Stomatopora bajocensis (d’Orbigny, 1850)

Zatoń, Michał & Taylor, Paul D., 2009, Middle Jurassic cyclostome bryozoans from the Polish Jura, Acta Palaeontologica Polonica 54 (2), pp. 267-288 : 269-270

Stomatopora bajocensis (d’Orbigny, 1850)

Fig. 2A .

1850 Alecto bajocensis sp. nov.; d’Orbigny 1850: 288. 1867 Stomatopora bouchardi Haime, 1854 ; Reuss 1867: 2 (partim). 1963 Stomatopora bajocensis (d’Orbigny, 1850) ; Illies 1963: 74, pl. 7:

1–2. 1970 Stomatopora bajocensis (d’Orbigny, 1850) ; Walter 1970: 36, pl.

1: 7. 2009 Stomatopora bajocensis (d’Orbigny, 1850) ; Taylor 2009: 22.

Material.—Two fragmentary colonies GIUS 8−3509−1–2.

Measurements.—FWL, 825–1575 µm; FWW, proximal: 120–140 µm, distal: 220–300 µm; LAM, 80 µm; LPM, 120 µm; TAM, 80 µm; TPM, 110 µm; PW, 6.3 µm.

Description and remarks.—This encrusting, uniserial species has been found on only two hiatus concretions. In both cases, the ancestrula is lacking and branches bifurcate at an angle of about 110 °, suggesting an early astogenetic stage. Autozooids are straggly, long and slender, proximally narrow but gradually widening towards the distal end. Peristomes and apertures are circular in outline, about 110 and 80 µm in diameter, respectively. Apertures may possess deep diaphragms. Pseudopores are widely−spaced and almost circular in outline.

Although the ancestrula is missing and the astogenetic stages of the colonies cannot therefore be determined exactly, the size of the autozooids is characteristic of Stomatopora bajocensis (d’Orbigny, 1850) among Jurassic species of this genus.

Stratigraphic and geographic ranges.—Middle Bathonian of Bugaj and Upper Bathonian of Ogrodzieniec, Polish Jura. This species is also known from the uppermost Bathonian– lowermost Callovian of Balin, southern Poland (see Taylor 2009), Upper Aalenian–Upper Bathonian of France and England ( Walter 1970) and Bajocian of Germany ( Illies 1963).

Figures

Fig. 2. Stomatoporid cyclostome bryozoans from the Middle Jurassic ore−bearing clays of the Polish Jura. A. Stomatopora bajocensis (d’Orbigny, 1850), Upper Bathonian, Ogrodzieniec, GIUS 8−3509−1. A1, autozooids showing high−angled bifurcations; A2, pseudopores. B. Stomatopora recurva Waagen, 1867, Middle Bathonian, Bugaj, GIUS 8−3509−2. B1, colony fragment showing early and later bifurcations; B2, pseudopores. C. Proboscinopora? sp., Middle Bathonian, Bugaj, GIUS 8−3509−7. C1, branching oligoserial colony, partly pyritised (white spots); C2, pseudopores. Scale bars: 300 µm (A1), 200 µm (B1, C1), 20 µm (A2, B2, C2). BSE SEM images of uncoated specimens.