Elliptoglossa polonica, Holmer & Biernat, 2002

Holmer, Lars E. & Biernat, Gertruda, 2002, Urban and Peri-urban small and medium-size Enterprise Development for sustainable Vegetable Production and Marketing Systems, Acta Palaeontologica Polonica 47 (1), pp. 141-156 : 142-143

Elliptoglossa polonica sp. nov.

Fig. 2 .

Schmidtites obtusus ( Mickwitz, 1896) ; Biernat 1973: 54, pl. 1: 1–3,

fig. 3.

Elliptoglossa sp. ; Bednarczyk and Biernat 1978: 297.

Holotype: RM Br133769, ventral valve (W = 0.56, L = 0.78, WI = 0.13, LI = 0.04).

Type locality: Wysoczki. Holy Cross Mountains, Poland.

Type horizon: Tremadoc chalcedonites.

Derivation of name: After the occurrence in Poland.

Material.—Total of 35 dorsal and 16 ventral valves. Figured ventral valves: RM Br133770 (W = 0.53, L = 0.78, WI = 0.13, LI = 0.04), RM Br133771 (W = 0.63, L = 0.92, WI = 0.16, LI = 0.07), RM Br133772 (W = 0.48, L = 0.84, WI = 0.11, LI = 0.06); dorsal valves: RM Br133767 (W = 0.60, L = 0.82), RM Br133768 (W = 0.62, L = 0.94), RM Br133773.

Diagnosis.—Shell elongate oval to subcircular, about 140– 180% as long as wide. Ventral pseudointerareas vestigial, with flattened triangular posterior projection. Dorsal pseudointerarea completely reduced.

Description.—Shell elongate oval, close to equi−biconvex, 140–180% as long as wide (N = 6); both valves gently and evenly convex in lateral profile. Ventral pseudointerarea forming characteristic flattened, narrow, undivided plate with posterior projection, occupying 23–25% of total valve width (N = 4) and only 5–8% of total valve length (N = 4); defined pedicle groove absent.

Dorsal valve lacking pseudointerarea, but with well defined marginal limbus, somewhat wider and higher posteriorly. Larval shell of both valves close to circular, around 0.2–0.3 mm wide and usually somewhat elongate.

Internal characters of both valves not impressed.

Discussion.— Biernat (1973) considered this taxon to represent juveniles of Schmidtites obtusus . However, following redescription of this taxon (e.g., Holmer and Popov 2000: 52, fig. 20: 4) it is clear that the Polish species is unrelated to Schmidtites . All characters (vestigial to completely absent pseudointerareas, lack of pedicle notch etc.) of the Polish taxon now indicate that it is a species of Elliptoglossa , as noted also by Bednarczyk and Biernat (1978) and Popov and Holmer (1994). E. polonica differs from all other species of the genus in having a vestigial ventral pseudointerarea forming a flattened, narrow, undivided plate with a posterior projection.

Figures

Fig. 2. A–K. Elliptoglossa polonica sp. nov. A, H. Dorsal valve RM Br133767, exterior (A, × 45) and oblique lateral view (H, × 45). B, G. Dorsal valve RM Br133768, interior (B, × 32) and oblique lateral view (G, × 40). C. Holotype, ventral valve RM Br133769, exterior, × 45. D. Ventral valve RM Br133770, interior, × 45. E, F, I. Ventral valve RM Br133771, exterior (E, × 38), oblique lateral view (F, × 40) and detail of larval shell (I, × 135). J. Ventral valve RM Br133772, detail of pseudointerarea, × 400. K. Dorsal valve RM Br133773, oblique lateral view of umbonal section of interior, × 100. All speci− mens from the Tremadoc chalcedonites, Wysoczki.