Catalog - Acarinina boudreauxi

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Acarinina boudreauxi

Citation: Acarinina boudreauxi Fleisher 1974

Type sample (& lithostrat): The holotype is illustrated on Plate 1, Figures 2 and 3, and is from Hole 219, Core 19, Section 6, 51-53 cm.

Type age (chronostrat): early Middle Eocene (Zone P 11)

Type repository: Washington; USNM

"The test is of moderate size and is subcircular to nearly round in outline, in the form of a planoconvex trochospire with four to five, but typically four and one-half to five, chambers in the final whorl. The subacute to rounded periphery is slightly lobate, particularly along the last two or three chambers. The test wall texture apparently consists of short blunt pseudospines on ventral surfaces; except around the umbilical region, the pseudospines have coalesced into a thick wall penetrated by moderately large pores, and the individual spines are not consistently recognizable. On the dorsal surface, pseudospine development is not evident. The early portions of the trochospire are obscured by the thickened wall and from a low projection above the dorsal plane of the test. The dorsal surface is otherwise nearly flat, but the dorsal chamber walls slope down to the depressed spiral sutures along the inner margin of the last whorl forming a shallow but distinct groove. The less distinct, slightly depressed, and nonlimbate dorsal intercameral sutures are tangential and straight, but may be slightly curved along the distal end near the periphery. Ventral sutures are straight, radial and depressed. The wedge-shaped (in ventral view) chambers increase rapidly in size and in dorso-ventral elevation. The umbilicus is narrow, but deep and distinct. Umbilical shoulders are moderately prominent and have a roughened surface consisting of pseudospines and secondary calcite dposits. In lateral view, the outer chamber walls are moderately inclined, but more steeply so in the last two chambers. The inner walls incline wery steeply into the umbilicus. The aperture consists of an extended low arch bordered by an imperforate rim at the base of the somewhat flattened apertural face.

Maximum diameter of the holotype is 0.33 mm; axial elevation is 0.25 mm.

Acarinina boudreauxi is named for Dr. Joseph E. Boudreaux, of Texaco, Inc., a co-participant on DSDP Leg 23.

Remarks: This form is somewhat similar to a number of other species of Acarinina, including several of those proposed in this report. From A. quetra (Bolli) and A. wilcoxensis (Cushman and Ponton) it may be distinguished by the more compact test and more closely appressed, wedge-shaped chambers in ventral view, the narrower umbilicus, and the less flattened dorsal surface. The rudimentary keel which forms in some specimens of A. quetra was not noted in A. boudreauxi. It differs from A. rotundimarginata Subbotina in having a more rounded and less subquadrate peripheral outline, a more pronounced umbilicus, and a larger aperture, as well as a more distinct spiral suture. It has fewer chambers and a somewhat longer aperture than either A. mattseensis (Gohrbandt) or A. planodorsalis n.sp. In addition, A.boudreauxi has more distinct chambers and ventral sutures than the former and lacks the very distinct dorsal sutures of the latter. It differs from A. naussi (Martin) in having a much more rounded periphery and in lacking the strongly tangential dorsal sutures and peripheral accumulation of pseudospines characteristic of that species. Juvenile specimens frequently have a small adventitious final chamber which partially covers the umbilicus. These are somewhat similar to A. nicoli (Martin), but are more distinctly planoconvex than that species.

References:

Berggren, W. A., Pearson, P. N., Huber, B. T. & Wade, B. S. (2006b). Taxonomy, biostratigraphy, and phylogeny of Eocene Acarinina. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 9): 257-326. gs O

Fleisher, R. L. (1974a). Cenozoic planktonic foraminifera and biostratigraphy, Arabian Sea, Deep Sea Drilling Project, Leg 23A. Initial Reports of the Deep Sea Drilling Project. 23: 1001-1072. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Acarinina boudreauxi Fleisher 1974

Acarinina boudreauxi

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