Morozovella allisonensis


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

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 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 - Atlas of Eocene Planktonic Foraminifera, chapter 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. 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: 22-7-2018

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