Chainodictyon minor Ulrich, 1890

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 : 18

Chainodictyon minor Ulrich, 1890

Figures 9 C-G, 10A; Appendix

1890 Chainodictyon laxum var. minor Ulrich , p. 640, pl. 62, figs. 3-3a.

Material. SNSB-BSPG 2020 XCI 37, SNSB-BSPG 2020 XCI 38, SNSB-BSPG 2020 XCI 42, SNSB-BSPG 2020 XCI 106, SNSB-BSPG 2020XCI 125.

Description. Reticulate colonies formed by anastomosing branches. Branches frequently bifurcating, flattened, bearing 2–4 alternating rows of autozooecia; dorsal wall rugose, 0.30–0.79 mm wide. Fenestrules elongate, rounded-polygonal, 0.65–1.10 mm wide, and 1.26–1.90 mm long. Autozooecial apertures oval. Diaphragms not observed. Hemisepta absent. Styles absent. Leptozooecia common to abundant, small, occurring between autozooecia on the obverse side of branches. Autozooecial walls in endozone 0.013 – 0.020 mm thick, hyaline; finely laminated in exozone.

Remarks. Chainodictyon minor Ulrich, 1890 , differs from C. laxum Foerste, 1887 , in having a smaller size of fenestrules (fenestrule width 0.65– 1.10 mm vs. ca. 1.3 mm in C. laxum ; fenestrule length 1.26–1.90 mm vs. 2.5 mm in C. laxum ). Chainodictyon minor differs from C. angustum Schulga-Nesterenko, 1952 , from the Lower Permian (Asselian) of Russia in having smaller fenestrules (fenestrule width 0.65–1.10 mm vs. 1.2–2.0 mm in C. angustum ; fenestrule length 1.26–1.90 mm vs. 3.6–4.1 mm in C. angustum ).

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

Figures

FIGURE 9. Rhombocladia delicata Rogers, 1900: (A) – transversal thin section (XCI 22c), (B) – branch longitudinal thin section (XCI 22b). Chainodictyon minor Ulrich, 1890, (C–G): C – branch fragment and colony surface showing autozooecial apertures (XCI 106); D – branch reverse side showing transversal striation (XCI 125); E–G – tangential thin section showing fenestrules, autozooecial apertures and chambers, and a leptozooecium (arrow) (XCI 37).