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7 Venezuelan Caribbean and Orinocoan Neogene Fish
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129 Venezuelan Caribbean and Orinocoan Neogene Fish Orangel A. Aguilera and John Lundberg In an effort to document the diversity and distribution of Neogene neotropical fishes in time and space, in this chapter we summarize and analyze previous records in the Venezuela sedimentary basin and include additional unpublished fossil records. The investigation has identified ~ 209 taxa (56 elasmobranchs and 153 teleosts), ranging in age from Late Oligocene to Pleistocene. Venezuelan Caribbean and Orinocoan Neogene fishes are examined in the context of the Caribbean and Tropical South American fossil assemblage . Detailed reviews of the fossil record of Caribbean Neogene teleostean fish are available for: Panama (Gillette 1984), Panama and Costa Rica (Aguilera and Rodrigues de Aguilera 1999; Collins et al. 1999; Laurito 1999), Trinidad (Nolf 1976), Venezuela (Nolf and Aguilera 1998; Aguilera and Rodrigues de Aguilera 2001, 2004a, b, c; Aguilera 2004), the Dominican Republic (Nolf and Stringer 1992), Cuba (IturraldeVinent , Hubbell, and Rojas 1996; Iturralde-Vinent et al. 1998), Puerto Rico (Nieves-Rivera 1999), and Jamaica (Stringer 1998; Donovan and Gunter 2001). Systematic reviews of Caribbean Neogene elasmobranchs have not been attempted since Sánchez-Roig (1920), Leriche (1938), Casier (1958), Gillette (1984), Kruckow and Thies (1990), Iturralde-Vinent, Hubbell, and Rojas (1996), Laurito (1999), and Aguilera (2004). However, these previous compilations reveal the scarce and scattered records of fossil selachians from the Caribbean. Additional detailed reviews of the fossil record of Orinocoan/Amazonian freshwater Neogene fish are available for: Brazil (Richter 1984, 1989; Silva-Santos 1987; Monsch 1998; Aguilera et al. 2008b; Bocquentin Villa nueva and Souza Mello 2001; Gayet et al. 2003), Colombia (Lundberg, Machado-Allison, and Kay 1986; Lundberg and Chernoff 1992; Lundberg 2005; Monsch 1998), Peru (Monsch 1998), and Venezuela (Lundberg et al. 1988, 2010; Lundberg and Aguilera 2003; Aguilera 2004; Dahdul 2004; Sabaj, Aguilera, and Lundberg 2007). Because fossil assemblages of fishes represent only a small fraction of the richness of the Recent fish fauna, we suggest that a large fraction of fossil taxa from the Venezuelan sedimentary basins still remain uncollected. 7 Aguilera and Lundberg 130 The units treated in the Venezuelan basins represent the most complete Neogene sedimentary sequence preserved around the Caribbean Sea. The oldest of these, the Castillo Formation (upper Oligocene to lower Miocene), central-western Venezuela, consists of clayey marls interbedded with numerous thin hardground units. The strata are underlain and overlain by sandstones. The biotic associations reflect near-shore tropical marine paleoenvironments (Sánchez-Villagra et al. 2000). The Cantaure Formation (lower Miocene), northwestern Venezuela, consists of limey shale, with sandy intervals rich in mollusks in the lower part. The upper part consists of shale intercalated with thin limestone (Ministerio de Energía y Minas 1997). The biotic associations reflect near-shore tropical marine paleoenvironments, around 50 m deep (Jung 1965; Nolf and Aguilera 1998; Aguilera and Rodrigues de Aguilera 1999). The Menecito Member of the San Lorenzo Formation (lower to middle Miocene), northwestern Venezuela is dominated by uniform gray clays, and consists of a 138.5 m thick type section (Ministerio de Energía y Minas 1997). As inferred from the fossil shark assemblage described by Leriche (1938), the unit reflects an outer neritic paleoenvironment. The Socorro Formation (Middle Miocene), northwestern Venezuela, consists of sandstone, shale, fossiliferous marl, and limestone in the lower interval, and sandstone, peat, and laminated shale without calcareous or fossiliferous horizons in the upper ones (Ministerio de Energía y Minas 1997). According to Gamero and Díaz de Gamero (1963) the sampled area in the Saladillo locality consists of shale-marl facies. The Cumaca Formation (Middle Miocene), north-central Venezuela , consists of gray, green, and black shale, and clayey shale. The biota reflects freshwater paleoenvironments (Ministerio de Energía y Minas 1997). The lower member of the Urumaco Formation (upper Miocene), northwestern Venezuela, is dominated by mudstones (Ministerio de Energ ía y Minas 1997). It is composed of dark-gray laminated mudstones and shales, and heterolithic intervals of lenticular to ripple cross-laminated, very fine grained sandstones, with biogenic structure, grading to coarsening -upward sequences of medium-bedded, hummocky, and ripple crossstratified , fine-grained sandstones, with trace-fossil assemblages. These coarsening-upward sequences form units up to 5 m thick and are commonly overlain by massive-bedded gray mudstones with root traces, interbedded with organic-rich, laminated mudstone and thin- to mediumbedded coal seams, and end with a thick-bedded coquinoidal limestone burrowed by Thalassinoides (Aguilera et al. this volume; Quiróz and Jaramillo this volume). Locally, the hummocky cross-stratified sandstones grade...