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6 Mesozoic and Cenozoic Decapod Crustaceans from Venezuela and Related Trace-Fossil Assemblages
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103 Mesozoic and Cenozoic Decapod Crustaceans from Venezuela and Related Trace-Fossil Assemblages Orangel Aguilera, Dione Rodrigues de Aguilera, Francisco J. Vega, and Marcelo R. Sánchez-Villagra The Tropical Caribbean Province is characterized by a high crustacean diversity (Boschi 2000), and 18% of the total corresponds to living brachyuran decapods. Fossil decapod crustaceans have been described ranging in age from Early Triassic to Pleistocene. Distribution patterns of Southern Hemisphere decapods reveal an amphitropical and interhemisphere distribution (Feldmann and Schweitzer 2006). This implies a favorable outlook for the discovery of a diverse crustacean fauna in Cretaceous to Quaternary Caribbean sediments, particularly from Venezuelan deposits. The first contribution on fossil crustaceans from Venezuela was published by Maury (1930), on the Eocene fauna of the Santa Rita Formation in the Maracaibo Basin. This contribution was followed by the discovery of new genera and species by Van Straelen (1933), based on numerous specimens collected from the middle to upper Eocene Santa Rita, and upper Oligocene to lower Miocene Castillo formations. The most recent reports on the fossil crustacean fauna from Venezuela were published by Sánchez-Villagra et al. (2000) and Feldmann and Schweitzer (2004), in which they discussed Van Straelen’s contribution and illustrated new specimens collected from additional outcrops of the Castillo Formation in the Cerro La Cruz, Lara state. Collins, Portell, and Donovan (2009) reviewed the Caribbean Neogene decapod crustaceans. Decapod crustacean species from Venezuela were also reported from the Paleocene Guasare Formation (Collins, Higgs, and Cortitula 1994), collected from a borehole core (4200 m deep) during oil research. Sánchez and Lorente (1977) noted the presence of crabs Callianassidae and Goneplacidae in the Cretaceous Quevedo Member of the Navay Formation, along with other crustaceans cited by La Marca (1997) from the middle to upper Eocene Caús Formation. We report here that articulated fossil crabs, abundant carapaces, and disarticulated appendages (meri, palms, and dactyli) are common finds in a complete geochronological sequence (from Late Cretaceous to Pleistocene) along basins of eastern and western Venezuela. This abundance reveals a remarkable crustacean diversity from typical tropical shallow water Caribbean sediments through geological time. We provide 6 Aguilera, Rodrigues de Aguilera, Vega, and Sánchez-Villagra 104 additional information on previously described species and specimens, new records, and an overview of potentially new species. Bioturbated sediments found at multiple outcrop localities, where trace-fossil assemblages can be studied, also represent the crustacean record. These traces are infills of three-dimensional burrow systems with vertical and horizontal components, mainly comprising the ichnogenus Thalassinoides morphotype. Other structures represent feeding-dwelling behavior, attributed to Grapsidae, Ocypodidae or Gecarcinidae crabs (Bright and Hogue 1997). Trace-fossil assemblages from Venezuelan outcrops were treated at length by Macsotay (1967), Padrón et al. (2000), and Buatois, Macsotay, and Quiroz (2009) and the biogenic structures in deep core from eastern Venezuela by Buatois et al. (2008) in the lower Miocene strata from the Tácata Field. Specimens from the Van Straelen collection (Falcón and Lara states) at the Natural History Museum of Basel in Switzerland, and from the Feldmann and Schweitzer collection (Lara state) at the Museo de Bio logía de la Universidad del Zulia in Venezuela, were studied, but the main bulk of this report is based on the study of new specimens collected during our own field trips, many of them representing either the first report of decapod crustaceans in many regions or localities in Venezuela or expansions of the temporal range of known species. The stratigraphic range of this collection covers mostly Oligocene to Pleistocene rocks (Lara, Falcón, Sucre, and Nueva Esparta states). Well-preserved ichnofacies from the Cantaure, Urumaco, and Paraguaná formations (Falcón state) are also reported here. The geochronologic sequence here discussed includes the upper Maastrichtian Mito Juan Formation, the Paleocene Guasare and Valle Hondo formations, the middle to upper Eocene San Rita Formation, the upper Oligocene to lower Miocene Castillo Formation, the lower Miocene Cantaure Formation, the upper Miocene Urumaco, Socorro, and Caujarao formations, the upper Miocene to lower Pliocene Cubagua Formation, the Pliocene Paraguaná Formation, the Pleistocene El Manglillo Formation, and Pleistocene Araya quarry. In plate 3 we present a map with localities and geographical features mentioned in the text. Table 6.1 shows the geochronologic sequence here discussed and fossil decapod distribution. The fossil crustacean diversity from Venezuela is treated under different headings, taxonomically organized. The term “Callianassa group” is used here because most of the fossil and living Callianassa species previously attributed to this genus in...