Catalog - Dentoglobigerina taci

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Other pages this level: D. eotripartita, D. juxtabinaiensis, D. taci

Dentoglobigerina taci

Citation: Dentoglobigerina taci Pearson & Wade 2015

Type specimens: Holotype (NHMUK PM PF 71165) and nine figured paratypes (NHMUK PM PF 71166 – 71174)

Wall cancellate and probably spinose in life. Test large, globular, approximately 12–13 chambers arranged in a moderate trochospiral, outline oval and slightly lobate, chambers globular and radially compressed; in spiral view 3½ appressed and embracing chambers in final whorl, increasing moderately to rapidly in size, sutures slightly curved, depressed; in umbilical view 3½ globular and appressed chambers, increasing moderately rapidly in size, sutures depressed, straight or slightly curved, umbilicus moderately wide, rectangular, and deep; aperture umbilical, centrally placed usually with a lip of constant thickness; in edge view chambers globular in shape, embracing, the final chamber tending to lean slightly over the umbilicus.

Maximium diameter of holotype 390 µm. May be dextral or sinistral, with a slight bias in favor of sinistral coiling.

Contraction from the Latin tacitum (secret or quiet) referring to the fact that this common morphology has long been overlooked.

Remarks. Taxonomic assignment of the abundant well-preserved dentoglobigerinids of Tanzania to previously established and relatively distinctive species such as galavisi, tapuriensis, ‘cf. tripartita’ and pseudovenezuelana, leaves frequent specimens that lack the distinguishing features of those species but which nonetheless are obviously closely related. These forms, which we include in the new species taci, first appear in the upper Eocene, that is, at a similar level to the first true tapuriensis, and they persist into the Oligocene. Previous workers (e.g., Coccioni et al., 1988) may have recorded similar specimens using open nomenclature by referring them to ‘‘cf. tapuriensis’’, as did we initially (as ‘Dentoglobigerina sp. 1’; Wade & Pearson, 2008, p. 253). The new species is similar in gross morphology to D. galavisi but has a more open umbilicus and lacks the irregular triangular lip projecting over the umbilicus that is part of diagnosis of D. galavisi sensu stricto (Blow, 1979; Olsson et al., 2006c). Unlike galavisi it generally has a lip of relatively constant thickness rather than a tooth, and a rectangular umbilical depression rather than triangular in galavisi. It differs from D. pseudovenezuelana principally by having a more open umbilicus than is normally seen in that species and by lacking the densely pustulose umbilical ornamentation characteristic of that species. It differs from D. tapuriensis principally by lacking the broad final chamber and broad, low aperture that is characteristic of that species. We regard the new species as being morphologically and evolutionarily intermediate between D. galavisi and D. tapuriensis. The taci n. sp. / tapuriensis group also intergrades with D. prasaepis which is distinguished from taci n. sp. by its larger test and more spherical morphology. It differs from Subbotina eocaena by its more pustulose wall texture and squarer umbilical aperture.

Stratigraphic range. Uppermost Eocene to lower Oligocene (becoming rare up section). The highest occurrence has yet to be determined.

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

CATALOG OF ORIGINAL DESCRIPTIONS: Dentoglobigerina taci Pearson & Wade 2015

Dentoglobigerina taci

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