Theonella ukrainica, Pisera, 2000

Pisera, Andrzej, 2000, New species of lithistid sponges from the Paleogene of the Ukraine, Zoosystema 22 (2), pp. 285-298 : 288

Theonella ukrainica n. sp.

( Figs 2 A-D; 3)

MATERIAL. — 24 fragmentary specimens (NHM ZN5, ZN10). Holotype, specimen NHM ZN5A; paratype, NHM ZN10A.

ETYMOLOGY. — The species name refers to the Ukraine where the material was discovered.

DIAGNOSIS. — These are small branching Theonella with one to several longitudinal canals in the centre.

Choanosomal desmas as smooth regular tetraclones. Dermalia as phyllotriaenes with slender clads and pointed tips, or small irregular discotriaenes.

DESCRIPTION

Numerous fragments of small, up to 5 cm long, branching sponges with branches 6-8 mm thick. One to several vertical, 0.5 to 1.0 mm wide, round canals run along the sponge in the centre. Sometimes these canals approach the lateral surface and then may be partly open. In the main trunk several canals always occur, in branches less or only one. These canals usually do not open at the tips of the branches. Branches usually rounded more rarely laterally flattened with rounded tips, when preserved. Skeleton consists of smooth, regular tetraclones, with moderately branched terminal articulations; they are 255- 430 µ m in size. Dermal skeleton developed mostly as phyllotriaenes with slender pointed clads, which are 250-580 µ m in size. In some areas, however, small discotriaenes that are irregular in outline also occur, and are 220-280 µ m in size. Choanosomal tetraclones are very regular in the upper and inner part of branches and measure 255-430 µ m in size, while in lower (older) parts, close to the surface, and around canals they are very densely packed and irregular. The space between dermal phyllotriaenes is often infilled in the older part of branches with very densely packed and tightly interlocking small, flat, irregular spicules resembling rhizoclones.

REMARKS

The specimens included by me into T. ukrainica were most probably one of those included into Discodermia by Oakley (1942). The genus Theonella , to my knowledge, has never been found as fossil before, except for an indication by Laubenfels (1955) which I was unable to resolve. Assignment of my material to Theonella is based on the type of desmas and their articulation and accompanying dermal phyllotriaenes. No microscleres have been found. Most theonellas have a spongocoel developed, but my specimens are tiny-branching in habit, and thus lack of spongocoel, instead several vertical canals are developed.

Figures

FIG. 2. — Habit of the investigated sponges; A-D, Theonella ukrainica n. sp.; A, NHM ZN10D; B, holotype NHM ZN5A; C, NHM ZN5E; D, NHM ZN5F; E-H, Chenendopora piaskovskii n. sp.; E, F, paratype NHM ZN11 in lower side (E) and upper side (F) views; G, H, holotype NHM ZN1 in upper (G) and lower side (H) views; I-K, Lerouxia digitata n. sp.; I, NHM ZN4; J, holotype, NHM ZN7; K, paratype, NHM ZN8; L, Plinthosella magna n. sp., holotype NHM ZN3, oblique view. Scale bars: A-D, G, H, L, 1 cm; E, F, I-K, 2 cm.