S115

Spongopyle osculosa Dreyer

Spongopyle osculosa Dreyer, 1889, p. 42, pl. 11, figs. 99, 100; Riedel, 1958, p. 226, pl. 1, fig. 12

Spongodiscus (?)osculosus (Dreyer), Petrushevskaya, 1967, p. 42 figs. 20-22

DESCRIPTION

"Spongy shell in form of biconvex lens. Its shape varies: approximates to a more or less regular circle. Spongy tissue fine; central thickened part of shell constructed of denser spongy mass than marginal. Entire surface of shell in adult specimens covered by mantle similar to that of Spongurus pylomaticus. Because of mantle shell has clear contours. Radial pieces pass among cross-pieces of spongy tissue in form of indistinct radial striation...do not emerge to the outside, and shells devoid of radial needles. Distinct pylome characteristic. This is not a simple funnel in spongy tissue...but specialized formation in form of porous tubule with notches at end." (translated from Petrushevskaya, 1967).

"Well preserved specimens with mantle and pylome are easily distinguished from other species. When badly preserved or not well developed (?) and the mantle and pylome are not well preserved, it is difficult to differentiate from some variants of Spongotrochus glacialis. As described by Dreyer, Riedel and Petrushevskaya the shell has the shape of a biconvex lens. The central thickened part is made of a denser spongy mass. The entire surface of the shell in adult specimens is covered with a mantle so the shell has a well defined contour. It is also characterized by the presence of a tubular pylome...However, under subantarctic and subtropical waters a variant is found which has flat sides in lateral view acquiring a subhexagonal outline...and some specimens are difficult to differentiate from a variant of [Spongotrochus glacialis]." (from Lozano, 1974).

DIMENSIONS "Diameter of disk of adult specimen - 190 - 270 microns" (translated from Petrushevskaya, 1967).

REMARKS

1. Petrushevskaya (1975) synonymized the genera Spongodiscus Ehrenberg, 1854 (type species = Spongodiscus resurgens Ehrenberg, 1854, pl. 35B, IV, fig. 16) and Spongopyle Dreyer, 1889 (type species = Spongopyle setosa Dreyer, p. 119, pl. 11, figs. 97, 98). This synonymy is based on the belief that a pylome may or may not be present.

Plate 15, figure 1

S116

At this time, there appears to be so much difficulty in distinguishing and defining Spongopyle osculosa, Spongopyle setosa and Spongotrochus glacialis (see Lozano, 1974) as well as some less well known species of this general form , that the present authors prefer to retain familiar names until generic and specific revisions can be made simultaneously. Petrushevskaya's synonymy has the disadvantage of giving us Ehrenberg's poorly illustrated type species (only half a specimen is shown) rather than Dreyer's excellent illustration.

RECENT DISTRIBUTION

1. Benson, 1966; "...rare but cosmopolitian in the Gulf [of California]."

2. Lozano, 1974 (fig. IV-13); "It is found in all but three samples from subtropical water where it is generally less abundant but without displaying a preferred distribution pattern. It reaches a maximum of 3.5 percent in core RC12-292. Because of the difficulty of differentiating between some specimens of S. osculosa and S. glacialis ...they were combined for the factor analysis. Figure IV-4 shows the percent distribution of S. glacialis plus S. osculosa. Due to the almost constant and comparatively low abundance of S. osculosa the characteristics of the distribution for both of them are essentially the same as for S. glacialis alone."

3. Molina-Cruz, 1975, Code S44; mistakenly counted together with Spongotrochus glacialis and Stylochlamydium venustrum. It now appears that each of these species has a defined distribution. Therefore, this category was not used in factor analysis of southeast Pacific assemblages.

4. Morley, 1977, fig. I-19 "Since it is difficult to differentiate this species from Spongotrochus glacialis without its characteric mantle and pylome, only specimens with a distinguishable mantle and/or pylome were counted...

"This species loads highest in factor 3 (gyre margin). At present this species is most abundant under subantarctic waters. While keeping approximately the same southern boundary at 18,000 YBP, this species appears to slightly increase in abundance in sampling along the western coast of Africa."