pforams@mikrotax - Rugoglobigerina spinosa

Citation: Rugoglobigerina spinosa Masters 1993

Basionym: Rugoglobigerina spinosa

Taxonomic discussion: Bronnimann (1952) recognized the spinose morphotype in his paratype series of Rugoglobigerina reicheli pustulata, a rarely used name. An examination of the types in the U.S. National Museum shows that his holotype does not exhibit the spinose periphery that most of the paratypes do but shows the characteristic morphology of and is regarded as a junior synonym of R. rugosa. Therefore, the name pustulata is not available for this distinctive form and a new name is necessary. Subsequent workers generally have confused pseudospines (R. spinosa) with tubulospines (P. reicheli). A. pseudospine, as used here, is a modified pustule, a solid structure in which the length tends to exceed the diameter; whereas, tubulospines are by definition hollow extensions to the chamber. Additionally, distinction can be made on chamber shape: subspherical throughout (R. spinosa) vs. radially elongate to mixed (P. reicheli). Although diagenesis can be a factor in the preserved length of the pseudospine, species recognition is always possible because no other Rugoglobigerina exhibits a peripheral zone of pseudospines. Rugoglobigerina rugose (Plummer) has well developed costellae over the entire surface which never break up into pseudospines at the periphery as occurs in R. spinosa. The costellate ridges in R. rugosa and others of the genus can be discontinuous, breaking up into shorter segments, but never develop a peripheral zone of pseudospines. Some paratypes of El-Naggars Rugoglobigerina arwae may rightly belong to R. spinosa, but the holotype of his species lacks the spines along the periphery. [copied from Chronos database]

Original description: Test a flat trochospire, early whorl often depressed below final whorl; equatorial periphery lobate and axial periphery broadly rounded, the outlines of each interrupted by short pseudospines. Chambers 4.5 to typically 5 well inflated chambers in final whorl; meridionally oriented costellae generally are not well developed and tend to break up at the periphery to become pseudospines or may be replaced altogether by pustules and pseudospines. Aperture a low, interiomarginal, umbilical-extraumbilical arch. A tegillum covers a moderately wide, shallow umbilicus. Sutures depressed, straight and radial on both sides. Surface entirely perforate except for the tegillum, costellae and pseudospines. Variation. Toward the periphery, the length of the costellae tends to become shorter and then rapidly breaks up into a broad band consisting of pustules which grade into peripheral pseudospines (PI. 4, Fig. 1). The costellae tend to be best developed on the sides of the chambers (PI. 4, Figs. 3, 7), but even here they may be replaced by pustules (PI. 4, Figs. 4, 6). The zones of costellae and of pseudospines vary in width (PI. 4, Figs. 2, 5, 8). The pseudospines also vary in length, but are typically longest at the periphery when well preserved. Other features are generally stable.

Geological Range:
Last occurrence (top): within A. mayaroensis zone (67.64-69.27Ma, top in Maastrichtian stage). Data source: [copied from Chronos database]
First occurrence (base): within A. mayaroensis zone (67.64-69.27Ma, base in Maastrichtian stage). Data source: [copied from Chronos database]

References:

Masters, B. A. (1993). Re-evaluation of the species and subspecies of the genus Plummerita Brönnimann and a new species of Rugoglobigerina Brönnimann (Foraminiferida). Journal of Foraminiferal Research. 23: 267-274. gs

test outline:	Lobate	chamber arrangement:	Trochospiral	edge view:	Equally biconvex	aperture:	Umbilical
sp chamber shape:	Globular	coiling axis:	Very low	periphery:	N/A	aperture border:	Tegilla
umb chbr shape:	Globular	umbilicus:	Narrow	periph margin shape:	Broadly rounded	accessory apertures:	Infralaminal
spiral sutures:	Strongly depressed	umb depth:	Deep	wall texture:	Meridional costellae	shell porosity:	Finely Perforate: 1-2.5µm
umbilical or test sutures:	Strongly depressed	final-whorl chambers:	4.5-5	N.B. These characters are used for advanced search. N/A - not applicable

Rugoglobigerina spinosa

References:

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