Acanthodesia variegata, Martino & Taylor, 2018

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 7-8

Acanthodesia variegata n. sp.

( Figs 5–7 ; Table 2)

Figured material. Holotype, RGM.1350542, Holocene, UPGG 041, off South Sulawesi.

Diagnosis. Colony encrusting with zooids arranged in sinuous rows. Zooids rounded rectangular, surrounded by a very narrow, crenulate mural rim. Cryptocyst changing during ontogeny from narrow and smooth, to extensive and evenly granular, comprising up to half of zooid length. Plectriform-type apparatus large and rectangular, or small and fan-shaped, denticulate, directing distally.

Etymology. Alluding to the variability of the cryptocystal texture with ontogeny, and shape and size of the plectriform-type apparatus.

Description. Colony encrusting, multiserial, unilaminar. Autozooids arranged in sinuous, parallel rows separated by fine fissures, rounded rectangular, longer than wide (mean L/W = 1.82), narrower at row bifurcations (L/W = 2.20–2.80). Mural rim salient, very narrow, crenulate. Gymnocyst lacking. Cryptocyst narrow and smooth in younger zooids, occupying up to half of zooid length and evenly granular in older zooids, and expanding into a median, plectriform-type apparatus, variable in size and shape, from large and rectangular, occupying almost the entire length of the proximal opesial margin, to small and fan-shaped, in both cases denticulate. Opesia oval to rounded quadrangular, occupying half to two-thirds of the frontal area.

Remarks. Following Taylor & Tan (2015), we use here the genus Acanthodesia Canu & Bassler, 1919 to include membraniporiform species having encrusting colonies, reserving Biflustra (d’Orbigny 1852) for erect adeoniform or vincularian cheilostomes in accordance with the type species as well as d’Orbigny’s concept for the genus. Two colonies of Acanthodesia variegata n. sp. were found in our samples, both encrusting erect bryozoan fragments of Adeonellopsis and Triphyllozoon . Harmer (1926) reported A. savartii ( Audouin, 1826) from several stations off the Indonesian Archipelago. Based on the original illustrations of A. savartii from Egypt ( Savigny 1817, pl. 10, figs 10.1, 10.2), this species lacks a median plectriform-type apparatus in the cryptocyst. Taylor & Foster (1994) depicted a colony of presumed A. savartii from Alexandria, which must be close to the Egyptian type locality. This too lacks a plectriform-type apparatus. In his description of A. savartii , however, Harmer (1926) described encrusting colonies with a high intracolonial variability in both the texture of the cryptocyst and the development of the plectriform-type apparatus. Although A. savartii has been reported as cosmopolitan, some of these records may refer to different species. A revision of the specimens is needed to ascertain the conspecificity of Harmer’s material, or at least part of it, with A. variegata n. sp.

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

Figures

FIGURES 5–7. Acanthodesia variegata n. sp., holotype, RGM.1350542, Holocene, off South Sulawesi. 5. General view of the colony encrusting a fragment of Adeonellopsis, and showing the high intracolonial variability. 6. Close-up of two zooids with granular cryptocyst, and large, rectangular plectriform-type apparatus. 7. Close-up of a zooid with smooth cryptocyst, and small, fan-shaped plectriform-type apparatus. Scale bars: Fig. 5 = 400 µm; Fig. 6 = 100 µm; Fig. 7 = 50 µm.