Polypora aff. hexagona Moore, 1929

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 : 30

Polypora aff. hexagona Moore, 1929

Figures 16 H-I, 17A-E; Appendix

1929 Polypora hexagona Moore , p. 122, pl.

15, figs. 13, 17.

Material. SNSB-BSPG 2020 XCI 32, SNSB-BSPG 2020 XCI 55, SNSB-BSPG 2020 XCI 118.

Exterior description. Reticulate colonies composed of moderately wide branches joined by moderately wide dissepiments. Autozooecia arranged in 3–5 alternating rows on branches. Autozooecial apertures rounded to oval, 5–6 spaced per length of fenestrule. Fenestrules subrectangular to oval, longer than wider.

Interior description. Autozooecial chambers generally rhombic to roughly hexagonal in the mid-tangential section. Hemisepta absent. Extrazooidal skeleton well-developed, protruded by abundant microstylets. Microstylets 0.008 –0.010 mm in diameter, spaced densely. Circular to elliptical nodes irregularly arranged between autozooecial rows, 0.040 –0.065 mm in diameter. Apparent reproductive heterozooecia in form of isolated zooecia with enlarged endozonal chambers present. Chambers rounded, 0.18–0.30 mm in diameter, covered by roofs that are slightly depressed in their central parts. Skeletal material of roofs covered by abundant pustules. Nanozooecia present.

Remarks. The present species is very close to the species Polypora hexagona Moore, 1929 , but has longer fenestrules (fenestrule length 1.25–1.52 mm vs. 0.9 mm in P. hexagona ). The present species differs from P. aspera Rogers, 1900 , from the Pennsylvanian of Kansas in having shorter fenestrules (fenestrule length 1.25–1.52 mm vs. 2.0 mm in P. aspera ). The present species differs from P. gzhelensis Schulga-Nesterenko, 1951 , from the Gzhelian of the Russian Platform in having narrower branches (branch width 0.38–0.70 mm vs. 0.70–0.95 in P. gzhelensis ).

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

Figures

FIGURE 16. Polypora triangularis Rogers, 1900 (A–G): A–C – colony fragments with intact chambers of reproductive heterozooecia (XCI 114); D – branch fragment with nanozooecia (XCI 115); E, F – branch fragment with autozooecial apertures with proximal pores (arrows) (XCI 116); G – branch fragment with nodes on the reverse side (XCI 117). Polypora aff. hexagona Moore, 1929 (H, I) – colony fragment with fenestrules, autozooecial apertures, and nodes (XCI 118).