Volgia Stuckenberg, 1905

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 : 162

Genus Volgia Stuckenberg, 1905

Ramiporina Schulga-Nesterenko, 1933: 40 .

TYPE SPECIES. — Coscinium arborescens Stuckenberg, 1895 , by original designation. Pennsylvanian ; Russia.

DIAGNOSIS. — Colony consisting of erect bifoliate lobes, with secondary branches diverging at right angles in crucifix-shaped pattern. Mesotheca with a dark and thin middle layer and two light and thick outer layers, containing median tubuli and longitudinal ridges parallel to growth direction. Autozooecia recumbent on the mesotheca or epitheca for a long distance, then bending upwards abruptly or gently, intersecting the surface almost perpendicularly. Hemisepta absent. Thin, complete diaphragms in autozooecia, common to abundant. Autozooecial apertures circular to oval, with thick peristomes. Lunaria obscure. Autozooecia separated by vesicular skeleton in endozone and by thick stereom in exozone. Microacanthostyles (tubuli) in stereom. Maculae lacking.

OCCURRENCE. — Carboniferous; Russia, Germany, France.

COMPARISON

Volgia Stuckenberg, 1905 differs from Prismopora Hall, 1883 in colony shape (branched with crucifix-pattern of branch diversion versus trifoliate, irregularly branching in Prismopora ), as well as in absence of hemisepta. Volgia differs in colony shape from Glyptopora Ulrich, 1884 (radially trifurcating and fused together branches which form a honeycomb-shaped structure), and from Evactinopora Meek & Worthen, 1865 (multifoliate colony consisting of 4-8 vertical bifoliate branches radiating from centre).