Calloporina biavicularia Kataoka, 1961

Calloporina biavicularia Kataoka, 1961 View in CoL

Figure 45 View FIGURE 45

v. 1961 Calloporina biavicularia Kataoka , p. 255, pl. 33, fig. 2.

Figured material. PMC EDM-Collection J.H.B.140a, sample 19093; Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, separated by deep furrows, oval to rounded hexagonal, longer than wide (mean ZL/ZW 1.22); circular pore chamber-windows, 30–40 µm in diameter, visible along distolateral margins. Frontal shield flat to slightly convex coarsely ornamented with sculptured ridges outlining polygonal depressions housing circular pores mainly along zooidal perimeter (i.e., marginal areolae, 30–55 µm in diameter), with a few centrally located (20–30 µm in diameter). Ascopore a short distance (60–90 µm) from proximal margin of orifice, circular (44–66 µm in diameter), encircled by a thin, raised rim. Orifice longitudinally elongate, semicircular and high-arched, with straight and crenulated proximal margin; nine oral spine bases (20–30 µm in diameter); a ridge of the frontal shield forming a small bowl-shaped platform below the proximal margin. Avicularia long, slender, single or paired, falciform, originating laterally to ascopore and extending the entire length of orifice; rostrum elongate, triangular, with a slight curvature towards the distal edge of orifice, directed distally; crossbar complete. Ovicells not observed.

Measurements (µm). ZL 612±12, 593–622 (1, 5); ZW 500±45, 438–563 (1, 5); OL 126±6, 120–134 (1, 5); OW 118±2, 116–120 (1, 5); AvL 248±26, 202–274 (1, 8); AvW 63±7, 55–71 (1, 8).

Remarks. This species was first described from the Pleistocene Ryukyu Limestone of Kagoshima, Japan (Kataoka, 1961). Despite the small size of our fragment, we observed some intracolonial variability, which was not mentioned by Kataoka (1961). This author noted the presence of generally eight spines. However, in the fragment available to us all zooids have nine spines. A similar discrepancy applies to avicularia; while Kataoka (1961) described them as paired, we observed both paired and single avicularia. Another species of Calloporina is known from the Pleistocene of Japan, C. hayamiae Arakawa, 1995 . This species differs in having a crescentic ascopore (transversely C-shaped) and smaller avicularia with needle-like rostra positioned approximately at zooidal mid-length, aligned with the ascopore.