Penniretepora flexistriata Richards, 1959

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 : 32-34

Penniretepora flexistriata Richards, 1959

Figure 18 D-J; Appendix

1959 Penniretepora flexistriata Richards , p.1116, text-figs. A7, A8.

1980 Penniretepora flexistriata Richards, 1959 ; Simonsen and Cuffey, p. 23-24, figs. 3K, 4K, 5K, 6K, 7K.

Material. SNSB-BSPG 2020 XCI 82, SNSB-BSPG 2020 XCI 83, SNSB-BSPG 2020 XCI 84, SNSB-BSPG 2020 XCI 85, SNSB-BSPG 2020 XCI 91, SNSB-BSPG 2020 XCI 93, SNSB-BSPG 2020 XCI 121, SNSB-BSPG 2020 XCI 122, SNSB-BSPG 2020 XCI 123.

Exterior description. Pinnate colonies consisting of straight main branches with frequent lateral branches. Main branches 0.22–0.43 mm wide, lateral branches 0.12–0.24 mm wide, diverging at angles 59–82° from main branches, spaced 0.59– 0.85 mm from centre to centre. Autozooecia having circular apertures with stellate structure, arranged in two rows both on main and lateral branches; regularly one aperture at the base of each lateral branch and one aperture between two neighbouring lateral branches. Median keels low, undulating, nodes absent.

Interior description. Autozooecial chambers arranged in two alternating rows on branches, triangular to pentagonal or trapezoid in mid-tangential section both on main and secondary branches, short, inflated, with moderately long vestibules. Axial wall strongly undulating to zigzag from base to crest. Hemisepta absent. Apertural pore present, positioned proximally to the autozooecial aperture, 0.02–0.03 mm in diameter. Extrazooecial skeleton moderately developed, traversed by abundant microstylets; microstylets without hyaline core, regularly spaced across entire colony surface, 0.005 – 0.008 mm in diameter. Coarse longitudinal striation developed both on main and lateral branches.

Remarks. Penniretepora flexistriata Richards, 1959 , is similar to P. cyclotriangulata Shishova, 1959 , from the Upper Carboniferous (Moscovian) of Russia but differs from it in having narrower lateral branches (lateral branch width 0.12–0.24 mm vs. 0.20–0.25 mm in P. cyclotriangulata ) and smaller apertures (aperture width 0.06–0.08 mm vs. 0.15–0.20 mm in P. cyclotriangulata ).

Occurrence. Lower Virgilian to upper Wolfcampian; Kansas, USA. Graham Formation, Pennsylvanian (Virgilian); TXV-200 (“Spillway section at Lost Creek Lake”), Texas, USA.

Figures

FIGURE 18. Septopora blanda Moore, 1929 (A–C): A, B – tangential section showing autozooecial apertures and chambers, and cyclozooecia (arrows) (XCI 47); C – tangential section showing autozooecial chambers and cyclozooecia (XCI 54). Penniretepora flexistriata Richards, 1959 (D–J): D–F – colony fragments with autozooecial apertures with apertural pores (arrows) and stellate structures, divided by low undulating keel (D: (XCI 121), E–F: (XCI 122); G – autozooecial aperture with apertural pore (arrow) and stellate structure (XCI 123); H, I – thin section showing autozooecial chambers (XCI 83); J – thin section showing autozooecial apertures with apertural pore (arrow) (XCI 82).