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Journal of South American Earth Sciences 39 (2012) 16e23

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Journal of South American Earth Sciences

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Footprints of large theropod dinosaurs and implications on the age of Triassicbiotas from Southern Brazil

Rafael Costa da Silva a,*, Ronaldo Barboni b, Tânia Dutra b, Michel Marques Godoy c,Raquel Barros Binotto d

aCPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Departamento de Geologia, Divisão de Paleontologia, Av. Pasteur, 404, Urca,22290-240 Rio de Janeiro, RJ, BrazilbGraduation Program in Geology, Universidade do Vale do Rio dos Sinos e UNISINOS, Av. Unisinos, 950, 93022-000 São Leopoldo, Rio Grande do Sul, BrazilcCPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Gerência de Recursos Minerais, Rua Banco da Província, 105, Santa Teresa,90840-030 Porto Alegre, RS, BrazildCPRM e Companhia de Pesquisa de Recursos Minerais e Serviço Geológico do Brasil, Gerência de Relações Institucionais e Desenvolvimento, Rua Banco da Província,105, Santa Teresa, 90840-030 Porto Alegre, RS, Brazil

a r t i c l e i n f o

Article history:Received 31 January 2012Accepted 23 June 2012

Keywords:EubrontesDinosaurCaturrita FormationGondwana

* Corresponding author.E-mail addresses: rafael.costa@cprm.gov.br

(R.C.da Silva), ronaldobarboni@hotmail.com (R. B(T. Dutra), michel.godoy@cprm.gov.br (M.M. Godoy)(R.B. Binotto).

0895-9811/$ e see front matter � 2012 Elsevier Ltd.http://dx.doi.org/10.1016/j.jsames.2012.06.017

a b s t r a c t

Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, SouthernBrazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate aboutits exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted ashaving been produced by large theropod dinosaurs. The morphological characteristics and dimensions ofthe footprints are more derived than those commonly found in the CarnianeNorian, and are moreconsistent with those found during the RhaetianeJurassic. The trackmaker does not correspond to anytype of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content ofthis unit also support a more advanced Rhaetian or even Jurassic age for this unit.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The study of tetrapod fossil tracks provides a great amount ofdata about diversity, functional morphology, behavior and ecolog-ical relationship of extant animals, beyond sedimentologicalfeatures of the substrate and paleoenvironmental aspects. Tradi-tionally, they are not used for biostratigraphic purposes, althoughthey may be important for determining the age of successionslacking body fossils or for the refinement of ages when associatedwith them (e.g. Lucas, 1998; Lucas and Tanner, 2007).

In southernmost Brazil (state of Rio Grande do Sul), the LinhaSão Luiz outcrop exposes levels of the Caturrita Formation and hasprovided numerous and well preserved fossils, including cyn-odonts, dinosaurs, possible pterosaurs, sphenodontids, procolo-phonids, fishes, insects, conchostraca, invertebrate ichnofossils andremains of several distinct types of gymnosperms. The diversefossil record of the Caturrita Formation and its lithological

, paleoicno@yahoo.com.brarboni), tdutra@unisinos.br, raquel.binotto@cprm.gov.br

All rights reserved.

relationships indicate an Early Norian age (Late Triassic) for thisunit (Rubert and Schultz, 2004), although more recent studiessuggest a NorianeRhaetian age (Abdala and Ribeiro, 2010).Recently, two footprints were found in the upper portion of theoutcrop. Together with some paleofloristic and other paleofaunisticdata, it reopens the debate about the age of the Caturrita Formation.This study aims to analyze these tracks and their paleontologicaland geological context.

2. Material and methods

The studied material was identified at the Linha São Luizoutcrop (29�3304500S; 53�2604800W), municipality of Faxinal doSoturno, state of Rio Grande do Sul (Fig. 1), and consists of twofootprints preserved in a tabular sandstone layer that representsthe upper part of a rhythmic succession of sand andmud layers andoverbank deposits (crevasse splay). They received the field codeFSSL-01 and FSSL-02 (FS ¼ Faxinal do Soturno; SL ¼ São Luiz). Thefirst one was collected in 2008 and housed at the paleontologicalcollection of Museu de Ciências Naturais, Fundação Zoobotânica doRio Grande do Sul, Porto Alegre, Rio Grande do Sul, under thenumber MCN-PIC.030. The second footprint, FSSL-02, was found in2009 less than a meter away from the first, covered by a layer of

Fig. 1. Location of the Linha São Luiz outcrop in the state of Rio Grande do Sul, Southern Brazil (based on Schultz et al., 2000).

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sandy siltstone. It was studied and prepared in situ and kept inplace. This footprint was moistened to enhance the contrast for thephotographic record. A plaster model was made in the field anddeposited in the mentioned institution. The specimens wereprepared by mechanical processes. Footprint parameters werebased on Leonardi (1987) and measured using the computerprogram ImageJ (Abramoff et al., 2004).

3. Geological context

The Caturrita Formation is considered a Triassic independentunit from the Paraná Basin (Andreis et al., 1980; Faccini, 1989). Itwas subdivided in two parts based on its fossil content (Zerfasset al., 2003; Faccini, 2007). The basal one was considered EarlyNorian due to its vertebrate fauna (Barberena, 1977; Schultz et al.,2000; Rubert and Schultz, 2004), and the youngest one (“MataSandstones”), probably Rhaetian by the presence of allocthonousAraucarioxylonwood logs (Faccini, 1989, 2007; Guerra-Sommer andCazzulo-Klepzig, 2000).

According to sequence stratigraphic concepts, the CaturritaFormation corresponds to a transgressive tract system that includestwo possibly incomplete third order sequences, deposited ina tectonically and structurally disturbed area (Zerfass et al., 2003,2004). Deposition occurred in high energy, low sinuous andephemeral river systems with associated plains or lakes in anextensional basin, contemporaneous to those from Waterberg,South Africa, and Cuyo and Ischigualasto, western Argentina(Zerfass, 2007). The active tectonism that affected the Triassicsuccessions from Rio Grande do Sul (Andreis et al., 1980; Da-Rosaand Faccini, 2005; Zerfass, 2007) led to a progressive increase inaccommodation rate that supported delta progradation andlongitudinal and transversal faults. The related block dislodgementaffect correlations.

The Linha São Luiz outcrop (Fig. 2) is about 20 m high andcomposed of sandstones in the basal portion, mudstones in the

middle, and rhythmic sandstones and mudstones at the top. Thebasal portion is composed of low angle cross bedded and wellsorted fine to medium sandstones, as well as short scale troughcross-bedded sandstones (fluvial system) followed by massive orsigmoidal trough cross-laminated fine sands associated withcrevasse deposits (Faccini, 2007), generated into a fluvio-deltaicsystem (Faccini, 1989; Zerfass, 2007).

The following laminated mudstone-siltstone interval representsa more permanent lake and yielded autochthonous and para-utochthonous gymnosperm wood material (Pires and Guerra-Sommer, 2004; Dutra and Crisafulli, 2009), branches of diversi-fied conifers and rare Equisetales, and impressions of sterile andreproductive parts of Bennettitales (Wilberger et al., 2004; Barboniand Dutra, in press), accompanied by conchostraca, insects and fishscales. The upper portion of the outcrop is represented by hetero-lithic sandstone and mudstone deposits with evidences ofepisodically subaerial exposure. These are considered to representa crevasse splay deposition and contain the two large dinosaurfootprints herein discussed, associated with desiccation cracks, inthe surface of a thick tabular sandstone layer.

4. Systematic ichnology

Ichnogenus Eubrontes Hitchcock, 1845Eubrontes isp.

Material: MCN-PIC.030 and FSSL-02, isolated footprints (Fig. 3).Description: The footprints are digitigrade, tridactyl and

mesaxonic, with acute digital extremities and hypices and witha rear margin indented by a posteromedial notch or a heel-likebulge. The footprint MCN-PIC.030 is incomplete due to erosionand corresponds to the impression of a left foot with the plantarportion, digit IV and the proximal portion of the digits II and IIIpreserved. Digit IV presents three phalangeal pads and a clawmark.This footprint is oriented approximately to northwest, having 11 cm

Fig. 2. Detailed section of Linha São Luiz outcrop, Paraná Basin, Southern Brazil. A, General view of the outcrop; B, Fluvial (base), lacustrine (middle) and crevasse splay (top)deposits; C, General view of the crevasse splays deposits.

R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e2318

of sole length and 22 cm of sole width. The footprint FSSL-02corresponds to the complete impression of a right foot, with thedigits medially curved. It is longer than wide and there are nophalangeal or plantar pads. Digits II and IV are almost equal inlength while digit III is longer. This footprint is oriented approxi-mately southeast and presents 43 cm of length and 39 cm of width.Measurements of both footprints are given in Table 1.

Remarks: The footprints clearly fulfill the criteria of impressionsmade by dinosaurs and cannot be confused with archosaurian

chirotheroid footprints due to the strongmesaxonic and digitigradepattern. The studied footprints can be attributed to Eubrontes due tothe totally digitigrade instance, the typical tridactyl theropodmorphology and the big size, longer than 28 cm (as defined byOlsen et al., 1998). Morphologically, the studied material is closer toEubrontes veillonensis Lapparent and Montenat, 1967. However,given the absence of trackways or more specific details, the iden-tification at ichnospecific level is not possible. The footprints differfrom other ichnogenera of similar size like Gigandipus Hitchcock,

Fig. 3. Eubrontes isp., footprints from Caturrita Formation at Linha São Luiz outcrop. A, MCN.PIC.030, specimen at the field and after collecting; B, FSSL-02, specimen at the field onthe surface and cutted; C, Composite photograph illustrating the original position of the two footprints; D, Original and cast of the specimen FSSL-02.

R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e23 19

1855 by the absence of hallux impressions, and TyrannosauropusHaubold, 1971 by the presence of longer digits in relation to thesole. Gigandipus was also considered a behavioral variant ofEubrontes (Rainforth, 2004, 2005). An isolated footprint resemblingthe studiedmaterial was illustrated and briefly described by Turneret al. (2009: 63) as “.Large ornithopod footprint cf.Wintonopus, ca.

Table 1Parameters of the footprints from Caturrita Formation (L ¼ length, W ¼ width,SL ¼ sole length, SW ¼ sole width, D ¼ divarication, TD ¼ total divarication). Linearmeasures in cm.

L W SL SW L II L III L IV D IIeIII D IIIeIV TD

MCN-PIC.030 e e 11 22 e e 17 44� 25� 69�

FSSL-02 43 39 17 31 19 29 22 28� 24� 52�

48 cm long.”, but this footprint does not match the diagnosticpatterns of that ichnogenus like the smaller size, broad digits withrounded or bluntly angular tips, and digits III and IV close together,parallel or slightly divergent.

5. Discussion

The two footprints identified as Eubrontes isp. are typical of largetheropod dinosaurs (e.g. Haubold, 1971; Thulborn, 1990; Lockley,1991). The footprints are preserved in a tabular sandstone layerand show signs of deformation. During the preparation in the field,it was observed that the sandy siltstone layer that covers thefootprints was also deformed and revolved above them, whatmeans that the trackmaker stepped on the fresh silty sediment,crossing through it and reaching the sand below (e.g. Brand and

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Kramer, 1996; Milàn and Bromley, 2006). The imprints are notrecognizable in the siltstone because of the semi-fluid nature of theoriginal substrate, but they are preserved in the sandstone. Thisprocess may enhance the preservation potential of the footprints,because eliminates the aerial exposure after their generation. It canalso explain the differences in size between the two footprints,because the original footprint was probably larger than thepreserved one, with their size controlled by the depth of theimpression (Fig. 4). This kind of preservation can be understood asa variation of the classic undertracks and ghostprints, and is similarto what was called “cut undertracks” by Goldring and Seilacher(1971). It was also noted in tracks preserved in grainflows ofdune deposits of the Lower Jurassic Navajo Sandstone, south-western USA (Loope, 2006).

Also, there are no other, smaller tracks on the same surface,which probably results from the “Goldilocks” effect as noted byFalkingham et al. (2011). In such cases, only a narrow range of loadscan produce tracks, given that small animals failed to indent thesubstrate.

The total divarication of the studied footprints is slightly higherthan the average for the ichnogenus Eubrontes, indicating that theywere produced on a softer and wetter ground. Footprints producedon this kind of substrate tend to show higher divarication anglesthan those produced on firm ground (Currie and Sargeant, 1979;Thulborn, 1990). The heel-like bulges at the rear margin of thefootprints are occasionally produced when the foot does not sinkdeeply into the substrate. Such features are usually found intheropod footprints (Haubold, 1971; Thulborn, 1990), as those fromNortheast Brazil (Carvalho, 2000, 2004; Leonardi, 1994). It is notpossible to determine if the footprints were made by a singletrackmaker, because their size and direction are different.

The footprint FSSL-02 corresponds to a complete impression ofa right foot with 31 cm of sole width and 43 cm of total length. Thisfootprint was the base to estimate the size of the trackmakeraccording to the equations used by Thulborn and Wade (1984) andThulborn (1989). Employing both methods discussed by thoseauthors: morphometric ratios (h ¼ 4.9 FL when footprint length[FL] is higher than 25 cm, for large theropods) and allometricequations (h ¼ 8.6 FL0.85, when FL > 25 cm), it was possible toestimate the height at the hip joint (h) at 2.10 m, what correspondsto an animal with up to 8 m long, similar in size to a big Allosaurus.

Currently, the known paleofauna of Linha São Luiz outcropincludes mainly small animals, like the sphenodontian Clevosaurusriograndensis (Bonaparte and Sues, 2006), the procolophonid

Fig. 4. Preservation of the footprints (specimen FSSL-02) as “cut undertracks”, in which theallowed the impression in already buried layers.

Soturnia caliodon (Cisneros and Schultz, 2003), the lepidosaur-iformes Cargninia enigmatica (Bonaparte et al., 2010a), the cyn-odonts Riograndia guaibensis (Bonaparte et al., 2001), Brasilodonquadrangularis, Brasilitherium riograndensis (Bonaparte et al., 2003)and Minicynodon maieri (Bonaparte et al., 2010a), the possiblepterosaur Faxinalipterus minima (Bonaparte et al., 2010b), and themedium-sized dinosaur probably Guaibasaurus candelariensis(Rubert and Schultz, 2004; Bonaparte et al., 2006). All of them arerestricted until now to the massive sandstones of the basal crevassesplay deposits of São Luiz outcrop (Bonaparte et al., 1999, 2001,2003, 2006, 2010b; Cisneros and Schultz, 2003; Martinelli et al.,2005; Bonaparte and Sues, 2006; Arantes et al., 2009; Soareset al., 2011a,b). As a whole, the paleofauna of Caturrita Formationincludes also the medium-sized dicynodont Jachaleria candelar-iensis (Araújo and Gonzaga, 1980), an indeterminate phytosaur(Kischlat and Lucas, 2003), the cynodont Irajatherium hernandezi(Martinelli et al., 2005), indeterminated sphenodontians, a stereo-spondyl temnospondyl (Dias-da-Silva et al., 2009), the dinosaur-omorph Sacisaurus agudoensis (Ferigolo and Langer, 2006) andUnaysaurus tolentinoi (Leal et al., 2004), beyond more fragmentaryarchosaur and cynodont remains (Dornelles, 1990; Ribeiro et al.,2011).

Other dinosaurs recorded in the Brazilian Triassic include Pam-padromaeus, Staurikosaurus, Saturnalia and also Grallator footprintsfrom the lower Santa Maria Formation (Colbert, 1970; Langer et al.,1999; Silva et al., 2008; Cabreira et al., 2011). In addition, trackswere previously recorded in the Caturrita Formation at the NovoTreviso site and assigned to prosauropod dinosaurs (Silva et al.,2007). However, those rocks were reinterpreted in a recentmapping of the region as belonging to the Guará Alloformation,Late Jurassic to Early Cretaceous in age (Scherer et al., 2000, 2001;Zerfass, 2007). Dinosaur footprints were also recorded in otheroutcrops of the Guará Formation and assigned to Sauropoda andTheropoda (Schultz et al., 2003; Dentzien-Dias et al., 2005; Diasand Schultz, 2005; Dentzien-Dias and Bertoni-Machado, 2005;Scherer and Lavina, 2005). Thus, the structures found in NovoTreviso are similar in age and shape to the other imprints fromGuará Formation and could be related to the same trackmakers.

Of the above mentioned taxa, none represent potentialproducers for the footprints dealt with here. The largest knowndinosaurs from Caturrita Formation, U. tolentinoi and G. candelar-iensis, are considerably smaller than the Eubrontes trackmaker, aswell as the others known dinosaurs from the Triassic of the ParanáBasin (Fig. 5). In fact, the Grallator footprints from Santa Maria

semi-fluid nature of the original substrate controlled the depth of the impression and

Fig. 5. Dinosaurs recorded in the Brazilian Triassic, based on body fossils and ichnofossils. Note the incongruent size of Eubrontes trackmaker compared to the others.

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Formation (Silva et al., 2008) correspond to what would be ex-pected for the Brazilian Triassic dinosaurs.

Ichnologists have long debated about the age of the oldestoccurrence of the ichnogenus Eubrontes. Haubold (1971) regardedthe occurrence of Eubrontes as spanning both Late Triassic and EarlyJurassic. Olsen and Galton (1984) proposed that its lowest occur-rence matches with the base of the Jurassic, due to the corre-spondence between the appearance of this ichnogenus in theNewark Supergroup and the Passaic palynofloral event (but seeLucas and Tanner, 2007). Thereafter, most ichnologists began toconsider Eubrontes tracks as indicative of Jurassic age (e.g. Haubold,1986; Lockley and Hunt, 1994). Indeed, Olsen et al. (2002a, 2002b)concluded that the sudden appearance of Eubrontes giganteous inthe Early Jurassic of the Newark Supergroup indicates a dramaticsize increase in theropod dinosaurs at the TriassiceJurassicboundary. However, E. giganteous appears to also occur in thelatest Rhaetian based on the new definition of the base HettangianGSSP (Olsen et al., 2011).

Triassic theropod tracks were revised by Lucas et al. (2006), whoassigned all tridactyl footprints longer than 25 cm to Eubrontes.They listed distinct tracks, with varied sizes, from Australia (Car-nian? 43 cm long), Southern Africa (Norian, up to 35 cm), GreatBritain (NorianeRhaetian, 26 cm), Switzerland (Norian, 25e30 cm),France (Norian, 50 cm?; Rhaetian, 40 cm), Germany (Rhaetian,25 cm), Sweden (Rhaetian, 32 cm) and Greenland (Norian, 28 cm).However, the size criteria applied alone cannot provide a solidichnotaxonomic basis, and morphological elements should beconsidered for an appropriated identification. They also argued thatthe footprints from Great Britain, France, Germany and Greenlandare of grallatorid morphology. Lucas and Tanner (2007) also citedthat theropods large enough to have made at least some Eubrontes-size tracks are known from the Late Triassic body-fossil record asLiliensternus (Norian of Europe, estimated length of 5 m) andGojirosaurus (Norian of the USA, estimated length of 5.5 m), butanimals of this size do not explain the occurrence of footprints withmore than 30 cm long as those described. The problem of theidentification of some Triassic footprints as theropodan in originalso has been discussed by several authors (e.g. Olsen et al., 1998;Olsen et al., 2003; Lucas et al., 2006).

Although the subject is still far from being closed, it seems clearthat the emergence of Eubrontes trackmarkers occurred before thebeginning of the Jurassic, and that there are Triassic animalscapable of producing at least mid-sized Eubrontes-like footprints.Nevertheless, there is an agreement betweenmost researchers thatmost Eubrontes tracks are clearly Jurassic, or at least that theropodfootprints with more than 40 cm in length, and with eubrontidmorphology, are more characteristic of the Jurassic.

The age of Caturrita Formation is also subject of discussion in theliterature. Rubert and Schultz (2004) proposed the IctidosauriaCenozone to the upper part of Caturrita Formation. Soares et al.(2011a,b) have proposed to replace the “Ictidosauria Cenozone”for the Riograndia Assemblage Zone. It was correlated with thefaunas of Los Colorados Formation, from Argentina, traditionallyplaced in the Norian. A Norian age for the Caturrita Formation hasbeen used ever since, despite earlier works considered the depo-sition of the Los Colorados Formation as Rhaetian in age (Heckertand Lucas, 1998; Lucas, 1998; Arcucci et al., 2004).

According to Abdala and Ribeiro (2010), a late NorianeRhaetianage is more plausible for the cynodonts, as indicated by its corre-lation with the Los Colorados (Argentina) and the Elliot (SouthAfrica) formations faunas. The difficulties to correlate the faunisticcontent of São Luiz exposition results from the different positions ofregional structural blocks due to fault displacements (Da-Rosa andFaccini, 2005) and the endemic character of most of its faunalcomponents.

Other elements, such as J. candelariensis, apparently constrainthe age of the Caturrita Formation to the Triassic due to correlationswith the argentine basins and the extinction of the group at the endof the Triassic (Schwanke and Araújo-Barberena, 2002; Rubert andSchultz, 2004). However, remnants of dicynodonts with plesio-morphic characters have recently been identified in the LowerCretaceous of Australia (Thulborn and Turner, 2003). At this time,however, no record of J. candelariensis occurs at São Luis outcrop,which is known exclusively from one outcrop near Candelária,50 km east of the site herein studied.

In relation to paleofloristic content, Barboni and Dutra (in press)recently registered Bennettitales “flowers” in the São Luis outcrop.The derivedmorphology of the female coneWilliamsonia reinforcesa Rhaetian or younger age, which is also supported by comparisonswith other fossil floras, mainly those from Argentine basins (Artabeet al., 2005; Menéndez, 1966; Barboni, 2010).

6. Conclusion

The studied footprints were identified as Eubrontes isp., andtheir trackmarkers were most likely large theropod dinosaurs. Themorphological characteristics and dimensions of the footprints arenot commonly found in the CarnianeNorian, but more consistentwith those found after the RhaetianeJurassic. The trackmaker doesnot correspond to any type of dinosaur known in Triassic rocks fromBrazil. The occurrence of the footprints, along with paleofloristicand paleofaunistic data, indicate a Triassic age younger thanpreviously suggested for the Santa Maria Supersequence for theupper portion of the Caturrita Formation or at least for the Linha

R.C.da Silva et al. / Journal of South American Earth Sciences 39 (2012) 16e2322

São Luiz site, although an Early Jurassic age cannot be discarded.More data and detailed studies of the fossil content are needed fora better age estimate.

Acknowledgments

Thanks go to: Jorge Ferigolo and Ana Maria Ribeiro, FundaçãoZoobotânica do Rio Grande do Sul (FZB-RS), for receiving thematerial in the collection; to Henrique Zerfass (Petrobras) forassistance on the field and discussions on geology; and to CON-DESUS (Consórcio de Desenvolvimento Sustentável da QuartaColônia) for technical support; and to Peter L. Falkingham(University of Manchester) for the revision of the manuscript. Wealso thank the anonymous reviewers and the Editor for thesuggestions. Financial support was provided by CPRMeServiçoGeológico do Brasil, CNPq (Conselho Nacional de Desenvolvi-mento Científico e Tecnológico), FAPERGS (Fundação de Amparo àPesquisa do Estado do Rio Grande do Sul) and UNISINOS (Uni-versidade do Vale do Rio dos Sinos). Ronaldo Barboni thanks alsoCAPES (Coordenação de Aperfeiçoamento de Pessoal de NívelSuperior) for his Master degree Grant.

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