Biflustra cf. virgata ( Canu & Bassler, 1929 )

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 10-11

Biflustra cf. virgata ( Canu & Bassler, 1929)

( Figs 13–15 ; Table 5)

cf. Acanthodesia virgata Canu & Bassler, 1929: 69 , pl. 2, figs 2–5.

Figured material. RGM.1350546, Holocene, UPGG 041, off South Sulawesi.

Description. Colony erect vincularian; branch fragments subcircular in cross-section, with six longitudinal rows of zooids. Zooids arranged in alternating series, separated by shallow grooves between the raised mural rims, rounded hexagonal, slightly longer than wide (mean L/W = 1.28). Mural rim salient, thick, the thickness constant all around the zooid, crenulate. Gymnocyst lacking. Cryptocyst granular, narrow, broadest proximally where it forms a shallow planar shelf expanding into a plectriform-type apparatus, small, fan-shaped, denticulate. Opesia occupying almost two-thirds of the frontal area, oval.

Remarks. Five fragments of Biflustra cf. virgata were found in our samples. The fossil specimens differ from the Recent Philippine specimens of this species described by Canu & Bassler (1929) in the smaller size of the zooids, which are on average 370 µm long in the fossil versus 540–600 µm long in the Recent species. However, irregularly shaped zooids observed in the fossil fragments range from 300 up to 600 µm in length ( Fig. 14 ). Biflustra cf. virgata differs from B. cf. quadrata in having six longitudinal rows of zooids rather than four, cylindrical fragments rather than quadrangular, smaller hexagonal zooids rather than elongate rectangular, and in the shape of the plectriform-type apparatus, small and fan-shaped in the former species but long rectangular and curved inwardly in the latter species.

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

Figures

FIGURES 13–15. Biflustra cf. virgata (Canu & Bassler, 1929), RGM.1350546, Holocene, UPGG041, off South Sulawesi. 13. Branch fragment.14. Close-up of irregularly shaped zooids. 15. Close-up of regular zooids showing the denticulate, fan-shaped, plectriform-type apparatus. Scale bars: Fig. 13 = 400 µm; Figs 14, 15 = 100 µm.