Prata p aleontological district, Minas Gera
Transcription
Prata p aleontological district, Minas Gera
Geobios3 9( 2006)3 19–327 http://france.elsevier.com/direct/GEOBIO/ Original article Vertebrate fossils from the Adamantina Formation (Late Cretaceous), Prata p aleontological district, Minas Gerais State, Brazil Vertébrés fossiles du Crétacé supérieur de la Formation Adamantina, district p aléontologique de Prata, de Minas Gerais, Brésil État Vertebrados fósseis da Formação Adamantina (Neocretáceo) do Distrito Paleontológico do Prata, Estado de Minas Gerais, Brasil àà à Carlos Roberto A . Candeiro a,b,*, Adriano R. Santos a, Thomas H. Rich c,d, Thiago S. Marinho a,b, Emerson C. Oliveira a aMuseu de minerais e rochas, Universidadef ederal de uberlândia (UFU), Avenida J oão N aves de Á vila 2160, 38408-100 Uberlândia, MG, B razil bLaboratório de macrofósseis, departamento de g eologia, Universidadef ederal do Rio de Janeiro (UFRJ), avenida B rigadeiro Trompowski, s /n, I lha do Fundão, 21949-900 Rio de Janeiro, RJ, B razil cMuseum of Victoria, P O Box 666E, M elbourne, Victoria, A ustralia dSchool of geosciences, P O Box 28E, monash University, Victoria 3800, A ustralia Received 11 May 2004; accepted 21 October 2004 Available online 22 May 2006 Abstract In this contribution is given a p reliminary u p-to-date annotated list of all fossil vertebrates from the Turonian–Santonian Adamantina Forma- tion, Bauru Group where it occurs in the Prata p aleontological district which is located 45 km to the west of Prata in Minas Gerais State, Brazil. The A damantina Formation is a reddish sandstone in the Triângulo Mineiro region. These fluviolacustrine sediments were deposited in a semiarid environment. Three fossil vertebrate sites occur in the Prata p aleontological district. The diversity of vertebrates in the Adamantina Formation is modest, and its components comprise a mixture of typical austral Gondwana t axa (such as abelisaurids, A eolosaurus) and b oreal Gondwana taxa (such as Carcharodontosauridae). The absence of Laurasian taxa in the u pper p art of the Bauru Group is noteworthy. Excepting some turtles, crocodylians, and one titanosaurid, most of the specimens discovered in this Group are b ased on fragmentary and isolated remains, which make it difficult to correctly identify the fossils. For this reason, many of the t axa have only b een identified in a p reliminary manner. Despite this drawback, the dinosaurs are typical Gondwana forms with no evidence of Laurasian affinities. This is concordant with the idea that the Laurasian dinosaurs entered South America at the end of the Late Cretaceous; i.e. after the Turonian–Santonian, the age of the A damantina Formation. © 2006 Elsevier SAS. All r ights reserved. Résumé La liste des v ertébrés fossiles est mise j our dans la Formation Adamantina datée du Turonien-Santonien affleurant dans le district p aléonto- logique de Prata 45 km l’est de Prata (Minas Gerais, Brésil). La Formation A damantina est composée de grès rougeâtres dans la région du Triangle Minier. Les sédiments fluviolacustres se sont déposés dans u n environnement semi-aride. Trois sites vertébrés fossiles sont connus dans le district p aléontologique de Prata. La diversité des vertébrés de la Formation A damantina est réduite et comprend u n mélange de taxons typiques du Gondwana austral (comme des Abelisauridés, A eolosaurus) et des taxons du Gondwana b oréal (comme des Carcharodontosauridae). * Corresponding author. E-mail address: [email protected] (C.R.A. Candeiro). 0016-6995/$ - see front matter © 2006 Elsevier SAS. All rights r eserved. doi:10.1016/j.geobios.2005.10.003 320 C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 L’absence de t axons laurasiatiques dans la p artie supérieure du Groupe Bauru est r emarquable. Excepté quelques tortues, des crocodiliens et u n titanosauridé, la plupart des spécimens découverts dans ce Groupe Bauru sont r eprésentés par des restes fragmentaires et isolés. Pour cette raison, seules des identifications p réliminaires sont p roposées. Toutefois, les dinosaures sont typiques du Gondwana sans évidence d’affinité Laura- sienne. Ceci est en accord avec l’hypothèse que les dinosaures laurasiens ne seraient arrivés en Amérique du Sud qu’à la fin de Crétacé supérieur, c’est-à-dire après le Turonien-Santonien, âge de la Formation A damantina. © 2006 Elsevier SAS. All r ights reserved. Resumo Na presente contribuição é apresentada uma listagem p reliminar de todos os fósseis de vertebrados do Distrito Paleontológico do Prata (For- mação Adamantina, Turoniano-Santoniano, Grupo Bauru). As rochas da Formação Adamantina são compostas por arenitos avermelhados que afloram na região do Triângulo Mineiro. Esses sedimetnos de origem fluvio-lacustre foram depositados em u m ambiente semi-árido. São conhe- cidos três sítios de vertebrados fósseis que ocorrem no Distrito Paleontológico do Prata. A diversidade de v ertebrados na Formação Adamantina é modesta sendo representados por uma mistura típica de taxa austrais do Gondwana (abelisaurídeos e A eolosaurus) e boreais (carcarodotontosau- rídeos). A ausência de taxa laurasianos na p arte superior do Grupo Bauru é notável. Exceto p ela presença de tartarugas, crocodilianos e u m titanossaurídeo a maioria dos espécimes descobertos nessa unidade geológica é baseada em restos fragmentários e isolados os quais são de difícil identificação. Por essa razão, a maioria desses taxa têm sido somente identificados de forma p reliminar. Considerando essa desvantagem, se p ode afirmar que os dinossauros do Prata são tipicamente de formas gondwânicas com nenhuma evidência de formas laurasianas. Isso é concordante com a idéia de que os dinossauros laurasianos entraram n a América do Sul somente no final do N eocretáceo, ex. depois do Turoniano-Santo- niano, que é a idade da Formação Adamantina. © 2006 Elsevier SAS. All r ights reserved. Keywords: Late Cretaceous; Brazil; Crocodiles; Dinosaurs; Turtles Mots clés :Crétacé supérieur ; Brésil ; Crocodiliens ; Dinosaures ; Tortues Palabras-chaves: N eocretáceo; Brasil; Crocodilos; Dinossauros; Tartarugas 1. Introduction Since the b eginning of the last century, numerous specimens of fossil vertebrates have b een collected from continental Cretaceous r ocks of the Adamantina the Bauru Basin, Triângulo Formation, Bauru Group, in Mineiro region, Minas Gerais State. In the same area of Minas Gerais State, the Marília Formation (Ponte Alta and Serra da Galga Members) also has yielded fossil vertebrates. Both formations have produced faunas consisting p rimarily of fishes, turtles, crocodylians, and dinosaurs. All of these fossils occur in sandstones deposited in braided river channels. A large quantity of fossil bones has b een found in the continental Cretaceous rocks exposed in the Prata p aleontological district of the Triângulo Mineiro region of Minas Gerais State, Brazil (Fig. 1; Goldberg et al., 1995a, 1995b; Silva et al., 2001 ; Marinho, 2003; Candeiro For this reason, et al., 2003; Marinho et al., 2003). the Prata p aleontological district, located 45 km w est of the town of Prata, is k nown as one of the most important fossil locations, as it contains abundant remains of sauropod and theropod dinosaurs as w ell crocodylians and tur- tles. Many authors 1983; Barcelos, (Soares et al., 1980; Suguio and Barcelos, 1984; Candeiro, 2002) assign the sediments of Prata p aleontological district to the Adamantina Formation (Bauru Group), which was dated as Turonian–Santonian in age (Dias-Brito et al., 2001). This u nit is exposed at the Serra da Boa Vista Hill, in the vicinity of Prata. Some of the richest Cretaceous fossil vertebrate localities in Central Brazil occur in the Adamantina Formation. Many of the Adamantina Formation sites in the Prata p aleontological district have b een k nown since the 1920s (Price, 1961). Owing to a lack of reliable lithological and p aleontological data, the geological ages of these sites are not w ell established. The Adamantina Formation was formally proposed b y Soares et al. (1980). The u nit, 2–20 m t hick, consists of r ose to b rown fine grained, cross-bedded sandstone. The type section of this formation was in the town of Adamantina, São Paulo State. In Triângulo Mineiro, the A damantina Formation is the b asal lithostratigrafic u nit of the Bauru Group and is widely exposed in the area. In the Prata p aleontological district, Triângulo Mineiro (Fig. 1), three fossil vertebrate sites occur in the Adamantina Formation. These three fossil sites represent the b est record of Late Cretaceous vertebrates in the Minas Gerais State (Brazil). This makes those sites some of the most important w hen discussing the fossil r ecord of Late Cretaceous in Minas Gerais State. The vertebrates reported here are from the A damantina Formation near Prata, and b elong to the following groups: abelisaurs, carcharodontosaurs, A eolosaurus, and titanosaur dinosaurs, turtles, and crocodylians. More is known about the dinosaurs than any other group from the Prata p aleontological district. The p aleontologist Llewellyn Ivor Price first reported to the Departamento Nacional de Produção Mineral fragmentary dinosaur b ones in 1940. The fossils were transferred to Rio de Janeiro (Price, 1961). Since then, there have b een numerous fossil collecting trips to the Prata p aleontological district that have yielded new dinosaurs and other v ertebrate fossils (Silva et al., 2001). However, detailed stratigraphic studies based on dinosaur remains were not attempted. C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 321 Fig. 1. Location of the Prata p aleontological district, and geographic distribution of the Cretaceous fossiliferous location. 2. Geological setting The Adamantina Formation was defined b y Soares et al. (1980) and is known in the following states of Southeast Brazil: Goiás, Mato Grosso do Sul, Minas Gerais and São Paulo. These authors regarded it as p art of the Bauru Group, which occurs in the Paraná Basin. Based on variation in the regional lithology, Barcelos (1984) divided the Adamantina Formation into two units: the A raçatuba and São José do Rio Preto Members. The Prata p aleontological district is currently regarded as formed by rocks of the Bauru Group (Late Cretaceous) (Fig. 2). In the Triângulo Mineiro region, the A damantina, Marília and Uberaba formations sensu Fernandes and Coimbra (1996) form p art of Bauru Group. These rocks overlay the ba- salt layers of the Serra Geral Formation. Goldberg and Garcia (2000) described the A damantina Formation (Fig. 3) in the Prata p aleontological district as very fine to fine grained, w ell-sorted, cross-bedded red sandstones. Furthermore, t hese authors r ecognized intraformational conglomerates and subordinate red shales, which are massive or laminar. The top of this u nit is characterized b y the interbedding of (1) conglomerates, (2) fine- to m edium-grained crossbedded sandstones and (3) abundant nodular and h orizontal carbonate concretions, which coarsen and thicken upward. 322 C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 Fig. 2. Geological map of the Bauru Group (Upper Cretaceous) in the Triângulo Mineiro region, Minas Gerais State, Brazil (modified de Fernandes and Coimbra, 1996). Fig. 3. Bauru Group lithostratigraphic chart in Prata Suguio and Barcelos, 1983). area (modified from Von Huene (1927, 1939) regarded the Adamantina Fm as Senomanian b ased on a correlation made between the turtle Najadochelys and the sauropod “Titanosaurs australis” with similar taxa recorded in northern Patagonia, Argentina. Based on ostracods and caryophytes, Dias-Brito et al. (2001) considers the age of t his Formation to b e Turonian–Santonian (92–83 my). 3. Vertebrate paleontology The Late Cretaceous sequence of the Prata p aleontological district contains fossil remains of crocodylians, dinosaurs and turtles (Table 1; Silva et al., 2001 ; Marinho, 2003; Albuquerque et al., 2003; Marinho et al., 2003; Moraes et al., 2003). The fossil occurrences are in h illy areas located west of Prata (Fig. 1). Because of the fragmentary nature of the fossils collected thus far, they have not b een identified to a refined taxonomic level except the genus A eolosaurus. C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 323 Table 1 Vertebrate fauna of the Adamantina Formation from Prata p aleontological district. See footnotes for source r eferences included. 1 Goldberg et al. (1995a, 1995b), 2 Silva et al. (2001), 3 Marinho (2003), 4 Albuquerque et al. (2003), 5 Candeiro et al. (2003), 6 Marinho et al. (2003), 7 Moraes et al. (2003), 8 Henriques et al. (2002), 9 Almeida et al., 2003 (in p ress) TaxaLocation1 Location2 Location2 Boa vista hill GPS. 19°27′26.0″S Outskirt GPS. 19°26′21.0″S “Idelmo Bramh farm” GPS. 19°26′31.8″S and 49°14′42.6″W. and 49°15′41.3″W. and 49°14′27.8″W. Vertebrata 1–7 Vertebrata indet Reptilia Chelonia indet. Crocodylomorpha indet. Dinosauria Sauropoda Titanosauria Aeolosaurus Theropoda Theropoda indet. Abelisauridae Carcharodontosauridae 2 x x x 2 2–8 9 3, 7 x x x 3-7 x x x 3 x Fig. 4. Dinosaur remains from Prata p aleontological district. A, labial view, B, lingual view Abelisauridae tooth (MMR/UFU-PV 0006); C, labial view, D, lingual view, Carcharodontosauridae tooth (MMR/UFU-PV 005); E, labial v iew, F, lingual view, Theropoda tooth (MMR/UFU-PV 007). Bar scale represent 30 mm. G, lateral view, Titanosauria caudal vertebrae (MMR/UFU-PV 0001); H, I, lateral view, Titanosauria r ibs. Bar scale A , B, C, D, E, F bar scale = 30 mm; G = 10 mm; H, I= 50 mm. 3.1. Remarks about the dinosaurs of the P rata district Abbreviations: MACN, Museo Argentino de Ciencias N aturales, Buenos Aires, Argentina; Dinosaurs are collection; Prata Universidade Gerais, the Site. best-known This material and most diverse is housed mainly UFRJ-DG and briefly commented here. taxa from at MMR Universidad and Nacional MMR/UFU-PV, Federal de MUCPV-CH, de Comahue, El Museu de Minerais Uberlândia, Brazil; 324 Museo de la C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 Chocon e Rochas, Uberlândia, Minas RTMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Canada; U FRJ-DG-R, Departamento de Geologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, fossil reptilian collection. 3.1.1. S ystematic p aleontology Suborder THEROPODA Marsh, 1881 ABELISAURIA N ovas, 1992 Family ABELISAURIDAE Bonaparte and N ovas, 1985 Material: (MMR/UFU-PV 0006) (Fig. 4A, B). Locality: 2. Remarks: the Abelisauridae are represented b y a single tooth (MMR/UFU-PV 0006) from locality 2 on the western side of the Prata p aleontological district. This tooth was described recently b y Marinho (2003). It lacked a root but the preservation of the crown is good. It is small (32 mm), w ith serrated anterior and p osterior carinae, the denticles on the proximal p art of the anterior carina are smaller than t hose on the distal p art, and denticles on the m iddle are largest. All the denticles on the distal p art are pointed toward the crown apex. The denticles on the proximal and middle p art of the anterior carina are p erpendicular to the crown apex. The denticles on both carinae are higher than wide. The denticles of the p roximal and distal p arts of the p osterior carinae are the same size; those in the middle are larger. The cross-section of the t ooth has the anterior face compressed and p osterior face convex (MMR/UFU-PV 0006) has the labial and lingual faces more convex in cross-section nears the anterior edge and flatter p osteriorly; the lingual face is also slightly concave p roximodistally. The characters exhibited by the low crown tooth from MMR/UFU-PV 0006 clearly indicate that it represents an abelisaurid. Bonaparte (1996), Lamanna et al. (2002), Wilson and Upchurch (2003), and Candeiro et al. (2004) noted the p resence of a low crown in the Abelisauridae (e.g. A ucasaurus garridoi, Carnotaurus sastrei, R ajasarus narmadensis) teeth and regarded it as a diagnostic character of the family. Candeiro et al. (2004) pointed that abelisaurid teeth are characterized b y labial and lingual faces more convex in cross-section near the anterior edge and flatter p osteriorly; the lingual face is also slightly concave proximodistally. The cross-section of the specimen (MMR/UFU-PV 0006) is exactly as in the Abelisauridae. Family CARCHARODONTOSAURIDAE Stromer, 1931 Material: (MMR/UFU-PV 005) (Fig. 4C, D). Tooth. Locality: 2. Remarks: Marinho (2003) recently described MMR/UFUPV 005, w hich has a labial side of the tooth that is convex on its more anterior portion and p osteriorly flattened. A s on the labial side, the anterior p art of the lingual side is slightly convex, becoming p osteriorly flattened. The p osterior r egion of the lingual side b ears acute wrinkles on the enamel, which are very well developed, on the proximal and medial region, but t hese vanish toward the crown tip. Each wrinkle is obliquely oriented with respect to the tooth margin, but b ends along its length away from tooth margin until its orientation is transverse with respect t o the tooth’s long axis. The wrinkle then continues across the tooth surface as a horizontal b and. The p osterior denticles on the proximal and distal ends are equal, while the middle denticles are larger. The anterior denticles are smaller than the p osterior ones. All the denticles of b oth carinae are perpendicular to the crown apex, and are r ather higher than wide. The cross-section is chestnut-shaped. The outline of the tooth in lateral view is in the form of a rough isosceles triangle. The presence of wrinkles on a theropod teeth tooth crown has b een considered as a diagnostic feature for Carcharodontosauridae (Carcharodontosaurus s aharicus and Giganotosaurus carolinii) b y many authors (Larsson, 1996; Sereno et al., 1996; Vickers Rich et al., 1999; Candeiro et al., 2004). In Giganotosaurus carolinii different forms of wrinkles occur (Candeiro pers. obsers.) w hich can b e strong or subdued. These wrinkles may or may not b e close to the crown b order (e.g. Carcharo- dontosaurus and Giganotosaurus). The wrinkles on the crown of MMR/UFU-PV 005 are strong and similar to the wrinkles found in carcharodontosaurids. This specimen is mediolaterally compressed and thus quite similar to Carcharodontosaurus s aharicus (Stromer, 193 1) and the Giganotosaurus (MUCPV-CH-1 and casts of MACN S/N and RTMP 94.43.1, 94.43.2, 94.43.3, 94.43.4). The presence of carcharodontosaurids in the PPD is especially noteworthy as it r epresents the youngest record of this clade found to date (Turonian–Santonian). Previously, the youngest known records of carcharodontosaurids are from Cenomanian beds in Africa, Argentina and Maranhão State in Brazil. Carcharodontosaurid teeth from the MMR/UFU-PV 005 of Late Cretaceous age contrast with the osteological record of Carcharodontosauridae, which is mainly restricted to older p arts of the Cretaceous (e.g. Albian–Turonian) of Africa and South America. Order THEROPODA indet. Material: (MMR/UFU-PV 0007) (Fig. 4E, F). Tooth. Locality: 2. Remarks: no family assignment could b e made for MMR/ UFU-PV 0007, but there is no doubt that this specimen belongs to a theropod dinosaur as it is strongly labio-lingually compressed and shows denticles w ith great variation in size and shape throughout the carina. Their cross-sections are different from any of the k nown Gondwanan Theropoda, but it is important to note that the teeth of some Gondwanan dinosaurs are still unknown (Novas, 1997). TITANOSAURIA Bonaparte and Coria, 1993 Genus A eolosaurus Powell, 1986 Aeolosaurus indet. Material: (UFRJ-DG 270-R). Caudal vertebra. Locality: 2. Remarks: the sauropods are the most common and abundant fossil v ertebrate remains found in the region (Fig. 4G–I). Numerous p ostcranial b ones r epresent (2003, 2004) (UFRJ-DG them. Almeida et al. 270-R caudal vertebra) (Fig. 5A–C) C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 325 Fig. 5. A eolosaurus caudal vertebra UFRJ-DG 270-R. Lateral v iew (A), posterior (B) and anterior (C). Abbreviations: CN, neural canal; PRZ, postzigapophysis; PT, transverse process; PZ, postzygapophysy; SN, neural spine. Scale bar 50 mm. and Henriques et al. (2002) reported the presence of titanosaurid sauropods. Almeida et al. (2003, 2004) recognized the t itanosaurid genus A eolosaurus, w hich was first described from the Late Cretaceous of Patagonia (Argentina) (Powell, 1986, 2003; Salgado and Coria, 1993; Salgado, 2000). Although this vertebra is almost complete, it did suffer some damage. This damage made it possible to observe the internal spongy composition (Fig. 5B) of the b one. The v ertebral centrum is deep and r elatively low, p rocoelous, and b ears a h eart-shaped anterior articular facet (Fig. 5C). The transverse process is w ell developed and p ositioned at the centro-neural suture. The b ase of the neural arch is p ositioned anteriorly in relation t o the vertebral centrum. The neural canal is oval—the lateral diameter is the longer one. The neural spine is large and posteriorly oriented, showing a well-developed p respinal laminae (PRSL) (Fig. 5A). The spinoprezygapophyseal laminae are also well developed and b oth are j oined to the b ase of the PRSL. The postzygapophysis is w ell marked. The haemal arch is straight and laterally compressed. Although its proximal region is fragmented, its Y-shaped nature is readily seen. The open haemal canal indicates that this caudal vertebra belongs to the Camarasauromorpha. Within that group, the p rocoelous condition of this caudal vertebrate is a synapomorphic feature that allies it w ith the “Titanosauridae” (Bonaparte and Coria, 1993; Wilson and U pchurch, 2003). The h eart-shaped p osterior articular facet and w ide p rezygapophyses allow u s to r elate this vertebra to the taxa Gondwanatitan/Aeolosaurus. Recently, a titanosaurid (MN 5013-V) was recognized at the same locality (the Boa V ista Hill) (Table 1). However, Almeida et al. (2004) pointed out that the specimen lacked features of the Gondwanatitan/Aeolosaurus complex. Henriques et al. (2002) suggested that this fossil was a new taxon closely related t o these genera. TITANOSAURIA indet Material: (MMR-UFU-PV 001). Caudal v ertebrae. Locality: 2. Remarks: there are several fragments of disarticulated bones found in A damantina Formation sediments in the Prata paleontological district that have not p reviously b een attributed to the Titanosauridae (sensu Powell, 1986, 2003; McIntosh, 1990). These specimens are caudal v ertebrae (MMR-UFU-PV 001; Fig. 4G) that are strongly p rocoelous, having “ball socket” p osterior articular faces. According Powell (1986, 2003) and McIntosh (1990) among Titanosauria, titanosaurids developed anterior caudals w ith a deeply excavated anterior face much like a “socket” and a p osterior articulation like a p rominent “ball”. 3.1.2. A damantina F ormation f ossil localities in the P rata paleontogical district Price studied the first fossil site in the Prata p aleontological district in the 1950’s. However, it was only in 2002 that fossil localities in the Adamantina Formation were discovered in that area b y researchers from the Universidade Federal de Uberlândia (Museu de Minerais e Rochas). Three fossil v ertebrate sites in the A damantina Formation are mentioned in the literature (e.g. Albuquerque et al., 2003). The b est-known vertebrate fossils of A damantina Formation occur in the Prata p aleontological district and are listed in Table 1. 4. Concluding remarks The fossils from the Prata p aleontological district are all vertebrates mainly collected at the Boa Vista Hill fossil site, Locality 2. The b est-known taxa from the Adamantina Formation are referred to the Abelisauridae, Carcharodontosauridae and Titanosauria (Aeolosaurus and Titanosauria indet.). Although the vertebrate fossil record of Prata District is currently p oorly known, w ith few w ell-preserved specimens, many fragmentary remains have b een found. Fossil localities are centered in the western p arts of Prata municipality, and resemble the fauna from southern South America (Patagonia). The dinosaurs of the Prata District comprise two families of Gondwanan theropods (Abelisauridae and Carchadorodontosauridae), one genus of titanosaurs (Aeolosaurus). Single crocodilian and turtle records are reported in the literature from the Prata District. Their presence supports the earlier conclu326 C.R.A. Candeiro et al. / Geobios 39 (2006) 319–327 sions of Von Huene (1927, 1939) that correlated the fauna of Adamantina Formation with those found in the Late Cretaceous of Argentina or even those of Africa, India and Madagascar. Although only a few of the n amed Prata taxa h ave b een fully reported, a picture is emerging w hich suggests a Gondwanan origin for the assemblage (Bonaparte, 1986). Carcharodontosaurs are common in the early Late Cretaceous in South America (Coria and Salgado, 1995; Leanza et al., 2004), but in the Prata District of Minas Gerais State a record of this group indicates that it possibly survived into the Late Cretaceous. Titanosaurs and abelisaurs dominate the Late Cretaceous in the Gondwana landmasses. They are found also in Late Cretaceous of the Prata District. A eolosaurus is found not only in the Prata p aleontological district but also in the Late Cretaceous of A rgentina. Typical Laurasian taxa such as ornithischians have b een widely documented in several Late Cretaceous u nits of Southern South America (e.g. Bonaparte et al., 1984; Salgado and Coria, 1996; De Valais et al., 2003; N ovas et al., 2004). Because they are absent from earlier Turonian–Santonian deposits including the A damantina Formation, this suggests t hat the physical connection between N orth and South America was not established u ntil the end of the Cretaceous. Acknowledgments We thank Agustin G. Martinelli (Museo A rgentino de Ciencias N aturales, Buenos Aires) for thorough and helpful comments that greatly improved this manuscript. For references, we thank Jeffrey A. Wilson (University of Michigan), P. Up- church (University of Cambridge) and F. N ovas (Museo Ar- gentino de Ciencias N aturales). The authors also t hank Alberto Garrido (Museo Carmen Funes, Cipoletti) and an anonymous reviewer for critically reading the manuscript valuable suggestions. We Bergqvist, Leonardo specially thank and p roviding Lílian S. Avilla and Erika A branches tório de Macrofósseis, Departamento Paglarelli (Labora- de Geologia, U niversi- dade Federal do Rio de Janeiro) for allowing u s free access to laboratories ho, Cláudia and specimens in their charge. Adelino Carval- Regina A. Candeiro, Edeilson P. Silva, Edivane Cardoso, Flávio Oliveira, Jorge Augusto Albuquerque, Patricia Tavares (Uberlândia), and Sérgio Moraes (Prata) deserve many thanks for assistance during 2002–2003 Regina A. Candeiro (Uberlândia) and at Centre National de la Recherche résumé observations field seasons. Cláudia Éric Buffetaut Scientifique, (Research Paris) made and correction of the grammar. 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