Halloporina severozemelica, Nekhorosheva, 2002

Nekhorosheva, Lyudmila V., 2002, Paleozoic Bryozoa from Severnaya Zemlya (Russian Arctic), Geodiversitas 24 (2), pp. 317-327 : 322-324

Halloporina severozemelica n. sp. ( Figs 2F ; 3A, B ; Table 3)

HOLOTYPE. — CNIGR Museum, 4/13009, thin sections.

PARATYPES. — CNIGR Museum, 5-6/13009, thin sections.

TYPE LOCALITY. — Strojnaya River, October Revolution Island, Severnaya Zemlya.

TYPE LEVEL. — Ozernaya Formation, Middle Ordovician.

Formation. The species is found on October

Revolution Island in five localities (1-5, Fig. 1 ).

DIAGNOSIS. — Zoarium ramose, smooth branches thin about 1.5-3.0 mm in diameter; exozone thin;

zooecial

apertures polygonal or subpolygonal; exilazooecia angular without diaphragms vary in abundance. DESCRIPTION

Delicate, frequently bifurcating colonies with Family DYSCRITELLIDAE Astrova & Morozova, 1967 thin branches usually 1.5-1.8 mm, rarely 3 mm

in diameter. Surface smooth with inconspicuous Genus Dyscritella Girty, 1911

maculae. Zooecial apertures polygonal or subpolygonal, average 0.21-0.25 mm. There are TYPE SPECIES. — Dyscritella robusta Girty, 1911 by about nine to 11 apertures per 2 mm in all original designation from the Lower Carboniferous, directions, and eight apertures per 2 mm across Mississippian (Chester) of Arkansas, USA.

maculae. Exilazooecia vary in abundance, very often on maculae up to four exilazooecia Dyscritella cf. lucida Morozova, 1986 around a single zooecial aperture, in other ( Fig. 3 C-F; Table 4)

places there are rare exilazooecia. All exilazooe- cf. Dyscritella lucida Morozova in Morozova & cia are angular, about 0.06-0.08 mm in diame- Kruchinina 1986: 54, pl. XIV, fig. 6; pl. XV, fig. 2.

ter. Exozone narrow, commonly 0.21-0.25 mm M. — measureATERIAL EXAMINED Description and

wide. Zooecial walls in endozone are thin ments are based on eight fragmented colonies: (about 0.01 mm) and crenulated. The thickness CNIGR Museum, 7-10/13009, 23-27/13009, thin of zooecial walls in exozone averages 0.04- sections.

0.06mm. Diaphragms are lacking in exilazooe- OCCURRENCE. — Lower-Upper Permian, Kunguriancia and in majority of zooecia. In few by the Ufimian, Lower part of Zhuravlev strata; single zooecia there is one diaphragm at the Komsomolets Island, Slabyj Stream, loc. 20369.

endozone-exozone transition.

REMARKS

COMPARISON Because of the strong recrystallisation the specific H. severozemelica n. sp. is very similar to H. parva identification is denoted “cf.”.

( Ulrich & Bassler, 1904) regarding many zoarial and zooecial dimensions, but is distinguished in DESCRIPTION having singular diaphragms in zooecia, especially Ramose branching colonies 2.5-4.5 mm in in the branches more than 2 mm in diameter. diameter. Exozone 0.42-0.6 mm wide, clearly The type species of Halloporina , H. crenulata separated from endozone. Thickness of zooecial (Ulrich, 1893), has thicker branches (7-8 mm walls in exozone about 0.08-0.1 mm; in endoversus 1.5-1.8 mm in H. severozemelica n. sp.), zone about 0.015-0.02 mm. Zooecial apertures rounded monticules, numerous exilazooecia and are rounded or ovate, average 0.25-0.27 × 0.13- ridge-shaped walls of zooecia in endozone. 0.17 mm, rarely 0.31 × 0.17 mm. There are generally five to six apertures per 2 mm measured longitudinally, and seven apertures diagonally or across colony. Exilazooecia slightly angular or circular in outline, about 0.08- 0.12 mm in diameter. Acanthostyles with diameter 0.04-0.06 mm generally 4-5, rarely 6-10 around each zooecium.

COMPARISON

The present form seems to be quite identical to Dyscritella lucida , which was reported from Kapp Starostin Formation at Bjernoya, Spitsbergen ( Morozova & Kruchinina 1986). The difference between the present form and the type specimen of D. lucida from Bjernoyan lies only on the diaphragms in zooecia are lacking in the described form ( D. lucida from Bjernoya has single diaphragms at the endozone/exozone boundary).

Figures

FIG. 2. — A, B, Fistulipora sp.; A, longitudinal section, CNIGR Museum, 1a/13009; B, transverse section, CNIGR Museum, 2a/13009, Rusanov Formation, Emsian; Pioneer Island, Govorlivaya River, loc. 2369; C-E, Fistulotrypa sp. A; C, transverse section, CNIGR Museum, 3a/13009; D, tangential section, CNIGR Museum, 3b/13009; E, longitudinal section, showing endozone without vesicular tissue, CNIGR Museum, 3c/13009, Rusanov Formation, Emsian; Pioneer Island, loc. 2492; F, Halloporina severozemelica n. sp., transverse section, CNIGR Museum, 5a/13009, Ozernaya Formation, Middle Ordovician; October Revolution Island, Strojnaya River, loc. 49. Scale bars: A-E, 1 mm; F, 0.5 mm.

FIG. 3. — A, B, Halloporina severozemelica n. sp.; A, longitudinal section, showing narrow exozone and rare diaphragms in some zooecia at the endozone-exozone boundary, CNIGR Museum, 4c/13009; B, tangential section, CNIGR Museum, 4a/13009, Ozernaya Formation, Middle Ordovician; October Revolution Island, Strojnaya River, loc. 49; C-F, Dyscritella cf. lucida Morozova, 1986; C, F, tangential sections, CNIGR Museum, 9a/13009, and 10a/13009; D, longitudinal section, CNIGR Museum, 7a/13009; E, oblique transverse section, CNIGR Museum, 8a/13009, Zhuravlev Strata, Kungurian-Ufimian, Permian; Komsomolets Island, Slabyj Stream, loc. 20369. Scale bars: A, C-E, 1 mm; B, F, 0.5 mm.

FIG. 1. — Sketch of Severnaya Zemlya Archipelago, indicating sampling localities, which are coded as, Ordovician; 1, Matusevich River, loc. 34; 2, Ushakov River, loc. 46; 3, Strojnaya River, loc. 49; 4, Ozernaya River, loc. 1149; 5, Lednikovaya River, loc. 1032. Central October Revolution Island;, Devonian, South-western coast of Pioneer Island, Govorlivaya River, loc. 2369, and loc. 2492. South-West coast of Pioneer Island;, Permian Slabyj Stream, loc. 20369. North- West of Komsomolets Island.