Hantkenina australis


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

Taxonomy

Citation: Hantkenina australis Finlay 1939
Rank: Species
Basionym: Hantkenina australis
Synonyms:
Taxonomic discussion: Finlay (1939) did not provide a detailed description or designate a type specimen when he erected this species because the available specimens were incomplete. He stated that the holotype would be figured later when new material was found and instead figured a paratype from a different locality. This specimen differs significantly from the type description in lacking recurved tubulospines and having a more angular outline.
Jenkins (1965) produced the first detailed description of H. australis and selected a type specimen out of the six incomplete specimens from Finlay’s original sample that satisfactorily represents the taxon. This specimen is illustrated in SEM for the first time (Pl.8.5, Figs. 1-2). Bronnimann (1950) and Ramsay (1962) recorded H. australis in Trinidad and Tanzania respectively but in both cases the identification was
based on Finlay’s paratype and the illustrated specimens do not have recurved tubulospines.
Our concept of H. australis is based on Finlay’s (1939) and Jenkins’s (1965) notion of a form with backward curving tubulospines. Subbotina’s (1953) illustrations of ‘Hantkenina alabamensis’ clearly show this distinctive feature. We have found this species in correlatable sequences from the southern Labrador Sea (ODP Site 647), Uzbekistan, southern Russia and the Ukraine (Beniamovski, pers. comm., 2001), indicating that it has a global distribution. It appears to be most common at the high southerly and northerly extremes of the hantkeninid latitudinal range suggesting it was more tolerant of cold water than other hantkeninids. In parallel with the H. dumblei-H. compressa -H. alabamensis transition, there is a tendency for the test to become more inflated through time. Hantkenina compressa coexists with H. australis in the upper middle Eocene in New Zealand. A common feature of this taxon is for tubulospines to be absent on the early chambers as in H. primitiva, which makes it impossible to distinguish between them when the tubulospines are missing. [Coxall & Pearson 2006]

Catalog entries: Hantkenina australis;

Type images:

Short diagnosis: This species has a variable test morphology, showing features of H. dumblei and H. compressa. It differs from both, and all other species of Hantkenina in having posteriorly recurved tubulospines.

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: This species has a variable test morphology, showing features of H. dumblei and H. compressa. It differs from both, and all other species of Hantkenina in having posteriorly recurved tubulospines. [Coxall & Pearson 2006]

Wall type: Smooth, normal perforate, probably nonspinose; average pore size is often smaller than in other species of Hantkenina; tubulospines imperforate, smooth or with spiral rifling. [Coxall & Pearson 2006]

Test morphology: Planispiral, laterally compressed with 5-6 closely appressed subtriangular chambers in the final whorl; peripheral outline lobed or slightly angular, anterior chamber shoulder is minimal or non-existent; most or all of the adult chambers extend into a hollow tubulospine; primary aperture is an equatorial high arch extending about halfway up the apertural face, widening towards the base into weak basal lobes and bordered on each side by an imperforate lip; sutures depressed, straight or slightly sigmoidal; pustules common on early chambers of the final whorl and in the umbilical region; tubulospines slender, often long, curved backwards slightly in the opposite direction to coiling, tapering to a point, arising sharply from the supporting chamber, positioned at or just spanning the anterior chamber suture, sometimes partially contacting the adjacent younger chamber. [Coxall & Pearson 2006]

Size: Maximum diameter without spines: 0.45 mm, with spines, 0.56 mm (Jenkins, 1965). [Coxall & Pearson 2006]

Character matrix

test outline:Lobatechamber arrangement:Planispiraledge view:Compressedaperture:Equatorial
umb chamber shape:Subtriangularcoiling axis:N/Aperiphery:Tubulospinesaperture border:Thin lip
sp chbr shape:Subtriangularumbilicus:Wideperiph margin shape:Subangularaccessory apertures:Sutural
umbilical or test sutures:Moderately depressedumb depth:Shallowwall texture:Smoothshell porosity:Finely Perforate: 1-2.5
spiral sutures:Moderately depresseddiameter mm:0.56width mm:breadth mm:
final-whorl chambers:5.0-6.0

Biogeography and Palaeobiology


Geographic distribution: Global, low to mid latitudes, most common at the high northerly and southerly extremes of the hantkeninid range, i.e., New Zealand, southern Labrador Sea. [Coxall & Pearson 2006]
Aze et al. 2011 summary: Low to middle latitudes and commonly in high northerly and southerly extremes; 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: Probably evolved from H. dumblei in the middle Eocene. [Coxall & Pearson 2006]

Biostratigraphic distribution

Geological Range:
Notes: Middle Eocene, Zones E11-E13. [Coxall & Pearson 2006]
Last occurrence (top): within E13 zone (37.99-39.97Ma, top in Bartonian stage). Data source: Eocene Atlas
First occurrence (base): within E11 zone (40.40-41.89Ma, base in Lutetian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Coxall & Pearson 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 8, p. 232

References:

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

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.

Cushman, J.A., (1925). New foraminifera from the Upper Eocene of Mexico. Contributions from the Cushman Foundation for Foraminiferal Reseach, 1(1): 4-9.

Finlay 1939 89-128 89-128 [sorry, not in our bibliography yet]

Jenkins, D.G., (1965). Planktonic Foraminiferal zones and new taxa from the Danian to lower Miocene of New Zealand. New Zealand Journal of Geology and Geophysics, 8(6): 1088-1126.

Jenkins, D.G., (1965). A re-examinition of Globorotalia collactea Finlay, 1939. New Zealand Journal of Geology and Geophysics, 8: 843-848.

Ramsay, W.R., (1962). Hantkeninidae in the Tertiary rocks of Tanganyika. Contributions from the Cushman Foundation for Foraminiferal Research, 13: 78-89.

Thalmann, H.E., (1942). Foraminiferal genus Hantkenina and its subgenera. American Journal of Science, 240: 809-820.


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Hantkenina australis compiled by the pforams@mikrotax project team viewed: 21-8-2017

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