriorly, narrow in postero-ventral area ( Fig. 3C ).

Marginal pore-canals not observable.

Eye tubercles absent.

Hinge merodont: in the LV a curved smooth bar ( Fig. 3C, F ) with two little elongated lateral grooves at the anterior and posterior ends ( Fig. 3G, H ). RV with complementary elements.

Four adductor scars and a single dorsal muscle scar ( Fig. 3 C, D ).

REMARKS

Phlyctocythere sicula n. sp. shows general features, and particularly the outline, similar to those of Loxoconcha Sars, 1866 and, especially, to Loxoconchella Triebel, 1954 , but differs from both of them mainly because of the weak ornamentation of the carapace.

Relatively to the hinge, the genus Phlyctocythere seems to show a wide variability; despite, Keij (1958) described the hinge of the type species as adont in its original description. Several species assigned to Phlyctocythere actually have a more or less developed hinge. P. pellucida ( Müller, 1894) possesses a hinge as do some specimens, recorded by Van Morkoven (1963) and left in open nomenclature, which show traces of hinge terminal elements. Similarly, P. curva Van den Bold, 1988 shows a hinge “Weak, in the left valve consisting of a long, curved, very slightly crenulate bar with terminal, elongate, slightly, crenulate sockets” ( Van den Bold 1988: 52). Consequently, the presence of a merodont hinge in the observed species does not prevent its inclusion within the genus Phlyctocythere . Furthermore, the present species has been assigned to Anchistrocheles using some features belonging to the type species such as the four muscle scars in row, the different vestibula, the normal pore canals widely spaced and the light ornamentation of the outer surface of the carapace.

Phlyctocythere includes 12 living species and some fossil ones; some of them are reported in open nomenclature. It has a present-day and fossil worldwide distribution. The oldest species have been doubtfully reported from the Barremian of SE France ( Donze 1971), and further taxa are known from the Eocene of the Paris Basin ( Keij 1958), the Tortonian-Messinian of SE Sicily ( Ciampo 1980) and the Pleistocene of Italy ( Ciampo 1976; Moncharmont-Zei et al. 1985).

Living species have been reported from the Mediterranean ( Müller 1894; Ciampo 2003), the south Pacific ( Correge 1993), the NE Atlantic ( Freiwald & Mostafawi 1998), northwestern Europe ( Sars 1866; 1922 -1928), North Carolina (Atlantic Ocean) ( Hazel 1975), tropical West Africa ( Hartmann & Hartmann Schroeder 1975).

In the Recent Mediterranean the genus Phlyctocythere was formerly known only with P. pellucida ( Müller, 1894) . Phlyctocythere pellucida was reported from: 1) the Gulf of Naples associated with calcareuos algae down to a depth of 100 m ( Puri et al. 1964); 2) Malta, where it was collected from 9 and 128 m ( Bonaduce & Masoli 1970); 3) the east Mediterranean ( Liban), collected from 75 and 245 m (Bonaduce et al. 1970); 4) Adriatic Sea down to 150 m ( Uffenorde 1972; Bonaduce et al. 1975).

Phlyctocythere sicula n. sp. is distinguishable from P. pellucida because of the more rounded outline, the caudal process less marked, more obtuse and more shifted to the median side of the posterior end; the postero-ventral area inflated, the more acute anterior margin, the narrower marginal zone and vestibula.

Figures

FIG. 3. — Phlyctocythere sicula n. sp.: A, holotype (MNHN PMC.O8H.1.10.2012) right valve, external lateral view;B, I, paratype (MNHN PMC.O28P.1.10.2012);C, D, F-H paratype (MNHN PMC.O29P.1.10.2012); B, left valve,external lateral view;C, left valve,internal view; D, left valve, internal view, muscle scars; E, left valve, dorsal view, drawing of outline; F, left valve, internal view, detail of the central part of the hinge; G, left valve, internal view, detail of the anterior part of the hinge; H, left valve, internal view, detail of the posterior part of the hinge; I, left valve, detail of ornamentation in ventral area. Scale bars: A-C, E, 200 µm; D, 100 µm; F-H, 50 µm; I, 20 µm.

FIG. 1. — Geographical location of sampling stations in the Strait of Messina.