Siphonotretella popovi, 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 : 149

Siphonotretella popovi sp. nov.

Fig. 6 .

Siphonotreta acrotretomorpha Gorjansky, 1969 ; Biernat 1973: 105, pl. 27: 4–10; 28; 29; 30: 6–8.

Siphonotretella sp. ; Popov and Holmer 1994: 84, fig. 75. Siphonotretella sp. ; Holmer and Popov 2000: 145, fig. 80, 2d, e. Holotype: RM Br 133793, ventral valve (W = 1.52, L= 1.31, H = 0.50) Type locality: Wysoczki. Holy Cross Mountains, Poland.

Type horizon: Tremadoc chalcedonites.

Derivation of name: In honour of brachiopod specialist Leonid Popov.

Material.—Total of 17 ventral and 17 dorsal valves. Figured ventral valves: RM Br 133796 (W = 1.27, L= 1.10, H = 0.50), RM Br133798 (W = 1.64, L = 1.30, H = 0.48); dorsal valves RM Br133791 (W = 1.08, L = 0.85, WI = 0.45), RM Br133792 (W = 1.00, L = 0.81, WI = 0.42), RM Br133794 (W = 1.50, L = 1.08), RM Br133795 (W = 0.88, L = 0.75), RM Br133797 (W = 0.76, L = 0.64, WI = 0.40, H = 0.14).

Diagnosis.—Ventral valve subconical, up to 50% as high as long. Ventral pseudointerarea catacline to procline, poorly defined laterally. Apical pedicle foramen not enlarged by resorbtion, continued as extremely short interior pedicle tube.

Description.—Shell ventribiconvex, transversely subcircular, around 70–90% as long as wide (N = 8). Ventral valve subconical, around 35–50% as high as long (N = 3). Ventral pseudointerarea catacline to procline, poorly defined laterally. Apical pedicle foramen small (about 0.09 mm across) and rounded, not enlarged by resorbtion, continued as extremely short interior pedicle tube. Internal characters of both valves poorly impressed.

Dorsal valve gently convex with maximum height somewhat anterior to umbo, less than 25% as high as long (N = 1). Dorsal pseudointerarea reduced to thin plate, crescentshaped, occupying less than half of valve width and occupied mainly by median groove.

Shell surface covered by fine hollow spines of about equal size (around 20–70 µm across). Larval shell of both valves well−defined, close to circular, around 0.30–0.35 mm across.

Discussion.—This siphonotretid species was described by Biernat (1973) as Siphonotreta acrotretomorpha Gorjansky (1969) , but as noted by Popov and Holmer (1994), restudy of the type material of this taxon from the Leetse beds in Estonia clearly shows that the Estonian species differs in having a pedicle foramen that is enlarged by resorbtion. The Polish species differs mainly from the type species Siphonotretella jani in having a comparatively higher (up to half as high as long) conical ventral valve with the maximum height at he beak, and a procline pseudointerarea. It is conspecific with the forms described by Popov and Holmer (1994) as Siphonotretella sp. from the Early Ordovician of the South Urals and Kazakhstan.

Figures

Fig. 6. A–N. Siphonotretella popovi sp. nov. A, N. Dorsal valve RM Br133791, exterior (A, × 26), detail of spines (N, × 100). B. Dor− sal valve RM Br133792, exterior, × 32. C. Holotype, ventral valve RM Br133793, exterior, × 26. D, G, L. Dorsal valve RM Br133794, oblique posterior view (D, × 30), exterior (G, × 30), detail of larval shell (L, × 80). E, J. Dorsal valve RM Br133795, exterior (E, × 40) and detail of larval shell (J, × 120). F, H, I, K. Ventral valve RM Br133796, oblique lateral view (F, × 26), oblique posterior view (H, × 32), detail of larval shell and pedicle opening (I, × 80), de− tail of larval shell and pedicle opening (K, × 90). M. Dorsal valve RM Br133797, inte− rior, × 40. O. Ventral valve RM Br133798, interior, × 23. All specimens from the Tremadoc chalcedonites, Wysoczki.