pforams@mikrotax - Jenkinsina

pforams@mikrotax - Jenkinsina pforams@mikrotax - Jenkinsina

Jenkinsina

Classification: pf_cenozoic -> Guembelitrioidea -> Guembelitriidae -> Jenkinsina
Sister taxa: Cassigerinelloita, Globoconusa, Guembelitria, Jenkinsina, Parvularugoglobigerina, Woodringina

Daughter taxa (time control age-window is: 0-800Ma)
			Jenkinsina triseriata Like J. columbiana but larger; with 5 vs. 3-4 chamber whorls; lower apical angle.
			Jenkinsina columbiana Test small, elongate, subtriangular in outline, with high apical angle (55-62°), periphery rounded and lobulate; chambers inflated and subglobular, triserially arranged, umbilicus moderately deep; aperture a low arch with a thin lip.
			Jenkinsina sp. Specimens which cannot be assigned to established species

Taxonomy

Citation: Jenkinsina Haynes, 1981

taxonomic rank: Genus

Type species: Guembelitria stavensis Bandy,1949

Taxonomic discussion: Haynes (1981) distinguished Jenkinsina from Guembelitria based on the absence of pore mounds. In a study of Paleogene triserial planktonic foraminifera, Jenkins and others (1998) supported this distinction with SEM images of well-preserved specimens of both genera. Although Loeblich and Tappan (1988) considered Jenkinsina to be a junior synonym of Chiloguembelitria Hofker (1978) based on SEM observation of topotypes of the type species of both genera (the primary type specimens have been lost), further SEM study of topotype material led Jenkins and others (1998) to conclude that the type species of Chiloguembelitria, C. danica Hofker (1978), does have pore mounds and therefore is not synonymous.
SEM observation of the shell microstructure of a well preserved specimen of Jenkinsina columbiana (Pl. 16.1, Figs. 10-11) reveals that it has a monolamellar wall. This seems to be a consistent feature of the microperforates, as it has been observed in Guembelitria cretacea and several species of Tenuitella.
[Huber et al. 2006]

Catalog entries: Jenkinsina

Distinguishing features:
Parent taxon (Guembelitriidae): Tests triserial, trochospiral, or nearly triserial in initial whorl becoming biserial. Chambers usually globular or subglobular, increasing gradually in size. Aperture usually a loop-shaped arch, often slightly infolded on one side, marked by a fine lip.
This taxon: Lke Guembelitria, but without pore mounds.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.

Description

Morphology:

test high trochospiral, triserial throughout, chambers globular and inflated; aperture a small arch at the base of final chamber, rimmed by a distinct lip.
[Huber et al. 2006]

Wall type:

Microperforate, monolamellar, smooth to pustulose, and lacking pore mounds; [Huber et al. 2006]

Biogeography and Palaeobiology

Phylogenetic relations

Jenkins and others (1998) noted that there is no direct phylogenetic connection between Danian species of Guembelitria and early Eocene species of Jenkinsina, and postulated instead that Jenkinsina may have evolved from the biserial genus Chiloguembelina during the early Eocene. This assertion needs to be verified, as forms bearing an intermediate morphology between Chiloguembelina and Jenkinsina have not been observed. While there is still a considerable stratigraphic gap between the highest occurrence of Guembelitria (Zone P1) and the first occurrence of Jenkinsina (Zone E2), this gap was thought to be considerably larger in Jenkins’s study, which predates discovery of J. columbiana in lowermost Eocene sediments in Egypt and New Jersey (R. Olsson, pers. observ.). Examination of the fine fraction from Paleocene sediments may lead to further narrowing of this stratigraphic gap and would suggest a direct phylogenetic linkage between Jenkinsina and Guembelitria. Absence of Jenkinsina from strata separating the HO of J. columbiana in upper Zone E12 from the LO of J. samwelli in upper Zone E16 suggests that samwelli may have evolved independently from a different ancestor. Further investigation of middle-upper Eocene sediments is required to determine the phylogeny of this group.
SEM observation of the shell microstructure of a well preserved specimen of Jenkinsina columbiana reveals that it has a monolamellar wall (Pl. 16.1, Figs. 10-11). This may be a consistent feature of the microperforates, as it has now been observed in Guembelitria cretacea and several species of Tenuitella (see below).
[Huber et al. 2006]

Most likely ancestor: Benthic foraminifera - at confidence level 2 (out of 5). Data source: Premec Fucek et al. 2018.
Likely descendants: Cassigerinelloita; plot with descendants

Biostratigraphic distribution

Geological Range:
Notes: Lower Eocene-lower Oligocene Zones E2 to lower Zone O5.
[Huber et al. 2006]
Last occurrence (top): at top of M1 zone (100% up, 21.1Ma, in Aquitanian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within P2 zone (62.29-62.60Ma, base in Danian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Guembelitriidae

Primary source for this page: Huber et al. 2006 - Eocene Atlas, chap. 16, p. 465

References:

Bandy, O. L. (1949). Eocene and Oligocene foraminifera from Little Stave Creek, Clarke County, Alabama. Bulletins of American Paleontology. 32(131): 1-210. gs

Haynes, J. R. (1981). Foraminifera. John Wiley and Sons, New York. -. gs

Hofker, J. (1978). Analysis of a large succession of samples through the Upper Maastrichtian and Lower Tertiary of Drill Hole 47.2, Shatsky Rise, Pacific, Deep Sea Drilling Project. Journal of Foraminiferal Research. 8(1): 46-75. gs

Huber, B. T., Olsson, R. K. & Pearson, P. N. (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene microperforate planktonic foraminifera (Jenkinsina, Cassigerinelloita, Chiloguembelina, Streptochilus, Zeauvigerina, Tenuitella, and Cassigerinella) and Problematica (Dipsidripella). 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 16): 461-508. gs O

Jenkins, D. G., Whittaker, J. E. & Curry, D. (1998). Palaeogene triserial planktonic foraminifera. Journal of Micropalaeontology. 17: 61-70. gs

Loeblich, A. R. & Tappan, H. (1988). Foraminiferal Genera and Their Classification (Volume I-II). Van Nostrand Reinhold Co., New York. 1-1059. gs

Jenkinsina compiled by the pforams@mikrotax project team viewed: 7-9-2024

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