Hippoporina, Neviani, 1895

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 32

? Hippoporina sp.

( Figs 89–91 ; Table 20)

Figured material. RGM.1350566, Holocene, UPGG 041, off South Sulawesi.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, bounded by thin raised ridges of smooth calcification, rectangular to irregularly polygonal, longer than wide (mean L/W = 1.42). Frontal shield moderately convex to flat, minutely perforated by numerous, circular pseudopores, about 10 µm in diameter, set in polygonal depressions; marginal areolar pores sometimes distinguishable at zooidal corners. Orifice distally placed, almost as long as wide, a pair of robust, rounded condyles separate a semicircular anter from a wide, shallow, bowl-shaped sinus. Avicularia and ooecia not observed.

Remarks. A single colony of? Hippoporina sp. was found in our samples, encrusting a bivalve shell. This species is only tentatively referred to Hippoporina because of the lack of avicularia, while for the shape of the orifice and the pseudoporous frontal shield it may also fit in Calyptotheca . Although some species assigned to Calyptotheca are deprived of adventitious avicularia, such as C. suluensis Harmer, 1957 , they are present in the type species, C. wasinensis ( Waters, 1913) . Ooecial ontogeny is essential to discriminate between the two genera: in Hippoporina , the ooecium is of the smittinid type (i.e. with a calcified, pseudoporous ectooecium which can be totally covered by secondary calcification during ontogeny); in Calyptotheca , the ooecium is of the schizoporelloid type (identical to the frontal shield, with a membranous ectooecium). Furthermore, Hippoporina has monomorphic orifices, while Calyptotheca has dimorphic orifices (enlarged in ovicellate zooids). Unfortunately, the specimen available lacks fertile zooids essential for a certain identification.

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

Figures

FIGURES 89–91.?Hippoporina sp., RGM.1350566, Holocene, UPGG041, off South Sulawesi. 89. General view of the colony encrusting a bivalve shell fragment. 90. Close-up of two zooids. 91. Close-up of an orifice. Scale bars: Fig. 89 = 500 µm; Fig. 90 = 100 µm; Fig. 91 = 50 µm.