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

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 [acione@museo.fcnym.unlp.edu.ar] and Soledad Gouiric-Cavalli [sgouiric@museo.fcnym.unlp.edu.ar], 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.

     

A new Late Famennian lungfish from New South Wales,Australia, and its bearing on Australian-Asian terrane relations

A new genus and species of lungfish with toothplates, Adelargo schultzei, is described from the Hunter Siltstone (Devonian, Late Famennian) near Grenfell, New South Wales. Materials assigned to Adelargo schultzei gen. et sp. nov., include a portion of the left side of the skull comprising B, I (postparietal) and J (parietal) bones, pterygoid and prearticular toothplates, a parasphenoid with a long posterior stalk, vertebrae, ribs, anal fin supports and scales. Toothplates are similar to Dipterus, although morphology of the skull, parasphenoid and postcranial elements is more derived. Biogeographic relationships of the Grenfell fauna were based on the presence of the antiarch group Sinolepidoidei, also present on Asian terranes during the Late Devonian. A small number of lungfish scales have been described from Asian sinolepid localities of this age, but differ from those of Adelargo schultzei, and other faunal similarities between these areas appear limited. Paucity of eastern Australian Devonian taxa on the North and South China blocks implies that strong biogeographic relationships between eastern Australia and Euramerican localities during the Late Devonian were not the result of Asian migration routes, but the closer proximity of these areas.