Margaretta tenuis Harmer, 1957

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 41-42

Margaretta tenuis Harmer, 1957

( Figs 124–126 ; Table 26)

Margaretta tenuis Harmer, 1957: 840 , pl. 55, figs 13–18.

Figured material. RGM.1350574, Holocene, UPGG 041, off South Sulawesi.

Description. Colony erect, articulated. Internodes cylindrical, tapering proximally; basis rami tripartite, originating at the side of a peristome, raised, about 200 µm in diameter. Autozooids in whorls of three, distinct with shallow, interzooidal furrows, oval, elongate (mean L/W = 2.36). Frontal shield convex, smooth, regularly and evenly perforated by small, circular to slit-like pseudopores, 30–45 µm long, arranged in longitudinal rows, ascopore distomedial, located immediately proximally of the peristomial ridge, large, 60–80 µm in diameter, surrounded by a slightly raised, denticulate rim. Primary orifice transversely D-shaped; secondary orifice elliptical, about 120–140 µm long by 175 µm wide. Peristome moderately developed, longer proximally than distally, almost at right angle to the frontal plane, ridged with ridges projecting frontally to give the appearance of a denticulate oral rim, valleys between ridges porous, basal ridge distinct. Brooding zooids not observed.

Remarks. Two broken internodes of Margaretta tenuis were found in our samples. This species is distinguishable by the number of autozooids in each whorl (3), tripartite articulation, distinct zooidal boundaries and peristomial ridge, moderate, ridged peristome, and the ascopore adjacent to the peristomial ridge. Margaretta tenuis is widely distributed in the Indo-Pacific, from the Philippines south to Indonesia and Australia, with a depth range of 0– 45 m.

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

Figures

FIGURES 124–126. Margaretta tenuis Harmer, 1957, RGM.1350574, Holocene, UPGG041, off South Sulawesi. 124. View of an internode. 125. Close-up of a secondary orifice, with the peristome showing the basal ridge and the adjacent ascopore. 126. Close-up of a tripartite basis rami adjacent to a peristome and a transversely D-shaped primary orifice. Scale bars: Fig. 124 = 500 µm; Fig. 125 = 100 µm; Fig. 126 = 200 µm.