Hantkenina


Classification: pf_cenozoic -> smooth non-spinose -> Hantkeninidae -> Hantkenina
Sister taxa: Clavigerinella, Cribrohantkenina, Hantkenina,
Daughter taxa (blue => in age window 0-300Ma)
Hantkenina alabamensis can be distinguished from H. compressa by the greater lateral inflation of the final 1-2 chambers, the more compact and involute coiling and more forward leaning tubulospines. The species intergrades with H. compressa at the beginning of its range, but H. compressa appears stratigraphically lower and is closer in morphology to H. dumblei. It differs from H. primitiva in the greater lateral chamber inflation and by having a full complement of tubulospines in the adult whorl, and from H. nanggulanensis in the smaller size and absence of extremely globular final chambers.
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.
Hantkenina compressa differs from H. dumblei in the trans-sutural position and more forward-inclined orientation of the tubulospines, often angular periphery and less rapid increase in chamber height in the adult whorl. It is distinguished from H. alabamensis in lacking the sub-tangential adult tubulospines and in having more laterally compressed chambers. As in H. alabamensis, the final 2-3 tubulospines of H. compressa are in contact with the posterior wall of the adjacent chambers, but this is not as pronounced as in the former.
Hantkenina dumblei is distinguished from H. liebusi by the larger size, more continuous peripheral outline, greater number of chambers in the adult whorl and by the anterior, near sutural position of the tubulospines. It is differentiated from H. lehneri by the more continuous periphery and broad-based, triangular shape of the final whorl chambers. It is distinguished from H. compressa and H. alabamensis by two principal features. Firstly, the peripheral outline is more rapidly expanding along the radial axis, and second, chambers are usually free of contact with the tubulospine of the previous chamber, whereas in the latter species the tubulospines contact and overlap with the posterior wall of the adjacent younger chamber. In addition, tubulospines in H. dumblei are inclined at a relatively low angle, whereas in H. alabamensis they are strongly inclined with respect to the test periphery. It differs from H. australis in the larger size and having straight tubulospines.
Hantkenina lehneri is distinguished from H. liebusi by having cylindrical, finger-like chambers in the latest growth stages, a more deeply incised and more stellate peripheral outline and, on average, one more chamber in the final whorl. It differs from H. dumblei by the higher aspect ratio of the final chambers and the more deeply incised peripheral outline. The finger-like chambers of this species are reminiscent of early examples of H. mexicana. H. lehneri can be distinguished from the earlier morphotype by the longer sutures, unequal chamber shoulders and more slender tubulospines.
Hantkenina liebusi shares features of wall texture, aperture and tubulospines with H. mexicana but differs in having a more compressed test, more closely appressed chambers and a less stellate peripheral outline. The tubulospines are also in a more forward position with respect to the radial chamber axis (i.e. there is a short anterior chamber-shoulder). Hantkenina liebusi usually has fewer chambers in the final whorl than H. dumblei and H. lehneri (4½-6, compared to 5-7 in the latter). It can be distinguished from H. dumblei by the slightly incised peripheral outline and shorter adult chambers and from H. lehneri in being generally less stellate.
Hantkenina mexicana is distinguished from H. liebusi by the more central position of the tubulospines on each chambers. The peripheral outline of H. mexicana is also more distinctly stellate. It differs from H. lehneri (sensu stricto), which also has elongate ‘finger-like’ chambers, by having a more deeply incised peripheral outline and fewer chambers in the final whorl.

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.
Hantkenina singanoae differs from Clavigerinella caucasica by possessing rudimentary terminal constrictions and/or cylindrical extensions to the chamber ends. It differs from H. mexicana in lacking true non-porous tubulospines.
Specimens which cannot be assigned to established species

Taxonomy

Citation: Hantkenina Cushman, 1924
Rank: Genus
Type species: Hantkenina alabamensis Cushman, 1924.
Synonyms:
Taxonomic discussion: We regard Hantkenina as a monophyletic clade and do not support Blow’s (1979) view that the early middle Eocene and late middle Eocene to late Eocene species were separately derived. Although the shells are compressed and planispiral, the earliest morphotypes (H. singanoae and H. mexicana) show signs of asymmetry in aperture shape and in the distribution of pre-adult whorls on one or other side of the shell. This feature, which is also seen in the sister genus Clavigerinella, testifies to a trochospiral ancestry.
[Coxall & Pearson 2006]

Catalog entries: Hantkenina;

Type images:

Short diagnosis: The most prominent feature of Hantkenina is the presence of tubulospines, which distinguish it from the ancestral genus Clavigerinella. Tubulospines also occur in closely related Cribrohantkenina, which differs from Hantkenina in having a multiple areal aperture system. The Cretaceous genus Schackoina, which is the only other planktonic foraminiferal genus to possess tubulospines, is readily distinguished from Hantkenina by having a microperforate wall, fewer chambers and much smaller test size (0.63-1.50 mm).

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: The most prominent feature of Hantkenina is the presence of tubulospines, which distinguish it from the ancestral genus Clavigerinella. Tubulospines also occur in closely related Cribrohantkenina, which differs from Hantkenina in having a multiple areal aperture system. The Cretaceous genus Schackoina, which is the only other planktonic foraminiferal genus to possess tubulospines, is readily distinguished from Hantkenina by having a microperforate wall, fewer chambers and much smaller test size (0.63-1.50 mm).
[Coxall & Pearson 2006]

Wall type: Smooth, normal perforate, probably nonspinose. [Coxall & Pearson 2006]

Test morphology: Planispiral, biumbilicate or showing a subtly raised spiral side and very shallow umbilicus; 4-7 chambers in the final whorl; chambers rounded in the early stages, adult chambers radially elongated, triangular, polygonal or spherical, laterally compressed or highly inflated; some or all of the adult chambers extend into hollow non-porous tubulospines, of variable length, shape and orientation, or, in the case of H. singanoae n. sp., the chambers possess a distinct terminal nub or porous “proto-tubulospine”; peripheral outline (excluding tubulospines) varies from stellate, with deep incisions between chambers, to angular, smooth-continuous or gently lobed; the aperture is a single equatorial arch bordered by a distinctive lip of variable width, symmetrical or slightly asymmetrical.
[Coxall & Pearson 2006]

Biogeography and Palaeobiology


Phylogenetic relations: Hantkenina evolved gradually from Clavigerinella caucasica in the latest early Eocene (Coxall and others, 2003). It gave rise to Cribrohantkenina in the late Eocene and the entire
family went extinct at the Eocene/Oligocene boundary (33.7 Ma). [Coxall & Pearson 2006]

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within Priabonian Stage (33.89-37.75Ma, top in Priabonian stage). Data source: Total of range of species in this database
First occurrence (base): within Lutetian Stage (41.15-47.84Ma, base in Lutetian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Coxall & Pearson 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 8, p. 229

References:

Bermudez, P.J., (1937). Nuevas especies de Foraminiferos del Eoceno de las cercanias de Guanajay, provincia Pinar del Rio, Cuba. Memorias de la Sociedad Cubana de Historia Natural, 11(4): 237-248.

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.

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

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


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Hantkenina compiled by the pforams@mikrotax project team viewed: 25-9-2017

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