DOI: 10.5327/Z0375-75362012000200008 42(2): 323-330, junho de 2012 Theropod teeth from the Marília Formation (late Maastrichtian) at the paleontological site of Peirópolis in Minas Gerais State, Brazil Carlos Roberto A. Candeiro1*, Philip J. Currie2, Lílian P. Bergqvist3 Abstract Theropod teeth can be separated at the family level using the basal cross-section, and by the presence or absence of wrinkles in the enamel of the tooth crowns. Theropods comprise the most common vertebrate remains in the fossil assemblage from the Serra da Galga Member, Marília Formation (late Maastrichtian) in the Bauru Basin Peirópolis paleontological site (Uberaba Town, Minas Gerais State), in southeastern Brazil. In this study, cross-sectional outlines of the teeth and wrinkles on the surfaces of the crowns were used to group the teeth into nine morphological classes. The tooth cross-sections were drawn using a copper wire to contour the outlines of the most proximal portions of the tooth crowns. Other features were analyzed using a microscope. Within the nine morphological classes, morphotypes one and two can be assigned to the Abelisauridae, and morphotypes three to seven belong to the Carcharodontosauridae. This is the most abundant record of Abelisauridae in Minas Gerais State, Brazil. Morphotypes eight and nine were not identified because they do not have any diagnostic features of known Gondwanan or Laurasian taxa. The presence of Carcharodontosauridae teeth in the Member of Serra da Galga (late Maastrichtian) is the youngest record for this family. Keywords: dinosaur; Late Cretaceous; theropod teeth; Minas Gerais State; Brazil. Resumo Dentes de terópodes da Formação Marília (Neomaastrichtiano) do sítio paleontológico de Peirópolis do estado de Minas Gerais, Brasil. Dentes de dinossauros terópodes possuem várias características morfológicas a nível familiar. As principais características diagnósticas são: a forma do dente em seção transversal e a presença de enrugamentos na coroa do dente. Terópodes representam os restos de vertebrados mais comuns na assembleia fóssil do Membro Serra da Galga, Formação Marília (Neomaastrichtiano), Bacia Bauru, no sítio paleontológico de Peirópolis (cidade de Uberaba, estado de Minas Gerais), no Sudeste do Brasil. Neste estudo, seções transversais dos dentes e enrugamentos nas faces das coroas foram utilizadas para agrupar os dentes em nove classes morfológicas. As seções transversais dos dentes foram desenhadas utilizando-se um fio de cobre para contornar as porções mais proximais de suas respectivas coroas. Outras características foram analizadas, usando-se um microscópio. Dentro das dez classes morfológicas, os morfotipos um e dois podem ser atribuídos ao Abelisauridae, enquanto que os morfotipos três a sete pertencem a Carcharodontosauridae. Os dentes de Abelisauridae são os mais abudantes no registro fossilífero no Sítio de Peirópolis, em Minas Gerais, no Brasil. Os morfotipos oito e nove não foram identificados pois não apresentam nenhuma característica diagnóstica de terópodes conhecidos no Gondwana ou na Laurásia. A presença de dentes Carcharodontosauridae, no Membro Serra da Galga (Neomaastrichtiano), é o registro geológico mais recente desta família. Palavras-chave: dinossauros; Neocretáceo; dentes de terópodes; estado de Minas Gerais; Brasil. INTRODUCTION Theropod teeth (carnivorous Another problem with isolated teeth is the lack dinosaurs) are relatively abundant in the geological of studies that have been done on the taxonomic sig- record, but they are rarely studied and identified. The nificance of theropod dental morphology (Currie, 1987; main reason for this situation is the lack of sufficiently Farlow & Brinkman, 1987; Currie et al., 1990; Farlow diagnostic material, as usually only isolated teeth and et al., 1991). Many studies have been carried out on den- tooth fragments are recovered. Identification can be dif- tition replacement (Cooper et al., 1970; Osborn, 1971, ficult in the absence of association with more readily di- 1975; Kline & Cullum, 1984; Bolt & Demar, 1986), but agnostic cranial bones. Additionally, it is necessary to most of them focus on the relationships between diet have complete dentitions in order to recognize variation and dentition (Hotton, 1955; Massare, 1987; Tanke & within the jaws (Chandler, 1990; Currie et al., 1990). Currie, 1998; Candeiro & Tanke, 2008). 1Laboratório de Geologia, Curso de Geografia,Campus Pontal, Universidade Federal de Uberlândia - UFU, Ituiutaba (MG), Brazil. E-mail: [email protected] 2Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Building, Edmonton, Alberta, Canada. E-mail: [email protected] 3Laboratório de Macrofósseis, Departamento de Geologia, Universidade Federal do Rio de Janeiro - UFRJ, Rio de Janeiro (RJ), Brazil. E-mail: [email protected] *Autor correspondente Arquivo digital disponível on-line no site www.sbgeo.org.br 323 Theropod teeth from Marília Formation at the paleontological site of Peirópolis Theropod teeth are the most abundant cranial • CPP: Centro de Pesquisas Paleontológicas material found at the Paleontological Site of Peirópolis Llewellyn Ivor Price, Peirópolis; (Fig. 1) near Uberaba Town in Minas Gerais State, in • DG/UFRJ: Departamento de Geologia of Brazil. The exposures at the site are composed of Marília Universidade Federal do Rio de Janeiro, Rio de Formation sediments (late Maastrichtian). Other verte- Janeiro; brates from the site include disarticulated bones from • MACN: Museo Argentino de Ciencias Naturales, fish, turtles, lizards, crocodiliforms, titanosaurs, and Buenos Aires; theropods (Candeiro et al., 2006, 2008, Candeiro, 2007, • MCF-PVPH: Museo Municipal Carmen Funes, 2009 and references therein). However, the only crani- Paleontologia de Vertebrados, Plaza Huincul; al theropod elements found are teeth. These are labio- • UNPSJB-PV: Universidad Nacional de la lingualy compressed and have carinae with denticles. Patagonia, “San Juan Bosco”, Comodoro Previous to this study, the theropod tooth collections Rivadavia; from the Paleontological Site of Peirópolis housed in • PVL: Fundación-Instituto Miguel Lillo, Centro de Pesquisas Paleontológicas Llewellyn Ivor Tucumán; Price (Peirópolis) included 55 specimens. Kellner (1995, • MUCPV-CH: Museo de la Universidad Nacional 1996) and Candeiro et al. (2004) studied the morpho- de Comahue, El Chocon collection; logic aspects of these theropod teeth. Other studies by • RTMP, Royal Tyrrell Museum of Palaeontology, Franco & Bertini (1997) and Franco (2000) focused on Drumheller. theropod tooth taxonomy. This study presents a detailed description of the teeth from Peirópolis, based on tooth MATERIAL AND METHODS Fifty-five isolated morphology. theropod teeth were micro-photographed using a scan- ning electron microscope (SEM) and a ZENIT 12 cam- Institutional abbreviations era. The following measurements were taken: tooth • AMNH: American Museum of Natural History, crown height (TCH); fore aft basal width – FABL New York; (Currie et al., 1990, Farlow et al., 1991; Sankey et al., 0° 10°S 1N 70°W 60°W 20°S Brazil 18° 40°W 50°W Paranaíba River Minas Gerais Goiás State State Grande River 20° São Paulo State 0 100 km BAURU GROUP Marília Formation Uberaba Formation Adamantina Formation Figure 1 – Locality and geological map of the Triângulo Mineiro region, Minas Gerais State, Brazil (modified from Fernandes & Coimbra 1996). 324 Revista Brasileira de Geociências, volume 42(2) 2012 Carlos Roberto A. Candeiro et al. 2002; Smith & Dodson, 2003); and numbers of denti- HORIZON AND AGE All the teeth are from the cles per millimeter on the proximal and distal portions Serra da Galga Member of Marília Formation – late of the anterior and posterior carina. Cross-sections of Maastrichtian (Dias-Brito et al., 2001). each specimen were traced from a copper thread, which had been wrapped around the base of the tooth crown. DESCRIPTION Teeth of morphotype one (Figs. 2A to The geological subdivision of the Bauru Group (Bauru D) are characterized by slightly convex labial and lingual Basin) hereafter follows Fernandes & Coimbra (1996). surfaces, which are compressed along the margins where they have contact at the carina. The denticles at the prox- SYSTEMATIC PALEONTOLOGY imal end of the anterior carina are smaller than those in THEROPODA (Marsh, 1881); the posterior carina, but the middle denticles of the ante- CERATOSAURIA (Marsh, 1884); rior carina are larger than at either end. All the denticles at NEOCERATOSAURIA (Novas, 1991); the distal ends of both carinae point towards the apex of ABELISAURIA (Novas, 1992); the crown, but this is less pronounced in the proximal and ABELISAUROIDEA (Bonaparte, 1991); middle denticles. All the denticles of both carinae are re- ABELISAURIDAE (Bonaparte & Novas, 1985). stricted to the enameled part of the crown. The denticles of the proximal and distal regions of the posterior carina Morphotype 1 are the same size, while the middle ones are larger. REFERRED matErial CPP 002, 020, 021, 121, 134, 136, 144, 150, 158, 205, 206, 207, 242, 452, 463, 477. Morphotype 2 REFERRED matERIAL CPP 123, 129b, 129c, 131, LOCALITY Peirópolis site, near Uberaba Town, 132, 135, 154, 161/1, 198, 211, 372, 375/2, 446, 451/1, Minas Gerais State, Brazil. 452/1, 476, 478. 500 µm 5 mm 200 µm 500 µm C 200 µm H A E F G B 2 mm 2 mm F I D 200 µm 200 µm 500 µm 500 µm 200 µm 200 µm P T L R J N O 2 mm S 2 mm K 2 mm U M Q Figure 2 – Abelisauridae teeth. (A and C) SEM microphotograph of anterior and posterior denticles,