Fabifenestella macrofenestrata, 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 : 188

Fabifenestella macrofenestrata n. sp.

( Figs 24 G-I; 25A-E; Appendix)

ETYMOLOGY. — The species name refers to the distinctive large size of fenestrules of the new species.

HOLOTYPE. — SMF 21.915 .

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

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

DIAGNOSIS. — Branches straight; dissepiments relatively wide; fenestrules about twice as long as wide; autozooecial apertures with 8 nodes; 4-6 apertures per fenestrule length; median keel wide, low, with densely spaced alternating nodes; nodes varying in size; autozooecia fabiform with distinct inferior and superior hemisepta; axial wall weakly or strongly undulating; heterozooecia present in form of elliptical chambers on obverse branch surface.

EXTERIOR DESCRIPTION

Reticulate colony formed by straight branches joined by relatively wide dissepiments. Fenestrules oval to rectangular, about twice as long as wide. Autozooecia arranged in two rows on branches. Autozooecial apertures circular, with low peristome, containing 8 nodes; 4 to 6 apertures spaced per fenestrule length. Keel wide, low, containing densely spaced alternating nodes. Nodes varying in size, elliptically shaped.

INTERIOR DESCRIPTION

Autozooecia relatively long, roughly pentagonal to rectangular in deep tangential section, becoming fabiform in mid tangential section; with short to moderately long vestibule in longitudinal section. Axial wall between autozooecial rows weakly to strongly undulating; aperture positioned at distal end of chamber. Both superior and inferior hemisepta present, positioned in the distal half of autozooecial chamber. External laminated skeleton well-developed on both obverse and reverse sides. Heterozooecia in form of elliptical chambers (apparent brooding structures), positioned on obverse branch side, having own 0.010 -0.015 thick laminated walls, 0.11-0.16 mm wide and 0.18-0.25 mm long.

COMPARISON

Although Fabifenestella macrofenestrata n. sp. is erected on the basis of a single specimen, a rigorous comparison of other Fabifenestella species shows it to be unique in relation to the large size of the fenestrules and meshwork. Although a single specimen cannot show potential variation in meshwork parameters these are generally constant within a species. Fabifenestella macrofenestrata n. sp. is similar to F. fabalis ( Shishova, 1960) from the Pennsylvanian of Transbaikalia and Mongolia, but differs from it in presence of 4-6 apertures per fenestrule length instead of 2-3 in F. fabalis . Fabifenestella macrofenestrata n. sp. differs from F. praevirgosa (Schulga-Nesterenko, 1951) from Pennsylvanian (Gzhelian) of Russia in longer fenestrules (1.14-1.50 mm vs 0.75-0.90 mm in F. praevirgosa ). Fabifenestella macrofenestrata sp. nov differs from Fabifenestella binodosa ( Shcherbatykh, 1970) in wider branches (0.35-0.43 mm vs 0.27 mm in F. binodosa ), and in longer fenestrules (1.14-1.50 mm vs 0.78-0.80 mm in F. binodosa ). Fabifenestella edzhekalensis Morozova, 1981 from the Mississippian (Visean-Serpukhovian) of Russia has similar heterozooecia (oval chambers 0.24 mm long and 0.16 mm wide). However, this species has considerable smaller fenestrules than the new one.

Figures

FIG. 24. — A-F, Laxifenestella kondrovensis (Schulga-Nesterenko, 1955); A-D, tangential section showing autozooecial apertures and low median keel with nodes (arrows), SMF 21.912; E, mid-tangential section showing autozooecial chambers with hemisepta, SMF 21.912; F, mid-tangential section showing autozooecial chambers with hemisepta, SMF 21.914. G-I, Fabifenestella macrofenestrata n. sp., holotype SMF 21.915; G-H, mid-tangential section showing autozooecial chambers with hemisepta (arrow); I, tangential section showing keel nodes (arrow). Scale bars: A, G, 2 mm; B, C, E, F, 1 mm; D, 0.2 mm; H, I, 0.5 mm.