Revalidation of the genus Chiloguembelitria Hofker: Implications for the evolution of early Danian planktonic foraminifera

Abstract

Guembelitria is the only planktonic foraminiferal genus whose survival from the mass extinction event of the Cretaceous/Paleogene (K/Pg) boundary has been clearly proven. The evolution of Guembelitria after the K/Pg boundary led to the appearance of two guembelitriid lineages in the early Danian: one biserial, represented by Woodringina and culminating in Chiloguembelina, and the other trochospiral, represented by Trochoguembelitria and culminating in Globoconusa. We have reexamined the genus Chiloguembelitria, another guembelitriid descended from Guembelitria and whose taxonomic validity had been questioned, it being considered a junior synonym of the latter. Nevertheless, Chiloguembelitria differs from Guembelitria mainly in the wall texture (pustulate to rugose vs. pore-mounded) and the position of the aperture (umbilical-extraumbilical to extraumbilical vs. umbilical). Chiloguembelitria shares its wall texture with Trochoguembelitria and some of the earliest specimens of Woodringina, suggesting that it played an important role in the evolution of early Danian guembelitriids, as it seems to be the most immediate ancestor of both trochospiral and biserial lineages. Morphological and morphostatistical analyses of Chiloguembelitria discriminate at least five species: Chg. danica, Chg. irregularis, and three new species: Chg. hofkeri, Chg. trilobata and Chg. biseriata.

No Cretaceous‐Paleogene Boundary in Exposed Rajahmundry Traps: A Refined Chronology of the Longest Deccan Lava Flows From40Ar/39Ar Dates, Magnetostratigraphy, and Biostratigraphy

“…Guembelitria might be the only surviving planktic foraminiferal genus of the end‐Cretaceous mass extinction (Arenillas & Arz, 2017; Smit, 1982). Nevertheless, the highest occurrence of the genus Guembelitria is in the lower part of Zone Pα, as has been recently proposed by Arenillas et al (2018), and it is subsequently replaced by species of the genus Chiloguembelitria (Arenillas et al, 2017). If the carbonate intertrappean unit belongs to Subzone P1b, then the G. cretacea specimen found in GQN12 is reworked and probably Cretaceous in age.…”

Blooms of aberrant planktic foraminifera across the K/Pg boundary in the Western Tethys: causes and evolutionary implications

“…A second acme of triserials is identified in the lower part of PFAS-3, that is, in the transition between the Pv. eugubina and P. pseudobulloides Zones (Arenillas et al 2017). This acme has been attributed to the genus Chiloguembelitria Hofker, 1978, not Guembelitria , and spans approximately from 70 to 200 Kyr according to the GTS12.…”

“…The systematic scheme in Supplementary Figure 1 is a good reflection of the morphological and textural diversity that appeared after the extinction event. As illustrated in Figure 1, the planktic foraminifera evolutionary radiation of the early Danian happened in two pulses (see also Arenillas et al 2000a,b, 2017; Arenillas and Arz 2017). The first occurred between approximately 5 and 26 Kyr after the K/Pg boundary according to the GTS12, with the appearance of tiny, trochospiral species belonging to the parvularugoglobigerinids ( Pseudocaucasina , Palaeoglobigerina , and Parvularugoglobigerina ) and biserial taxa ( Woodringina and Chiloguembelina ), as well as triserial species of the genus Chiloguembelitria (Supplementary Figs.…”

“…1), because the abnormal morphologies among guembelitriids are of another kind. Arenillas et al (2017) attributed irregularis to the genus Chiloguembelitria instead of Guembelitria , on the basis of differences in the wall texture and position of the aperture. Chiloguembelitria irregularis groups Danian specimens with twisted triserial arrangements of irregular appearance, corresponding to the irregular morphophase of the model of Tyszka (2006).…”

“…Guembelitria comprised opportunistic species whose relative abundance strongly increased in ecological stress conditions, mainly related to eutrophication episodes (see e.g., Keller and Pardo 2004). Chiloguembelitria replaced Guembelitria in the early Danian, occupying a similar ecological niche (Arenillas et al 2017), so its blooms indicate similar conditions of ecological stress. Maxima in aberrant specimens thus seem to coincide with guembelitriid blooms in the early Danian, as occurs in PFAS-1 and the lower part of PFAS-3.…”