Catalog - Subbotina tecta

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.

Subbotina tecta

Citation: Subbotina tecta Pearson & Wade 2015

Type specimens: Holotype (NHMUK PM PF 71158) and six figured paratypes (NHMUK PM PF 71159 – 71164)

Wall symmetrically cancellate, sacculifer-type, probably spinose in life. Test composed of 10 to 13 near spherical chambers arranged in a low trochospiral, oval and strongly lobate in outline; in spiral view 3½ to occasionally 4 globular, embracing chambers in final whorl, increasing rapidly in size, sutures straight and depressed, becoming moderately incised between later chambers; in umbilical view 3½ globular chambers, increasing rapidly in size, sutures depressed to incised, straight, umbilicus small, aperture umbilical to slightly extraumbilical in position, obscured by a distinctive trapezoidal to triangular, nonporous, often pustulose tooth, with relict teeth of earlier chambers sometimes visible, the adjacent chamber shoulders sometimes distinctly pustulose; in edge view chambers globular in shape, embracing, tooth convex and arching over the umbilicus.

Maximum diameter of holotype 610 µm. Coiling direction is approximately random.

Named for tecta, Latin, a shield, with reference to the prominent tooth that shields the umbilicus.

? Globigerina yeguanesis Weinzierl and Applin in Postuma, 1971, p. 162, pl. on p. 163 (Sample E 227, Alabama). (Not Weinzierl and Applin, 1929.)
? Globigerina galavisi Bermudez in Raju, 1971, p. 24, pl. 5, figs. 2a–3 (G. mexicana zone, borehole NGT- 1, Cauvery Basin, south-east India). (Not Bermu _dez, 1961.)
? Dentoglobigerina galavisi Bermudez in Blow, 1979 (partim), p. 1301–1305, pl. 177, figs. 8-9 (middle Eocene, Kilwa area, Tanzania). (Not Bermu _dez, 1961.)
Subbotina yeguaensis (Weinzierl and Applin) in Olsson et al., 2006b (partim), p. 162–163, pl. 6.18, fig. 12, 16 (Zone E15/16, Shubuta Clay, Wayne County, Mississippi). (Not Weinzierl and Applin, 1929.)

Remarks. This species was referred to as ‘Subbotina sp. 1’ in Wade & Pearson (2008). Subbotina tecta n.sp. is closely related to S. eocaena (Guembel) from which it probably evolved in the uppermost Eocene. It is distinguished from S. eocaena in our study by its more spherical chambers (although note that the neotype drawing of S. eocaena has very spherical chambers) and by possessing a large and prominent tooth, which is evidently a modification of the slightly pustulose lip of S. eocaena. When well developed, the tooth is positioned high over the umbilicus and forms a distinct platform above the primary aperture (Fig. 13.6b, Fig. 13.7b). The two species are linked by intermediate forms (Fig. 10.7a-b) and their distinction may be subjective; however, a distinct tooth rather than an irregular lip is critical for our diagnosis of S. tecta and in such specimens the chambers are almost always more spherical. The distinctive apertural system and tooth in S. tecta may have been related to feeding, for example for securing prey in the umbilical region, and if this is correct it could indicate that S. tecta was a separate biospecies with a particular dietary specialization. The new species is distinguished from S. yeguaensis by having a lower trochospire and less embracing, more spherical chambers. It is distinguished from Subbotina sp. of this work (see below) by having a lower trochospiral and narrower umbilicus, and generally, a less slender, blunter tooth. A specimen of S. tecta was illustrated by Olsson et al. (2006b, plate 6.18, fig. 12) as S. yeguaensis. In the past, other specimens may have been assigned to either D. galavisi or S. yeguaensis (possibly including the specimen illustrated as Globigerina yeguaensis by Postuma, 1971); however, S. tecta is a very distinctive morphotype which may be confined to the uppermost Eocene and lowermost Oligocene. We have found comparable specimens in DSDP Site 242 (Indian Ocean), ODP Site 647 (North Atlantic Ocean), IODP Site U1334 (equatorial Pacific Ocean), Armenia, and the US Gulf Coast, some of which we intend to illustrate in the forthcoming Oligocene Atlas. No stable isotope data are available.

Stratigraphic range. In Tanzania this species is known from Zones E15/16 and O1. Specimens we have found from other localities (see above) are all from this same interval. Questionable specimens illustrated by Raju (1971) are from the G. mexicana zone of India, equivalent to Zone E14, hence likely from a lower stratigraphic level than we have been able to confirm and he recorded the highest occurrence in G. sastrii zone, equivalent to Zone O1. We did not find this species in any middle Eocene cores from Tanzania. Blow (1979) illustrated a specimen from the middle Eocene of Tanzania (Zone P11 1⁄4 Zone E9) that is quite convincingly S. tecta, but we have studied the type locality including many outcrop and borehole samples and never found this morphology, so we suspect contamination with an upper Eocene sample.

References:

Pearson, P. N. & Wade, B. S. (2015). Systematic taxonomy of exceptionally well-preserved planktonic foraminifera from the Eocene/Oligocene boundary of Tanzania. Cushman Foundation for Foraminiferal Research, Special Publication. 45: 1-85. gs

Wade, B. S., Olsson, R. K., Pearson, P. N., Edgar, K. M. & Premoli Silva, I. (2018b). Taxonomy, biostratigraphy, and phylogeny of Oligocene Subbotina. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 10): 307-330. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Subbotina tecta Pearson & Wade 2015

Subbotina tecta

References:

Add Comment

Comments