Fistulotrypa sp. A

Nekhorosheva, Lyudmila V., 2002, Paleozoic Bryozoa from Severnaya Zemlya (Russian Arctic), Geodiversitas 24 (2), pp. 317-327 : 320-322

Fistulotrypa sp. A ( Fig. 2 C-E; Table 2)

MATERIAL EXAMINED. — One colony, CNIGR Museum, 3/13009.

OCCURENCE. — Lower Devonian, Emsian, Rusanov Formation; Pioneer Island, loc. 2492.

DESCRIPTION

Ramose species of Fistulotrypa with smooth branches surface and rounded maculae. Exozone and endozone are quite distinct. Vesicular tissue only in exozone; apertures rounded without lunaria. Ramose zoarium with branches about 6- 7 mm in diameter and with quite distinct exozone of 2.1-2.4 mm wide. On the smooth surface of the branches there are maculae, which are formed by the accumulations of vesicles. Distance between maculae centres is about 4-5 mm. Zooecial apertures rounded without lunaria, usually 0.17-0.19 mm in diameter. The maculae are surrounded by zooecial apertures, which diameter is about 0.21-0.25 mm. There are about six to seven zooecial apertures per 2 mm in any direction. Zooecial walls are uniformly thin (about 0.02 mm) in exozone and endozone. In endozone thin-walled zooecial tubes with singular thin diaphragms form subparallel bunch. Within exozone zooecial tubes contain thin diaphragms 0.21-0.31 mm apart each other. Vesicular tissue is developed only in exozone. Vesicles about 0.09-0.17 mm in diameter are densely packed on maculae. The smallest vesicles are developed in subsurface part of zoarium, which width is about 0.6-0.9 mm. Between maculae there are one or two rows of vesicles surrounding each zooecium.

COMPARISON

This species is partly similar to F. proavus Kopajevich, 1984 which was described from

Givetian-base of Frasnian: Ulanobin Beds of Mongolia ( Kopajevich 1984). Fistulotrypa sp. A differs from F. proavus in having thicker branches (6-7 mm versus 2,5- 3 mm in F. proavus ) and rounded zooecial apertures ( F. proavus has ovate apertures), which are smaller than in F. proavus (0.17-0.19 mm to 0.21-0.25 mm versus 0.22- 0.31 × 0.11-0.21 mm in F. proavus ).

Order TREPOSTOMATA Ulrich, 1882 Suborder AMPLEXOPODOIDEA Astrova, 1965 Family AMPLEXOPORIDAE Ulrich in Miller, 1889

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.