Metaceratodus kaopen comb. nov. and M. wichmanni comb. nov., two Late Cretaceous South American species of an austral lungfish genus (Dipnoi)

Abstract

Cione, A.L. & Gouiric-Cavalli, S., June 2012. Metaceratodus kaopen comb. nov. and M. wichmanni comb. nov., two Late Cretaceous South American species of an austral lungfish genus (Dipnoi). Alcheringa 36, 203–216. ISSN 0311-5518.

Metaceratodus wollastoni, an Australian species, was reported from Upper Cretaceous beds of Patagonia in 1997. Later, three new species (Ceratodus wichmanni, Ptychoceratodus kaopen and Ptychoceratodus cionei), based on scarce material, were described from the same region. Two of these species were later referred to Ferganoceratodus. After examining much more abundant and better-preserved material, we conclude that neither the occurrence of Metaceratodus wollastoni nor those of Ptychoceratodus and Ferganoceratodus in the Cretaceous of South America are supported. We consider that C. wichmanni and P. cionei are synonyms and we reassign the three putative species to Metaceratodus under two new combinations: M. kaopen comb. nov. and M. wichmanni comb. nov. Both differ from the other species of the genus in having pits over most of the occlusal surface and a different occlusal profile of the tooth plate, and most have four ridges in the lower and upper tooth plates. Metaceratodus wichmanni differs from M. kaopen in oclussal profile, inner angle, and symphysis development among other features. Metaceratodus kaopen is known from the upper Santonian–lower Campanian Anacleto Formation of Río Negro province and M. wichmanni from upper Campanian–lower Maastrichtian units of Chubut, Río Negro, Neuquén and Mendoza provinces, Argentina. The occurrence of Metaceratodus in southern South America corroborates a close biogeographical relationship with Australia in the latest Cretaceous.

Alberto Luis Cione [[email protected]] and Soledad Gouiric-Cavalli [[email protected]], División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, W1900FWA La Plata, Argentina. Received 23.11.2010, revised 11.7.2011, accepted 7.8.2011.

Key words:

• Lungfish
• Dipnoi
• Cretaceous
• Argentina
• South America
• Australia

Acknowledgements

For partial financial support: ANPCyT (PICT 913), CONICET (PIP 5608) and Universidad Nacional de La Plata. For valuable information: A. Kemp, J.R. Casciotta, N. Krupina, A. Murray and M. Manceñido. For permision to examine dipnoan material: Museo Padre Molina, Río Gallegos, Argentina (A. Tauber); Museo de La Plata, La Plata, Argentina (M. Reguero); Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Buenos Aires, Argentina (A. Kramarz); Museo ‘Carmen Funes’, Plaza Huincul, Argentina (R. Coria); Museo Patagónico de Ciencias Naturales, General Roca, Río Negro, Argentina (P. Chafrat); Museo Prof. Dr Juan Olsacher (A. Garrido); Natural History Museum, London, England (A. Longbottom). For photographic material: P. Chafrat. For assistance with the figures and English: Lic. L.L. Rasia and Lic. D.A. Cabrera. For review of the manuscript and valuable comments: L. Cavin and an anonymous reviewer.