pforams@mikrotax - Protoheterohelix obscura

Protoheterohelix obscura

Classification: pf_mesozoic -> Heterohelicidae -> Protoheterohelix -> Protoheterohelix obscura
Sister taxa: P. obscura, P. washitensis, P. sp.


Citation: Protoheterohelix obscura Georgescu & Huber 2009
Rank: Species
Basionym: Protoheterohelix obscura

Type images:

Original description: Test is small, consisting of 11-13 biserially arranged chambers throughout. Proloculus is small (9.1-14.3 microns) and followed by a slightly larger second chamber. Earlier chambers are subglobular, those of the adult portion of the test subglobular to reniform and oblique to the test axis of growth. Sutures are straight to slightly curved, distinct and depressed and oblique to the test axis of growth. Tests are symmetrical in edge view, with periphery broadly rounded. Aperture is an interiomarginal, low- to medium-high arch bordered by two unequally developed periapertural flanges. Chamber surface is smooth. Test wall is calcitic, hyaline, and nannoperforate to microperforate; pore diameter ranges 0.4-0.9 microns.

Entries in the Catalog of original descriptions: Protoheterohelix obscura

Emended description:

Haynes et al, 2015, JFR, 45(1):49. Test is small (averaging 147 microns in length, n = 11) and consists of 10‰€“13 (n = 11) biserially arranged chambers with a straight or twisted orientation. Earliest chambers are globular, but become reniform, and begin to overlap previous chambers by the fourth or fifth chamber. Proloculus is small (12‰€“18 microns in diameter, n = 9) and subsequent chambers gradually increase in size resulting in a subtriangular outline in side view. Sutures are moderately depressed and straight to slightly curved, meeting the central axis at an oblique angle, creating a zigzag medial suture. Aperture is an asymmetrical semicircle with a low arch at the base of the final chamber and is bordered by asymmetrical flanges. Test wall is calcitic, hyaline, and microperforate, with pore diameters ranging from 0.6-0.8 microns (n = 4). Surface is usually smooth, but some specimens are ornamented with faint striations and weakly developed, flat-topped pore mounds ,2 microns in diameter (n = 3); however, these features are exceptionally rare. [copied from Chronos database]


Wall type:


Character matrix
test outline:Triangularchamber arrangement:Biserialedge view:Compressedaperture:Interiomarginal
sp chamber shape:Reniformcoiling axis:N/Aperiphery:N/Aaperture border:Thin flange
umb chbr shape:Reniformumbilicus:N/Aperiph margin shape:Broadly roundedaccessory apertures:N/A
spiral sutures:Moderately depressedumb depth:N/Awall texture:Smoothshell porosity:
umbilical or test sutures:Moderately depressedfinal-whorl chambers:2.0-2.0 N.B. These characters are used for advanced search. N/A - not applicable

Geological Range:
Last occurrence (top): within H. helvetica zone (92.56-93.52Ma, top in Turonian stage). Data source: [copied from Chronos database]
First occurrence (base): within P. appenninica zone (100.50-101.92Ma, base in Albian stage). Data source: [copied from Chronos database]

Plot of range and occurrence data:


Georgescu, M. D. & Huber, B. T. (2009). Early evolution of the Cretaceous serial planktic foraminifera (late Albian-Cenomanian). Journal of Foraminiferal Research. 39: 335-360. gs

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


Protoheterohelix obscura compiled by the pforams@mikrotax project team viewed: 28-9-2022

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