A New Fossil Helmeted Frog that Supports a Biogeographical Link Between South America and Australasia


The Chilean Helmeted Toad, Calyptocephalella gayi. 
Photo Credit José Grau de Puerto Montt
The southern part of South America east of the Andes has a dry, cool climate with open grasslands and a relatively poor frog fauna, with most of the living species present being leptodactylid frogs and their relatives. However, in the Paleogene the environment was warm and humid with a subtropical forest. Raul Gomez and colleagues have recovered fossils from an Eocene lake deposit that included anuran remains that represent pipoids and basal hyloids, frog lineages not represented in the living fauana. And, they have recently describe an articulated, hyperossified neobatrachian frog, Calyptocephalella pichileufensis (Calyptocephalellidae) from Rıo Pichileufi in northwestern Patagonia, Argentina. The fossil frog was found rocks dated at 47.46 MYA and the authors estimate the median annual temperature at this time was 19.2◦C. The new amphibian was estimated to have a body length of 110 mm. The authors note that Michael Tyler anticipated that frogs associated with the Australian myobatrachids should occur in the cool temperate austral fauna of South America in 1979. Decades later, the sister-group relationship of the endemic South American calyptocephalellids and Australian myobatrachids (clade Australobatrachia), was recovered in several molecular analyses. To date the oldest records of calyptocephalellids are from Patagonia, where they can be traced back to the Late Cretaceous. Today the family Calyptocephalellidae (Helmeted Water Frogs) is restricted to Chile and maybe Argentina and it host four species (Calyptocephalella gayi and three species of Telmatobufo). Telmatobufo inhabit fast-flowing streams in temperate Nothofagus forest while C. gayi lives more slow moving streams and lakes in the lowlands of Chile, up to 500 m in elevation.

Citation
Gómez, R. O., A. M. Báez and P. Muzzopappa. 2011. A new helmeted frog (Anura: Calyptocephalellidae) from an Eocene subtropical lake in northwestern Patagonia, Argentina. Journal of Vertebrate
Paleontology, 31:50-59

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