Lopez de Bertodano Formation

Lopez de Bertodano Formation Stratigraphic range: Maastrichtian to Danian 70 to 65.5 Ma
Type	Geological formation
Unit of	Marambio Group
Underlies	Sobral Formation
Overlies	Snow Hill Island Formation
Lithology
Primary	siltstone, mudstone
Other	concretion, sandstone
Location
Region	Seymour Island, James Ross Island group
Country	Antarctica

The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous (upper-lower Maastrichtian stage^[1]) to the Danian stage of the lower Paleocene, about 70-65.5 million years ago.^[2]

Dinosaur remains are among the fossils that have been recovered from the formation^[3] and include at least two and probably as much as six lineages of indisputably modern birds: one related to waterfowl, a primitive shorebird or related form, 1-2 species of possible loons, a large and possibly flightless bird belonging to a lineage extinct today as well as a partial skull that might belong to either of the smaller species or represent yet another one. The formation also contains a rich fossil invertebrate fauna, including bivalves, gastropods,^[4] and cephalopods (ammonites and nautiloids^[5]).

The Cretaceous-Paleogene boundary (K-Pg) outcrops on Seymour Island in the upper levels of the López de Bertodano Formation.^[6] A small (but significant) iridium anomaly occurs at the boundary on Seymour Island, as at lower latitudes, thought to be fallout from the Chicxulub impactor in the Gulf of Mexico.^[7] Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event.^[6] Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction,^[8] but the extent to which these affected marine biodiversity is debated. Based on extensive marine fossil collections from Seymour Island, recent work has confirmed that a single and severe mass extinction event occurred at this time in Antarctica just as at lower latitudes.^[9]

Dinosaurs of the Lopez de Bertodano Formation
Genus	Species	Unit	Material	Notes	Images
Polarornis[3]	P. gregorii[3]	Lower Sandwich Bluff Member	Partial skull and skeleton, holotype	A loon?
	P.? sp.	Lower Sandwich Bluff Member	Partial skeleton including wing and hindlimbs	Possibly a more primitive form with strong flight ability and lighter bones
Vegavis	V. iaai[10]	Lower Sandwich Bluff Member	Partial skeleton, holotype	An anseriform
Undescribed Cariamae[11]	Unnamed species	Cape Lamb Member	Isolated femur	Close relative of cariamids and phorusrhacids
Undescribed charadriiform[12]	Unnamed species	Cape Lamb Member	Partial skeleton
Unidentified Neornithes[13]	Unnamed species		Partial skull	Relationships undetermined, cranium some 5–6 cm long.
Morrosaurus[14]	M. antarcticus[14]
Undescribed hadrosaurid[1]	Unnamed species		Isolated tooth[1]
Undescribed non-avian theropod[1]	Unnamed species		Fragments[1]

See also

• List of dinosaur-bearing rock formations

References

1. Olivero, E.B., Ponce, J.J., Marsicano, C.A. and Martinioni, D.R. (2007). "Depositional settings of the basal Lopez de Bertodano Formation, Maastrichtian, Antarctica." Revista de la Asociación Geológica Argentina, 62(4): 521-529.
2. Bowman, V.; Ineson, J.; Riding, J.; Crame, J.; Francis, J.; Condon, D.; Whittle, R.; Ferraccioli, F. (2016). "The Paleocene of Antarctica: Dinoflagellate cyst biostratigraphy, chronostratigraphy and implications for the palaeo-Pacific margin of Gondwana". Gondwana Research. 38. doi:10.1016/j.gr.2015.10.018.
3. Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, Antarctica)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. p. 606. ISBN 0-520-24209-2.
4. Crame, J.A.; Beu, A.G.; Ineson J.R.; Francis J.A.; Whittle R.J.; Bowman V.C. (2014). "The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications". PLOS ONE. 7. doi:10.1371/journal.pone.0114743.
5. Witts, J.D.; Bowman V.C.; Wignall P.B.; Crame J.A.; Francis, J.E.; Newont, R.J. (2015). "Evolution and extinction of Maastrichtian (Late Cretaceous) cephalopods from the López de Bertodano Formation, Seymour Island, Antarctica". Palaeogeography, Palaeoclimatology, Palaeoecology. 418: 193–212. doi:10.1016/j.palaeo.2014.11.002.
6. Zinsmeister, W.J. (1998). "Discovery of fish mortality horizon at the K-T Boundary on Seymour Island: Re-evaluation of events at the end of the Cretaceous". Journal of Paleontology. 72 (3).
7. Elliot D.H.; Askin RA; Kyte FT; Zinsmeister WJ (1994). "Iridium and dinocysts at the Cretaceous-Tertiary boundary on Seymour Island, Antarctica: Implications for the K-T event". Geology. 22. doi:10.1130/0091-7613(1994)022<0675:IADATC>2.3.CO;2.
8. Petersen, S.V.; Dutton A; Lohmann KC (2016). "End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change". Nature Communications. 7.
9. Witts J.D.; Whittle RJ; Wignall PB; Crame JA; Francis JE; Newton RJ; Bowman VC (2016). "Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica". Nature Communications. 7. doi:10.1038/ncomms11738.
10. Clarke, J.A., Tambussi, C.P., Noriega, J.I., Erickson, G.M. and Ketcham, R.A. (2005). "Definitive fossil evidence for the extant avian radiation in the Cretaceous." Nature, 433: 305-308. DOI:10.1038/nature03150 PDF fulltext Supporting information
11. Case, J., Reguero, M., Martin, J. and Cordes-Person, A. (2006). "A cursorial bird from the Maastrictian of Antarctica." Journal of Vertebrate Paleontology, 26(3): 48A.
12. Cordes, (2002). "A new charadriiform avian specimen from the Early Maastrichtian of Cape Lamb, Vega Island, Antarctic Peninsula". Journal of Vertebrate Paleontology, 22(3): 46A.
13. NUEVOS RESTOS DE DINOSAURIA DEL CRETÁCICO DE LAS ISLAS JAMES ROSS Y MARAMBIO, PENÍNSULA ANTÁRTICA
14. Sebastián Rozadilla, Federico L. Agnolin, Fernando E. Novas, Alexis M. Aranciaga Rolando, Matías J. Motta, Juan M. Lirio and Marcelo P. Isasi (2016). "A new ornithopod (Dinosauria, Ornithischia) from the Upper Cretaceous of Antarctica and its palaeobiogeographical implications". Cretaceous Research. in press. doi:10.1016/j.cretres.2015.09.009.