Fil: Castro, Alicia Susana. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cione, Alberto Luis. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Civalero, María Teresa. INAPL. Ciudad Autónoma de Buenos Aires; ArgentinaFil: De Nigris, Mariana. INAPL. Ciudad Autónoma de Buenos Aires; Argentin

Castro, Alicia Susana

Cione, Alberto Luis

Civalero, María Teresa

De Nigris, Mariana

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A fossil shark tooh in early contexts of Cerro Casa de Piedra 7, southwest Patagonia, Argentina

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PROOF COPYA Fossil Shark Tooth in Early Contexts of Cerro Casa de Piedra 7, Southwest  Patagonia, ArgentinaAlicia Castro1, Alberto Luis Cione2, María Teresa Civalero3, and Mariana De Nigris3➤Keywords: Fossil tooth, early Holocene, PatagoniaCasa de Piedra hill is located in one of the highest glacial lake basins of Patagonia (900 masl) (Figure 1). Belgrano and Burmeister lakes are the most important ones in this basin. Cerro Casa de Piedra 7 (CCP7) is one of several caves and rockshelters located on the northern side of the hill. CCP7 has a stratigraphic sequence which begins at the Pleistocene-Holocene transition. A fossil shark tooth was found in archaeological deposits dated to about 9000–9700 rcybp; it belongs to the genus Isurus (Elasmobranchii, Lamniformes, Isuridae). This species, unknown today in Santa Cruz marine coasts, lived in Patagonian seas during the Miocene epoch, at a time when there were sea ingressions. These ingressions flooded large areas within the present Patagonian territory and generated marine deposits in which abundant remains of extinct fauna (including shark teeth) can be found (Figure 1). In this paper, the recorded fossil tooth is described and its possible modification by human action is discussed. Tooth DescriptionThe tooth has a slender and straight crown. Both cutting edges are complete. Both mesial and distal  1 Departamento científico de Arqueología, Museo de La Plata. FCNyM-UNLP. Argentina; e-mail: aliciacastro52@gmail.com 2 CONICET-División Paleontología de Vertebrados, Museo de La Plata, 1900. La Plata, Argentina;  e-mail: acione@fcnym.unlp.edu.ar 3 María Teresa Civalero and Mariana De Nigris. CONICET-INAPL 3 de Febrero 1370 C1426BJN, Ciudad Autónoma de Buenos Aires, Argentina;  e-mails:  mtcivalero@gmail.com denigris@retina.arA Fossil Shark Tooth of Cerro Casa de Piedra 7, Patagonia, Argentina1451932PROOF COPYcutting edges are straight. At the base, the crown becomes wider and the cutting edges are concave. The labial crown base does not overhang the root. The crown labial face is transversely flat but the lingual face is slightly convex. There are no lateral cusplets. The root is badly damaged (Figure 2).  Traditionally (e.g., Leriche 1926), Cenozoic shark teeth similar to those of the living species Isurus oxyrinchus and I. paucus (i.e., lamnids without lateral denticles and serrations, commonly named makos) were included in this genus, as was I. hastalis, but this taxonomy is equivocal. The genus Cosmopolitodus recently has been used by some authors, assuming that the species hastalis is ancestral to the great white shark and is not closely related to the mako sharks (Siverson 1999; Ward and Bonavia 2001). Other authors, e.g., Purdy et al. (2001), continue to use the name Isurus xiphodon for broad-crowned specimens of hastalis; however, Ward and Bonavia (2001) consider Isurus xiphodon as a nomen dubium. Cosmopolitodus, which includes several species, is a paraphyletic taxon. A different solution could be to assign the species usually included in this genus (I. hastalis, I. xiphodon, and I. planus) to the genus Carcharodon. Until a thorough study of the different species of lamnids is done, however, we prefer to refer to these species as Isurus because we do not accept the paraphyletic genus Cosmopolitodus. Besides, Whitenack and Gottfried (2010) demonstrated morphometrically that I. hastalis is different from I. xiphodon. Morphology and size of the tooth support the genus Isurus assignment, but it is difficult to assign it to a certain species.  Isurus teeth are common in Patagonia in early Miocene Leonian beds (Monte León, Chenque and Gaiman formations [Cione 1988; Cione and Expósito 1980]), and the middle-late Miocene Puerto Madryn and Paraná formations (Cione et al. 2000).Figure 1. Map of Upper Oli-gocene and Lower Miocene sea ingressions in Patagonia (modified from Parras and Casadío 2006) and Cerro Casa de Piedra 7 (CCP7) location. 16 Castro et al.82076PROOF COPY Lamnid sharks are strictly marine fishes (Compagno 2001). The two recent species of Isurus are distributed in tropical and warm temperate seas, Carcharodon carcharias lives in a wider range of temperatures, and the two recent species of Lamna are cold temperate sharks. Tooth Microwear AnalysisWith the purpose of determining the possible use of the shark tooth, we analyzed it with a metallographic microscope (280X) and binocular magnify glasses. To establish possible differences and following functional protocols, distinctive paleontological shark teeth specimens, with diverse sizes and colors, were observed as comparative references. Six fossil items were analyzed: two of Carcharias taurus coming from Punta Indio and Río de La Plata (Buenos Aires), and four of Isurus hastalis coming from Bryn Gwyn, Gaiman Formation (Chubut). All these present functional or micropolish-like surface alterations most probably due to taphonomic conditions.Alteration of the Archaeological SpecimenThe archaeological specimen shares the same superficial natural aspect of the paleontological specimens examined. Nevertheless, the tooth shows structural damages on the edges and the apex, which under the microscope are seen to be microfractures. The microsurface presents an abraded surface due to natural agents; however, the occurrence of a large number of striations and multidirectional forms distinguish it from the paleontological specimens. The striations on the archaeological specimen are thin, straight, regularly parallel, and transverse standing 0 1cmFigure 2. A, shark tooth (lingual view) found in CCP7 early archaeological contexts; B, striations observed with metallographic microscope (280X) (right).A BA Fossil Shark Tooth of Cerro Casa de Piedra 7, Patagonia, Argentina91011122113PROOF COPYout from the comparative samples (Figure 2). Therefore, it is possible that the archaeological tooth may have suffered alterations that are not taphonomically natural.Discussion and ConclusionsEven though we do not have yet a precise diagnosis, it can be said that differences between the CCP7 tool and natural specimens exist. The tooth found in the archaeological context has abraded microsurfaces and striations, probably non-natural alterations. In discrepancy with other examples in the archaeological literature (Cione and Bonomo 2003), the CCP7 tooth does not present clearly oriented modifications which could suggest its use as an ornament. The preliminary findings presented here suggest that the tooth might have been used as a tool. This hypothesis means that early humans selected certain objects that did not need further modification for use as tools because of the advantages of their morphology. These objects would have been kept as tools for future uses. Thus, the exaptation concept (Gould and Vrba 1982, adapted to archaeology by Borrero 1993) could be useful to explain the presence of the shark tooth in the archaeological context of the CCP7 site. This unique finding in an early archaeological context of Andean Patagonia allows us to investigate more deeply human behavior towards the use of raw materials other than those usually considered.This research was supported by Agencia Nacional de Promoción Científica y Tecnológica, PICT 2488 and PICT 2006-913.References CitedBorrero, L. A. 1993 Artefactos y evolución. Palimpsesto. Revista de Arqueología 3:15–32.Cione, A. L. 1988 Los peces de las formaciones marinas del Cenozoico de Patagonia. Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata. Unpublished manuscript.Cione, A. L., and M. Bonomo 2003 Great White Shark Teeth Used As Pendant and Possible Tools by Early-Middle Holocene Terrestrial Mammal Hunter-Gatherers in the Eastern Pampas (Southern South America). International Journal of Osteoarchaeology 13:222–31.Cione, A. L., and E. Expósito 1980 Chondrichthyes del “Patagoniano” s.l. de Astra, Golfo de San Jorge, provincia de Chubut, Argentina. Su significado paleoclimático y paleobiogeográfico. Actas del II Congreso Argentino de Paleontología y Bioestratigrafía y I Congreso Latinoamericano de Paleontología 2:275–90. Cione, A. L., M. Azpelicueta, M. Bond, A. Carlini, J. Casciotta, M. A. Cozzuol, M. d. l. Fuente, Z. Gasparini, F. Goin, J. Noriega, G. J. Scillato-Yané, L. Soibelzon, E. Tonni, D. Verzi, and M. G. Vucetich 2000 Miocene Vertebrates from Entre Ríos Province, Argentina. Serie Correlación Geológica 14:191–238.Compagno, L. J. V. 2001  Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Volume 2. Bullhead, Mackerel and Carpet Sharks (Heterodontiformes, Lamniformes and Orectolobiformes. FAO, Rome. Gould, S. J., and E. S. Vrba 1982 Exaptation—A Missing Term in Science of Form. Paleobiology 8:4–15. Leriche, M. 1926 Les poissons néogènes de la Belgique. Mémoires du Musée Royal d‘Histoire Naturelle de Belgique 32:369–472.Purdy, R., V. Schneider, S. Applegate, J. McLellan, R. Meyer, and R. Slaughter 2001 The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In Geology and Paleontology of the Lee Creek Mine, North Carolina, edited by C. E. Ray & D. J. Bohaska Smithsonian Contributions to Paleobiology 90. Smithsonian Institution Press, Washington D.C. 18 Castro et al.1516171814PROOF COPYSiverson, M. 1999 A New Large Lamniform Shark from the Uppermost Gearle Siltstone (Cenomanian, Late Cretaceous) of Western Australia. Transactions of the Royal Society of Edinburgh: Earth Sciences 90:49–66.Ward, D. J., and C. Bonavia 2001 Additions to, and a Review of, the Miocene Shark and Ray Fauna of Malta. The Central Mediterranean Naturalist 3:131–46.Whitenack, L. B., and M. D. Gottfried 2010 A Morphometric Approach for Addressing Tooth-Based Species Delimitation in Fossil Mako Sharks, Isurus (Elasmobranchii: Lamniformes). Journal of Vertebrate Paleontology 30:17–25.A Fossil Shark Tooth of Cerro Casa de Piedra 7, Patagonia, Argentina

A fossil shark tooh in early contexts of Cerro Casa de Piedra 7, southwest Patagonia, Argentina

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