Psammocleidochasma, Winston & Vieira, 2013

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 53-54

Psammocleidochasma sp.

( Figs 158–159 ; Table 35)

Figured material. RGM.1350589, early Pleistocene, Java.

Description. Colony encrusting a shell fragment, multiserial, unilaminar. Autozooids distinct by shallow interzooidal furrows, hexagonal, longer than wide (mean L/W = 1.31). Pore-chamber windows visible along inner walls of broken zooids. Frontal shield convex, finely granular, nodular, imperforate except for a pair of small (about 20 µm long), elliptical, rimmed, marginal areolar pores, leant against the zooidal margin slightly below the orifice; a few additional marginal pores may occur proximally. Orifice placed terminally, cleithridiate, anter deeply rounded separated from the slightly narrower, shallowly concave sinus by pair of small, rounded, downwardly directed condyles. An uncertain number of oral spine bases obscured by distal calcification. Peristome slightly raised, thick, made of 3–5 projecting solid tubercles. Two additional tubercles may develop proximally on the frontal shield with ontogeny. Avicularia absent. Ooecia not observed.

Remarks. A single specimen of Psammocleidochasma sp. was found in our samples, encrusting both sides of a small shell fragment. The genus Psammocleidochasma was introduced by Winston & Vieira (2013) for ‘ Cleidochasma ’-like species with uni- to pluriserial small-sized colonies encrusting sand grains, and was characterized by its relatively small autozooids, tatiform ancestrula, lack of avicularia, thickened calcification of the ovicells, and solid tubercles encircling the orifice. The Florida species P. angustum ( Winston & Håkansson 1986) differs from the Javanese species in having four tubercles arranged distolaterally and proximolaterally around the peristome, while P. tridentatum Winston & Vieira, 2013 from Brazil differs in having three massive peristomial tubercles, one proximal and two lateral, as well as uniserial colonies with ovicellate zooids occurring precociously. Although probably new, we prefer to keep the species in open nomenclature because the single specimen available lacks ooecia.

N, Number of colonies and number of zooids measured; SD, standard deviation.

Figures

FIGURES 158, 159. Psammocleidochasma sp., RGM.1350589, early Pleistocene, Java. 158. View of the colony encrusting a shell fragment. 159. Close-up of zooids showing oral and frontal tubercles, marginal areolar pores, cleithridiate orifice, oral spine bases usually covered by distal calcification (see arrow), and pore-chamber windows. Scale bars: Fig. 158 = 400 µm; Fig. 159 = 200 µm.