pforams@mikrotax - Polycamerella

Polycamerella


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

Differs from all species of Planohedbergella and Laeviella by having: (1) consistent presence of a biapertural final chamber bearing broad, low apertural slits that open along the outer margin of the umbilicus and are bordered by infolding tubular apertural flaps that usually project directly into the umbilicus, (2) a more weakly lobate peripheral outline, (3) the slowest, continuously log-linear chamber expansion rate (text-figs. 4a, 4e, 6), and (4) the greatest total number of chambers in the adult test (average = 23).


Taxonomy

Citation: Polycamerella Huber & Petrizzo, in Huber et al 2022
Rank: Genus
Taxonomic discussion:

X-ray images of Po. tardata (Pl. 21, Figs. 1c, 2c, 5c) elegantly capture details of the ontogenetic profile, showing the very slow and uniform chamber expansion rate, evolute coiling, and curvature of the sutures. The 14 mm average diameter of measured proloci is similar to most species, but the average of 6.8 chambers surrounding the proloculus is higher than most other species. Magnified views of the test wall (Pl. 21, Figs. 1d, 3c) show the fine perforations and small, blunt muricae that are evenly distributed on the test wall.

Original description:

Type of wall: Finely perforate with pores averaging 1.9 mm and ranging from 1.1–2.4 mm, wall surface with randomly scattered, fine muricae.

 Test morphology: Test planispirally coiled, biumbilicate, moderately evolute with a relatively broad, shallow umbilicus (UD:TD ratio average 0.31), equatorial outline weakly lobate, subcircular in peripheral outline with a rounded to subrounded peripheral margin, symmetrical in edge view, always biapertural; chambers weakly inflated, enlarging very slowly in size (y = 0.092x + 1.77) with uniform, log-linear growth throughout ontogeny (text-figs. 4a, 4e, 6), 22–23 total chambers in adult specimens usually coiled in 2.5 whorls (e.g., Pl. 21, Figs. 1c, 2c, 5c), average of 7.7 chambers and range of 7.0–8.5 chambers in the final whorl (Table 1), kummerform chambers rare (UCL:PCL ratio average 1.0); sutures slightly curved, weakly depressed; final chamber biapertural with a low arch or slit opening into the umbilicus, may show inward flexure along suture (Pl. 21, Figs. 1a, 3a, 5a, 6a, 8, 9a), bordered by a narrow, imperforate flap that extends into the umbilicus connecting with previous chambers, and may become outwardly folded and tubular shaped (e.g., Pl. 21, Figs. 1a, 3a, 5a, 6a, 11); relict apertures and apertural flaps visible surrounding the umbilicus.

Entries in the Catalog of original descriptions: Polycamerella

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:

Differs from all species of Planohedbergella and Laeviella by having: (1) consistent presence of a biapertural final chamber bearing broad, low apertural slits that open along the outer margin of the umbilicus and are bordered by infolding tubular apertural flaps that usually project directly into the umbilicus, (2) a more weakly lobate peripheral outline, (3) the slowest, continuously log-linear chamber expansion rate (text-figs. 4a, 4e, 6), and (4) the greatest total number of chambers in the adult test (average = 23).


Emended description:


Morphology:

Planispiral, biumbilicate, moderately evolute, peripheral outline weakly lobate, peripheral margin rounded to subrounded; chambers weakly inflated, increasing very slowly in size, 7.0–8.5 in final whorl; final chamber always biapertural with broad, low apertures opening into umbilicus and bordered by a narrow, imperforate flap that usually terminates in a tube-shaped hood; relict supplementary apertures and apertural flaps visible surrounding the umbilicus.


Wall type:
Finely perforate with pore diameter averaging 1.9 m and ranging from 1.1- 2.4 m, wall surface with randomly scattered muricae.

Size:
Type species maximum diameter 252 microns, maximum breadth 110 microns; paratype maximum diameter 234 microns, maximum breadth 95 microns, range 116–139 microns; hypotypes maximum diameter average 231 microns and range from 202–277 microns.

Most likely ancestor: Planohedbergella - at confidence level 0 (out of 5). Data source: Huber et al 2022 fig. 2.

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): in upper part of Campanian Stage (63% up, 76.3Ma, in Campanian stage). Data source: Total of range of species in this database

Plot of range and occurrence data:

References:

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

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Short stable page link: https://mikrotax.org/pforams/index.php?id=110599 Go to Archive.is to create a permanent copy of this page - citation notes



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