Cavernella praecavifera ( Schulga-Nesterenko, 1951 )

Ernst, Andrej, Claussen, Anna Lene, Seuss, Barbara & Wyse Jackson, Patrick N., 2022, Stenolaemate bryozoans from the Graham Formation, Pennsylvanian (Virgilian) at Lost Creek Lake, Texas, USA, Palaeontologia Electronica (a 15) 25 (2), pp. 1-56 : 24

Cavernella praecavifera ( Schulga-Nesterenko, 1951)

Figures 12H , 13 A-F, 14A-D; Appendix

1951 Fenestella praecavifera Schulga-Nesterenko , p. 44-45, pl. 9, fig. 4, text-fig. 9.

1951 Fenestella dvinensis Schulga-Nesterenko , p. 45-48, pl. 9, figs. 2, 5, text-fig. 10.

non 1983 Fenestella dvinensis Schulga-Nesterenko, 1951 ; Yang and Lu, p. 273-274, pl. 5, figs. 11-14.

2001 Cavernella dvinensis ( Schulga-Nesterenko, 1951) ; Morozova, pl. 7, fig. 2.

Material. SNSB-BSPG 2020 XCI 69, SNSB-BSPG 2020 XCI 71, SNSB-BSPG 2020 XCI 73, SNSB-BSPG 2020 XCI 78, SNSB-BSPG 2020 XCI 79, SNSB-BSPG 2020 XCI 112, SNSB-BSPG 2020 XCI126, SNSB-BSPG 2020 XCI 127, SNSB-BSPG 2020 XCI 128.

Exterior description. Reticulate colonies formed by straight branches joined by relatively narrow dissepiments. Fenestrules oval to rectangular. Autozooecia arranged in two rows on branches. Autozooecial apertures circular, with low peristome and stellate structure; two to four apertures spaced per fenestrule length. Rounded nodes on the low keel, regularly spaced. Reverse side finely striated containing rounded nodes 0.025 –0.040 mm in diameter.

Interior description. Autozooecia relatively long, roughly pentagonal to triangular in mid-tangential section; with short to moderately long vestibule in longitudinal section. Axial wall between autozooecial rows strongly undulating; aperture positioned at distal end of chamber. Superior hemisepta long; inferior hemisepta indistinct. External laminated skeleton well-developed on both obverse and reverse sides traversed by microstylets. Microstylets 0.008 –0.010 mm in diameter. Heterozooecia are cavernozooecia in form of elongated chambers, arranged in pairs on the reverse side of branches or on dissepiments, opening into the fenestrule, 0.06–0.10 mm in width and with rounded openings 0.04–0.05 mm in diameter.

Remarks. Differences between Cavernella dvinensis ( Schulga-Nesterenko, 1951) and C. praecavifera ( Schulga-Nesterenko, 1951) are minimal, therefore, C. dvinensis is regarded as being junior synonym of C. praecavifera . As far as Morozova (1974, p. 65) designated Fenestella dvinensis Schulga-Nesterenko, 1951 , as the type species of the genus Cavernella , this name is retained for the type species of the genus, despite its junior status (Code of Zoological Nomenclature, Article 67.1.2).

The species identified as Fenestella dvinensis Schulga-Nesterenko, 1951 , from the Kankerin Formation of Kalpin of western Xinjiang, China ( Yang and Lu, 1983) does not belong to this species because it lacks cavernozooecia. It differs also in some other morphological characters. This bryozoan has stellate nodes instead of rounded ones in C. dvinensis . Furthermore, the Chinese material has significantly smaller fenestrules (fenestrule length 0.40–0.45 mm vs. 0.60–0.65 mm in the material from the Russian Platform and 0.53–0.71 mm in the studied material from the Finis Shale).

Cavernella praecavifera ( Schulga-Nesterenko, 1951) differs from Cavernella supercarbonica ( Schulga-Nesterenko, 1951) from the Pennsylvanian (Gzhelian) of the Russian Platform in having smaller fenestrules (fenestrule width 0.19–0.39 mm vs. 0.27–0.40 mm in C. supercarbonica ; fenestrule length 0.53–0.71 mm vs. 0.50– 0.75 mm in C. supercarbonica ).

Occurrence. Pennsylvanian (Upper Carboniferous, Kasimovian); Russia. Graham Formation, Pennsylvanian (Virgilian); TXV-200 (“Spillway section at Lost Creek Lake”), Texas, USA.

Figures

FIGURE 12. Laxifenestella texana n. sp. (A–G): A–C – tangential section showing autozooecial apertures and chambers, and reproductive heterozooecia (arrows) (holotype XCI 81). D – colony fragment showing fenestrules, autozooecial apertures divided by keels with nodes (paratype XCI 109); E – colony fragment showing reproductive heterozooecia (arrows) (paratype XCI 109); F – almost intact chamber of a reproductive heterozooecium (paratype XCI 110); G – colony fragment showing secondary nanozooecia (arrows) (paratype XCI 111). Cavernella praecavifera (Schulga-Nesterenko, 1951) (H) – colony fragment showing fenestrules, autozooecial apertures divided by keels with nodes (XCI 112).

FIGURE 13. Cavernella praecavifera (Schulga-Nesterenko, 1951) (A–F): A–B – colony fragment with broken autozooecial chambers (XCI 126); C – autozooecial aperture with preserved stellate structure (XCI 127); D – colony fragment showing a weathered cavernozooecium (arrow) (XCI 128); E, F – tangential section showing autozooecial apertures and chambers (XCI 69).