pforams@mikrotax - Pearsonites broedermanni pforams@mikrotax - Pearsonites broedermanni

Pearsonites broedermanni

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


Citation: Pearsonites broedermanni (Cushman & Bermudez 1949)
taxonomic rank: Species
Basionym: Globorotalia (Truncorotalia) broedermanni
Taxonomic discussion: This (predominantly) Eocene taxon figures prominently in early and early middle Eocene (sub)tropical assemblages. It may be considered the central form of the “Morozovella broedermanni group” (Premoli Silva and Boersma, 1988, p. 344) which is closely related to, and descended from, the group of “biconvex morozovellids” (Premoli Silva and Boersma, 1988: 344), characterized by Igorina convexa/ tadjikistanensis and related forms (see also Premoli
Silva and Boersma, 1989; Blow, 1979, p. 934). Pearson (1993, p. 20; text-fig. 14) included broedermanni in the group of “biconvex morozovellids” ( “Acarinina pusilla group”) recognizing that it (and related forms) was probably not referable to either Morozovella or Acarinina. Berggren and Norris (1997) included these forms in Igorina (see also Olsson and others, 1999 for further discussion).
Blow (1979) distinguished Globorotalia broedermanni lodoensis Mallory (from the lower Eocene part of the Lodo Fm. of California) as a lower Eocene (Zone P5-P8b) ancestor of broedermanni s. str., which was said to range from Zone P8a to P11 (=Zone E5-9 of this paper). Distinction between the two was based upon subtle (but distinct) differences such as: usually lower number of chambers in last whorl, relatively more tightly coiled test resulting in narrower umbilicus, more smoothly recurved dorsal intercameral sutures and more lobulate periphery (lodoensis) vs proximally more radial but marginally/distally sharply retorse sutures, more evolute coiling resulting in somewhat larger umbilicus particularly in younger forms, slightly more inflated chambers ventrally and dorsally in some instances, somewhat more equally biconvex and greater appression of chambers in the last convolution of the test, and slightly more tightly coiled test (broedermanni; see further discussion under lodoensis below).
We have observed that Igorina broedermanni evolved from I. lodoensis in the middle part of (former) Zone P5, just below the Paleocene Eocene Thermal Maximum (PETM) in the Dababiya, Qreiya and Owaina sections of Egypt and in the Bass River borehole of the New Jersey Coastal Plain. It occurs relatively commonly in the middle to upper part of the Esna Shale Fm. (Zones P6 and P7= Zones E3-5) at Dababiya and other sections in Egypt. In the PETM interval, the chambers on the umbilical side of individuals of broedermanni are relatively weakly inflated; it is only above the Carbon Isotope Excursion/PETM (i.e., above Zone E1) that the chambers exhibit an inflational tendency, the test becomes distinctly umbilico-convex and the taxon broedermanni assumes its typical appearance.
Included by us in broedermanni are the taxa Globorotalia mattseensis and Globorotalia wartsteinensis of Gohrbandt (1967) and Acarinina planodorsalis of Fleisher (1974). Together, these taxa illustrate a gradual morphologic trend in middle Eocene Igorina broedermanni towards increasing number of chambers in the final whorl and flattening of the dorsal side that culminates in the evolution of Igorina anapetes. [Berggren et al. 2006]

Catalog entries: Globorotalia (Truncorotalia) broedermanni, Acarinina planodorsalis, Globorotalia mattseensis, Globorotalia wartsteinensis

Type images:

Distinguishing features:
Parent taxon (Pearsonites): small Morozovellids with biconvex–planoconvex tests with an overall rounded periphery
This taxon: Biconvex to planoconvex test with 6-7 chambers in fine whorl. Like I. lodoensis but with less lobulate periphery and flatter spiral 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.


Test low trochospiral, subcircular, weakly lobulate outline, planoconvex to weakly biconvex, blunt-tipped muricae covering both sides of test; in umbilical view involute, 6-7 essentially equidimensional, broadly triangular-shaped chambers, sutures depressed, radial, umbilicus narrow, deep, bordered by coalescing circumumbilical muricate, triangular chamber tips, aperture a low slit extending towards peripheral margin; in spiral view about 11-12 chambers in 2½ whorls gradually increasing in size in an evolute coil, broadly subquadrate to subrectangular in shape, intercameral sutures curved and retorse at junction with peripheral margin, planoconvex to weakly biconvex; in edge view, rounded to subangular, noncarinate. [Berggren et al. 2006]

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

dimensions of holotype: length: 0.33 mm; breadth: 0.28 mm; thickness: 0.18 mm (Cushman and Bermudez, 1949, p. 40). [Berggren et al. 2006]

Character matrix
test outline:Subcircularchamber arrangement:Trochospiraledge view:Planoconvexaperture:Umbilical
sp chamber shape:Subrectangularcoiling axis:Lowperiphery:Muricocarinateaperture border:N/A
umb chbr shape:Subtriangularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Flushumb depth:Deepwall texture:Moderately muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:6-7 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution

Widespread in Caribbean (Cuba, Trinidad), Atlantic and Indo-Pacific realms as well as in Tethys (Syria, Egypt, Tunisia, Senegal, Yugoslavia, Italy), Caucasus regions. Krasheninnikov (1974, p. 121) noted that broedermanni occurs in the Atlantic (Sites 6, 19, 20, 21, 22), Pacific (Sites 47, 162, 200) and Indian (Sites 219, 223) Oceans. It has not been reliably reported from high southern (austral) latitudes according to our information. [Berggren et al. 2006]
Aze et al. 2011 summary: Low to middle latitudes; based on Berggren et al. (2006a)

Isotope paleobiology
Recorded by Pearson and others (1993) (as ‘Morozovellabroedermanni) and Pearson and others (2001) as a surface mixed-layer species with very positive δ13C indicating a mixed layer symbiotic habitat. [Berggren et al. 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): Pearson et al. (1993, 2001a)

Phylogenetic relations
Descended from Igorina lodoensis and evolved into I. anapetes by increase in number of chambers. [Berggren et al. 2006]

Most likely ancestor: Pearsonites lodoensis - at confidence level 4 (out of 5). Data source: Berggren et al. (2006), f12.1.
Likely descendants: Pearsonites anapetes; plot with descendants

Biostratigraphic distribution

Geological Range:
Notes: Just below E1 to top of Zone E9. [Berggren et al. 2006]
Last occurrence (top): in upper part of E9 zone (80% up, 43.4Ma, in Lutetian stage). Data source: Berggren et al. (2006), f12.1
First occurrence (base): in upper part of P5 zone (80% up, 56.2Ma, 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. 384


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Pearsonites broedermanni compiled by the pforams@mikrotax project team viewed: 3-3-2024

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