pforams@mikrotax - Laeviheterohelix reniformis

Citation: Laeviheterohelix reniformis (Marie, 1941)

Basionym: Ventilabrella reniformis

Original description: Test à partie initiale réduite et effilée, composée de loges nettement croissantes, suivies dans l'adulte de loges croissantes, presque globuleuses et assez régulières à la périphérie des flancs, nettement allongées et reniformes à leur intérieur. Surface très finement striée longitudinalement.

Translation: Test showing a reduced and fringed initial part, with chambers increasing sharply in size as added; mature chambers enlarging as added, almost globular and fairly regular at the periphery of the sides, sharply elongated and reniform in their internal part. Surface finely striated longitudinally.

Test size ranges from 210 to 306 microns in length (n = 6) and consists of 10 to 14 chambers that are biserially arranged in the earlier portion of the test and may become multichambered in final growth stage. Globular early chambers become reniform later in ontogeny. Proloculus size ranges from 15 to 25 microns in diameter (n = 5); early chambers increase gradually in size and then more rapidly later, becoming fan-shaped in side view. In edge view, tests generally remain compressed throughout ontogeny. Sutures are depressed and oblique to the central axis, and they widen to create a flattened indentation of the intercameral area on the later chambers. Aperture is a symmetrical, high-arch at the base of the final chamber, with symmetrical apertural flanges and an imperforate margin. Test wall is calcitic and hyaline, and the surface absent of costae. Early-formed chambers are smooth, whereas later chambers are ornamented with distinct, well-developed pore mounds that are randomly distributed over the test. Pores (0.6 to 0.8 microns in diameter, n = 5) are microperforate and pore mound rims are 2.2 to 3.3 microns (n = 5) in thickness. [copied from Chronos database]

Geological Range:
Last occurrence (top): within Campanian Stage (72.05-83.64Ma, top in Campanian stage). Data source: [copied from Chronos database]
First occurrence (base): within H. helvetica zone (92.56-93.52Ma, base in Turonian stage). Data source: [copied from Chronos database]

References:

Haynes, S., Huber, B. T. & MacLeod, K. G. (2015). Evolution and phylogeny of mid-Cretaceous (Albian-Coniacian) biserial planktic foraminifera. Journal of Foraminiferal Research. 44: 42-81. gs

Marie, P. (1941). Les foraminiferes de la craie a Belemnitella mucronata du Bassin de Paris. Mémoires du Muséum National d'Histoire Naturelle, Paris. 12: 1-296. gs V O

test outline:	Palmate	chamber arrangement:	Multiserial	edge view:	Compressed	aperture:	Interiomarginal
sp chamber shape:	Reniform	coiling axis:	N/A	periphery:	N/A	aperture border:	Thin lip
umb chbr shape:	Reniform	umbilicus:	N/A	periph margin shape:	N/A	accessory apertures:	None
spiral sutures:	Strongly depressed	umb depth:	N/A	wall texture:	Pore mounds	shell porosity:	Microperforate: <1µm
umbilical or test sutures:	Strongly depressed	final-whorl chambers:	2.0-2.0	N.B. These characters are used for advanced search. N/A - not applicable

Laeviheterohelix reniformis

References:

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