Hyporosopora tenera ( Reuss, 1867 )

Zatoń, Michał & Taylor, Paul D., 2009, Middle Jurassic cyclostome bryozoans from the Polish Jura, Acta Palaeontologica Polonica 54 (2), pp. 267-288 : 282-283

Hyporosopora tenera ( Reuss, 1867)

Fig. 12 .

1867 Berenicea tenera sp. nov.; Reuss 1867: 8 (partim), pl. 1: 9.

2009 Hyporosopora tenera ( Reuss, 1867) ; Taylor 2009: 37, figs. 7C, 9A–F.

Material.—GIUS 8−3509−12.

Measurements.— FWL, 300–440 µm; FWW, 112–137 µm; LAM, 75–112 µm; TAM, 75–100 µm; LPM, 100–125 µm;

TPM, 100–125 µm; GDL, 500 µm; GW, 1000 µm; OL, 66 µm; OW, 91 µm; PL, 15–17.5 µm; PW, 2.5 µm.

Description.—Colony encrusting, sheet−like, multiserial, bereniciform, unilamellar, discoidal in shape ( Fig. 12A ).

Autozooids small, elongate, with slightly convex frontal walls exhibiting fine growth lines; zooidal boundaries distinct, shallowly grooved. Preserved peristomes short, upright. Apertures small−sized, generally circular but sometimes longitudinally elongate, occasionally closed by terminal diaphragms. Pseudopores longitudinally elongate, narrow, slit−like, rather sparse ( Fig. 12D ).

Gonozooids represented by one example close to colony margin. Brood chamber inflated, much wider than longer, rounded subtriangular in shape, distal edge almost straight, roof densely pseudoporous ( Fig. 12C ). Proximolateral margins indented by apertures of neighbouring autozooids. Ooeciopore terminal, wider than longer but almost circular, smaller than an autozooidal aperture.

Remarks.—The morphology of the gonozooid and the size and other characteristics of the autozooids in this specimen match those of the holotype of Hyporosopora tenera ( Reuss, 1867) from the Upper Bathonian–Early Callovian of Balin, as recently redescribed by Taylor (2009). The only difference is the somewhat smaller brood chamber. However, as the colony described has only one gonozooid preserved, we cannot compare the full size−range of gonozooids between the holotype and the new specimen.

Hyporosopora tenera ( Reuss, 1867) differs from the most similar species Hyporosopora typica by having much smaller autozooids, the width of which is well below 200 µm.

Stratigraphic and geographic range.—Middle Bathonian of

Bugaj, Polish Jura and Upper Bathonian to Lower Callovian of Balin, southern Poland.

Figures

Fig. 12. Plagioeciid cyclostome bryozoan Hyporosopora tenera (Reuss, 1867) from the Middle Jurassic ore−bearing clays of the Polish Jura, GIUS 8−3509−12. A. Colony view. B. Marginal autozooids. C. Gonozooid with ooeciopore (arrowed). D. Pseudopores. Scale bars: 300 µm (A), 100 µm (B, C), 30 µm (D). BSE SEM images of uncoated specimens.