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Linked specimens: London, UK; NHM (50836) London, UK; NHM (PM P 50835) London, UK; NHM (50838) London, UK; NHM (50834) London, UK; NHM (50837)
Current identification/main database link: Plummerita kennerleyi Whittaker 1980
Diagnosis: A moderately inflated species of Plummerita with 4-5 chambers in the final whorl. Tubulospines developed only in last three chambers, paired. one at each angle of the periphery and oblique to the plane of coiling. Ornament of meridionally arra nged ridges strongly developed.
Description: Test a low trochospire consisting of about two whorls. Outline in spiral and umbilical views lobulate then tubulospinate; five chambers in final whorl, subglobular at first, gradually increasing in size, with last two chambers each produced into two tubulospines at opposite angles to the mid-line of the periphery. Lower periphery rounded in edge view, upper margin tubulospinose. Sutures moderatelly depressed, curved. Wall calcareous, finely perforate, test surface ornamented by strong, meridionally arranged ridges which extend to the tubulospines. Umbilicus shallow, aperture appears to be an interiomarginal, umbilical-extraumbilical arch; tegillum not preserved.
Size: Dimensions. - Holotype (tfs. 21-23): maximum test diameter (excluding tubulospines) 0.25 mm; (including tubulospines) 0.28 mm; maximum width (including tubulospines) 0.17 mm.
Extra details from original publication
Variation. - (Paratypes). The maximum test diameter of the four figured paratypes. P 50834 and P 50836-P 50838, varies 0.22-0.33 mm (excluding tubulospines) and 0.25-0.34 mm (including tubulospines); the greatest width (including tubulospines) varies 0.17-0.26 mm. The number of chambers in the final whorl varies between four and five (figured and unfigured paratypes); all specimens have about two whorls.
The paired tubulospines are developed only on the last two or three chambers; their length varies considerably (tfs. 18-31) and in extreme cases they become antler-like (tfs. 18-20). Four tubulospines occur on the final chamber of one unfigured specimen. The apparent presence of a single tubulospine in some specimens (tfs. 28-31) is due to one of the pair being broken off at the base. The last-formed chamber sometimes lacks tubulospines and is globose (tfs. 18-20).
Remarks. - Plummerita kennerleyi differs from P. hantkeninoides (Bronnimann) and P. reicheli (Bronnimann) in being much more inflated and in possessing paired tubulospines; the tubulospines in P. hantkeninoides and P. reicheli are single and are situated in the plane of coiling. P. kennerleyi and P. hantkeninoides are ornamented by meridionally arranged costae which are longer and much more strongly developed in the former than in the latter, at least in the material available. P. reicheli has discrete, coarse, blunt spines rather than ridges.
The tubulospines now shown to occur in Plummerita species are closely analogous to those found in another, but not closely related, Cretaceous planktonic genus, Schackoina. In this genus are found species which are both single-tubulospinose chambered, such as S. cenomana (Schacko), and multi-tubulospinose chambered, such as S. multispinata (Cushman and Wickenden). Cushman and Wickenden (1930) proposed several growth stages to account for the varying number of tubulospines in S. multispinata. The small forms, with a single tubulospine per chamber, they assumed to be juveniles, while larger individuals with several tubulospines per chamber they regarded as adult or gerontic growth stages. Since Plummerita hantkeninoides and P. kennerleyi are of similar size and do not occur together it is unlikely that they are growth stages of the same species; furthermore, the latter never possesses chambers which are radially elongate in the plane ofcoiling, even in very small individuals. The two species must have evolved separately in the Maastrichtian from rugoglobigerine ancestors, probably Rugoglobigerina rugosa (Plummer) in the case of P. kennerleyi (compare tfs. 17-31 with tfs. 32-34, Whittaker, 1980, both from Ecuador). P. kennerleyi may prove to be a geographically restricted form. At present it is not possible to suggest why its curious morphology developed.
A definite tegillum has not been found on any specimens of P. kennerleyi. This is, however, thought to be a preservation defect since specimens of R. rugosa from the same samples (tfs. 32-34) also lack this feature. As the most fragile of apertural coverings, it is generally only preserved in specimens obtained from soft clays and marts (see Smith and Pessagno, 1973), and would not be expected to survive extraction from compacted shales.
Cushman, J. A. & Wickenden, R. T. D. (1930). The development of Hantkenina in the Cretaceous with a description of a new species. Contributions from the Cushman Laboratory for Foraminiferal Research. 6(2): 39-43. gs V O Smith, C. C. & Pessagno, E. A. (1973). Planktonic foraminifera and stratigraphy of the Corsicana formation (Maestrichtian) North-central Texas. Cushman Foundation for Foraminiferal Research, Special Publication. 12: 1-67. gs Whittaker, J. E. (1980). Revision of Plummerita Brönnimann (Foraminiferida) and a new Maastrichtian species from Ecuador. Bulletin of the British Museum (Natural History) Geology. 34(4): 289-297. gs
Cushman, J. A. & Wickenden, R. T. D. (1930). The development of Hantkenina in the Cretaceous with a description of a new species. Contributions from the Cushman Laboratory for Foraminiferal Research. 6(2): 39-43. gs V O
Smith, C. C. & Pessagno, E. A. (1973). Planktonic foraminifera and stratigraphy of the Corsicana formation (Maestrichtian) North-central Texas. Cushman Foundation for Foraminiferal Research, Special Publication. 12: 1-67. gs
Whittaker, J. E. (1980). Revision of Plummerita Brönnimann (Foraminiferida) and a new Maastrichtian species from Ecuador. Bulletin of the British Museum (Natural History) Geology. 34(4): 289-297. gs
Plummerita kennerleyi compiled by the pforams@mikrotax project team viewed: 25-10-2020
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