Microeciella mokrskoensis, Zatoń & Taylor, 2009

Zatoń, Michał & Taylor, Paul D., 2009, Middle Jurassic cyclostome bryozoans from the Polish Jura, Acta Palaeontologica Polonica 54 (2), pp. 267-288 : 275-276

Microeciella mokrskoensis sp. nov.

Fig. 6 .

Etymology: From the type locality Mokrsko.

Holotype: GIUS 8−3509−14.

Type locality: Mokrsko, Polish Jura, Poland.

Type horizon: Upper Bajocian ( Parkinsonia parkinsoni Zone ).

Material.—One colony, the holotype.

Measurements.—FWL, 807–923 µm; FWW, 115–161 µm; LAM, 92–115 µm; TAM, 69–92 µm; LPM, 138–161 µm; TPM, 104–161 µm; GTL, 1086 µm; GDL, 657 µm; GW, 428 µm; PL, 12.5–17 µm; PW, 5 µm.

Diagnosis.— Microeciella with longitudinally elongate gonozooids, the brood chamber about 1.5 times longer than wide; autozooids small, frontal wall width less than 165 µm; pseudopores elongate, pyriform, pointed distally.

Description.—Colony encrusting, multiserial, unilamellar, bereniciform, with distinct rejuvenative growth ( Fig. 6A ).

Autozooids small, elongate with frontal wall flat proximally but slightly convex distally; zooidal boundaries shallowly grooved or indistinct. Peristomes short, upright, tapering distally. Apertures circular to longitudinally elongated, some closed by deep terminal diaphragms. Pseudopores closely spaced, longitudinally elongated, pyriform, pointed distally ( Fig. 6D ).

Gonozooids represented by one aborted and one roofless example. Proximal frontal wall indistinguishable from an autozooid. Brood chamber longitudinally elongate, about 1.5 × longer than wide ( Fig. 6C ). Ooeciopore not observed, inferred to have been subterminal.

Remarks.—All of the gonozooids observed in the studied colony are either aborted or have lost the roofs of their brood chambers. Nevertheless, their overall morphology is sufficiently different from that seen in the other species of Microeciella described in this paper to justify the recognition of M. mokrskoensis as a separate species. The long gonozooid is somewhat reminiscent of M. beliensis Taylor and Sequeiros, 1982 , from the Lower Jurassic of Spain (see Taylor and Sequeiros 1982), and M. duofluvina ( Cuffey and Ehleiter, 1984) from the Middle Jurassic Carmel Formation of Utah (see Taylor and Wilson 1999). However, M. mokrskoensis differs from M. beliensis in having wider and much longer gonozooids, whereas the brood chamber of M. duofluvina is more than 2 × longer than wide compared with 1.5 × in M. mokrskoensis .

Stratigraphic and geographic range.—Upper Bajocian of Mokrsko, Polish Jura.

Figures

Fig. 6. Oncousoeciid cyclostome bryozoan Microeciella mokrskoensis sp. nov. from the Middle Jurassic ore−bearing clays of the Polish Jura. Holotype, GIUS 8−3509−14, Mokrsko, Upper Bajocian. A. General colony view. B. Autozooids. C. Close−up of the gonozooids, the one of which is roofless and the second one is aborted (arrowed). D. Pseudopores. Scale bars: 300 µm (A), 100 µm (B, C), 30 µm (D). All images from SEM BSE, specimens uncoated.