Pearsonites lodoensis


Classification: pf_cenozoic -> Truncorotaloididae -> Pearsonites -> Pearsonites lodoensis
Sister taxa: P. anapetes, P. broedermanni, P. lodoensis,

Taxonomy

Citation: Pearsonites lodoensis (Mallory 1959)
Rank: Species
Basionym: Globorotalia broedermanni lodoensis
Synonyms:
Taxonomic discussion: This form was described from lowermost Eocene levels of the Lodo Fm. (California) and distinguished from the closely related form broedermanni by its “larger umbilical opening, straighter radial sutures, more lobulate periphery” (Mallory, 1959, p. 253). In a restudy of type material of Mallory and Cushman and Bermúdez at the USNM and his own comparative material, Blow (1979, p. 912) drew attention to the fact that lodoensis is, in fact, an early representative of a plexus of forms stemming from the late Paleocene convexa ( =tadjikistanensis of this paper) group distinguished by small, involutely coiled, equally biconvex tests (~ 0.2 mm diameter), with 5-6 chambers coiled around a narrow umbilicus. During the course of its evolution the umbilicus expands in extent, the coiling relaxes to yield a more evolute test which in some individuals contains 7-9 chambers, the test becomes more plano-convex and spiral sutures become distally more sharply retorse (broedermanni). While Blow (1979, p. 913) indicated that the gradual evolution of lodoensis to broedermanni occurred during the early Eocene and that broedermanni s.s. was confined to his Zones P8a-P11 (=Zones E4-9 of this paper), we have observed the transition between these two forms in Zone P5 (just below the CIE/PETM), in the lower part of the Esna Shale Fm. of Egypt. Both broedermanni and lodoensis are common elements in the CIE/PETM interval of the Bass River borehole in the New Jersey coastal plain. [Berggren et al. 2006]

Catalog entries: Globorotalia broedermanni lodoensis, Globorotalia caylaensis,

Type images:

Distinguishing features: Test small, lobulate, equally biconvex, densely muricate; narrow umbilicu; essentially straight radial sutures on the umbilical side.

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 distinguished by its small size, lobulate, equally biconvex, densely muricate test, narrow umbilicus and essentially straight radial sutures on the umbilical side. [Berggren et al. 2006]

Wall type: Muricate, normal perforate, nonspinose. [Berggren et al. 2006]

Test morphology: Test low trochospiral; subcircular, lobulate peripheral outline, biconvex; in umbilical view 5½ - 6 moderately inflated, wedgeshaped chambers increasing gradually in size, coalescing around a relatively narrowly open and deep umbilicus, sutures radial, straight, weakly incised, surface distinctly and densely muricate, covered with short pustules; in spiral view approximately 10 chambers in 2 - 2½ whorls, chambers radially elongate, lunate/semicircular, smoothly recurved intercameral sutures, surface densely muricate; in edge view equally biconvex, periphery subangular. [Berggren et al. 2006]

Size: holotype diameter 0.21 mm, thickness 0.13 mm (Mallory, 1959, p. 253). [Berggren et al. 2006]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:N/A
umb chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Subangularaccessory apertures:None
spiral sutures:Moderately depressedumb depth:Deepwall texture:Moderately muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:5.0-6.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Widely distributed (but seldom identified) in the Atlantic-Tethyan region (Aquitaine Basin, East Africa, Egypt), Caribbean, California. [Berggren et al. 2006]
Aze et al. 2011 summary: Low to middle latitudes; based on Berggren et al. (2006a)

Isotope paleobiology: No data available. [Berggren et al. 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): this study

Phylogenetic relations: This taxon is the ancestor of Igorina broedermanni; it evolved from Igorina tadjkistanensis in the upper part of Zone P5 (as redefined here). [Berggren et al. 2006]

Most likely ancestor: Acarinina esnehensis - at confidence level 2 (out of 5). Data source: Soldan et al. 2104 (fig 10, p.25-26); NB Berggren et al. (2006), f12.1 suggested an alternative origin..
Likely descendants: Pearsonites broedermanni;

Biostratigraphic distribution

Geological Range:
Notes: Zone P5 (lower part) to Zone E6. [Berggren et al. 2006]
Last occurrence (top): in upper part of E6 zone (70% up, 50.3Ma, in Ypresian stage). Data source: Berggren et al. (2006), f12.1
First occurrence (base): in lower part of P5 zone (30% up, 56.8Ma, in Thanetian stage). Data source: Berggren et al. (2006), f12.1

Plot of occurrence data:

Primary source for this page: Berggren et al. 2006 - Eocene Atlas, chap. 12, p. 388

References:

Berggren, W. A., Olsson, R. K. & Premoli Silva, I. (2006a). Taxonomy, biostratigraphy and phylogenetic affinities of Eocene Astrorotalia, Igorina, Planorotalites, and Problematica (Praemurica? lozanoi). 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: 377-400. gs

Bermudez, P. J. (1949). Tertiary smaller foraminifera of the Dominican Republic. Cushman Laboratory for Foraminiferal Research, Special Publication. 25: 1-322. gs

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. 2: 1-1413. gs

Bolli, H. M. (1957d). The genera Globigerina and Globorotalia in the Paleocene-Lower Eocene Lizard Springs Formation of Trinidad. In, Loeblich, A. R. , Jr. , Tappan, H. , Beckmann, J. P. , Bolli, H. M. , Montanaro Gallitelli, E. & Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin. 215: 61-82. gs

Gartner, S. & Hay, W. W. (1962). Planktonic foraminifera from the type Ilerdian. Eclogae Geologicae Helvetiae. 55(2): 561-. gs

Mallory, V. S. (1959). Lower Tertiary biostratigraphy of the California Coast Ranges. American Association of Petroleum Geologists, Tulsa, Oklahoma. 1-416. gs


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Pearsonites lodoensis compiled by the pforams@mikrotax project team viewed: 22-7-2019

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