pforams@mikrotax - Planohedbergella

Planohedbergella


Classification: pf_mesozoic -> Globigerinelloididae -> Planohedbergella
Sister taxa: Eohastigerinella, Globigerinelloides, Hastigerinoides, Laeviella, Planohedbergella, Polycamerella, Pseudoschackoina
Daughter taxa (time control age-window is: 0-800Ma)
Planohedbergella aspera

Planohedbergella circularis

Differs from other Planohedbergella species as it has more evolute coiling, greater final whorl and total number of chambers that increase more slowly in size and are nearly equidimensional in the final whorl, its more circular peripheral outline, and its wider umbilicus;
Differs from species included in Laeviella by its coarsely pustulose wall surface texture;
Differs from Plh. impensa by its more rounded peripheral margin, more even distribution of moderate to coarse pustules on the test surface, and absence of costellae on the equatorial periphery;
Differs from Po. tardata n. sp. by its larger size, more lobate peripheral outline and slower chamber expansion rate in the final whorl.
Planohedbergella escheri

Planohedbergella impensa

Planohedbergella messinae

Planohedbergella multispina

Planohedbergella prairiehillensis

Planohedbergella subcarinata

Planohedbergella ultramicra

Planohedbergella yaucoensis

Taxonomy

Citation: Planohedbergella Boudagher-Fadel, Banner, Whittaker, and McCarthy 1997, in Boudagher-Fadel et al. 1997, emend Huber et al. 2022
Rank: Genus
Taxonomic discussion:

The genus Planohedbergella was originally defined by Boudagher-Fadel et al. (1997) as having a macroperforate test wall, but it is not clear what size limits were used to differentiate their macroperforate from microperforate tests. Most likely their definitions followed that of Banner and Desai (1988) with microperforate having pore diameters 5 mm. It is puzzling why Boudagher-Fadel et al. (1997) considered Planohedbergella to be macroperforate when their magnified view of Planomalina ehrenbergi holotype (see Pl. 20, Figs. 6a-c for re-illustration), which is the type species of the genus, clearly shows a finely perforate test wall (Boudagher-Fadel et al. 1997, plate appendix 1, fig. 6). Moreover, the primary type (Pl. 20, Fig. 2d) and metatype (identified by original author; Pl. 20, Fig. 5c) of Globigerinelloides yaucoensis, the senior synonym of Pl. ehrenbergi, have pore diameters that range from 1.1–1.3 mm.

Species included in Planohedbergella are both microperforate and finely perforate with average pore diameters ranging from 0.8–2.0 mm, with the exception of Plh. circularis, which is exclusively finely perforate with pore diameters ranging from 1.6 to 2.0 mm and averaging 1.8 mm (Table 1). Measurement of pore diameters from additional well-preserved specimens is needed to determine whether there is phylogenetic significance to grouping of species that have average pore diameters ranging between 0.8 – 1.2 mm (i.e., Plh. aspera, Plh. multispina, Plh. prairiehillensis, Plh. yaucoensis and Plh. impensa) versus those that have average pore diameters >1.5 mm (i.e., Phl. circularis, Plh. escheri, Plh. messinae, and Plh. subcarinata).

            According to Boudagher-Fadel et al. (1997), Planohedbergella was derived from Hedbergella (=Muricohedbergella in current usage) during the Cenomanian, and their description “planospiral [sic] in adult” implies a possible trochospiral early ontogeny. The authors did not identify the ancestral species that gave rise to the genus or the direct species descendent, and they did not list which species should be included in the genus other than Phanerostomum asperum Ehrenberg, 1854, which they considered significant because it occurs in “the first publication which dealt with the form we are calling Planohedbergella”.

Despite the problematic and ambiguous genus description, we are emending the definition of Planohedbergella since the name is available for use. In the current definition, species included strongly differ in their internal and external test morphology, but all are grouped under Planohedbergella because of their muricate and finely to microperforate wall microstructure. The proposed phylogeny (text-fig. 2) postulates an escheri-messinae-subcarinata evolutionary series but we choose not to distinguish this lineage by naming a new genus because they do not share an evolutionary novelty that would unite them at a higher taxonomic level. There is greater justification for placing Plh. impensa in a new genus because of its very distinct ontogenetic growth morphology and its tendency toward alignment of pustules parallel to the equatorial periphery, but inconsistency in its wall texture and uncertainty in its evolutionary derivation preclude its placement in a new monospecific genus.

Entries in the Catalog of original descriptions: Planohedbergella

Distinguishing features:
Parent taxon (Globigerinelloididae): Test planispiral, chambers globular to radially elongate; aperture at the base of the chamber face and equatorial in position, lateral portions of primary aperture may remain open as new chambers are added, forming relict openings around the umbilical region.
This taxon:

Test planispiral throughout, biumbilicate, peripheral margin rounded to acute; wall micro-finely perforate and muricate throughout; coiling involute to evolute, chambers globular to axially compressed; may be uniapertural or biapertural with bordering lip. Differs from Laeviella by having a muricate rather than smooth test surface; differs from Polycamerella by lacking any infolding of the test wall along the sutural margin of biapertural portici.


Emended description:

Planispiral, biumbilicate with a shallow to wide umbilicus, tests varying from mostly involute to mostly evolute; peripheral outline weakly to strongly lobate, peripheral margin varying from rounded to acute; chamber growth rate highly variable among included species from very gradual to rapid, with 3.5 – 9.5 chambers in the final whorl and from 8–26 total chambers; final chamber may be uni- or bicameral, uniapertural forms with aperture centered on equatorial periphery and extending part way toward umbilicus, biapertural forms with aperture opening near umbilici.

Morphology:

Wall type:
Microperforate to finely perforate with pore diameter of type species averaging 1.2 µm and included species with wall pore diameters averaging from 0.8-2.0 µm; surface with randomly distributed muricae on most or all chambers.

Size:
Dimensions of type species: 314 microns maximum diameter, 136 microns breadth; included species range from 140–490 microns in maximum diameter.

Character matrix
test outline:Circularchamber arrangement:Planispiraledge view:Hourglassaperture:Interiomarginal
sp chamber shape:-coiling axis:-periphery:-aperture border:Thin lip
umb chbr shape:-umbilicus:-periph margin shape:-accessory apertures:None
spiral sutures:-umb depth:Shallowwall texture:-shell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:3.5-9.5 N.B. These characters are used for advanced search. N/A - not applicable

Most likely ancestor: Planomalina - at confidence level 5 (out of 5). Data source: Huber et al 2022 fig. 2.
Likely descendants: Polycamerella; plot with descendants

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Danian stage). Data source: Total of range of species in this database
First occurrence (base): near top of Albian Stage (89% up, 101.9Ma, in Albian stage). Data source: Total of range of species in this database

Plot of range and occurrence data:

References:

BouDagher-Fadel, M. K., Banner, F. T. & Whittaker, J. E. (1997). The Early Evolutionary History of Planktonic Foraminifera. Chapman and Hall, London. -. gs

Huber, B. T., Petrizzo, M. M. & Falzoni, F. (2022). Taxonomy and phylogeny of Albian–Maastrichtian planispiral planktonic foraminifera traditionally assigned to Globigerinelloides. Micropaleontology. 68(2): 117-183. gs


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Planohedbergella compiled by the pforams@mikrotax project team viewed: 5-10-2022

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