Microporina Levinsen, 1909

Arakawa, Shinji, 2016, Taxonomy of Some Microporids (Bryozoa: Cheilostomata) from the Pacific Coast of Japan, Species Diversity 21 (1), pp. 9-30 : 18

Genus Microporina Levinsen, 1909

Diagnosis. Colony erect, jointed, attached by kenozooidal rootlets. Zooids with lateral walls raised as mural rim. Frontal shield cryptocystal, minutely perforate, with pair of completely occluded opesiules near the orifice. Oral spines and ovicells lacking. Avicularia interzooidal, distal to orifice, with complete pivot bar. Uniporous septula present.

Type species. Cellularia articulata Fabricius, 1821 .

Remarks. Levinsen (1909) established Microporina for two species, Cellularia articulata Fabricius, 1821 and Steganoporella elongata Hincks, 1880 , with the former selected as the type species. However, C. articulata grows as an erect colony with internodes whereas S. elongata apparently forms an encrusting sheet (see also Waters 1889).

Sakakura (1936), Silén (1942) and Cheetham (1966) considered Microporina to include both erect and encrusting species, aπer Levinsen (1909). Other authors (e.g., Osburn 1950; Kluge 1962) considered Microporina to be restricted to species with erect, jointed colonies, as in the type species, and I concur with this view.

Microporina articulata (Fabricius, 1821) and M. okadai Silén, 1942 have been reported from northern Japan and neighbouring areas ( Okada 1921, 1933; Sakakura 1936; Silén 1942; Mawatari 1956; Androsova 1958; Kluge 1962; Hayami 1973; Arakawa 1984, 1999; Rho and Seo 1985, 1990; Seo 1996; Grischenko 2013). The fossil record of the type species can be traced back to the Miocene in northern Japan ( Hayami 1970, 1975, 1976; Nishizawa and Sakagami 1986), although these records need careful reexamination. Recently, Gontar (1993b) described a new species, Microporina ivanovi Gontar, 1993 from the Kuril Islands, but because the colony is not jointed and has ovicells, M. ivanovi may belong in some other genus.

Sakakura (1936) concluded that Microporina japonica Canu and Bassler, 1929 from the Tsugaru Strait is synonymous with M. articulata , but this may be incorrect, as discussed below. He also proposed a subspecies, Microporina articulata notoensis Sakakura, 1936 based on Miocene fossil material from the Noto Peninsula. This form should probably be raised to species rank, because it has multiple opesiules, although no specimens of this bryozoan have been reported since Sakakura (1936).