Polypora triangularis Rogers, 1900

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 : 27-30

Polypora triangularis Rogers, 1900

Figures 15 E-H, 16A-G; Appendix

1900 Polypora triangularis Rogers , p. 8-9, pl.

4, figs. 3-3c.

1929 Polypora aestacella Moore , p. 24-25, pl.

3, figs. 9, 10.

1929 Polypora sigillaria Moore , p. 121-122, pl.

15, figs. 12, 14.

Material. SNSB-BSPG 2020 XCI 24, SNSB-BSPG 2020 XCI 25, SNSB-BSPG 2020 XCI 26, SNSB-BSPG 2020 XCI 30, SNSB-BSPG 2020 XCI 48, SNSB-BSPG 2020 XCI 50, SNSB-BSPG 2020 XCI61, SNSB-BSPG 2020 XCI 72, SNSB-BSPG 2020 XCI 114, SNSB-BSPG 2020 XCI 115, SNSB-BSPG 2020 XCI 116, SNSB-BSPG 2020 XCI 117.

Exterior description. Reticulate colonies composed of moderately wide branches joined by moderately wide dissepiments. Autozooecia arranged in 5–7 alternating rows on branches. Autozooecial apertures rounded to oval, 7–10 spaced per length of fenestrule. Proximal pores at apertures developed, 0.025 –0.027 mm in diameter, often continued in the proximal slit ( Figure 16 E-F). Fenestrules subrectangular to oval, longer than wider. Nodes on the reverse side of branches, 0.06–0.11 mm in diameter.

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 –0.015 mm in diameter, spaced densely. Circular to elliptical nodes irregularly arranged between autozooecial rows, 0.045 –0.115 mm in diameter. Apparent reproductive heterozooecia in the form of isolated zooecia with enlarged endozonal chambers present. Chambers rounded, 0.18–0.30 mm in diameter, covered by roofs with slightly depressed central parts. Skeletal material of roofs covered by abundant pustules. Nanozooecia present.

Remarks. Polypora sigillaria Moore, 1929 , and P. aestacella Moore, 1929 , are identical with P. triangularis Rogers, 1900 . Their sizes are similar, and they both possess characteristic proximal pores at apertures. Polypora triangularis Rogers, 1900 , differs from P. gzhelensis Schulga-Nesterenko, 1951 , from the Pennsylvanian (Gzhelian) of the Russian Platform in having longer fenestrules (fenestrule length 2.30–3.25 mm vs. 1.30–1.45 mm in P. gzhelensis )

Polypora triangularis differs from P. vereyensis Schulga-Nesterenko, 1951 , from the Pennsylvanian (Moscovian) of the Russian Platform in having narrower branches (branch width 0.54–1.03 mm vs. 0.95–1.05 mm in P. vereyensis ) and in possessing longer fenestrules (fenestrule length 2.30– 3.25 mm vs. 1.12–1.75 mm in P. vereyensis ).

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

Figures

FIGURE 15. Acupipora elliptica (Rogers, 1900) (A–D): A – branch fragment with autozooecial apertures, nodes and nanozooecium (arrow) (XCI 113). B, C – deep tangential section showing autozooecial chambers with hemisepta (XCI 70); D – tangential section showing autozooecial apertures (XCI 70). Polypora triangularis Rogers, 1900 (E–H): E, F – tangential section showing autozooecial apertures and chambers (XCI 50); G, H – tangential section showing autozooecial apertures and reproductive heterozooecia (arrows) (XCI 26).

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).