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Giant-Toothed White Sharks and Wide-Toothed Mako (Lamnidae) from the Venezuela Neogene: Their Role in the Caribbean, Shallow-Water Fish Assemblage

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Giant-Toothed White Sharks and Wide-Toothed Mako (Lamnidae) from the Venezuela Neogene: Their Role in the Caribbean, Shallow-Water Fish Assemblage Caribbean Journal of Science, Vol. 40, No. 3, 368-382, 2004 Copyright 2004 College of Arts and Sciences University of Puerto Rico, Mayagu¨ez Giant-toothed White Sharks and Wide-toothed Mako (Lamnidae) from the Venezuela Neogene: Their Role in the Caribbean, Shallow-water Fish Assemblage ORANGEL AGUILERA1,2 AND DIONE RODRIGUES DE AGUILERA1 1Universidad Nacional Experimental Francisco de Miranda, Centro de Investigaciones en Ciencias Ba´sicas, Complejo Docente Los Perozos, Carretera Variante Sur, Coro, 4101, Estado Falco´n, Venezuela. <[email protected]>, and 2Research Associated to the Smithsonian Tropical Research Institute, Center for Tropical Paleoecology and Arqueology, Box 2072, Balboa, Republic of Panama. ABSTRACT.—The role of Neogene giant-toothed lamnid sharks in the Caribbean neritic fish assemblage is discussed based on predator-prey relationships in three different tropical paleoenvironments from the Lower Miocene to Lower Pliocene. New records of extinct giant-toothed white sharks Carcharodon megalodon (Agassiz), Carcharodon subarticulatus (Agassiz), and wide-toothed mako Isurus xiphodon (Agassiz) from coastal shallow waters, coastal upwelling, swampy, coastal lagoon, and sandy littorals of the Venezuela Neogene, suggest these species were large transient piscivores that may have had enough behavioral flex- ibility to occupy different environments. Giant-tooth shark species, that probably fed mainly on fish, turtles, cetaceans and sirenids, did not exhibit large population sizes. The trophic role that large consumer sharks have carried out represents the higher trophic category, the type of selective pressure, and the control performed in the marine environment. The dynamics of these associations during Neogene is deeply dif- ferent. KEYWORDS.—Caribbean, Neogene, sharks, predator INTRODUCTION nid Neogene specimens and the associated Fossil remains of Neogene lamnid sharks fish fauna in a wide geochronological sedi- have been the subject of investigations on mentary sequence (Lower Miocene to tooth morphology, taxonomy, phylogeny Lower Pliocene) in Venezuela, we interpret and distribution as compiled by Purdy et the role of giant predators in the Caribbean al. (2001). Published literature reflects a ten- neritic fish assemblage during the Neogene dency to establish a close relationship be- and provide additional records of the giant- tween cetacean and pinniped abundance, toothed white sharks Carcharodon megalodon cold and temperate waters and presence of (Agassiz), Carcharodon subarticulatus (Agas- giant-toothed sharks, (e.g., Carcharodon siz), and wide-toothed mako Isurus xipho- megalodon). The scarcity of records of Car- don (Agassiz) from the Venezuela Neogene. ibbean lamnids (Kruckow and Thies 1990) and limited records from Barbados and MATERIAL AND METHODS Trinidad (Casier 1958, Flemming and Mac- Farlane 1998), Costa Rica (Laurito 1999), Ja- The study area includes localities in the maica (Donovan and Gunter 2001), Puerto northwestern and northeastern Venezuela Rico (Nieves-Rivera et al. 2003), Cuba (Itur- sedimentary basin (Fig. 1). Precise stratig- ralde-Vinent et al. 1996), Panama (Gillette raphy placement of the fossil samples in 1984), and Venezuela (Leriche 1938; Agui- relation to unit boundaries is unknown. lera and Rodrigues de Aguilera 2001) may However, studies of the stratigraphy are in be an artifact of sampling; thus, it may be progress (A. Coates pers. comm.). We col- erroneously interpreted as fortuity and lected samples of shark teeth from surface scarce giant-toothed shark distributions in collections within the scope of the Panama the Caribbean sedimentary basin. Paleontology Project (Jackson et al. 1999). Based on the recovery of additional lam- Shark classification was arranged following 368 CARIBBEAN NEOGENE TROPHIC STRUCTURE 369 FIG. 1. Location of the Venezuelan sampling sites discussed in the text (see Table 1). 1, Cantaure Formation; 2, Paraguana´ Formation; 3, Urumaco Formation; 4 Codore Formation; 5, Socorro Formation; 6, Caujarao For- mation; 7, Cubagua Formation. Purdy et al. (2001), and specimens were de- Pliocene Paraguana´ formations (Amuay posited in the Universidad Nacional Member)] is the most complete Neogene Experimental Francisco de Miranda sedimentary sequence preserved near the (UNEFM), Coro, Estado Falco´n, Venezuela. Caribbean Sea (Table 1). For additional in- The geological unit from which teeth formation about the geology of these geo- were obtained [Lower Miocene Cantaure, logical units see Ministerio de Energı´a y Middle Miocene Socorro, Upper Miocene Minas (1997). Urumaco (Middle Member) and Caujarao In order to reconstruct lower trophic lev- (TaraTara Member), Upper Miocene to els in Neogene food webs we used pub- Lower Pliocene Cubagua (Cerro Verde lished and unpublished data on fish assem- Member), Upper Miocene to Pliocene blages (Table 1). The topology of the food Codore (Chiguaje Member) and Lower web was suggested by E. Sala (pers. 370 O. AGUILERA AND D. RODRIGUES DE AGUILERA comm.), and it is based on trophic relation- (1999), and Nieves-Rivera et al. (2003). This ships of present Caribbean food webs. reinforces the information about the pres- ence of giant-toothed white sharks in the Neogene Caribbean. RESULTS Carcharodon megalodon is characterized by a triangular, broad, high and slightly The giant-toothed white shark Carcha- curved crown; cutting edge incised by nu- rodon subauriculatus (Agassiz) (Fig. 2.1-2.18) merous, small, and regular serrations; neck is the first record for the Caribbean; par- very marked, strongly curved toward the ticularly from the Lower Miocene Cantaure top; labial boundary of the enameled with a Formation, Upper Miocene to Lower median obtuse angle directed toward the Pliocene Codore Formation, and Lower top. The presence of C. megalodon along the Pliocene Paraguana´ Formation of Venezue- wide Neogene geochronologic sequence in la. Purdy et al. (2001) and Purdy (1996, the tropical Caribbean neritic deposit is 1998) reported from US an early record of contradictory, with warm and cold water the Oligocene Chandler Bridge Formation, preferences noted by Purdy (1996). In the Middle Miocene Calvert Formation, Neogene Caribbean tropical environment, Miocene Purgo River Formation, and C. megalodon probably fed mainly on small Lower Pliocene Yorktown Formation. Car- cetaceans, sirenids, turtles, and fish. charodon subauriculatus is distinguished The wide-toothed mako Isurus xiphodon from C. megalodon by a low, slender, curved (Agassiz) (Fig. 2.29-2.34) is the first record crown, strong marginal serration and by for the Caribbean; particularly from the the presence of lateral heels feebly serrated. Upper Miocene to Lower Pliocene Cubagua According to Purdy (1996), giant-toothed Formation of Venezuela. Isurus xiphodon is sharks Carcharodon sokolowi (Jaekel) characterized by a long and stronger crown (Eocene), C. angustidens (Agassiz) (Oli- without lateral cusplets, cutting edges com- gocene), C. subauriculatus (Oligocene), and pletely smooth reaching the base; root C. megalodon (Miocene/Pliocene) were bulky with short divergent asymmetric more common in warm waters and fed on lobes. According to Purdy et al. (2001), the whales. However, their discovery of C. sub- wide-toothed mako with convergent teeth auriculatus in shallow-waters of the Car- to those of the white shark may have been ibbean suggests that this species may the main predator of tropical monk seals in change habitat preferences through time, or the north Atlantic coast, reaching 7.6 m in it may have enough behavioral flexibility to length. A single Caribbean fossil record of occupy different environments at different wide-toothed mako is associated with times. coastal upwelling (Aguilera and Rodrigues Carcharodon megalodon (Fig. 2.19-2.28) de Aguilera 2001), and probably they fed represents an additional fossil record for on fish, turtles and cetaceans. the Caribbean Neogene; particularly from the Lower Miocene Cantaure Formation, Upper Miocene Urumaco Formation, DISCUSSION Middle Miocene Socorro Formation, Upper Miocene Caujarao Formation, Upper Most of the sedimentary basins included Miocene to Lower Pliocene Codore Forma- in the present study are neritic environ- tion, and Lower Pliocene Paraguana´ For- ments. Among them some exceptional de- mation of Venezuela. posits and their associated assemblages Kruckow and Thies (1990) compiled an may be used to interpret and discuss dif- early record of C. megalodon from the Car- ferent paleoenvironments along with their ibbean, with additional published records the trophic setting. by Aguilera (2004), Aguilera and Rodrigues Coastal shallow water environments (Fig. de Aguilera (2001), Donovan and Gunter 3).—The Cantaure Formation (Lower (2001), Flemming and MacFarlane (1998), Miocene, northwestern Venezuela) is char- Iturralde-Vinent et al. (1996), Laurito acterized by a diverse association of TABLE 1. Venezuelan Neogene marine sedimentary basins with giant-toothed sharks. Age Formation/Member Lithology Marine vertebrate biota/Paleoenvironments Reference Lower Cantaure Formation, Gypsies slime claystone, with GINGLYMOSTOMATIDAE Ginglymostoma delfortriei Daimeries; LAMNIDAE Geology: Miocene northwestern Venezuela. sandy intervals in the lower Carcharodon megalodon (Agassiz), Carcharodon subauriculatus Agassiz; D´ıaz de Gamero 1974 part. Claystone intercalated HEMIGALEIDAE Hemipristis serra Agassiz, Paragaleus sp.; Hunter and Bartok with thin limestone in the CARCHARHINIDAE Carcharhinus ackermani Santos and Travasos, 1974
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