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Species Igorina lodoensis Mallory 1959


Diagnosis / Definition:
Pearson et al. (2006):
DESCRIPTION.- Type of wall: Muricate, normal perforate nonspinose. Test morphology: Test low trochospiral; subcircular, lobulate peripheral outline, biconvex in umbilicla view 5 1/2-6 moderatly inflated, wedge-shaped chambers increasing gradually in size, coalescing around a relatively narrowly open and deep umbilicus sutures radial, straight, weakly incised, surface distinctly and densely muricate, convered with short pustules; in spiral view approximately 10 chambers in 2-2 1/2 whorls, chambers radially elongate, lunate/semicircular, smoothly recurved intercameral sutures, surface densely muricate; in edge view equally biconvex, periphery subangular. Size): holotype diameter 0.2 l mm, thickness 0.13 mm (Mallory, 1059, p. 253).
Discussion / Comments:
Pearson et al. (2006):
DISTINGUISHING FEATURES.- 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. 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 Bermudez 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. 91 3) indicated that the gradual evolution of lodoensis to broedermanni occurred during the early Eocene and that broedermanni ss. was confined to his Zones P8a- PII (=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. PHYLOGENETIC RELATIONSHIPS.- This taxon is the ancestor of Igorina broedermanni; it evolved from Igorina tadjkstanensis in the upper part of Zone P5 (as redefined here). STRATIGRAPHIC RANGE.- Zone P5 (lower part) to Zone E6. GEOGRAPHIC DISTRIBUTION.- Widely distributed (but seldom identified) in the Atlantic- Tethyan region (Aquitaine Basin, East Africa, Egypt), Caribbean, California. STABLE ISOTOPE PALEOBIOL0GY.- No data available.
Systematics:

35
 Ordo Foraminiferida
  Superfamilia Globigerinaceae
   Familia Truncorotaloididae
    Genus Igorina
     Species Igorina lodoensis
Synonym list:
Pearson et al. (2006):
p 1957 Globorotalia broedermanni Cushman & Bermudez. - Bolli : p.80 pl. 19; fig. 13-15 (not pl. 37, figs. 13a-c =Igorina broedermanni); [lower Eocene G. formosa formosa Zone, Upper Lizard Springs Fm., Trinidad]; [Not Cushman and Bermudez, 1949]
1959 Globorotalia broedermanni var. lodoensis Mallory. - Mallory : p.253 pl. 23; fig. 3a-c [lower Eocene (Bulitian Stage) Bulimina bradburyi Zone, lower part of Lodo Fm., Kern County, Califonia]
1962 Globorotalia caylaensis Gartner & Hay. - Gartner & Hay : p.561 pl. 1; fig. 2a-c [lower Eocene Zone Ph. Marné Bleue, Mont Cayla, Aude, castel 11 Aquitaine, France]
1979 Globorotalia (Acarinina) lodoensis Mallory. - Blow : p. 933-935 pl. 17; fig. 1-6 [lower Eocene Zone P7, Sample RS. 80, Kilwa area, Tanzania]
2006 Igorina lodoensis Mallory. - Pearson et al. : p.385 pl. 12.3; fig. 1-16
Specimen:
University of California - Berkeley, Inventory number: 41,947
University of California - Berkeley, Inventory number: 41,971
References:

Bolli,H.M. (1957):
The genera Globigerina and Globorotalia in the Paleocene-Lower Eocene Lizard Springs Formation of Trinidad, B.W.I . Bulletin of the U.S. National Museum Vol. 215 p. 61-82

Mallory,V.S. (1959):
Lower Tertiary Biostratigraphy of the California Coast Ranges. p. 146

Gartner,S. and Hay,W.W. (1962):
Planktonic Foraminifera from the type Llerdian . Ecoglae geologicae Helvetiae Vol. 55 p. 553-572

Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp

Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513
Anonymous: Unedited TaxonConcept data
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