Lerouxia digitata, Pisera, 2000

Pisera, Andrzej, 2000, New species of lithistid sponges from the Paleogene of the Ukraine, Zoosystema 22 (2), pp. 285-298 : 292

Lerouxia digitata n. sp.

( Figs 2 I-K; 4)

MATERIAL. — Six variously preserved specimens. Holotype NHM ZN7; paratype NHM ZN8.

ETYMOLOGY. — The name of the species refers to its digitate shape.

DIAGNOSIS. — Large digitate sponge pierced by numerous sinuous or irregular longitudinal canals, which may approach the lateral surface and then may be partly open. Choanosomal desmas are irregular tetraclones with smooth clads and tuberculated apices. Articulation of several desmas form large spherical centres. Dermalia are phyllotriaenes with rounded clad tips. Between dermalia is a dense layer of interlocking flat spicules resembling rhizoclones.

DESCRIPTION

Large up to 15 cm high digitate sponge, sometimes with knobby protuberances, up to 4 cm thick at the base. No spongocoel or osculum. Entire sponge pierced by numerous loosely spaced, more or less vertical but sinuously or irregularly longitudinal canals, which at the base may reach 2 mm in diameter, but on average are only 0.7-1.0 mm large. They also may be close to the surface, so when dermal skeleton removed, in many cases they are visible as sinuous furrows of the same diameter. In the centre of a branch (in 50% of cases) there is a loose bunch of smaller, 0.1 to 0.5 mm diameter, vertical canals. Branches have rounded tips. The whole sponge is covered by the dense dermal skeleton of phyllotriaenes (470-650 µ m in size) or, more rarely, small (230 µm in size) irregular discotriaenes. Between dermal phyllotriaenes occurs a dense layer of tightly interlocking irregular flat spicules resembling rhizoclones. Choanosomal skeleton composed of irregular (except at a pole of a branch and in the centre) tetraclones 400-530 µ m in size with smooth clads and strongly branched tuberculated apices. Articulation of several desmas forms large spherical articulation centres. Generally, the skeleton, except at the tips, gives the impression of oversilicification by being very dense. In the lower portion of the sponge, skeleton becomes extremely dense and tetraclones interwoven and strongly modified (irregular) to the point when they resemble rhizoclones.

REMARKS

The specimens included by me in L. digitata were most probably included into Discodermia by Oakley (1942). This is the first report of this Cretaceous genus (see Moret 1926) from the Tertiary. The holotype of this species, here on the Fig. 2J , was also illustrated earlier by Piaskovsky (1929: 138, fig. 1 left-larger specimen). This new species differs from the Cretaceous species of Lerouxia in the shape of dermal phyllotriaenes and choanosomal desmas.

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.