Microeciella beliensis Taylor and Sequeiros, 1982

Taylor, Paul D. & Zatoń, Michał, 2008, Taxonomy of the bryozoan genera Oncousoecia, Microeciella and Eurystrotos (Cyclostomata: Oncousoeciidae), Journal of Natural History 42 (39 - 40), pp. 2557-2574 : 2569-2570

Microeciella beliensis Taylor and Sequeiros, 1982

( Figure 6A–E )

Microeciella beliensis Taylor and Seqeiros 1982, p. 119 , Figures 1 , 2 , 8, 10.

Material

Holotype. NHM D53321a, Jurassic, Upper Toarcian , Belcite, Zaragoza, Spain, L. Sequeiros Collection.

Paratype. NHM D53321b, details as for holotype .

Description

Colony encrusting ( Figure 6A ), small, generally less than 5 mm in diameter, multiserial, initially fan-shaped, becoming discoidal with a circumferential growing edge. Ancestrula partly overgrown by later zooids hiding protoecium, distal tube long, curved to one side ( Figure 6D ). Growing edge low, usually only one generation of zooids visible at budding zone.

Autozooids elongate, frontal walls 0.64–0.81 mm long by 0.16–0.17 mm wide, gently convex; pseudopores ( Figure 6E ) teardrop-shaped, pointed distally, apparently without spines. Apertures longitudinally elongate, 0.11–0.16 mm long by 0.09– 0.14 mm wide, arranged more or less quincuncially, diameter varying according to preservation of the distally tapering peristome; terminal diaphragms not observed.

Gonozooids ( Figure 6B, C ) frequently present, proximal frontal wall long and indistinguishable from an autozooid, brood chamber ovoidal to subpyriform, small, 0.63–0.66 mm long by 0.34–0.37 mm wide, densely pseudoporous. Ooeciopore subterminal, tiny, considerably smaller than an autozooidal aperture, approximately circular,, 0.06 mm in diameter, ooeciostome curved slightly in a proximal direction.

Remarks

The small gonozooids of M. beliensis are indistinguishable from autozooids proximally but expand distally to become about twice the width of an autozooid. Ooeciopores are minute and located close to the distal end of the inflated brood chamber, i.e. subterminally (cf. terminal ooeciopores which are located beyond the dilated brood chamber). Apart from the type locality, this Lower Jurassic species is also present in slightly older Jurassic sediments of Pliensbachian age in Gloucestershire (P.D. T. unpublished results) .

Figures

Figure 1. Photographs of type specimens of some Recent oncousoeciid cyclostome species. (A) Lectotype of Oncousoecia dilatans (Johnston, 1847) showing colony ramifying across the interior of a small bivalve shell (NHM 47.9.18.59). (B) Lectotype of Alecto compacta Norman, 1867, a subjective junior synonym of O. dilatans (NHM 11.10.1.63). (C) Lectotype of Oncousoecia lobulata Canu, 1918, the colony figured by Hincks (1880, Plate 50, Figure 5, 5a) as Tubulipora lobulata Hassall, 1841 which apparently formed the basis for Canu’s type species of Oncousoecia (NHM 1911.10.1.86). (D) Lectotype of Microeciella suborbicularis (Hincks, 1880), a subcircular colony with associated spirorbids (NHM 99.5.1.1427a). Scale bars: 5 mm (A, D); 1 mm (B, C).

Figure 2. Oncousoecia lobulata Canu, 1918, lectotype (NHM 1911.10.1.86). (A) Lobate, oligoserial branches; (B) autozooids; (C) gonozooid; (D) gonozooidal pseudopores showing partial occlusion by spines. Scale bars: 1 mm (A); 200mm (B, C); 50 mm (D).

Figure 6. Microeciella beliensis Taylor and Sequeiros, 1982, holotype from the Lower Jurassic of Spain (NHM D53321a). (A) Subcircular colony; (B) gonozooid; (C) another gonozooid; (D) early astogeny with partly overgrown ancestrula at centre; (E) autozooidal frontal wall showing pseudopores. Scale bars: 1 mm (A); 200 mm (B, C, D); 50 mm (E).