Citation: Morozovella allisonensis Kelly et al. 1998taxonomic rank: SpeciesBasionym: Morozovella allisonensisSynonyms:
Morozovellaallisonensis Kelly, Bralower, and Zachos, 1998:158, figs. 5A [holotype], 5B [paratype]; figs. 8D-G [Zone P5; (from a part equivalent to Zone E1 in this work, from within carbon isotope excursion of Paleocene-Eocene Thermal Maximum), ODP Hole 865C Allison Guyot, equatorial Pacific Ocean].
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]
Distinguishing features: Parent taxon (Morozovella): Test typically plano-convex, chambers strongly anguloconical. Wall strongly pustulose (muricate) on parts of spire and umbilicus. Most species with muricocarina. This taxon: 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
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] Wall type: Normal perforate, muricate, nonspinose [Berggren & Pearson 2006] Size: Holotype maximum diameter: approximately 0.35 to 0.40 mm. [Berggren & Pearson 2006]
Character matrix
test outline:
Subcircular
chamber arrangement:
Trochospiral
edge view:
Equally biconvex
aperture:
Umbilical-extraumbilical
sp chamber shape:
Crescentic
coiling axis:
Low
periphery:
Muricocarinate
aperture border:
N/A
umb chbr shape:
Subtriangular
umbilicus:
Narrow
periph margin shape:
Subangular
accessory apertures:
None
spiral sutures:
Weakly depressed
umb depth:
Deep
wall texture:
Moderately muricate
shell porosity:
Finely Perforate: 1-2.5µm
umbilical or test sutures:
Moderately depressed
final-whorl chambers:
5-9
N.B. These characters are used for advanced search. N/A - not applicable
Biogeography and Palaeobiology
Geographic distributionThis 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 paleobiologyInferred 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 _13C and relatively light _18O. Sources cited by Aze et al. 2011 (appendix S3): Kelly et al. (1998) Phylogenetic relationsThis 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 Thanetian stage). Data source: Berggren & Pearson (2006) f11.1
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
Taxon plotted: Morozovella allisonensis, synonyms included - Morozovella allisonensis;
Primary source for this page: Berggren & Pearson 2006 - Eocene Atlas, chap. 11, p. 345
References:
Berggren, W. A. & Pearson, P. N. (2006a). Taxonomy, biostratigraphy, and phylogeny of Eocene Morozovella. 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 11): 343-376. gsO
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. gs
Morozovella allisonensis compiled by the pforams@mikrotax project teamviewed: 9-9-2024
Eocene_Atlas_pl11-2_fig13-16.jpg
Eocene_Atlas_pl11-2_fig9-11.jpg
Eocene_Atlas_pl11-2_fig13-16.jpg
Eocene_Atlas_pl11-2_fig9-11.jpg
holotype: M. allisonensis
holotype: M. allisonensis
paratype: M. allisonensis
paratype: M. allisonensis
