Reptomultisparsa aff. cobra ( Pitt and Thomas, 1969 )

Zatoń, Michał & Taylor, Paul D., 2009, Middle Jurassic cyclostome bryozoans from the Polish Jura, Acta Palaeontologica Polonica 54 (2), pp. 267-288 : 279-280

Reptomultisparsa aff. cobra ( Pitt and Thomas, 1969)

Fig. 9 .

Material.—Three colonies on two samples: GIUS 8−3509− 17–18, two of which possess gonozooids.

Measurements.—FWL, 472–980 µm; FWW, 120–180 µm; LAM, 66–100 µm; TAM, 57–85 µm; LPM, 100–133 µm; TPM, 100–116 µm; GTL, 1760 µm; GDL, 1120–1216 µm; GW, 600–733 µm; OL, 121 µm; OW, 114 µm; PL, 7.5–10 µm; PW, 6.3–7.5 µm.

Description.—Colony encrusting, multiserial, sheet−like, bereniciform, multilamellar; surface planar. Spiral overgrowths are common ( Fig. 9A ). Growing edge low, only one generation of zooids visible at the budding zone ( Fig. 9A ). Early growth stages unknown.

Autozooids slender, variable in length but mostly long, with flat or very gently convex frontal walls, zooidal boundaries indistinct. Apertures widely spaced, circular or slightly elongated, some closed by terminal diaphragms. Peristomes short, upright. Pseudopores teardrop−shaped, densely spaced, longer than wide, usually pointed distally, located at boundaries between narrow longitudinal strips of calcification ( Fig. 9D ).

Gonozooids preserved in two colonies, uncommon, crushed and/or filled with pyrite. Proximal frontal wall flat, indistinguishable from an autozooid. Brood chamber evidently more convex than an autozooid, longitudinally elongated, spindle−like in shape with maximum width at midlength ( Fig. 9C ). Ooeciopore subterminal, circular in outline, larger than an autozooidal aperture.

Remarks.—The Polish material described here differs from the holotype of R. cobra ( Pitt and Thomas, 1969) , originally described from the Lower Bathonian of southern Britain (Oxfordshire), which has a more elongate, less spindle−shaped brood chamber. However, the differences are slight, the British and Polish material having autozooids and pseudopores of similar sizes and shapes. A related species from Balin with larger autozooids was recently described under the name R. aff. cobra ( Pitt and Thomas, 1969) by Taylor (2009).

Stratigraphic and geographic range.—Middle Bathonian of Bugaj, Polish Jura.

Figures

Fig. 9. Multisparsid cyclostome bryozoan Reptomultisparsa aff. cobra (Pitt and Thomas, 1969) from the Middle Jurassic ore−bearing clays of the Polish Jura, GIUS 8−3509−17. A. Colony with spiral overgrowth. B. Proximal regrowth from broken edge (arrowed). C. Crushed and partly worn gonozooid. D. Pseudopores. Scale bars 200 µm (A), 100 µm (B, C), 20 µm (D). BSE SEM images of uncoated specimens.