Specimens which cannot be assigned to established species
| Daughter taxa (time control age-window is: 0-800Ma) | ||||
| | | Planoheterohelix globulosa | |
| | | Planoheterohelix moremani | |
| | | Planoheterohelix olssoni | |
| | | Planoheterohelix papula | |
| | | Planoheterohelix paraglobulosa | |
| | | Planoheterohelix planata | |
| | | Planoheterohelix postmoremani | |
| | | Planoheterohelix praenuttallii | |
| | | Planoheterohelix reussi | |
| | Planoheterohelix rumseyensis | ||
| species here provisionally placed in Planohetorohelix | ||||
| | | Planoheterohelix labellosa | |
| | | Planoheterohelix sphenoides | |
| Planoheterohelix stenopos | |||
| | | Planoheterohelix vistulaensis | |
| | Planoheterohelix sp. Specimens which cannot be assigned to established species | ||
Taxonomy
Original description: Description. Test is biserial throughout. Proloculus is small and followed by larger second chamber. Chambers are subglobular to globular in early portion of test and often reniform in adult. Periphery is broadly rounded. Aperture is a low- to medium-high arch situated at base of last-formed chamber; it is bordered by two symmetrically developed flanges. Chamber surface is smooth or with fine longitudinal costae in earlier species and completely costate in evolved ones. Test wall is calcitic, hyaline, microperforate to finely perforate. Pores are situated in intercostal spaces or they might penetrate and interrupt costae.
Entries in the Catalog of original descriptions: Planoheterohelix, Globoheterohelix
Distinguishing features: Biserial throughout, aperture symmetrically positioned, wall texture costate.
Emended description: Test is moderate in size and has globular to subglobular chambers that are biserially arranged throughout and become reniform in some species. Proloculus diameters range from 12–72 mm and subsequent chambers increase in size at varying rates. Aperture is a symmetrical semicircular arch at the base of the final chamber. Sutures are depressed and form at an oblique angle to the central axis. Apertural structures vary but typically consist of symmetrical flanges or an imperforate apertural lip. Test wall is calcitic, ornamented with fine, continuous costae and is microperforate to finely perforate (pore diameter 0.6–3.2 µm).
Morphology: Test is moderate in size and has globular to subglobular chambers that are biserially arranged throughout and become reniform in some species. Proloculus diameters range from 12–72 µm and subsequent chambers increase in size at varying rates. Aperture is a symmetrical semicircular arch at the base of the final chamber. Sutures are depressed and form at an oblique angle to the central axis. Apertural structures vary but typically consist of symmetrical flanges or an imperforate apertural lip. Test wall is calcitic, ornamented with fine, continuous costae and is microperforate to finely perforate (pore diameter 0.6–3.2 µm).
Geological Range:
Last occurrence (top): within Maastrichtian Stage (66.04-72.05Ma, top in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): within Cenomanian Stage (93.90-100.50Ma, base in Cenomanian stage). Data source: Total of range of species in this database
Plot of range and occurrence data:
References:
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Planoheterohelix compiled by the pforams@mikrotax project team viewed: 13-6-2021
Short stable page link: https://mikrotax.org/pforams/index.php?id=110399 Go to Archive.is to create a permanent copy of this page - citation notes |