Siphonosphaera brachysiphonia Dumitrică, 1978

Dumitrica, Paulian, 2019, On The Status Of The Collosphaerid Radiolarian Species Siphonosphaera Brachysiphonia Dumitrică, 1978 And Siphonosphaera Arkys Su, 1982, Acta Palaeontologica Romaniae 15 (1), pp. 35-38 : 35-37

Siphonosphaera brachysiphonia Dumitrică, 1978

Figs. 1 a-h

1978b Siphonosphaera brachysiphonia Dumitrică nov. sp., p. 235, pl. 5, fig. 1.

1982 Siphonosphaera arkys Su nov. sp., p. 276, pl. 2, figs. 3, 4.

1990 Collosphaerid sp. A – Abelmann, p. 690, pl. 1, fig. 2.

1992 Siphonosphaera magnisphaera? Takahashi , part. – Lazarus, p. 795, pl. 2, figs. 9-10; pl. 5, figs. 13-14, non figs. 11-12.

1999 Siphonosphaera arkys Su. – Tan & Chen, p. 139, pl. 5, fig. 41.

2001 Trisolenia sp. - De Wever et al., p. 170, Fig. 104.2.

Description. Shell spherical, exceptionally ellipsoidal with thin wall perforated by a small number (some 10-15 or more) of wide pores with margins prolonged outside in very short tubes. Surface of test covered with numerous and dense minuscule pits. These pits disappear on the tubes, their surface remaining smooth.

Dimensions: Diameter of shell 120-180 μm.

Etymology. From the Latin brachys – short and siphon – tube, pipe.

Remarks. Siphonosphaera arkys Su resembles perfectly Siphonosphaera brachysiphonia Dumitrică (see Figure 1 i-h) by its shape, number, shape and length of tubes and pitted surface of shell, and is undoubtedly a junior synonym of the Badenian species. These pits were considered pores by Su, but they are certainly just a superficial ornamentation. The same species was illustrated by Abelmann (1990, pl. 1, fig. 2) as collosphaerid sp. A from the Middle Miocene of the Antarctic area (Maud Rise, Weddell Sea). A very close species to S. brachysiphonia Dumitrică is Siphonosphaera magnisphaera Takahashi, 1991 (not Lazarus 1992) by being spherical, by having pitted surface except the borders of pores, but differs from the Badenian species by being larger (having a diameter of 190-197 μm) and by having a much more perfect spherical shape. Under the same name Lazarus (1992) illustrated from Antarctic area (Kerguellen Plateau, ODP Leg 120) two morphotypes: a larger morphotypes (pl. 5, figs. 11, 12) and a smaller one (pl. 2, figs. 9, 10 and pl. 5, figs. 13, 14). The larger morphotype differs from S. magnisphaera Takahashi in having fewer and longer tubes, and the smaller ones in being smaller and having a less perfect spherical shape. The smaller morphotypes illustrated by Lazarus are rather similar to S. brachysiphonia and could be considered as belonging to it. The larger one should belong to a new species.

Anyway, all species discussed here seem to form a closely related group characterized by a rather similar morphology and especially by having a pitted surface. For more or less distinct morphologies we should take into account that they occur at different latitudes. The morphotypes (species) illustrated by Abelmann (l. cit.) and Lazarus (l. cit.) come from high south latitudes whereas the species described by Takahashi (1991 come from the tropical area of the Pacific Ocean (15°21.1’N / 151°28.5’W). Accordingly, they could be characteristic of different latitudes.

Occurrence. Until present the species Siphonosphaera brachysiphonia Dumitrică was recorded in the late middle Miocene of Romania (late Badenian), Antarctic area (Weddell Sea and Kerguellen Plateau), and Quaternary of China and Antarctic area. My German colleague Johan Renaudie who very kindly provided a photo of this species mentioned (in lit.) that he observed it in the middle and late Miocene of the ODP sites 689B, 748B and 751A from ca. 9 to 14 Ma. For Romania it is the only collosphaerid recorded in the Radiolarian Shale Formation, and this occurrence fit well in this interval because the Upper Badenian age of the Radiolarian Shale Formation corresponds to the lower Serravallian Mediterranean stage (13.8-12.8 Ma) (see Hohenegger et al., 2014 and Dumitrică, 2016 for detailed discussion). I know no record of this species in the Pliocene, but it should have existed in some places because the synonymy between the middle Miocene species and the Quaternary one is doubtless.

Figures

Fig. 1 a-h Siphonosphaera brachysiphonia Dumitrică, 1978. d holotype, original photo. Scale bar A (for drawings, a-c) = 100 μm, scale B (for figures in optical microscope) (d-h, k), all from sample 1315, Radiolarian Shale Formation, Păușești Otăsău, Getic Depression, Romania. i-j Siphonosphaera arkys Su, 1982, holotype; k Siphonosphaera brachysiphonia, specimen from ODP Leg 120, sample 751A-13H-CC, Middle Miocene, approximately 14.4 Ma, kindly provided by Dr. Johan Renaudie.