Psammocleidochasma tridentatum, Winston, Judith E. & Vieira, Leandro M., 2013

Winston, Judith E. & Vieira, Leandro M., 2013, Systematics of interstitial encrusting bryozoans from southeastern Brazil, Zootaxa 3710 (2), pp. 101-146 : 134

Psammocleidochasma tridentatum sp. nov.

( Fig. 21 ; Table 19 )

Material examined. Holotype: MZUSP 746 ( Fig. 21 A, E), BIOTA Stn 211. Paratypes: MZUSP 691, specimen #20, near BIOTA Stn 205, 15 m; MZUSP 692, #21 [7 colonies], near BIOTA Stn 205, 15 m; MZUSP 747, specimen #3, BIOTA Stn #3; MZUSP 748 ( Fig. 21 F), BIOTA Stn 205; MZUSP 749, measured specimen #1, BIOTA Stn 205; VMNH 70028, measured specimen #2, BIOTA Stn 205; VMNH 70029, BIOTA Stn 205; VMNH 70030, BIOTA Stn 205. Additional material: MZUSP 693, #22 [several colonies], near BIOTA Stn 205, 15 m; MZUSP 711, BIOTA Stn 211.

Supplementary video. http://cifonauta.cebimar.usp.br/taxon/psammocleidochasma-tridentatum/

Etymology. Latin, tridentatum , three-toothed, aluding to the three tubercles, one proximal and two lateral, which adorn the peristome.

Diagnosis. Sand-encrusting Psammocleidochasma with 3 peristomial tubercles arranged laterally and proximally.

Description. Colony encrusting on sand grains, including very small mineral grains. Zooids oval, convex, frontal shield smoothly and thickly calcified, imperforate except for a very few small marginal pores; zooid margins indistinct. Distal end of zooids raised in a thick collar made up of a very thick proximal tubercle and 2 lateral tubercles. Orifice keyhole shaped, anter transversely oval, ending in two rounded, proximomedially pointed condyles, poster a narrow to broad, shallowly concave sinus. Articulated oral spines 2–3, often obscured by distal calcification. No avicularia. Reproduction precocious; ovicells may occur only 2 zooids from ancestrula. Ovicells thickly calcified, with a central tubercle and vertical proximal wall ending in an opening that is separate from the operculum. Ancestrula tatiform with a thick mural rim and 5 hollow spines. Polypides with 7–8 translucent white tentacles.

Remarks. This species prefers the ridges and raised edges of grains, including very small and sharp-edged mineral grains. It is the most abundant species found encrusting sand in the Brazilian fauna. The Brazilian species is very similar to the interstitial Floridan species Psammocleidochasma angustum , however that species has four peristomial tubercles, arranged distolaterally and proximolaterally along the rim of the peristome.

Distribution. São Paulo state, Brazil.

Figures

FIGURE 21. Psammocleidochasma tridentatum sp. nov.: A, a colony attached to one side of a grain. B, a uniserial colony encrusting the edge of a grain. C, three zooids of the colony in B. D, profile of zooids showing projecting peristomial tubercles. E, ovicell and orifice with three tubercles surrounding it. F, zooidal orifice. Scale bars: A, B, 0.5 mm; C, 0.3 mm; D, 0.15 mm; E, 0.1 mm; F, 0.05 mm.

Tables

TABLE 19. Measurements (in mm) of Psammocleidochasma tridentatum sp. nov..

	Lz	Wz	Lo	Wo	Lov	Wov
N	13	13	11	11	2	2
Mean	0.242	0.195	0.066	0.056	0.117	0.162
SD	0.022	0.049	0.012	0.007	0.013	0.000
Min	0.216	0.126	0.054	0.045	0.108	0.162
Max	0.288	0.306	0.090	0.072	0.126	0.162