Revision of the fossil pulmonates of Itaborai Basin

In a paper just released, Salvador & Simone (2013) present a revision of the pulmonate snail fauna from the Itaboraí Basin (Paleocene) in southeastern Brazil. The fossils are known a limestone site which has been exploited till the early 1980s, after which the quarry was abandoned and a lake formed in the basin. All known fossils are now in two institutions in Rio de Janeiro.

The authors have done a nice job in re-studying all type material, complementing the diagnoses and descriptions of species which were too brief by their original authors; they also have put the fauna in the perspective of our current knowledge of the Neotropical malacofauna.

The abstract reads: The limestones of Itaboraí Basin (Middle Paleocene), Rio de Janeiro, Brazil, harbor a rich fossil molluscan fauna consisting exclusively of pulmonate snails, both terrestrial and freshwater. An extensive taxonomic revision of this paleofauna is conducted here. A new genus, Cortana, is described as well as two new species, Eoborus fusiforme and Gastrocopta itaboraiensis. The revised classification is as follows: Austrodiscus lopesi (Charopidae); Biomphalaria itaboraiensis (Planorbi- dae); “Brachypodella” britoi (Urocoptidae); Brasilennea arethusae, Brasilennea guttula, Brasilennea minor (Cerionidae); Bulimulus fazendicus, Bulimulus trindadeae, Cortana carvalhoi, Cyclodontina coelhoi, Itaborahia lamegoi, Leiostracus ferreirai, Plagiodontes aff. dentatus (Orthalicidae); Cecilioides sommeri (Ferussaciidae); Eoborus rotundus, Eoborus sanctijosephi, Eoborus fusiforme (Strophocheilidae); Gastrocopta mezzalirai, Gastrocopta itaboraiensis (Gastrocoptidae); Temesa magalhaesi (Clausiliidae). The species Strobilopsis mauryae was considered a synonym of Brasilennea arethusae; Bulimulus sommeri a synonym of Itaborahia lamegoi; andVorticifex fluminensis a synonym of Eoborus sanctijosephi. Itaboraí Basin has the most ancient records of the families Orthalicidae, Gastrocoptidae, Ferussaciidae and Strophocheilidae. Moreover, the basin’s records of Charopidae, Clausiliidae, Cerionidae, and Urocoptidae are among the most ancient in the world and, among these, those of Cerionidae, Clausiliidae and Urocoptidae deserve special attention since they are greatly removed from these families’ current distribution. Additionally, Itaboraí has the most ancient records for the genera Austrodiscus, Brachypodella, Bulimulus, Cecilioides, Cyclodontina, Eoborus, Gastrocopta, Leiostracus, Plagiodontes and Temesa. There are three endemic genera in the basin: Brasilennea, Cortana and Itaborahia. Further discussion on paleobiogeography and evolution of this paleofauna is also provided.

A new monotypic genus, Cortana, is erected for Bulimulus carvalhoi Brito, 1967 on account of the shape of the aperture and the fusiform shell. Only the holotype is known. Comparisons are being made to Eudolichotis and Otostomus, genera occurring at present more northern in Brazil.

Eoborus fusiforme n.sp. is described as a new species of Strophocheilidae, also on the basis of one shell.

Paleontology often remains a lot of guess work and may be considered as quite subjective. However, the authors provide an important contribution with a discussion on the relationships of this fauna related to the current distribution of extant taxa in the Neotropics. Unfortunately, the current situation does not give much opportunity to dig for other fossils at the Itaborai Basin, which leaves this paper as a monograph for the years to come.

Reference:
Salvador, R.B. & Simone, L.R.L., 2013. Taxonomic revision of the fossil pulmonate mollusks of Itaborai Basin (Paleocene), Brazil. Papeis Avulsos de Zoologia 53(2): 5-46. Available at http://bit.ly/YLGZS2.

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