Hantkenina primitiva


Classification: pf_cenozoic -> smooth non-spinose -> Hantkeninidae -> Hantkenina -> Hantkenina primitiva
Sister taxa: H. nanggulanensis, H. alabamensis, H. primitiva, H. compressa, H. australis, H. dumblei, H. lehneri, H. liebusi, H. mexicana, H. singanoae, H. sp.,

Taxonomy

Citation: Hantkenina primitiva Cushman & Jarvis 1929
Rank: Species
Basionym: Hantkenina alabamensis primitiva
Synonyms:
Taxonomic discussion: Hantkenina primitiva is a variable form representing the trend in some late middle and late Eocene hantkeninids for the shell to become more evolute and for the tubulospines to form later in ontogeny (i.e. the early final whorl chambers genuinely lack tubulospines and are not broken-off, as is more commonly the case in hantkeninids). Blow (1979) regarded this feature as ‘regressive’ or ‘phylogerontic’, recapitulating what he considered to be the ancestral Pseudohastigerina condition. In contrast to Blow, we consider Hantkenina to be a monophyletic clade that evolved from the Clavigerinella group rather than Pseudohastigerina (Coxall and others, 2003), and therefore suggest these characters are the result of changes in the timing of developmental processes.
Some forms displaying a reduced number of tubulospines are significantly smaller than the holotype specimen (0.20-30 mm). These ‘dwarf’ morphotypes tend to have a total of only 8-9 chambers, compared to the usual 10-13 chambers that make up the shells of most species of Hantkenina (Coxall, 2000). It is possible that these represent juvenile stages; however, we note that small forms are most common in the upper middle and upper Eocene and mainly occur in continental shelf environments, e.g., Ecuador (Hofker, 1956), New Zealand and the New Jersey, suggesting that this form is a distinctive variety with particular oceanographic preferences. Under this taxonomy H. primitiva is retained in the strict sense (H. primitiva sensu stricto) outlined in the original description and exemplified by the holotype, but it also includes the dwarf variety (H. primitiva sensu lato). The dwarf variety may prove to be of paleoenvironmental significance. [Coxall & Pearson 2006]

Catalog entries: Hantkenina alabamensis primitiva;

Type images:

Short diagnosis: Like H. compressa but tubulospines absent on early adult chambers and test generally smaller test

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: Hantkenina primitiva is distinguished from H. compressa by the absence of tubulospines on early adult chambers and the generally smaller test size. It is distinguished from H. australis by having straight rather than recurved tubulospines and lacks the forward leaning arrangement of tubulospines and lateral chamber inflation characteristic of H. alabamensis. [Coxall & Pearson 2006]

Wall type: Smooth, normal perforate and probably nonspinose; tubulospines imperforate, smooth or with fine striations. [Coxall & Pearson 2006]

Test morphology: Planispiral, biumbilicate, laterally compressed, somewhat evolute, often small for the genus; 5-7 closely appressed, rounded or polygonal chambers in the adult whorl, increasing steadily in size as added; peripheral outline is continuous or somewhat angular; first 1-3 chambers of the adult whorl are rounded, commonly pustulose and lack a tubulospine; final 2-5 chambers only are extend into hollow tubulospines; aperture is an equatorial arch, pinched laterally into a narrow slit, flaring at the base into lateral lobes, bordered by a wide imperforate lip; tubulospines positioned at or very close to the anterior chamber edge, usually spanning the suture between adjacent chambers and partially contacting the posterior wall of the adjacent youngest chamber, arising sharply from the supporting chamber; slender and tapering to a point, inclined forward in the direction of coiling. [Coxall & Pearson 2006]

Size: Maximum diameter (excluding tubulospines) 200-400 µm. [Coxall & Pearson 2006]

Character matrix

test outline:Subcircularchamber arrangement:Planispiraledge view:Compressedaperture:Equatorial
umb chamber shape:Subtriangularcoiling axis:N/Aperiphery:Tubulospinesaperture border:Thick lip
sp chbr shape:Subtriangularumbilicus:Wideperiph margin shape:Subangularaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:Shallowwall texture:Smoothshell porosity:-
spiral sutures:Moderately depresseddiameter mm:200-400width mm:breadth mm:
final-whorl chambers:5.0-7.0

Biogeography and Palaeobiology


Geographic distribution: Global, most common in shelf environments and at the periphery of the hantkeninid latitudinal range. H. primitiva sometimes dominates otherwise impoverished planktonic foraminiferal assemblages. [Coxall & Pearson 2006]
Aze et al. 2011 summary: Cosmopolitan, most common in shelf environments; based on Coxall & Pearson (2006)

Isotope paleobiology: No data available. [Coxall & Pearson 2006]
Aze et al. 2011 ecogroup 3 - Open ocean thermocline. Based on light δ13C and relatively heavy δ18O. Sources cited by Aze et al. 2011 (appendix S3): this study

Phylogenetic relations: Hantkenina primitiva may have evolved from H. compressa at the base of Zone E13. [Coxall & Pearson 2006]

Most likely ancestor: Hantkenina compressa - at confidence level 4 (out of 5). Data source: Coxall & Pearson (2006) fig 8.1.

Biostratigraphic distribution

Geological Range:
Notes: Base of Zone E13 to the Eocene/Oligocene boundary. [Coxall & Pearson 2006]
Last occurrence (top): at top of E16 zone (100% up, 33.9Ma, in Priabonian stage). Data source: Coxall & Pearson (2006) fig 8.1
First occurrence (base): at base of E12 zone (0% up, 40.4Ma, in Bartonian stage). Data source: Coxall & Pearson (2006), fig. 8.1

Plot of occurrence data:

Primary source for this page: Coxall & Pearson 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 8, p. 250

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden, 1413 pp.

Brönnimann, P., (1950). The Genus Hantkenina Cushman in Trinidad and Barbados, B. W. I. Journal of Paleontology, 24(4): 397-420.

Coccioni, R., (1988). The genera Hantkenina and Cribrohantkenina (Foraminifera) in the Massignano section (Ancona, Italy),: Ancona II. In: Premoli Silva, I., Coccioni, R. and Montanari, A. (Editors), The Eocene-Oligocene Boundary in the Marche-Umbria Basin (Italy). International Subcommission on Paleogene Stratigraphy, Special Publication II, pp. 81-96.

Coxall, H.K. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of the Hantkeninidae (Clavigerinella, Hantkenina and Cribrohantkenina). In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Allen Press, Lawrence, Kansas, pp. 213-256.

Coxall, H.K., (2000). Hantkeninid planktonic foraminifera and Eocene palaeoceanographic change. PhD Thesis, University of Bristol, unpublished, 264 pp.

Coxall, H.K.; Huber, B.T. & Pearson, P.N., (2003). Origin and morphology of the Eocene planktonic foraminifera Hantkenina. Journal of Foraminiferal Research, 33: 237-261.

Cushman, J.A. & Jarvis, P.W., (1929). New foraminifera from Trinidad. Contributions from the Cushman Laboratory for Foraminiferal Research, 5: 6-17.

Cushman, J.A., (1924). A new genus of Eocene foraminifera. Proceedings of the United States National Museum, 66(2567): 1-4.

Hofker, J., (1956). Tertiary foraminifera of coastal Ecuador; Part II - Additional notes on the Eocene species. Journal of Paleontology, 10(4): +955+.


logo

Hantkenina primitiva compiled by the pforams@mikrotax project team viewed: 21-11-2017

Taxon Search:
Advanced Search

Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet. Be the first!

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics