Homotrypa subramosa Ulrich, 1886

Ernst, Andrej & Carrera, Marcelo G., 2022, A cool-water bryozoan association from the La Pola Formation (Sandbian, Ordovician) of Argentine Precordillera, Geodiversitas 44 (20), pp. 563-601 : 572-574

Homotrypa subramosa Ulrich, 1886

( Fig. 7 A-C; Appendix 1)

Homotrypa subramosa Ulrich, 1886: 81 ; 1893: 239-340, pl. 19, figs 21- 28. — Bassler 1911: 187-189, text-figs 99-100. — Bork & Perry 1968: 1053-1055, pl. 136, figs 1-3. — McKinney 1971: 234-237, pl. 49, fig. 4-8, pl. 50, fig. 1. — Marintsch 1998: 53-55, pl. 9, figs 1-5.

Homotrypa insignis Ulrich, 1886: 82 .

MATERIAL EXAMINED. — CEGH-UNC 27516 a, d, CEGH-UNC 27519 a, b, CEGH-UNC 27530 a-g, CEGH-UNC 27531 b, CEGH-UNC 27536 a, CEGH-UNC 27537 a, b, CEGH-UNC 27542 a, c, d, e, CEGH-UNC 27545b.

DESCRIPTION

Irregularly branched, submassive or encrusting colony. Branches and fronds 5.6-9.4 mm thick, encrusting sheets 0.7-1.6 mm thick. Exozones indistinct. Autozooecia prismatic, growing for long distance along branch axis and bending gently to the colony surface. Autozooecial diaphragms common, thin, planar. Autozooecial apertures polygonal in tangential section. Cystiphragms abundant, densely spaced, constricting middle part of zooecia, about a half of their diameter. Mesozooecia few, polygonal. Autozooecial walls granular, 0.003 -0.005 mm thick in endozone; amalgamated, 0.02-0.03 mm thick in exozone. Acanthostyles few, small to moderate in size. Maculae consisting of macrozooecia, 0.80-0.95 mm in diameter.

COMPARISON

Homotrypa subramosa Ulrich, 1886 differs from H. callosa Ulrich, 1893 in larger autozooecial apertures (average aperture width 0.16 mm vs 0.14 mm in H. callosa ; measurements for H.callosa from Marintsch, 1998). Homotrypa subramosa Ulrich, 1886 differs from H.tuberculata Ulrich, 1893 in less abundant and smaller acanthostyles and in smaller autozooecial apertures (average aperture width 0.16 mm vs 0.20 mm in H. tuberculata ; measurements for H. tuberculata from Marintsch 1998).

Figures

FIG. 7. — A-C, Homotrypa subramosa Ulrich, 1886, CEGH-UNC 27537 b: A, B, longitudinal thin section showing autozooecial chambers with cystiphragms; C, tangential thin section showing autozooecial apertures,mesozooecia,and acanthostyles;D-I, Homotrypa vacuaMcKinney,1971: D, E, branch longitudinal thin section showing autozooecial chambers with cystiphragms, CEGH-UNC 27545 a; G, H, tangential thin section showing autozooecial apertures, mesozooecia, and acanthostyles, CEGH-UNC 27545 a; I, branch transverse section, CEGH-UNC 27507 b. Scale bars: A, D, E, G, I, 1 mm; B, C, F, H, 0.5 mm.