Morozovella praeangulata


Classification: pf_cenozoic -> Truncorotaloididae -> Morozovella -> Morozovella praeangulata
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 praeangulata (Blow 1979)
Rank: Species
Basionym: Globorotalia (Acarinina) praeangulata
Synonyms:
Taxonomic discussion: Examination of the holotype (3514/6) and several paratypes of Acarinina quadratoseptata Davidzon and Morozova, 1964, in the micropaleontological collections of GAN in Moscow suggests that this form may be a senior synonym of M. praeangulata Blow. We retain the name
praeangulata in this work, however, for the reasons given below. The holotype and one of the paratypes (3514/7) of quadratoseptata are characterized by 5 chambers in the last whorl and slightly (but distinctly) curved sutures sloping to a rounded to subangular, lobulate, noncarinate periphery. In both specimens, the early whorls are obscured, the tests are poorly preserved (strongly recrystallized), and the last chamber for each is missing. Paratype 3514/8 has a quadrate test and flat early whorls, and the chambers of its last whorl slope toward a distinctly subangular periphery. The test of this paratype is homeomorphic with the Pliocene noncarinate Globorotalia crassaformis. The remaining paratype (3514/9) is distinctly different, as it comes from a different locality and stratigraphic level, and it is referable to Acarinina mckannai. The drawing of this specimen is misleading and gives the impression of a morozovellid. A further problem lies in the fact that the specimens coil in the opposite direction to what is shown in the illustrations. The negatives were apparently retouched and printed backwards.
The Russian authors compared their new species with Acarinina pentacamerata Morozova, 1961, and A. praecursoria Morozova, 1961. Although believing that quadratoseptata may indeed be a senior synonym of praeangulata by 15 years, the fact that the type material of quadratoseptata is very poorly preserved and has been virtually ignored in Soviet/Russian literature (it was not mentioned by Shutskaya, 1970a, 1970b, in her comprehensive review of Paleocene-lower Eocene planktonic foraminifera) leads us to retain the name praeangulata for this morphospecies. [Olsson et al. 1999]

Catalog entries: Globorotalia (Acarinina) praeangulata;

Type images:

Distinguishing features: Planoconvex, moderately lobulate test with 5-6 tangentially elongate chambers in last last whorl; umbilical sutures straight to weakly curved, incised; spiral intercameral sutures incised, weakly muricate, strongly recurved; peripheral margin strongly muricate but not muricocarinate; umbilicus narrow, deep; aperture an interiomarginal, umbilical-extraumbilical slit (with distinct lip in well preserved specimens).

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: Planoconvex, moderately lobulate test with 5-6 tangentially elongate chambers in last last whorl; umbilical sutures straight to weakly curved, depressed/incised; spiral intercameral sutures incised, weakly muricate, strongly recurved; peripheral margin strongly muricate but not muricocarinate; umbilicus narrow, deep with aperture an interiomarginal, umbilical-extraumbilical slit (bordered by a distinct intraperiumbilical lip in well preseved specimens) extending nearly to the peripheral margin. [Olsson et al. 1999]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Planoconvexaperture:-
umb chamber shape:Subtriangularcoiling axis:Lowperiphery:Muricocarinateaperture border:Thin lip
sp chbr shape:Crescenticumbilicus:Narrowperiph margin shape:Moderately roundedaccessory apertures:None
umbilical or test sutures:Moderately depressedumb depth:Deepwall texture:Moderately muricateshell porosity:Finely Perforate: 1-2.5µm
spiral sutures:Raised muricatefinal-whorl chambers:5.0-6.0

Biogeography and Palaeobiology


Geographic distribution: The few localities where this
species has been identified suggests a low to middle latitude distribution. [Olsson et al. 1999]
Aze et al. 2011 summary: Low to middle latitudes; based on Olsson et al. (1999)

Isotope paleobiology: Morozovella praeangulata has ∂13C and ∂18O values similar to M. angulata and more positive ∂13C
18 and more negative 8 0 values than Subbotina spp. (Shackleton etal., 1985). [Olsson et al. 1999]
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): Shackleton et al. (1985)

Phylogenetic relations: Bolli (1957a) proposed that Globorotalia (= Morozovella) angulata was derived from Globorotalia (= Praemurica) uncinata. He illustrated a form (pl. 17: figs. 10-12) that he considered transitional between M. uncinata and M. angulata. Blow (1979) accepted Bolli's proposed phylogeny and selected this specimen as a paratype to support his documentation of M. praeangulata as the stem form of the morozovellid lineage. The transition to M. praeangulata would have involved the development of a more pronounced conicotruncate test and concomitant change toward equidimensional (as opposed to tangentially elongate) chambers, as well as formation of a thicker (and ultimately) muricocarinate peripheral margin. This has been the traditional view of the origin of Morozovella. An alternate view, as noted in "Wall Texture, Classification, and Phylogeny," is that the wall texture of M. praeangulata developed with pustule buildup on a smooth "globorotaliid" surface in contrast to the praemuricate wall texture of uncinata. In this view M. praeangulata originated from a smooth-walled Globanomalina, such as G. imitata, which has pustules covering the walls of early formed anguloconical chambers (Plate 4: Figures 11-13, 16, Plate 36: Figures 8-12). These chambers are similar to those observed in the modern Globorotalia scitula (Plate 3: Figure 8), which was a stem form for several globorotaliid lineages in the Neogene. Thus, the initial step in the evolution of M. praeangulata would have involved the suppression of the later stages of ontogeny by speeding up the rate of maturation and the development of a more pustulose, conicotruncate adult test. This change in the timing of maturation would account for the small size of the early forms of M. praeangulata. [Olsson et al. 1999]

Most likely ancestor: Praemurica uncinata - at confidence level 3 (out of 5). Data source: Olsson et al. (1999) f5a (following Blow 1979) - alternative interpretation given on fig 5b, origin from Globanomalina imitata, following Olsson & Hemleben (1996). See evolution comments above..

Biostratigraphic distribution

Geological Range:
Notes: Zone P2 to Zone P3a. [Olsson et al. 1999]
Last occurrence (top): at top of P3a subzone (100% up, 61.3Ma, in Selandian stage). Data source: Olsson et al. 1999
First occurrence (base): near base of P2 zone (10% up, 62.6Ma, in Danian stage). Data source: Olsson et al. 1999

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 64

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea), 2. E. J. Brill, Leiden, 1413 pp.

Bolli, H.M., (1957). The genera Globigerina and Globorotalia in the Paleocene-Lower Eocene Lizard Springs Formation of Trinidad. In: Loeblich, A.R., Jr. et al. (Editors), Studies in Foraminifera, U.S. National Museum Bulletin 215. U.S. Government Printing Office, Washington, D.C., pp. 61-82.

Davidzon, R. & Morozova, V.G., (1964). Планктонные и бентосные известковые фораминиферы бухарских слоев (палеоцен) Тадхикской депрессиы - Planktonic and benthonic calcareous foraminifers of the Bukhara Beds (Paleocene) of the Tadzhik depression. 3: 23-29. Paleontological Journal., 3: 23-29.

Olsson, R.K. & Hemleben, C., (1996). Phylogeny of Normal Perforate Paleocene Planktonic Foraminifera based on Wall Texture. [Abstract.]. North American Paleontology Conference. Washington, D.C, Abstracts with Program,: 294.

Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology, 85. Smithsonian Institution Press, Washington, DC, 1-252 pp.


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

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