pforams@mikrotax - Hantkenina australis pforams@mikrotax - Hantkenina australis

Hantkenina australis


Classification: pf_cenozoic -> Hantkeninidae -> Hantkenina -> Hantkenina australis
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 australis Finlay 1939
taxonomic 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 (1966) 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 (1966) 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:

Distinguishing features:
Parent taxon (Hantkenina): Final chambers with tubulospines
This taxon: Species showing features of H. dumblei and H. compressa, but unique in having posteriorly recurved tubulospines.

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:
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]

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]

Size:
Maximum diameter without spines: 0.45 mm, with spines, 0.56 mm (Jenkins, 1966). [Coxall & Pearson 2006]

Character matrix
test outline:Lobatechamber arrangement:Planispiraledge view:Compressedaperture:Equatorial
sp chamber shape:Subtriangularcoiling axis:N/Aperiphery:Tubulospinesaperture border:Thin lip
umb chbr shape:Subtriangularumbilicus:Wideperiph margin shape:Subangularaccessory apertures:Sutural
spiral sutures:Moderately depressedumb depth:Shallowwall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:5-6 N.B. These characters are used for advanced search. N/A - not applicable

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 _13C and relatively heavy _18O; based on comparison with other species of the genus.

Phylogenetic relations
Probably evolved from H. dumblei in the middle Eocene. [Coxall & Pearson 2006]

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

Biostratigraphic distribution

Geological Range:
Notes: Middle Eocene, Zones E11-E13. [Coxall & Pearson 2006]
Last occurrence (top): near top of E13 zone (90% up, 38.2Ma, in Bartonian stage). Data source: Coxall & Pearson (2006) fig 8.1
First occurrence (base): at top of E11 zone (100% 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 - Eocene Atlas, chap. 8, p. 232

References:

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

Coxall, H. K. & Pearson, P. N. (2006). Taxonomy, biostratigraphy, and phylogeny of the Hantkeninidae (Clavigerinella, Hantkenina and Cribrohantkenina). 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 8): 213-256. gs O

Finlay, H. J. (1939d). New Zealand Foraminifera: The Occurrence of Rzehakina, Hantkenina, Rotaliatina, and Zeauvigerina. Transactions of the Royal Society of New Zealand. 68(4): 534-543. gs

Jenkins, D. G. (1966b). Planktonic foraminiferal zones and new taxa from the Danian to lower Miocene of New Zealand. New Zealand Journal of Geology and Geophysics. 8 [1965](6): 1088-1126. gs

Ramsay, W. R. (1962). Hantkeninidae in the Tertiary rocks of Tanganyika. Contributions from the Cushman Foundation for Foraminiferal Research. 13(3): 79-89. gs

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

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Hantkenina australis compiled by the pforams@mikrotax project team viewed: 8-9-2024

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