Adeonellopsis arculifera

Fig. 6

Measurements Autozooids. ZL: 505 ̅ 762 (590 ± 62); ZW: 207 ̅ 387 (288 ± 53); n = 39. SOrL: 54 ̅ 91 (71 ± 10); SOrW: 62 ̅ 103 (83 ± 9); n = 30. SAvL: 76 ̅ 147 (100 ± 13); SAvW: 50 ̅ 85 (64 ± 7); n = 38. SpL: 12 ̅ 27 (20 ± 4); SpW: 16 ̅ 25 (20 ± 3); n = 28. Description Colony small, slender, dichotomously branching (Fig. 6 A); yellowish white. Branches subcylindrical or flat (Fig. 6 B); slender, on average 1 mm wide (0.9 – 1.3 mm, n = 8), multiserial, zooids opening on both sides. Zooids oval, boundaries indistinct, delineated by shallow groove and opposing single rows of tiny, irregular areolar pores (Fig. 6 D). Frontal shield smooth, or finely granulate and slightly wrinkled. Zooids raised distally towards a low peristomial rim; primary orifice D-shaped, with straight or convex proximal margin; secondary orifice broader than long. Spiramen small, uniporous, circular, situated close to center of frontal shield proximal to orifice, often in depressed frontal zone (Fig. 6 C). Suboral avicularium abutting proximal margin of peristome, smaller in area than secondary orifice, rostrum slightly raised and sometimes hooked distally, slightly curved toward distal side, directed distolaterally; no crossbar; mandible equilaterally triangular (Fig. 6 C). No other types of avicularia observed. Autozooids distal to branch bifurcations elongate, sometimes bearing up to three umbonate bosses 47 – 76 μm in diameter (average 61 μm, n = 18), on one or both sides proximolateral to orifice and toward proximal end of frontal shield (Fig. 6 D). Older autozooids in basal part of branch broad, irregular in outline; zooidal boundaries indistinct; frontal shield heavily secondarily calcified; spiramen often lacking; suboral avicularium lies in depression in thickened frontal shield (Fig. 6 F). Rarely, kenozooids occur at basal bifurcations (Fig. 6 E); same size as autozooids. Gonozooids not found.

Remarks Canu & Bassler (1929) originally described Adeona arculifera from Jolo and Sulade Islands, Sulu Archipelago, Philippines, on the basis of the single spiramen, although the branched colony resembles the condition in Adeonellopsis. Harmer (1957) then transferred the species to Adeonellopsis on the basis of the operculum, which is not widely sinuate. Adeonellopsis arculifera resembles A. subsulcata (Smitt, 1873) in the arrangement of the suboral avicularia but differs from the latter in having a circular spiramen in the center of the frontal shield.

Distribution Adeonellopsis arculifera has previously been reported from the Philippines, Indonesia, and the Indian Ocean, at depths of 38 – 53 m. In Japan, it has been detected only in the southwestern region, from Okinawa and near Yakushima Island, at depths of 47 – 88 m. Although this is the first Recent record for Japan, Hayami (1971) reported the species from the Pliocene Shinzato Tuff on Okinawa Island.

Material examined JAPAN: many branches collected from Hirase, southwest of Yakushima Island, 87 – 88 m depth (NSMT- Te 781, Te 783, Te 784, Te 785, Te 786, Te 787, Te 788, Te 789); single colony collected from South of Nagannu Island, 47 – 52 m depth (NSMT-Te 782).

(Figs 53 – 57; Table 12)

Description. Colony rigidly erect, adeoniform. Branches strap-like, about 2 mm wide, arising from an encrusting base, bifurcating at angles of 80 – 90 ˚, bilaminate, tapering proximally with 6 – 12 longitudinal rows of alternating autozooids, with the zooids in the central rows aligned parallel to the branch axis and the outer zooids directing outwards. Autozooids distinct with shallow interzooidal furrows, apparently monomorphic, rhomboidal to hexagonal, longer than broad (mean L / W = 1.60). Frontal shield flat, finely granular with suboral avicularium and frontal spiramen. One or two small tubercles present at sides of orifice in some autozooids. Areolar pores circular to oval, 10 – 25 µm in diameter, forming a complete row around periphery of zooid; accessory pores delimiting the suboral avicularian cystid. Spiramen circular, relatively large, 30 – 40 µm in diameter, placed at about one-forth from the proximal end of the zooid. Orifice circular to semicircular. Suboral avicularium present on each autozooid, extending obliquely from a point distal to the spiramen to proximolateral corner of the orifice without indenting it except in a few cases; rostrum pointed triangular distolaterally and outwardly directed; a pair of blunt pivotal condyles define a pear-shaped opening. Additional frontal avicularia observed only in a few zooids, similar in shape and size to suboral avicularia, placed on the proximal end of the zooid, rostrum proximolaterally directed. Vicarious avicularia rare, placed on the branch margins, rostrum triangular and channelled, distally directed; cystid lozenge-shaped, finely granular, bordered by a row of areolar pores. Orifice sealed in some zooids as ontogenetic calcification progresses. Gonozooids not recognized.

Remarks. Sixty-six branch fragments of Adeonellopsis arculifera were found in our samples. This Indo- Pacific species has been recorded from the Sulu Archipelago (Philippines) at 38 – 53 m depth (Canu & Bassler 1929), and the Makassar Strait and off Halmaheira (Indonesia) at 0 – 45 m depth (Harmer 1957). N, Number of colonies and number of zooids measured; SD, standard deviation; Av, avicularium; Vic, vicarious.

Figured material. RGM. 1350556, RGM. 1350557, Holocene, UPGG 041, off South Sulawesi.