Paleogene larger rotaliid foraminifera from the western and central Neotethys

Abstract

Large Paleogene Rotaliidae all represent moderate K-strategists similar to the nummulitids to which they are associated. They arise as Tethys-wide groups during the Paleocene and reach their highest diversity during the earliest Lower Eocene (SBZ 5). They document a Global Community Maturation cycle that ends for the rotaliids by their disappearance after the Middle Eocene while other groups like the nummulitids and the orthophragminiforms continue up to the Eocene-Oligocene boundary. Under the generic definitions the species are grouped in order to reflect what is supposed to represent a phylogenetic lineage in the order of their appearance in geological time. This meets the demands of an easier taxonomic identification and to reflect in the same time a phylogenetic hypothesis. OverviewLarge Paleogene Rotaliidae belongs to the new subfamilies Daviesininae, Kathininae, Laffitteininae, Cincoriolinae and Lockhartiinae.By their large size, their strong dimorphism and their distribution of canal orifices on the surface of their shells they all represent moderate Kstrategists similar to the nummulitids to which they are associated. Their strategy of life obliges them to adapt rapidly to the changing conditions in shallow water. They arise as Tethys-wide groups during the Paleocene and reach their highest diversity during the earliest Lower Eocene (SBZ 5). Later, the representatives of the lockartiines, Lockhartia, Dictyoconoides and Sakesaria, dominate the rotaliid associations and sometimes the complete shallow benthic communities. The rotaliid distribution pattern on the time scale reflects the basic rules of global community maturation (GCM) cycles, that is: (a) preparing the metabolism for K-strategy, (b) experimenting with ways of life, (c) revelling in success, (d) gaining size and endemism. Thus, they document a GCM cycle that ends for the rotaliids by their disappearance after the Middle Eocene while other groups like the nummulitids and the orthophragminiforms continue up to the Eocene-Oligocene boundary. In the Middle Eocene already the first K-strategists of the conservative neorotalias appear with a new species that has microspheric specimens with incomplete chamberlet cycles like a L. Hottinger, Paleogene larger rotaliid foraminifera from the western and central Neotethys,

Early Eocene orthophragminids (Foraminifera) from the type-locality ofDiscocyclina ranikotensisDavies, 1927, Thal, NW Himalayas, Pakistan: insights into the orthophragminid palaeobiogeography

“…The LBF in the early Palaeogene shallow-marine sediments of Himalayan belt play an important role in understanding the distribution of foraminiferal communities along the northern margin of Indian Plate, and their distribution and interaction in Tethys (Adams, 1983;Afzal et al, 2010;Haynes et al, 2010;Hottinger, 2009Hottinger, , 2014Zhang et al, 2013). It is generally agreed that LBF assemblages from Indo-Pakistan (eastern Tethys) and peri-Mediterranean regions (western Tethys) differ partly from each other across the P/E boundary, resulting in the formation of bioprovinces across the Tethys Hottinger, 1998Hottinger, , 2009Hottinger, , 2014.…”

“…The late Paleocene to early Eocene larger benthic foraminifera (LBF) in shallow marine sediments of Tethyan Himalayas are represented by LockhartiaRanikothalia-Miscellanea-Daviesina communities which serve as index fossils for so called 'Lockhartia Sea' reaching in Asia from Tibet to southern Turkey, in Africa from Somalia to Egypt (Hottinger, 2009(Hottinger, , 2014. The LBF assemblages of the 'Lockhartia Sea', an eastern Tethyan biogeographic province, have been extensively studied from Paleocene and early Eocene sediments in Pakistan, India, Tibet and Oman, although orthophragminids still remain poorly known (Afzal, Williams, Leng, Aldridge, & Stephenson, 2010;Davies, 1927;Davies & Pinfold, 1937;Eames, 1951aEames, , 1951bHaynes, Racey, & Whittaker, 2010;He, Zhang, Hu, & Sheng, 1976;Hottinger, 2009Hottinger, , 2014Racey, 1995;Zhang, Willems, & Ding, 2013).…”

“…The LBF assemblages of the 'Lockhartia Sea', an eastern Tethyan biogeographic province, have been extensively studied from Paleocene and early Eocene sediments in Pakistan, India, Tibet and Oman, although orthophragminids still remain poorly known (Afzal, Williams, Leng, Aldridge, & Stephenson, 2010;Davies, 1927;Davies & Pinfold, 1937;Eames, 1951aEames, , 1951bHaynes, Racey, & Whittaker, 2010;He, Zhang, Hu, & Sheng, 1976;Hottinger, 2009Hottinger, , 2014Racey, 1995;Zhang, Willems, & Ding, 2013). The previous records of orthophragminids in 'upper Paleocene' -lower Eocene sediments in Pakistan mostly refer only to Discocyclina ranikotensis Davies, 1927, a poorly known species considered to be endemic to Tethyan Himalayas in Indo-Pakistan region, suggesting a less diverse character of eastern Tethys orthophragminids compared to those of western Tethys in this time span.…”

“…Many new species of 'Lockhartia Sea' have been described from this unit in Thal area and Salt Range in north Pakistan (Davies, 1927;Davies & Pinfold, 1937), which later became index taxa on a regional scale Haynes et al, 2010;He et al, 1976;Hottinger, 2009Hottinger, , 2014Nagappa, 1959;Racey, 1995;Smout, 1954;Smout & Haque, 1956;Zhang et al, 2013). Davies (1927) noted the occurrence of orthophragminids in the Patala Formation ('upper Ranikot beds' of Davies, 1927) from the Thal area and erected D. ranikotensis based on its supposedly larger embryon than that of D. archiaci, which according to him, had been only known from Europe.…”

“…Consequently, species definitions for the orthophragminid taxa, thought to be endemic to Indo-Pakistan region, have yet to be clearly established. This has further implications that the proposed LBF diversity and distribution models by Hottinger (2014) in 'Lockhartia Sea' are incomplete in the absence of detailed taxonomical works on orthophragminids, closely associated with nummulitids and rotaliids in eastern Tethys.…”