Volume 53(2):5‑46, 2013 TAXONOMIC REVISION OF THE FOSSIL PULMONATE MOLLUSKS OF ITABORAÍ BASIN (PALEOCENE), BRAZIL 1,2 RODRIGO BRINCALEPE SALVADOR 1,3 LUIZ RICARDO LOPES DE SIMONE ABSTRACT 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 ex- tensive 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 clas- sification is as follows: Austrodiscus lopesi (Charopidae); Biomphalaria itaboraiensis (Planorbi- dae); “Brachypodella” britoi (Urocoptidae); Brasilennea arethusae, Brasilennea guttula, Brasi- lennea minor (Cerionidae); Bulimulus fazendicus, Bulimulus trindadeae, Cortana carvalhoi, Cyclodontina coelhoi, Itaborahia lamegoi, Leiostracus ferreirai, Plagiodontes aff. dentatus (Orthalicidae); Cecilioides sommeri (Ferussaciidae); Eoborus rotundus, Eoborus sanctijose- phi, Eoborus fusiforme (Strophocheilidae); Gastrocopta mezzalirai, Gastrocopta itaboraiensis (Gastrocoptidae); Temesa magalhaesi (Clausiliidae). The species Strobilopsis mauryae was con- sidered a synonym of Brasilennea arethusae; Bulimulus sommeri a synonym of Itaborahia lame- goi; and Vorticifex 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. Fur- ther discussion on paleobiogeography and evolution of this paleofauna is also provided. Key-Words: Itaboraí; Middle Paleocene; Mollusca; Pulmonata; Rio de Janeiro. INTRODUCTION of the smallest basins in the country: it has an ellipti- cal shape, with ~1,400 m in its biggest axis, ~500 m Itaboraí Basin is located in the municipality of in the smallest and ~125 m of maximum depth (Ro- Itaboraí (Fig. 1), Rio de Janeiro state, Brazil, and is one drigues Francisco & Cunha, 1978; Bergqvist et al., 1. Museu de Zoologia, Universidade de São Paulo. Caixa Postal 42.494, 04218-970, São Paulo, SP, Brasil. 2. E-mail: [email protected] 3. E-mails: [email protected], [email protected] 6 Salvador, R.B. & Simone, L.R.L.: Fossil mollusks from Itaboraí Basin occurrence) were added to this list by Salvador & Simone (2012). In any case, up to this moment the studies dealing with Itaboraí Basin’s molluscan fauna consist almost exclusively of the original descriptions; no taxonomic revision under a larger scope has been so far produced. As such, many taxonomic problems and inconsistencies have been readily identified, most stemming from the fact that the original descriptions were overly based on comparisons with European genera and species. Therefore, this work intends to review the taxonomy of the entire Itaborahian mol- luscan fauna. As the original descriptions (with the ex- ception of Maury, 1935) are too brief and incomplete, FIGURE 1: Location of Itaboraí Basin, Rio de Janeiro state, Brazil. we expand and complement them, figuring all type Adopted from http://commons.wikimedia.org. material and other well-preserved specimens, and of- fering a proper diagnosis for each taxon. Additionally, 2006). Despite its small size, Itaboraí Basin houses an two new species, previously misidentified, were found astounding fossil record in its limestones. in museum collections and are described herein. These limestones started to be explored in 1933 for the production of cement, and fossils were found there almost as soon as the excavations had begun. Geological Setting The first fossils discovered were the gastropods, but, as excavations proceeded, many other were found, Itaboraí Basin is a small tectonic depression dat- including plants, mammals, reptiles, birds, palyno- ing from the Mesozoic, probably related to the tec- morphs, coprolites and, of course, more mollusks tonic activities during the separation of Gondwana; it (Maury, 1929, 1935; Bergqvist et al., 2006). These rests on a Pre-Cambrian crystalline basement, over the fossils alongside the basin’s geology were studied al- Brazilian Southeastern Continental Rift (Beurlen & most exclusively by researchers of two institutions Sommer, 1954; Rodrigues Francisco & Cunha, 1978; from Rio de Janeiro: the Museu Nacional (National Rodrigues Francisco, 1989; Medeiros & Bergqvist, Museum) and the Divisão de Geologia e Mineralogia 1999; Sant’Anna & Riccomini, 2001; Sant’Anna of the Departamento Nacional de Produção Mineral et al., 2004). The basin was then filled by carbonatic (Division of Geology and Mineralogy of the National sediments during the Paleocene (Rodrigues Francisco Department of Mineral Production). & Cunha, 1978; Medeiros & Bergqvist, 1999). The The exploration lasted until 1984, at which resulting limestones were named “Itaboraí Forma- point the vast majority of Itaboraí’s outcrops were al- tion” by Oliveira (1956), but this name was almost ready destroyed by the quarrying, and little of its lime- never used afterwards; the majority of authors prefer stone remained. After the limestone extraction ceased, simply “Itaboraí Basin”. We follow this practice here. the quarry was abandoned and a lake formed in the The first work dealing with the basin’s geology basin, leaving the few remaining outcrops underwater (Leinz, 1938) defined three rock horizons: laminated (Bergqvist et al., 2008). Therefore, it is currently hard limestone, gray limestone and eluvial sediment. This to obtain new fossil specimens from Itaboraí, as they definition still remains basically valid, having received can only be found in a few restricted sites above water only posterior refinements. The most up-to-date geo- level. As such, any posterior work depended heavily logical profile (Medeiros & Bergqvist, 1999) defines upon data from the literature and museum specimens and names two stratigraphic sequences for the basin’s (e.g., Medeiros & Bergqvist, 1999). Still, Itaboraí is a Paleocene limestones: Sequence S1 lies at the bottom, very important fossiliferous site and on December 12, directly above the Pre-Cambrian rocks; and Sequence 1985 a park was created for its preservation, called S2 consists of sediments that filled fissures opened in Parque Paleontológico de São José de Itaboraí (Beltrão S1 by water activity. et al., 2001; Bergqvist et al., 2008). Sequence S1 is composed of an intercalation According to the last works that listed the fos- of carbonatic rocks of chemical and detrital origins. sil mollusks from Itaboraí, there are 18 (Simone & The chemically originated rocks (named Facies A) are Mezzalira, 1994) or 17 species (Bergqvist et al., 2006) mainly travertine, linked to hydrothermal activity in- in the basin. Three more (two new species and a new side the basin. The grey detrital limestones (Facies B) Papéis Avulsos de Zoologia, 53(2), 2013 7 are the product of gravitational and hydrodynamic material used in the species’ original descriptions, but it fluxes towards the basin’s interior and contain all also contains specimens from later collecting. known fossil mollusks as well as some plant, reptilian Unfortunately, the specimens’ labels are very and mammalian remains. Facies C is composed of oo- incomplete and stratigraphical information is al- litic-pisolitic limestone, being associated to Facies A. ways lacking. Also, there is no information regarding Sequence S2 is also carbonatic and the result of the quarry localities (however, their precise location torrent and gravitational flows. Its clastic rocks con- would not be of much help, for the basin was almost tain the bulk of the basin’s fossil vertebrate fauna as completely destroyed by the limestone exploration well as plants and palynomorphs. A third sequence, and the old quarries do not exist anymore). Therefore, named S3, is composed of conglomerates and was de- the stratigraphic occurrences of the species presented posited on top of the others much later, in the Eocene- here are extracted from the original works and also Oligocene. It harbors reptilian and mammalian fossils. from the compilations made by Medeiros & Bergqvist After much disagreement about Itaboraí Ba- (1999) and Bergqvist et al. (2006). For the new species sin’s age, the mammalian fossils allowed the correla- described herein, stratigraphic occurrence is assumed tion with the Upper Paleocene fauna of Rio Chico to be the same as their congeneric Itaborahian species. Formation, Argentina (Paula Couto, 1952). It is cur- All pulmonate species occur in Facies B of Sequence rently agreed that both Sequences S1 and S2 belong S1 sensu Medeiros & Bergqvist (1999). However, a to a time interval ranging from the end of the Lower few species are also believed to occur in Sequence S2 Paleocene to the beginning of the Upper Paleocene (Bergqvist et al., 2006): Bulimulus fazendicus, Eoborus (from about 59 to 57 Ma, according to Bergqvist et al. sanctijosephi, and Itaborahia lamegoi. Still, these re- 2006), which has been informally