Dybowskiella rotunda, Ernst & Wyse Jackson & Aretz, 2015

Ernst, Andrej, Wyse Jackson, Patrick N. & Aretz, Markus, 2015, Bryozoan fauna from the Mississippian (Visean) of Roque Redonde (Montagne Noire, southern France), Geodiversitas 37 (2), pp. 151-213 : 160

Dybowskiella rotunda n. sp.

( Figs 8G , 9 A-C; Appendix)

ETYMOLOGY. — The species name refers to the rounded shape of apertures and lunaria (from Latin “ rotundus ” – rounded).

HOLOTYPE. — SMF 21.777 .

PARATYPE. — SMF 21.778- SMF 21.780.

TYPE LOCALITY. — Roque Redonde (Montagne Noire, southern France).

TYPE HORIZON. — Carboniferous, Mississippian (upper Visean).

DIAGNOSIS. — Moderately thick encrusting colonies; apertures large, with well developed rounded lunaria; autozooecial diaphragms common to abundant; vesicles large, separating autozooecia in 1-2 rows, 6-10 surrounding each autozooecial aperture.

DESCRIPTION

Encrusting colony, 0.9-2.9 mm thick. Autozooecia growing from thin epitheca, bending in the early exozone to the colony surface. Basal diaphragms straight or slightly inclined, common to abundant, 2-7 in each autozooecium. Autozooecial apertures circular to oval. Lunaria well-developed, rounded, rounded; ends of lunaria indenting deeply autozooecia. Vesicles large, irregular, separating autozooecia in 1-2 rows, 6-10 surrounding each autozooecia aperture, with rounded roofs, polygonal in tangential section. Autozooecial walls granular prismatic, 0.010 -0.015 mm thick.

COMPARISON

Dybowskiella rotunda n. sp. differs from Dybowskiella piriforme n. sp. in larger autozooecial apertures (average aperture width 0.34 mm vs 0.21 mm in D. piriforme ) and in presence of diaphragms. Dybowskiella rotunda n. sp. differs from D. regularis Perry & Gutschick, 1959 from the Amsden Formation (Late Mississippian) of Montana, USA, in larger apertures, larger vesicles and smaller number of vesicles around autozooecial apertures (6-10 vs 11-13 in D. regularis ).

Figures

FIG. 8. — A-C, Fistulipora parvilabrum Schulga-Nesterenko, 1955; A, longitudinal section, SMF 21.770; B, tangential section, SMF 21.771; C, tangential section showing autozooecial aperture with lunarium, SMF 21.771. D, F, Fistulipora sana Trizna, 1958; D, longitudinal section, SMF 21.775; E, tangential section, SMF 21.774; F, tangential section showing autozooecial aperture with lunarium, SMF 21.774. G, Dybowskiella rotunda n. sp., holotype SMF 21.777. Scale bars: A, E, 1 mm; B, D, 0.5 mm, C, F, G, 0.2 mm.

FIG. 9. — A-C, Dybowskiella rotunda n. sp.; A, tangential section, holotype SMF 21.777; B, tangential section, paratype SMF 21.780; C, longitudinal section, holotype SMF 21.777. D-F, Dybowskiella piriforme n. sp., holotype SMF 21.781: D, tangential section, E, F, tangential section showing autozooecial aperture with lunarium. Scale bars: A, B, D, 0.5 mm; C, 2 mm; E, 0.2 mm; F, 0.1 mm.