Oncosclera kaniensis Matsuoka and Masuda, 2000

Pronzato, Roberto, Pisera, Andrzej & Manconi, Renata, 2017, Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review, Acta Palaeontologica Polonica 62 (3), pp. 467-495 : 484

Oncosclera kaniensis Matsuoka and Masuda, 2000

Fig. 19 .

Type horizon: Nakamura Formation, early Miocene.

Type locality: River bed on the Kiso River , Dota, Gifu Prefecture, Central Japan .

References: Matsuoka 1983; Matsuoka and Masuda 2000; Manconi et al. 2012.

Description (emended from Matsuoka and Masuda 2000).— Growth form encrusting (<1 mm in thickness) on surfaces of bivalve shell and wood fragments. Surface even. Megascleres moderately small (100–179 × 7–15 μm) almost straight, from dominant, stout, cylindrical, spiny strongyles to less frequent spiny oxeas, covered with distinct spines at tips. Microscleres absent. Gemmules subspherical (ca. 500 μm in diameter) firmly adhering to basal portion of sponge body. Gemmuloscleres strongyles (23–100 × 4–7 μm) stout, variably curved with smooth concave area, inflated at middle, densely covered with distinct spines numerous at both tips; some aberrant polyfurcate spines.

Remarks.— Oncosclera kaniensis is assigned to the genus Oncosclera on the basis of its growth form and ornamentations of megasclere and gemmuloscleres. Authors note that this species is similar to some Recent species from Argentina, namely O. ponsi , O. atrata , and O. tonollii . The most similar is O. ponsi in spicular components, but it differs in having spiny oxeas as megascleres. O. kaniensis differs from O. atrata in having strongyles (gemmuloscleres) densely covered with distinct spines at both tips. It also differs from O. tonollii in having less spiny surface of gemmuloscleres and megascleres. O. kaniensis has gemmuloscleres similar to the Recent species O. jewelli and O. schubarti , but differs distinctly from the latter species in its spiny strongyles and oxeas as megascleres. Extant species belonging to the genus Oncosclera are reported from the whole tropical zone i.e., South America, Africa, South-East Asia, and Pacific Islands (see Manconi et al. 2012).

Figures

Fig. 19. Oncosclera kaniensis Matsuoka and Masuda, 2000, Spongillida: Potamolepidae, TMNH; Nakamura Formation, early Miocene, River bed on the Kiso River, Dota, Gifu Prefecture, Central Japan. A. Sponge encrusting a shell (Anodonta, Mollusca, Bivalvia). B. Sponge encrusting a wood fragment retaining its annual rings. C. Gemmule (cross section). D. Megascleres. E. Oxea tip (megasclere). F. Strongyles tips (megasclere). G. Strongyles gemmuloscleres). H. Spiny tips of strongyles (gemmuloscleres). I. Strongyle and oxea (megascleres). J. Strongyles (gemmuloscleres). A, B, explanatory drawings; C–H, SEM images; I, J, drawings of the spicular complement. Modified from Matsuoka and Masuda (2000).