Morozovella allisonensis


Classification: pf_cenozoic -> Truncorotaloididae -> Morozovella -> Morozovella allisonensis
Sister taxa: M. caucasica, M. crater, M. aragonensis, M. lensiformis, M. marginodentata, M. formosa, M. gracilis, M. subbotinae, M. aequa, M. apanthesma, M. edgari, M. allisonensis, M. acuta, M. occlusa, M. acutispira, M. pasionensis, M. velascoensis, M. conicotruncata, M. angulata, M. praeangulata, M. sp.,

Taxonomy

Citation: Morozovella allisonensis Kelly et al. 1998
Rank: Species
Basionym: Morozovella allisonensis
Synonyms:
Taxonomic discussion: This taxon exhibits a wide range of morphological plasticity that is a function of degree of axial compression. We have observed the relatively high conical morphotypes intermediate between the typical end members of the velascoensis-allisonensis group within the CIE in the Dababiya and Qreiya sections in Egypt. [Berggren & Pearson 2006]

Catalog entries: Morozovella allisonensis;

Type images:

Distinguishing features: Like M. velascoensis but axially compressed and less ornate; biconvex to mildly planoconvex in edge view; umbilical tips of chambers are relatively rounded and unornamented.

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


Diagnostic characters: This taxon is characterized by varying degrees of axial compression; it is biconvex to mildly planoconvex in edge view; umbilical tips of chambers are relatively rounded and unornamented. [Berggren & Pearson 2006]

Wall type: Normal perforate, muricate, nonspinose [Berggren & Pearson 2006]

Test morphology: Low to medium trochospiral test, subcircular, weakly to non-lobulate peripheral outline, chambers triangular on umbilical side, trapezoidal to subquadrate on spiral side as a function of degree of curvature of intercameral sutures; in umbilical view primary aperture low arch to subcircular, umbilical to extraumbilical in position extending to peripheral margin; typically 5-9 chambers in the final whorl; sutures depressed, straight to slightly curved, radial; umbilicus generally small, deep varying with tightness of coiling; chambers with unornamented rounded umbilical shoulders, slight tendency to be umbilically inclined as a function of axial compression; on the spiral side approximately 12-17 chambers arranged in about 3 whorls; chambers flattened to moderately inflated; gradual increase in chamber size throughout; sutures muricate, strongly to weakly curved, varying from raised to slightly depressed; in edge view umbilico-convex to planar; spiral side flat to slightly convex; test periphery subrounded to acute; weakly muricate keel. [Berggren & Pearson 2006]

Size: Holotype maximum diameter: approximately 0.35 to 0.40 mm. [Berggren & Pearson 2006]

Biogeography and Palaeobiology


Geographic distribution: This taxon is most abundant in warm-water, (sub)tropical regions; common in central-equatorial Pacific Ocean (ODP Site 865) and in northern (Spain) and southern (Egypt) Tethyan deposits; rare occurrences recorded on Blake Ridge of North Atlantic (ODP Site 1051). [Berggren & Pearson 2006]
Aze et al. 2011 summary: Low latitudes; based on Berggren & Pearson (2006)

Isotope paleobiology: Inferred depth-habitat varies over time; initially occupied deeper portions of mixed-layer to upper thermocline and subsequently inhabited shallow mixed-layer; carbon isotope signature exhibits strong covariance with shell size, while oxygen isotope composition displays a modest negative correlation with shell size (overall stable isotopic signature is analogous to that of modern, symbiotic species) (Kelly and others, 1998). [Berggren & Pearson 2006]
Aze et al. 2011 ecogroup 1 - Open ocean mixed-layer tropical/subtropical, with symbionts. Based on very heavy δ13C and relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): Kelly et al. (1998)

Phylogenetic relations: This ephemeral taxon intergrades with more ornate morphotypes of its ancestor, M. velascoensis, and has no descendants. [Berggren & Pearson 2006]

Most likely ancestor: Morozovella velascoensis - at confidence level 4 (out of 5). Data source: Berggren & Pearson (2006) f11.1.

Biostratigraphic distribution

Geological Range:
Notes: Zone E1; restricted to Carbon Isotope Excursion (CIE) interval of Paleocene-Eocene Thermal Maximum (PETM). [Berggren & Pearson 2006]
Last occurrence (top): at top of E1 zone (100% up, 55.8Ma, in Ypresian stage). Data source: Berggren & Pearson (2006) f11.1
First occurrence (base): at base of E1 zone (0% up, 56Ma, in Ypresian stage). Data source: Berggren & Pearson (2006) f11.1

Plot of occurrence data:

Primary source for this page: Berggren & Pearson 2006 - Eocene Atlas, chap. 11, p. 345

References:

Berggren, W.A. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Morozovella. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera. Cushman Foundation Special Publication. 41 Allen Press, Lawrence, Kansas, pp. 343-376.

Kelly, D.C.; Bralower, T.J. & Zachos, J.C., (1998). Evolutionary consequences of the latest Paleocene thermal maximum for tropical planktonic foraminifera. Palaeogeography, Palaeoclimatology, Palaeoecology, 141: 139-161.


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Morozovella allisonensis compiled by the pforams@mikrotax project team viewed: 16-11-2018

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