Acanthodesia cf. lamellosa Canu & Bassler, 1929

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 8-9

Acanthodesia cf. lamellosa Canu & Bassler, 1929

( Figs 8, 9 ; Table 3)

cf. Acanthodesia lamellosa Canu & Bassler, 1929: 68 , pl. 2, fig. 1.

Figured material. RGM.1350543, early Pleistocene, Java; RGM.1350544, Holocene, UPGG 041, off South Sulawesi.

Description. Colony encrusting, multiserial, uni- or multilaminar. Autozooids arranged in alternating rows, separated by fine fissures, rectangular with a rounded, raised distal edge, longer than wide (mean L/W = 1.34), narrower at row bifurcations. Mural rim salient distally, narrow, crenulate. Gymnocyst lacking. Cryptocyst narrow, broadest at proximolateral corners, concave, with sparse granules aligned in short parallel rows around the opesia. Opesia oval, occupying almost the entire frontal area. Plectriform-type apparatus lacking. Kenozooids sporadically present, irregularly shaped, with small, oval opesia.

Remarks. Three colonies of Acanthodesia cf. lamellosa were found in our samples, one as a loose fragment ( Fig. 8 ), the others encrusting bivalve shells ( Fig. 9 ). The main feature of this species is the mural rim that is salient only distally. Autozooid size in the fossil specimens falls within the range reported by Canu & Bassler (1929, p. 68) for their Recent colonies. Zooids of Acanthodesia grandicella Canu & Bassler, 1929 , resemble those of A. cf. lamellosa but differ in having a regular raised mural rim and larger size. Harmer (1926, pl. 13, fig. 12) illustrated a species, identified as Conopeum reticulum ( Linnaeus, 1767) , which looks rather similar to this species of Acanthodesia , with kenozooids occasionally present, while paired kenozooids are constantly associated with each autozooid in Conopeum . The most striking difference between Acanthodesia cf. lamellosa and A. variegata n. sp. is the lack of the plectriform-type apparatus in the former species. They also differ in the size of the zooids, larger in A. cf. lamellosa , and in the extension and texture of the proximal cryptocystal shelf.

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

Figures

FIGURES 8, 9. Acanthodesia cf. lamellosa Canu & Bassler, 1929, early Pleistocene and Holocene, off South Sulawesi. 8. RGM.1350544, group of autozooids. 9. RGM.1350543, group of autozooids and a kenozooid. Scale bars: 200 µm.