Catalog - Igorina isabellae Catalog - Igorina isabellae

CATALOG OF ORIGINAL DESCRIPTIONS: Igorina isabellae Soldan & Petrizzo 2013

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> I -> Igorina -> Igorina isabellae
Other pages this level: I. isabellae, I. paraspiralis, I. praecarinata

Igorina isabellae

Citation: Igorina isabellae Soldan & Petrizzo 2013
Taxonomic rank: species
Type specimens: Holotype (Pl. 1, 1a-c; Micro-Unimi no. 1985), paratype 1 (Pl. 1, 2a-c; Micro-Unimi no. 1986) and paratype 2 (Pl. 1, 3a-c; Micro-Unimi no. 1987)
Type sample (& lithostrat): 198-1209B-23H-7, 11-12 cm.;
Type age (chronostrat): Paleocene, zone P4
Type locality: Shatsky Rise, Northwest Pacific Ocean. ODP Site 1209 (32.65N; 158.51E;)
Type repository: Milan; Micropalaeontological Collection, Universitˆ degli Studi di Milano, Dipartimento di Scienze della Terra ÔÔA. DesioÕÕ, Italy

Current identification:


Original Description

Diagnosis - Igorina isabellae n. sp. is characterised by small to medium sized test with a well developed muricocarina and a large number of chambers (7-9, rarely 10) in the last whorl.

Description - Test almost equally biconvex; equatorial periphery almost circular to subcircular, very slightly lobate; test surface with pustules, the wall of the inner chambers on the spiral side is clearly covered by a crust; in edge view the peripheral margin is subacute to acute with a distinct keel; umbilical side with 7 to 10 equidimensional and subtriangular chambers, sutures straight and radial, umbilicus small, narrow and deep; spiral side with 2½ whorls; whorls tightly coiled with seven-nine (rarely ten) crescentic/petaloid chambers in the final whorl, increasing very slowly in size as added, sutures strongly recurved and weakly incised; aperture an interiomarginal, umbilical-extraumbilical, moderately high arch extending nearly to the periphery.

Size:
Diameter = 0.39 mm, thickness = 0.20 mm.

Etymology:
- Named in honor of Professor Isabella Premoli Silva for her outstanding contributions to the study of planktonic foraminifera.

Extra details from original publication
Synonyms

Occurrence - Zones P4a-P4c (basal part), late Paleocene. Geographic distribution - This taxon has been recorded at low and mid latitudes and it commonly occurs in the (sub)tropical planktonic foraminiferal assemblages from the Pacific Ocean (DSDP Leg 6, ODP Leg 143 and ODP Leg 198).

Wall texture - Praemuricate, nonspinose.

Discussion - Igorina isabellae n. sp. is an important component of the (sub)tropical assemblages of the northwestern and central Pacific Ocean. This keeled taxon is usually very distinctive in the assemblage assigned to Subzones P4a-P4b. Specimens similar to Igorina isabellae n. sp. and characterised by an imperforate carina along the peripheral margin were described by Blow (1979) from the Pacific Ocean as Globorotalia (Globorotalia) albeari Cushman & Bermúdez, 1949. These specimens are here included in the variability of Igorina isabellae n. sp. Typical forms of Igorina isabellae n. sp. have been previously illustrated by Petrizzo (2005) and Soldan et al. (2011) from Shatsky Rise sites.
Cladistic analyses performed on Paleocene specimens (Soldan et al., 2011) suggest that Igorina isabellae n. sp. is closely related to I. laevigata from which it evolved by increasing the number of chambers in the last whorl at the base of Subzone P4a. To date, its highest occurrence has been recorded in the lower part of Subzone P4c.
Igorina isabellae n. sp. is distinguished from I. laevigata in having a more circular equatorial periphery and for its larger number of chambers in the last whorl. It differs from I. albeari in possessing a distinct and well-developed keel around the peripheral margin.

References:

Soldan, D. M. & Petrizzo, M. R. (2013). A new planktonic foraminifera species (Igorina isabellae n. sp.) from the late Paleocene of the Pacific Ocean. Bollettino della Societa Paleontologica Italiana. 52: 141-143. gs


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Igorina isabellae compiled by the pforams@mikrotax project team viewed: 29-4-2025

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