Eocene bryozoan assemblages from the La Meseta Formation of Seymour Island, Antarctica

Abstract

Early to Late Eocene bryo zoans from the La Meseta For ma tion of Sey mour Is land were col lected at two lo cal i ties within the Cucullaea I Allomember (Telm4 and Telm5) on the northwest ern side of the is land and in two lo cal i ties within the Submeseta Allomember (Telm6 and Telm7) on the northeast ern side. This fauna is rep re sented by cyc lo stomes of the suborders Tubuliporina and Cerioporina and suborders of Neocheilostomata, among which nine spe cies have been rec og nized. The fol low ing new spe cies are in tro duced: Micropora nordenskjoeldi sp. nov., Lunulites marambionis sp. nov., Otionellina antarctica sp. nov. and Otionellina eocenica sp. nov. Some other taxa rec og nized in the stud ied ma te rial, such as Reticrescis plicatus, Uharella seymourensis and Celleporaria mesetaensis, were pre vi ously de scribed from the low er most (Telm1) or up per most parts (Telm6-7), thus their strati graphi cal ranges within the La Meseta For ma tion are ex tended. The di verse growth-forms of the bryo zoans in clude a sole ball-shaped celleporiform col ony and re tic u lated and bilamellar-foliaceous colony, as well as rich en crust ing and free-liv ing forms (so-called sand fau nas), in di cat ing the ex is tence of lo cally re stricted shal low-ma rine en vi ron ments. This is par tic u larly true in the mid dle and up per parts of the La Meseta For ma tion (Telm4-7). Re tic u lated, sphe roi dal and ro bust, branched col o nies, which thrived in the en vi ron men tal con di tions of the lower part (Telm1), are rep re sented only by a sparse bryo zoan biota in the up per part of the La Meseta For ma tion. Lunulitiforms, such as Lunulites and Otionellina which are warm wa ter, free-liv ing bryo zoans, dom i nate in the siliciclastic sed i ments of Telm5, but erect folded sheets form ing a shell bed com posed of ?Goodonia oc cur in Telm6-7. These three gen era are rec og nized in Antarctica for the first time. The aus tral ge nus Otionellina has its ear li est fos sil re cord here, show ing close biogeographical links with the Late Eocene-Mio cene fau nas of Aus tra lia and New Zea land. The tax o nomic com po si tion of the stud ied fauna to gether with their growth forms is a very good tool for re con struct ing palaeoenvironmental con di tions in the mid dle and upper parts (Telm4-7) of the La Meseta For ma tion, de pos ited dur ing the Late Ypresian-Priabonian.

Earliest fossils of giant-sized bony-toothed birds (Aves: Pelagornithidae) from the Eocene of Seymour Island, Antarctica

“…( b ) Generalized geologic map of Seymour Island (modified from Montes et al 13 ). Numbers indicate localities containing Antarctic pelagornithid specimens: 1: UCMP RV8405 (present study); 2: DPV 13/84 61 ; 3: Specimen MLP 78-X-26-1; 4: IAA 1/95 62 ; 5: IAA 1/90 62 ; 6: UCMP RV8702 47 , 63 (present study); and 7 : Specimen USNM 494035 37 , 42 . Uncertainty in the placement of MLP 78-X-26-1 is explained in the text.…”

Lunulite bryozoan biogeography – a convergent global success with a distinct Western Australian twist

“…And considering the assumed short-lived larval stages of modern lunulite taxa, this alternative would indeed seem more attractive. Three lunulite bryozoans recently described from the mid Ypresian of the Antarctic Peninsula (Hara et al 2018) offer some support to the existence of this connection, although just a single species -Otionellina antarctica Hara, Mörs, Hagström & Reguero, 2018 -is potentially showing any relation to the core Austral province. Nevertheless, the mere presence of a free-living Antarctic fauna clearly demonstrates that suitable habitats were present, hence providing supporting evidence for a trans-Antarctic route of migration between the Austral Realm and South America along the West Antarctica archipelago (Casadio et al 2010; our Fig.…”

“…7), it appears possible that the second entity of this geographically restricted and currently unnamed family may share a common ancestry with the Selenariidae. Schmidt 2007), from the Oligocene -Recent in New Zealand (Bock & Cook, 1999), and from the Late Oligocene to Middle Miocene in southern South America (Canu 1904;Pérez et al 2015; EH collections), as well as -possibly -from the Early Eocene in Antarctica (Hara et al 2018;their fig. 7, only).…”

Polish Polar Research

“…Nonetheless, the modern weathering zone over the Paleogene organic-rich mudstones of Seymour Island, including the lower portion of the La Meseta Formation, is characterized by a microbially induced oxidation of sulfides that can potentially generate sulfuric acid during weathering (Tatur et al 1993) and constitute a more plausible source for such hypothetical acid fluids. Moreover, this weathering condition was probably already present during the Eocene (Tatur et al 2011) and may have been an important factor behind the dissolution of the La Meseta Formation calcareous microfossils.…”