Thalamoporella bifoliata Ziko, 1985

Sonar, Mohan A., Pawar, Ravi V. & Wayal, Dyaneshwar V., 2022, Fossil Thalamoporellidae (Bryozoa) from Paleogene-Neogene sediments of western Kachchh, Gujarat, India, Zootaxa 5104 (2), pp. 251-274 : 260

Thalamoporella bifoliata Ziko, 1985

( Fig. 8 , Table 5)

Thalamoporella bifoliata Ziko, 1985: 54 , pl. 12, figs 1–4.

Thalamoporella domifera Guha & Gopikrishna, 2004: 9 , figs 2, 3.

Material examined. GIS/B 0183–0189. Gypseous shales Harudi, Harudi Formation, middle Eocene (Lutetian), 23 ° 31’25” N, 68 ° 41’07” E, elevation 10 m, 13 January 2011, DST project, New Delhi . GIS/B 0190–019. Yellow limestone, Murachbann, 2 km from Walaram Teerthdham, Chhasra Formation, late lower Miocene (Burdigalian), 23 ° 30’10” N, 68 ° 52’99” E, elevation 91–93 m, 14 January 2011, DST project, New Delhi .

Description. Colony erect, bilaminar. Autozooids arranged quincuncially, mostly elongate-rectangular, some almost subquadrate, with straight to weakly convex lateral margins; each zooid bordered by thin, raised margins ( Fig. 8A ). Orifice subpyriform, wider than long, the distal border highly arched, the proximal margin weakly concave. Adoral areas well developed with an indistinct tubercle on either side of orifice ( Fig. 8B ). Paired opesiules subequal to unequal, large and rounded, close to proximal rim of orifice and flanking a narrow, deeply sunken polypide tube; cryptocystal shelf elongate with sparse perforation ( Fig. 8C ). Avicularia at bifurcation of rows, elongate with spatulate rostrum expanded distally and constricted proximally at pivot points; proximal opesia transversely beanshaped, cryptocyst smooth; combined rostrum and opesia c. 55% or more of avicularium length ( Fig. 8B, D ). Ovicells not observed.

Remarks. Guha & Gopikrishna (2004) erected a new species, Thalamoporella domifera , having no tubercles and distinctive avicularia with a dome-shaped distal margin and prominent raised pivot margins. Re-examination of specimens, however, revealed that this species is conspecific with Thalamoporella bifoliata Ziko, 1985 , hence T. domifera is a junior subjective synonym. This species shows a close resemblance to Thalamoporella tubifera Levinsen, 1909 (see Soule et al. 1992, p. 60, figs 84–91) but in that species the avicularia are not so dome-shaped distally, and the opesia is not transversely bean-shaped. Thalamoporella mayori Osburn, 1940 also shows a superficial resemblance to the present specimens but orifices in T. mayori are wider than long (see Soule et al. 1992, p. 44, figs 63–65). Further, avicularia are spoon-shaped distally, not dome-shaped, and the avicularian cryptocyst is proportionately small and tapering with a pair of tiny opesiules. Thalamoporella liotica ( Ortmann, 1890) exhibits some resemblance to the present species in the shape of orifices and opesiules (see Levinsen 1909; Canu & Bassler 1929), but differs in having a thicker mural rim, vase-shaped avicularia and coarse frontal pores.

Figures

FIGURE 8. Thalamoporella bifoliata Ziko, 1985 (GIS/B 0183). A. General view of colony showing autozooids, orifices and opesiules. B. General view of colony showing autozooids, orifices and an avicularium. C. Detail of opesiules, cryptocyst and an avicularium. D. Detail of an avicularium. Scale bars: A, 500 µm; B, 500 µm; C, 100 µm; D, 100 µm.