Tarphophragma macrostoma ( Loeblich, 1942 )

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 : 580

Tarphophragma macrostoma ( Loeblich, 1942)

( Figs 10 E-G; 11A; Appendix 1)

Hallopora macrostoma Loeblich, 1942: 430 , pl. 62, figs 12-14.

Tarphophragma macrostoma – Key 1991: 207-209, figs 6.1-6.6.

MATERIAL EXAMINED. — CEGH-UNC 27520 c, d, CEGH-UNC 27539 c, d, g, CEGH-UNC 27537 d, CEGH-UNC 27538 d.

OCCURRENCE. — Bromide Formation, Upper Ordovician, lower Sandbian; Oklahoma, United States. La Pola Formation, Upper Ordovician, Sandbian; La Pola creek section near Albardon village, San Juan Province, Argentine Precordillera, western Argentina.

DESCRIPTION

Ramose colonies, branch diameter 3.0- 3.6 mm. Exozone distinct, 0.5-0.6 mm wide, endozone 2.0- 2.4 mm wide. Autozooecia long, growing parallel to branch axis for a long distance in endozone and bending sharply in exozone, having rounded-polygonal shape in transverse section in endozone. Autozooecial apertures oval to polygonal. Autozooecial diaphragms thin, planar, widely spaced in endozone; common to abundant in exozone, planar, rarely inclined, developed as extension of wall cortex. Mesozooecia arising in endozone, polygonal in transverse section, 2-6 surrounding each autozooecial aperture. Mesozooecial diaphragms planar, densely spaced. Acanthostyles absent. Autozooecial walls indistinctly laminated, 0.005 -0.008 mm thick in endozone; displaying distinct reverse V-shaped structure with dark autozooecial boundary, with weakly developed wall cortex continued in diaphragms, 0.04-0.12 mm thick in exozone. Maculae indistinct, consisting of macrozooecia.

COMPARISON

Tarphophragma macrostoma ( Loeblich, 1942) differs from T. ovata ( McKinney, 1971) from the Middle Ordovician of United States in larger autozooecial apertures (average aperture width 0.21 mm vs 0.17 mm in T. ovata ; measurements for T. ovata from McKinney 1971), as well as in less abundant and smaller mesozooecia. Tarphophragma macrostoma differs from T. multitabulata ( Ulrich, 1886) from the Middle Ordovician of United States in larger autozooecial apertures (average aperture width 0.21 mm vs 0.19 mm in T. multitabulata ; measurements for T. multitabulata from Karklins 1984).

Figures

FIG. 10. — A-D, Diplotrypa sp. A, CEGH-UNC 27543 a: A, B, longitudinal section showing autozooecial chambers with diaphragms and mesozooecia; C, D, tangential thin section showing autozooecial apertures and mesozooecia; E-G, Tarphophragma macrostoma (Loeblich, 1942), CEGH-UNC 27520 d: E, oblique section through the colony; F, longitudinal section showing autozooecial chambers and mesozooecia; G, tangential thin section showing autozooecial apertures and mesozooecia. Scale bars: A, E, 1 mm; B, C, F, G, 0.5 mm; D, 0.2 mm.