Wall texture classification of planktonic foraminifera genera in the lower Danian
Additional Document Info
The early Danian planktonic foraminifera from Zones P0, P-alpha, and P1a can be classified into four groups based on surface wall texture: microperforate, normal perforate smooth-walled, normal perforate cancellate non-spinose, and normal perforate cancellate spinose. One new genus, Praemurica, is erected for the cancellate nonspinose group and another new genus, Parasubbotina, is erected for species in the pseudobulloides lineage within the cancellate spinose group. Only two Cretaceous genera, Guembelitria s.l. and Hedbergella, are believed to have given rise to the early Danian planktonic foraminifera, Guembelitria to the microperforate group and Hedbergella to the smooth-walled and cancellate groups. No other Cretaceous planktonic foraminifera are involved in the phylogeny of the Danian planktonic foraminifera. The microperforate taxa are the most diverse group in the Danian and include the genera Parvularugoglobigerina, Guembelitria, Woodringina, Chiloguembelina, and Globoconusa and are included in the Superfamily Heterohelicacea. This group rapidly declined and most species became extinct before the end of the Danian. The great radiations of planktonic foraminifera of the Paleogene and Neogene are linked to the three other groups. The genera (with at least fifteen species) recognized in these groups include Globanomalina (smooth-walled), Praemurica (cancellate nonspinose), and Eoglobigerina, Parasubbotina, and Subbotina (cancellate spinose) which are placed in the Superfamily Globigerinacea. The absence or rarity of cancellate wall species in lowermost Danian sections such as at El Kef is most probably due to lack of preservation.