Porina australiensis ( Haswell, 1880 )

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 39-41

Porina australiensis ( Haswell, 1880)

( Figs 116–119 ; Table 25)

Myriozoum australiense Haswell, 1880: 43 , pl. 3, figs 9–11.

Haswellia australiensis: Busk, 1884: 172 , pl. 24, fig. 9a.

Figured material. RGM.1350572, RGM.1350573, early Pleistocene, Java.

Description. Colony erect, rigid, new branches arising laterally at right angle. Branches cylindrical, subcircular in cross section, about 1 mm in diameter. Autozooids in whorls of six, arranged in alternating, longitudinal series; zooidal boundaries indistinct. Frontal shield flat, smooth, regularly and evenly perforated by small, circular to elliptical pseudopores, 20–30 µm long, arranged in longitudinal rows; ascopore distomedial, located at a short distance from the peristome, large, circular, 65–70 µm in diameter. Primary orifice semicircular with a small sinus, about 155 µm long (including sinus) by 170 µm wide; secondary orifice subcircular, about 140 µm long by 165 µm wide. Peristome projecting proximally, bearing two adjacent, small, elliptical avicularia on the proximal rim with no evidence of crossbar or condyles, probably broken. Frontal avicularia typically occur between longitudinal zooidal series, drop-shaped, with triangular, pointed rostrum, proximally directed, seemingly with two small, pointed pivotal condyles. Brooding zooids inflated distally.

Remarks. Ten fragments of Porina australiensis were found in our samples. Based on the examination of the type specimen of Spiroporina vertebralis ( Stoliczka, 1865) , and non-type specimens of Haswellia australiensis ( Haswell, 1880) , Gordon & d’Hondt (1997) recognized the two species as distinct but congeneric, both belonging to Porina . Harmer (1957, p. 846) reported Porina vertebralis from several stations off the Indonesian Archipelago and considered this species as a junior synonym of Porina australiensis . The two species differ in the position of the peristomial avicularia, located only on the projecting proximal rim in P. australiensis (and in our specimens), but also distally in P. vertebralis ( Gordon & d’Hondt 1997) . To confirm the conspecificity of our fossil specimens with P. australiensis , we examined non-type specimens of P. australiensis from the Challenger Expedition ( Figs 120–123 ; NHMUK 87.12.9.700), identified and figured by Busk (1884, pl. 24, fig. 9a). The proximal peristomial rim of the Recent specimens appears more raised than that in the fossil material, and the avicularia clearly possess a complete pivotal bar, not observed in the fossil. However, these differences are likely due to preservation, as shown by the broken peristomes of the Recent specimens having exactly the same appearance as the fossils. It is more likely that Harmer’s specimens belong to the Recent P. australiensis than to the Miocene P. vertebralis , but these specimens need to be re-examined to affirm their conspecificity.

N, Number of colonies and number of zooids measured; SD, standard deviation; do, distance between midpoints of orifices of adjacent autozooids as an approximation of zooid size, following Berning (2007) and Rosso & Di Martino (2015); Per, peristomial, Av, avicularium.

Figures

FIGURES 116–119. Porina australiensis (Haswell, 1880), early Pleistocene, Java. 116, 117. RGM.1350572. 116. General view of a fragment with lateral offset. 117. Close-up of secondary orifices with peristomial avicularia and frontal avicularia. 118, 119. RGM.1350573. 118. General view of a fragment. 119. Close-up of an autozooid. Scale bars: Figs 116, 118 = 500 µm; Figs 117, 119 = 200 µm.

FIGURES 120–123. Porina australiensis (Haswell, 1880), Recent, Australia, Challenger Expedition (Busk 1884, pl. 24, fig. 9a), Station 186 (10˚30’S; 142˚18’E), coral sand, NHMUK 87.12.9.700. 120. General view of a dichotomously branched fragment. 121. Group of autozooids. 122. Close-up of peristome bearing a pair of small avicularia. 123. Close-up of a broken peristome. Scale bars: Fig. 120 = 1 mm; Fig. 121 = 400 µm; Figs 122, 123 = 100 µm.