Early Cretaceous non‐marine Ostracoda from theNorthFalklandBasin,SouthAtlantic

Abstract

Twenty-seven species of well-preserved and abundant Early Cretaceous non-marine ostracod crustaceans were recovered from the North Falkland Basin. The assemblage is unusually diverse for a non-marine palaeoenvironment and is sourced from cuttings samples collected during 2011 drilling of wells by Desire and Rockhopper Exploration, in the northern and southern areas of the basin. Ostracoda are entirely undocumented in published accounts from this basin, and all but one species appear to be new to science. For the new taxa, one new family (Alloiocyprideidae; type genus Hourcqia) is proposed and includes Hourcqia woodi sp. nov. Four new genera are erected: Falklandicypris gen. nov.; type species F. petrasaltata sp. nov., Gangamoncythere gen. nov.; type species G. colini sp. nov., Paraplesiocypridea gen. nov.; type species P. alloios sp. nov., and Musacchiocythere gen nov.; type species M. sarunata (Musacchio, 1978). Nine other species are described as new and are Falklandicypris desiderata, Clinocypris epacrus, Cypria poietes, Ilhasina? leiodermatus, Looneyellopsis tuberculatus, Theriosynoecum petasmathylacus, Theriosynoecum ballentae, Timiriasevia fluitans, and Vecticypris samesi. The remainder are left in open nomenclature due to paucity of material. The ostracod assemblage is largely restricted to the southern part of the basin (wells 25/5-1 and 26/6-1). In the northern part of the basin only four species, dominated by Vecticypris samesi, are present and with one possible exception are restricted there. There appears to have been little or no interchange of species suggesting that a barrier probably existed between the northern and southern regions. The more diverse southern assemblage indicates that more favourable conditions existed to the south. Stratigraphically, a distinct change in faunal composition recorded in both southern wells is likely to be an isochronous event correlatable across the southern area, and of an age no younger than Hauterivian.

Integrated biostratigraphy and chemical stratigraphy in the development of a reservoir-scale stratigraphic framework for the Sea Lion Field area, North Falkland Basin

“…In the NRB (containing the Sea Lion Field), ostracods are relatively rare, and there appears to be little in common with the Southern Rift Basin (SRB) in terms of species composition and abundance (Ayress & Whatley 2014). In the northern (Sea Lion) area there is a peak abundance of Vecticypris samesi (Plate 1, figs 20-22) and this is usually the only event (and taxon) seen within the Table 1.…”

“…The timescale follows Gradstein et al (2012) Valanginian?-Aptian interval. This facies-influenced event is not considered to have regional chronostratigraphic significance and, as this species is newly described (Ayress & Whatley 2014), its age significance is unknown. In addition to taxa with previously described stratigraphic ranges, other events, particularly algal, provide consistent and robust correlative markers.…”

Nonmarine ostracod fauna from the Lower Cretaceous Shinekhudag Formation (southwest Mongolia): taxonomy, biostratigraphy, and paleoecology

“…Trapezoidella sp. The elongate and thick lateral ridge is also confirmed in several trapezoidellid species, such as Falklandicypris petrasaltata Ayress and Whatley, 2014 from the North Falkland Basin, South Atlantic, and Limnocypridea bitumulosa Lübimova, 1956 from Mongolia. However, except for the existence of a lateral ridge, they are totally different in shape.…”

“…However, because it lacks a rostrum and alveolar notch, this subgenus has been excluded from the genus Cypridea as well as from the family Cyprideidae (e.g., Horne and Colin, 2005; Sames, 2011b). Yumenia has been placed into the Trapezoidellidae Sohn, 1979 (Nikolaeva and Neustrueva, 1999) or the Alloiocyprideidae Ayress and Whatley, 2014 (Wang et al, 2017b). Many representatives of the family Trapezoidellidae are, however, very different from Yumenia in carapace shape and local and area-wide ornamentation elements.…”

Ostracoda from the Santonian–Campanian (Upper Cretaceous) Nenjiang and Sifangtai formations, Songliao Basin, northeastern China

“…The record of the group extends back to the Ordovician, which coupled with their abundant fossil record ecology and dispersal mechanisms makes them good index fossils for biostratigraphy (Meisch, 2000; Horne, 2002, 2009; Sames, 2011a, b, d; Sames and Horne, 2012; Xi et al, 2012; Wang et al, 2016, 2017; Do Carmo et al, 2018). Cretaceous limnic ostracodes have been widely studied worldwide (e.g., Anderson, 1941, 1985; Netchaeva et al, 1959; Horne, 1995, 2002, 2009; Hou et al, 2002; Ye et al, 2002; Hayashi, 2006; Whatley and Bajpai, 2006; Khand et al, 2007; Do Carmo et al, 2008, 2013; Sames, 2008, 2011a, b; Antonietto et al, 2012; Poropat and Colin, 2012a, b; Sames and Horne, 2012; Ayress and Whatley, 2014; Tomé et al, 2014; Choi et al, 2017). However, ostracode fossils from the early- to mid-Late Cretaceous remain less understood, despite strata of such age being broadly distributed throughout terrestrial successions in China.…”