S65

Spongurus pylomaticus Riedel

Spongurus pylomaticus Riedel, 1958, p. 226, pl. 1, figs. 10,11; Petrushevskaya, 1967, p. 32, fig. 16, I-II; Ling et al., 1971, p. 711, pl. 1, fig. 5

Spongurus (?) pylomaticus Riedel, Petrushevskaya, 1975, p. 577, pl. 7, fig. 4; pl. 37, fig. 7

DESCRIPTION

"Shell subcylindrical or elongate ellipsoidal, approximately twice as long as broad. An inner densely spongy core is surrounded by a narrow mantle of less dense meshwork. Entire surface usually sparsely covered with bristle-like spines, which in many specimens tend to be longer at the two poles of the main axis. At one pole is a pylome, usually surrounded by short, irregular teeth." (from Riedel, 1958).

"... the Bering Sea specimens sometimes show that the side of the dense inner spongy shell core is slightly concave outward rather than straight. Also there is a range of intraspecific variation on length vs. width (or breadth) ratio." (from Ling et al., 1971).

DIMENSIONS

"Length 150-255 microns, breadth 78-125 microns. Length of surface spines 5-10 microns (usually broken off)." (from Riedel, 1958).

"Length 180-250 microns, width 75-100 microns." (from Ling et al., 1971).

REMARKS

1. Petrushevskaya (1975) considers this species to be so different from Ommatogramma dumitricai as to require a separate genus. However, in counting specimens, it may not be possible to readily distinguish between the two.

Plate 8, figures 3a, b

S66

RECENT DISTRIBUTION

1. Ling et al., 1971; "This is the first record for occurrence of the present species, though found only rarely, from the Bering Sea. We have also noticed the presence of the species from the eastern and central subarctic North Pacific deep-sea sediments, which are currently under intensive examination. By combining the previous information of RIEDEL and PETRUSHEVSKAYA from the Antarctic, KRUGLIKOVA from the northern Pacific, and the present study, S. pylomaticus can be considered as one of the cold-water and bipolar forms."

2. Sachs, 1973, Code 18I; counted together with Spongurus (?) sp.; "The maximum abundance of the two Spongurus species is less than 4%, but together they are widespread, favoring higher latitudes. They load preferentially on the northernmost (Polar) factor, with a decreased intermediate (Subarctic) influence."

3. Lozano, 1974; Fig. IV-21, counted together with Spongurus (?) sp.; "It has the distribution typical of the Antarctic assemblage. It reaches a maximum relative abundance of 5.5 percent in core RC13-268 which is located at the edge of the winter ice. The presence of well developed forms with mantle north of 40 degrees S... is an indication of northern transport by bottom currents, reworking or non-Recent sediments.

"As the other Antarctic species, its distribution is affected by bottom transport in the Argentine and Crozet basins. S. pylomaticus is found in sediments under August sea surface temperatures between 16 degrees C and -1.7°C reaching its maximum relative abundance at -1.7 degrees C."

4. Molina-Cruz, 1975, Code S41; not used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent S41 at each station.

5. Robertson, 1975; "This species loads most heavily in factor 3 (transitional). At present its greatest abundances are in the northwest Pacific north of 40 degrees N. Abundances are low in the Sea of Okhotsk and through most of the Bering Sea. At 18,000 YBP the region of higher abundances is significantly smaller and further to the east."

6. Morley, 1977 (Spongurus spp.), Fig. I-14; S. pylomaticus and Spongurus (?) sp counted together; "S. pylomaticus is most common in polar waters. Spongurus (?) sp. is found only in tropical, subtropical, and subantarcti waters... This taxonomic group loads highest in factor 2 (polar). At present this group is found most frequently south of 45 degrees S. At 18,000 YBP the 1% contour is displaced northward by 15 degrees to 20 degrees of latitude."