Conescharellina cf. angustata d’Orbigny, 1852

Martino, Emanuela Di & Taylor, Paul D., 2018, Early Pleistocene and Holocene bryozoans from Indonesia, Zootaxa 4419 (1), pp. 1-70 : 61-63

Conescharellina cf. angustata d’Orbigny, 1852

( Figs 184–189 ; Table 40)

cf. Conescharellina angustata d’Orbigny, 1852: 447 , pl. 714, figs 14–16; Harmer, 1957: 731, pl. 47, fig. 1.

Figured material. RGM.1350598, early Pleistocene, Java; RGM.1350599, RGM.1350600, Holocene, UPGG 041, off South Sulawesi.

Description. Colony small, 1.30–1.70 mm long by 1.10–1.30 mm wide, slightly elongated (mean L/W = 1.26), with 15–20 slightly raised, radial costules alternating with shallow intercostular valleys, rounded pyramidal, apical angle 55–70˚, basal angle 75–85˚. Autozooids arranged in alternating radial rows corresponding to the raised costules, with 8–12 zooids per row. Autozooids somehow rhomboidal, almost as long as wide (mean L/W = 1.02), outline marked by a few, small, marginal areolar pores. Frontal shield convex, coarsely nodular, imperforate apart from the marginal areolar pores. Primary orifice subcircular with a shallow, bowl-shaped sinus, slightly longer than wide, about 120 µm long by 110 µm wide, surrounded by a deep, funnel-shaped peristome becoming slightly raised from the colony surface in later ontogeny. Almost all autozooids bearing an oval, adventitious avicularium adapically, placed horizontally or slightly oblique with the rostrum directed laterally or antapically, crossbar complete; when missing, the adapical avicularium is replaced by an adapical pore adjacent to the orifice. Additional avicularia arranged in straight to sinuous rows on the intercostal valleys, subcircular, smaller than adventitious avicularia, obliquely directed, with complete crossbar. Circular kenozooids, larger than avicularia, about 60–65 µm in diameter, randomly appear in the intercostal valleys. Adapical surface occupied by chaotically arranged avicularia and kenozooids; antapical surface occupied by avicularia and kenozooids arranged in radial rows corresponding to the intercostular valleys. Ooecia not observed. The cross section of the colony shows a core made of small kenozooids.

Remarks. Seventy-five specimens of Conescharellina cf. angustata were found in our samples. The fossil species is very similar to the modern C. angustata , first described from the Philippines, and a species to which Harmer (1957) tentatively assigned three specimens he found in the Siboga collection from East Java. Based on the SEM images of d’Orbigny’s type specimen of C. angustata ( Figs 190–192 ), the two species differ in the length/ width ratio of the colony, with the fossil specimens generally having less elongated colonies (L/ W 1.3 vs 1.6 in the fossil and modern type specimens, respectively), and in the almost constant presence of an adapical avicularium associated with each autozooid in the fossils, replacing the adapical pore seen in the type. However, an identical adapical pore is visible in the fossil specimens in those zooids lacking the adapical avicularium. Bock & Cook (2004) believed that Harmer’s specimens and the type of C. angustata were not conspecific, noting the differences described above as well as the development of the peristome, which was defined as little or absent in the Siboga material. The development of the peristome seems variable in our specimens, becoming more raised and conspicuous in later ontogeny. Based on Harmer’s (1957) description and figure, the Siboga specimens might be conspecific with our material, but SEM study is required to confirm this hypothesis. Although the colonies available for study were numerous, no ooecia were found.

N, Number of colonies and number of zooids measured; SD, standard deviation; Av, avicularium; Intcost, intercostular.

Figures

FIGURES 184–189. Conescharellina cf. angustata d’Orbigny, 1852. 184–186. RGM.1350599, Holocene, UPGG041, off South Sulawesi. 184. General view of a colony. 185. General view of the adapical surface. 186. General view of the antapical surface. 187, 188. RGM.1350598, early Pleistocene, Java. 187. General view of a colony with well-developed peristomes. 188. Close-up of alternating series of autozooids and avicularia. 189. RGM.1350600, Holocene, Java. Cross section of a colony showing the core of small kenozooids. Scale bars: Figs 184–186, 189 = 200 µm; Fig. 187 = 300 µm; Fig. 188 = 100 µm.

FIGURES 190–192. Conescharellina angustata d’Orbigny, 1852, Recent, Ile de Basilan, holotype MNHN d’Orbigny Colln 13679. 190. General view of a colony. 191. Close-up of alternating series of autozooids and avicularia. 192. General view of the adapical surface. Scale bars: Figs 190, 192 = 200 µm; Fig. 191 = 50 µm.