Catalog - Globigerinita dissimilis ciperoensis

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Globigerinita dissimilis ciperoensis

Citation: Globigerinita dissimilis ciperoensis Blow & Banner 1962

Type age (chronostrat): Globigerina ampliapertura Zone

Type locality: From the type locality of the Globigerina ampliapertura Zone, southern Trinidad (see Bolli, 1957b, p. 100).

This subspecies differs from Globigerinita dissimilis dissimilis (Cushman & Bermudez, 1937) in possessing an anterio-posteriorly broad bulla which is attached to the umbilical margins of the ventral surfaces of not only the last-formed and the antepenultimate chambers, but also to the corresponding surface of at least one other chamber in the last whorl, so that at least one of the broad accessory apertures present in G. dissimilis dissimilis is divided to produce two arched accessory apertures situated over the intercameral sutures of the primary chambers of the last whorl. Three or four accessory apertures are thus present in the suture of the bulla of G. dissimilis ciperoensis. Globigerinita dissimilis ciperoensis possesses the thicker and more coarsely perforate walls, togetherwiththemoredepressedadultchambersand less lobulate periphery, typical of advanced forms of G. dissimilis dissimilis, from which it appears to have descended.

Maximum diameter of holotype 0·50 mm;

Catapsydrax dissimilis (Cushman & Bermudez), Bolli, Loeblich & Tappan, 1957 (part), Bull. U.S. Nat. Mus. 215, 36, pl. 7, figs. 8a-c (not figs. 6 and 7).
Catapsydrax dissimilis (Cushman & Bermtidez), Blow, 1959, Bull. Amer. Paleont. 39, no. 178, p. 203, pl. 12, figs. 88-90.

Remarks: As discussed above (Globigerinita dissimilis dissimilis, p. 106), the Lower Miocene (Cipero) forms referred by Bolli et al. (1957, p. 36) and by Bolli (l957b, p. 116; 1957c, p. 166) to 'Catapsydrax dissimilis', contain forms now referred to G. dissimilis ciperoensis which differ significantly from the Eocene forms of Cushman & Bermudez (1937). The acquisition of a greater number of accessory apertures appears to result from the anterio-posterior broadening of the bulla (cf. Globigerinita africana, p. 105); this may be associated with a narrowing umbilicus and tighter coiling, trends which are observable to a lesser degree in the evolution of G. dissimilis dissimilis. We have made an arbitrary distinction at the point in the evolution of G. dissimilis s.l. where more than two accessory apertures are present, as this appears to be the clearest way of distinguishing the most advanced forms (characteristic of the Aquitanian) from the other, more or less primitive, forms which range from the Eocene to the Aquitanian.

Stratigraphical range; In southern Trinidad this subspecies ranges from the Globigerina ampliapertura Zone to the top of the 'Catapsydrax' (vel Globigerinita) stainforthi Zone, Cipero formation, Aquitanian; it may also occur in the San Fernando beds, but this has not yet been published. It also occurs over the same interval in eastern Falcon, Venezuela. In East Africa it does not occur in either the Eocene or the ' Oligocene, but it has been observed in Aquitanian sediments. It also occurs in the Aquitanian of south-east Sicily (Ragusa limestone formation).

References:

Blow, W. H. & Banner, F. T. (1962). Blow, W. H. & Banner, F. T. (1962). The mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae. In, Eames, F. E. , Banner, F. T. , Blow, W. H. & Clarke, W. J. (eds) Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge 61-151. In, Eames, F. E., Banner, F. T., Blow, W. H. & Clarke, W. J. (eds) Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge 61-151. gs

Coxall, H. K. & Spezzaferri, S. (2018). Coxall, H. K. & Spezzaferri, S. (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene Catapsydrax, Globorotaloides, and Protentelloides. 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 4): 79-124. 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 4): 79-124. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinita dissimilis ciperoensis Blow & Banner 1962

Globigerinita dissimilis ciperoensis

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