Catalog - Sigalia incipiens

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.

Sigalia incipiens

Citation: Sigalia incipiens Georgescu 2010

Type specimens: Holotype.– WKB 010048. Paratypes.– Five specimens, WKB 010049-010053,

Type sample (& lithostrat): Sample 10-95-14-1, 102-105 cm

Type age (chronostrat): upper Santonian, D. asymetrica Biozone

Type locality: Type locality.– DSDP Site 95, Yucatan outer shelf; geographical coordinates: 24° 09.00’ N and 86° 23.85’ W.

Type repository: Willi Karl Braun Micropaleontological Collection at the University of Calgary (Calgary, Alberta, Canada.

Diagnosis.– Sigalia with biserial chamber arrangement throughout and calyptoridges.

Description.– Test with subtriangular outline, consisting of 13-15 chambers that gradually increase in size. Chambers are alternately added with respect to the test axis of growth resulting in a biserial arrangement; variable rate of chamber increase in size. Earlier chambers globular, those of the adult stage are subrectangular to petaloid. Sutures are distinct and depressed, straight to slightly oblique to the test growth axis; central suture nearly straight to distinctly indented; indentations are more prominent in the specimens with higher rate of chamber size increase (Pl.4, Figs. 9, 12). Calyptoridges may be developed in the central portion of the test (Pl. 4, Figs. 9, 12). Test compressed in edge view; periphery is simple and rounded, without peripheral structures (Pl. 4, Figs. 4, 8, 10, 11). Aperture is a low to medium high arch at the base of the last formed chamber; two symmetrically developed metaflanges border the aperture, ocassionally developing a small accessory aperture in the proximity of the central suture (Pl. 4, Figs. 1, 3). Chambers ornamented with lep- tocostae (3.4-9.9 µm), which may be more prominent in the peripheral region or over the earlier portion of the test; well-developed periapertural pustulose area (Pl. 4, Figs.4, 8, 10, 11). Test wall calcitic, hyaline and perforate (1.2-3.8 µm); pores simple, situated in the space between the leptocostae.

Dimensions.– L = 0.267-0.458 mm; W = 0.190-0.347 mm; W/L = 0.680-0.787; T = 0.082-0.130 mm; T/L =0.275-0.307; A = 44-57° (based on average measurements of 11 specimens: holotype, five paratypes and five topotypes).

Name derived from the Latin verb incipere (= to begin), suggesting it is the oldest species of the Sigalia directional lineage.

Remarks.– Sigalia incipiens differs from Planulitella sphenoides, its ancestor, by having (i) test composed of more chambers (13-15 rather than 10-13), (ii) lower rate of chamber size increase in the adult part and (iii) ocassionally developed calyptoridges in the central portion of the test. It differs from P. stenopos by (i) having constant rate of chamber size increase and (ii) having ocassionally developed calyptoridges. The two specimens figured in Honigstein et al. (1987) present calyptoridges on the earlier chambers of the test and are probably transitional to S. deflaensis.

References:

Georgescu, M. D. (2010d). Origin, taxonomic revision and evolutionary classification of the late Coniacian-early Campanian (Late Cretaceous) planktic foraminifera with multichamber growth in the adult stage. Revista Española de Micropaleontología. 42: 59-118. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Sigalia incipiens Georgescu 2010

Sigalia incipiens

References:

Add Comment

Comments