Biflustra adenticulata Boonzaaier-Davids & Florence & Gibbons 2020, n. sp.

Biflustra adenticulata n. sp.

(Fig. 2 A–E, Table 1)

zoobank.org/ 4BAD9356-CED3-4EA7-B182-AF9BD2785892

Material examined. Holotype: SAMC-A029105, station WCD 11 (34°9.4’S, 18°16.5’E), off Kommetjie, west of Cape Peninsula, UCT Ecological Survey, dredge, depth 75 m, 24 March 1959. Additional material: SAMCA077618 (in ethanol), SAMC-A077630 (in ethanol), FAL 475; SAMC-A077611 (dry), FAL 524; SAMC-A077502 (dry), FAL 576; SAMC-A077269 (in ethanol), FAL 67; SAMC-A073461 (dry), FAL 739; SAMC-A077474 (in ethanol), FAL 759; SAMC-A077323 (in ethanol), FAL 818; SAMC-A028915 (dry), TRA 122; SAMC-A029128 (dry), WCD 18.

Etymology. From the Latin, referring to the absence of cryptocystal denticles.

Diagnosis. Colony erect, bilaminar, foliaceous; fenestrulae present. Autozooids with relatively extensive, granular cryptocyst proximally, and prominent ridge distally; cryptocystal denticle projecting into the opesia from its proximal margin absent. Opesia occupying half zooidal length. Kenozooids present at branch margins and around fenestrulae.

Description. Colony erect, delicate; branches broad, foliaceous, bilaminar, anastomosing—some edges fusing to form small, irregularly polygonal or oval fenestrulae (the smallest about 1 mm in length). Available fragments up to 32 mm long by 18 mm wide. Specimens preserved in ethanol light brown; dried material light yellow to creamy white. Autozooids subrectangular with the distal margin rounded and the proximal margin concave; smaller, irregular shaped zooids (?kenozooids) placed where anastomose branches fuses. Lateral walls thick. Cryptocyst well-developed and granular, most extensive proximally, up to one-third to half of the total length of autozooid, less extensive in older autozooids, frequently forming a thickened distal ridge. Opesia oval to rectangular, generally occupying more than half of total zooid length. Operculum lightly chitinized. Kenozooids situated on the outer margins of the branch and/or around the margins of the fenestrulae; oval opening usually placed in the centre of the kenozooid, less often distally. Multiporous septula present (1–3) in the distal wall, mural pore chambers (1–2) in the lateral walls. Spines, avicularia and ovicells absent. Early astogeny unknown.

Remarks. The genus Biflustra d’Orbigny, 1852 has been frequently used in paleontology (see Berning 2006), but has been overlooked in recent faunas with species either assigned to genera Membranipora de Blainville, 1830 or Acanthodesia Canu & Bassler, 1920. Lagaaij (1952) attempted to resurrect the latter genus, however, the confusion between Acanthodesia and Biflustra continued to persist. Recent publications describe Biflustra as an erect vincularian or bifoliate membraniporid species, with no gymnocyst and moderate to extensive cryptocyst, whereas encrusting species may be assigned to Acanthodesia (Tilbrook et al. 2001; Taylor & Tan 2015). Taylor & Tan (2015) emphasized that the lack of ovicells and avicularia make species difficult to distinguish, and that molecular studies are required in Acanthodesia to clarify its diversity.

Biflustra species are widespread and from seemingly shallow waters (<30 m). Biflustra has been reported from localities in the North Atlantic Ocean (Álvarez 1990; Souto et al. 2014), Mediterranean Sea (Álvarez 1992a, b), Korean waters (Lee et al. 2011), Arabian Sea (Louis & Menon 2009), south Chinese waters (Canu & Bassler 1929; Liu 1992), South Pacific Ocean (Tilbrook et al. 2001; Tilbrook 2006), Atlantic Ocean (Canu & Bassler 1928), and the Indo-Pacific, including Australia (MacGillivray 1881; Tilbrook 2012) and New Zealand (Grange & Gordon 2005). In South Africa, O’Donoghue (1957) reported B. savartii Audouin, 1826 in Cape Town from the hull of the Sutherland vessel. No figure was associated in the report, but the description coincided with the known description of the species and noted “the presence of a proximal denticle on the cryptocyst…may be absent or present as a small projection or as a short lamina terminating in 4 or 5 teeth” (O’Donoghue 1957, p. 73). However, no record of B. savartii has been reported since and because the vessel was docked in Cape Town after returning from a voyage to England, Colombo, Durban and Brazil, this record can be considered as doubtful.

Of all the Biflustra species, the colony morphology of Biflustra adenticulata n. sp., while being more robust and reticulate, closely resembles the erect, bilaminar and anastomosing colonies of the widespread B. arborescens Canu & Bassler, 1928. The average size of Biflustra adenticulata n. sp. autozooids (0.36 mm long by 0.28 mm wide, see also Table 1) is comparable with that of B. arborescens (0.46 mm long by 0.32 mm wide, see Souto et al. 2014). However, B. arborescens has thin cryptocystal denticles along the proximal opesial rim (Souto et al. 2014), as in B. ramosa d’Orbigny, 1852 and B. savartii Audouin, 1826, but absent in this new species.

This is the first undoubtful record of Biflustra from South Africa. A number of partial, erect foliaceous colonies were found in the samples mainly collected through dredging off Kommetjie, west of the Cape Peninsula to False Bay area on the South Coast, at a depth range of 16– 75 m. The broad, bilaminar fronds were encrusted with other bryozoans and hydroids. One colony (SAMC-A077611) was found encrusting Adeonella sp. This may be the encrusting portion of the colony that only later becomes erect bifoliate.