Nannotax3 - ntax_cenozoic - Tribrachiatus orthostylus

Citation: Tribrachiatus orthostylus Shamrai, 1963

Synonyms:

Discoaster tribrachiatus Bramlette & Riedel 1954
Marthasterites tribrachiatus (Bramlette & Riedel 1954) Deflandre 1959
Discoaster rotans Stradner 1959 [cf. Bramlette & Sullivan 1961]
Rhomboaster orthostylus (Shamrai 1963) Bybell & Self-Trail 1995

Variants:

Rhomboaster weii Bybell & Self-Trail 1997 [heavily calcified form]
forms with one ray reduced - T. absidatus and T. lunatus of Self-Trail et al. 2017. These are arguably variants of T. orthostylus. According to Self-Trail et al. (2017) they are absent in the lower part of the range of the species (NP10) but go extinct at the same time as T. orthostylus (i.e. at end NP12).

Taxonomic discussion: The name T. orthostylus is "nom. subst. pro Discoaster tribrachiatus Bramlette & Riedel ; see ICBN Art. 55" according to Loeblich & Tappan 1966). This is probably because the combination Tribrachiatus tribrachiatus would have been a tautonym (both parts the same) which is not permitted under the ICBN. The type specimen and description of T. orthostylus is thus that of D. tribrachiatus.

Distinguishing features:
Parent taxon (Tribrachiatus): Solid nannoliths with three rays that typically have terminal bifurcations.
This taxon: Large, single-cycle tri-radiate nannoliths with little or no ray end bifurcation (<25% of the total arm length).

Geological Range:
Last occurrence (top): within NP12 zone (50.50-53.70Ma, top in Ypresian stage). Data source: Perch-Nielsen 1985b
First occurrence (base): near top of NP10 zone (90% up, 54.3Ma, in Ypresian stage). Data source: Agnini et al. 2007 fig 8, 9

References:

Agnini, C., Fornaciari, E., Raffi, I., Rio, D., Rohl, U. & Westerhold, T. (2007a). High-resolution nannofossil biochronology of middle Paleocene to early Eocene at ODP Site 1262: Implications for calcareous nannoplankton evolution. Marine Micropaleontology. 64: 215-248. gs

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs O

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs O

Bramlette, M. N. & Riedel, W. R. (1954). Stratigraphic value of discoasters and some other microfossils related to Recent coccolithophores. Journal of Paleontology. 28: 385-403. gs

Bramlette, M. N. & Sullivan, F. R. (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology. 7(2): 129-188. gs

Bybell, L. M. & Self-Trail, J. (1995). Evolutionary, biostratigraphic and taxonomic study of calcareous nanofossils from a continuous Palaeocene-Eocene boundary section in New Jersey. U.S. Geological Survey, Professional Paper. 1554: 1-36. gs O

Bybell, L. & Self-Trail, J. (1997). Late Paleocene and Early Eocene calcareous nannofossils from three boreholes in an onshore-offshore transect from New Jersey to the Atlantic continental rise. Proceedings of the Ocean Drilling Program, Scientific Results. 150: 91-110. gs O

Loeblich, A. R. & Tappan, H. (1966). Annotated index and bibliography of the calcareous nannoplankton. Phycologia. 5: 81-216. gs

Perch-Nielsen, K. (1967). Nannofossilien aus dem Eozan von Danemark. Eclogae Geologicae Helvetiae. 60: 19-32. gs O

Perch-Nielsen, K. (1971c). Elektronenmikroskopische untersuchungen an Coccolithen und verwandten Formen aus dem Eozan von Danemark. Biologiske Skrifter, Kongelige Danske Videnskabernes Selskab. 18(3): 1-76. gs O

Perch-Nielsen, K. (1985). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge (1): 427-555. gs

Perch-Nielsen, K., Sadek, A., Barakat, M. G. & Teleb, F. (1978). Late Cretaceous and Early Tertiary Calcareous nannofossil and Planktonic foraminifera zones from Egypt. Actes du VI Colloque Africain de Micropaléontologie - Tunis 1974. Annales des Mines et de la Géologie Tunissienne. 28: 337-403. gs

Pospichal, J. J. & Wise, S. W. (1990). Paleocene to Middle Eocene calcareous nannofossils of ODP sites 689 and 690, Maud Rise, Weddell Sea. Proceedings of the Ocean Drilling Program, Scientific Results. 113: 613-638. gs

Salomon, R. (1999). The Calcite Palace. Website - https://ina.tmsoc.org/galleries/CalcitePalace/index.htm. -. gs

Self-Trail, J. (2011). Paleogene Calcareous Nannofossils of the South Dover Bridge core, Southern Maryland (USA). Journal of Nannoplankton Research. 32(1): 1-28. gs

Self-Trail, J. M., Powars, D. S., Watkins, D. K. & Wandless, G. A. (2012). Calcareous nannofossil assemblage changes across the Paleocene–Eocene Thermal Maximum: Evidence from a shelf setting. Marine Micropaleontology. 92–93: 61-80. gs

Self-Trail, J., Seefelt, E. L., Shepherd, C. L. & Martin, V. A. (2017). Biostratigraphic and morphometric analyses of specimens from the calcareous nannofossil genus Tribrachiatus. Journal of Nannoplankton Research. 37(2-3): 177-188. gs

Shamrai, I. A. (1963). Nekotorye formy verkhnemelovykh i paleogenovykh kokkolitov i disko_asterov na yuge russkol platformy [Certain forms of Upper Cretaceous and Paleogene coccoliths and discoasters from the southern Russian Platform]. Izvestiya Vysshikh Uchebnykh Zavedeniy Geologiya i Razvedka. 6(4): 27-40. gs

Shepherd, C. L. & Kulhanek, D. K. (2016). Eocene nannofossil biostratigraphy of the mid-Waipara River section, Canterbury Basin, New Zealand. Journal of Nannoplankton Research. 36(1): 33-59. gs O

Steurbaut, E. (1990). Ypresian calcareous nannoplankton biostratigraphy and palaeogeography of the Belgian Basin. Bulletin de la Société Belge de Géologie. 97(1988): 251-285. gs

Varol, O. (1989b). Eocene calcareous nannofossils from Sile (northwest Turkey). Revista Española de Micropaleontología. 21: 273-320. gs

Varol, O. (1998). Palaeogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 200-224. gs

Wise, S. W. & Wind, F. H. (1977). Mesozoic and Cenozoic calcareous nannofossils recovered by DSDP Leg 36 drilling on the Falkland Plateau, south-west Atlantic sector of the Southern Ocean. Initial Reports of the Deep Sea Drilling Project. 36(269-491): -. gs O

Tribrachiatus orthostylus

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