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Lipsonia lipsonae Georgescu&Abramovich 2008 |
Current identification:
Type species. Lipsonia lipsonae nov. sp. Remarks. Only two Cretaceous serial planktic foraminiferal genera present raised sutures: Sigalia and Lipsonia nov. Although the two are nearly homeomorphs, they differ in a number of features, such as: (i) the multiserial stage is better developed in Lipsonia (up to ten chamberlet sets) when compared to Sigalia (maximum six chamberlet sets); (ii) test ornamentation in Lipsonia is completely devoid of costae, whereas fine costae are present in all species of Sigalia; (iii) the thickened early part of the test differs sharply in the two genera: it is completely irregular in Lipsonia and with a radial pattern in Sigalia. The finely costate surface and raised sutures of Sigalia suggest that the origin of this genus should be most likely in the costate contemporaneous Heterohelix sphenoides Masters, 1976, as suggested by Nederbragt (1991). The complete absence of costate ornamentation rules out a costate ancestor for Lipsonia (Fig. 2). The two genera are separated by a significant time gap, which encompasses the Campanian–Lower Maastrichtian stratigraphical interval (approximately 17 Ma). This gap is calculated from the last occurrence of Sigalia (Santonian, top of the Dicarinella asymetrica Biozone) to the first evolutionary occurrence of Lipsonia lipsonae (Upper Maastrichtian, Pseudoguem- belina hariaensis Biozone). Accordingly, it can be inferred that the two genera apparently evolved as the result of iterative evolution. The raised sutures are distinctive for Lipsonia when compared with Ventilabrella. There are significant differences between the smooth Lipsonia and strongly ornamented Planoglobulina, the latter presenting either strong longitudinal costae or small-sized structures arranged following a vermicular pattern Phylogenetic relationships. The origins of Lipsonia nov. gen. are unknown. The absence of the costate ornamentation suggests a possible ancestry among the non-ornamented Laeviheterohelix species, such as L. glabrans (Cushman, 1938) and L. dentata (Stenestad, 1968). However, these two species have compressed tests and, for this reason, cannot be considered among the potential direct ancestors of Lipsonia.
Original Description
Diagnosis. Multiserial planktic foraminifer with raised sutures throughout and coarse irregular ornamentation of the earlier part of the test and smooth in the portion with the last-formed chamberlet sets.
Description. Test is flabelliform in shape, with a very short biserial stage followed by a well-developed multiserial one consisting of up to ten chamberlet sets following the progressive chamber. Chambers are semicircular to subcircular, bordered by raised sutures throughout. The test has quasi-parallel sides in edge view and distinct thickening in the earlier part due to the addition of successive layers of calcite. Aperture is multiple in the adult stage, with circular to ovate transverse walls. Ornamentation consists of coarse and irregular structures on the earlier part of the test; the last-formed chambers are smooth. Test wall is calcareous, hyaline, with variable porosity, macroperforate with vuggy pores in the earlier part and microperforate to finely perforate in the adult.
Etymology:
Extra details from original publication
Species included. The genus is so far monospecific.
Georgescu, M. D. & Abramovich, S. (2008a). A new serial Cretaceous planktic foraminifer (Family Heterohelicidae Cushman, 1927) from the Upper Maastrichtian of the equatorial Central Pacific. Journal of Micropalaeontology. 27: 117-123. gs References:
Lipsonia compiled by the pforams@mikrotax project team viewed: 12-11-2024
Short stable page link: https://mikrotax.org/pforams/index.php?id=131839 Go to Archive.is to create a permanent copy of this page - citation notes |
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