New evidence on the origin of non-spinose pitted–cancellate species of the early Danian planktonic foraminifera

Abstract

Intermediate forms identified in some of the most continuous lower Danian sections allow a better understanding of the origin and evolution of pitted (Globanomalina) and cancellate (Praemurica) planktonic foraminifera. Both Globanomalina and Praemurica are part of a major Paleocene lineage, namely the "non-spinose lineage", which started to diverge in the early Danian. Transitional specimens strongly suggest the evolution from Parvularugoglobigerina to Globanomalina, and then to Praemurica. These evolutionary turnovers were quite rapid (probably lasting less than 10 kyr), and seem to have begun in the time equivalent of the lower part of the E. simplicissima Subzone, namely the middle part of the standard Zone Pa. The initial evolutionary trends within this non-spinose lineage were the increase of test size and lip thickness, and the evolution from tiny pore-murals to large pore-pits, and from smooth to pitted and finally cancellate walls. Biostratigraphic data suggest that evolution of the wall texture preceded the morphological evolution within each genus. The oldest species of both Globanomalina and Praemurica, namely G. archeocompressa and Pr. taurica, initially retained the external morphology of the ancestral Parvularugoglobigerina eugubina. Since their divergence, Globanomalina and Praemurica followed a separate evolutionary path, evolving into morphologically different species.

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

“…The first occurred between approximately 5 and 20 kyr after the K/Pg boundary (Arenillas et al 2016b), with the appearance of species belonging to the parvularugoglobigerinids (Parvularugoglobigerina Hofker, 1978, andPalaeoglobigerina Arenillas, Arz andNáñez, 2007) and biserial taxa (Woodringina Tappan, 1957, andChiloguembelina Loeblich andTappan, 1956). The second evolutionary radiation occurred between approximately 37 and 80 kyr after the K/Pg boundary, giving rise to species belonging to Trochoguembelitria Arenillas, Arz and Náñez, 2012, Eoglobigerina Morozova, 1959, Parasubbotina Olsson, Berggren and Liu, 1992, Globanomalina Haque, 1956, and Praemurica Olsson, Hemleben, Berggren and Liu 1992(Arenillas et al 2010, 2012Arenillas and Arz 2013a, 2013b, 2016a. Other genera appear shortly afterwards, such as Subbotina Brotzen andPozaryska, 1961, andGloboconusa Khalilov, 1956. One of the presumed ancestors of the earliest Danian taxa was Guembelitria Cushman, 1933, the only planktonic foraminiferal genus whose survival from the K/Pg mass extinction event has been clearly proven (Smit 1982;Olsson et al 1999;Arenillas et al 2000a;Ashckenazi-Polidova et al 2014;Arenillas et al 2016a).…”