GAIA N' 15, LlSBOAlLI SBON, DEZEMBRO/DECEMBER 1998, pp. 369-378 (ISSN: 0871-5424)

BRAZILIAN THEROPODS FROM THE EQUATORIAL ATLANTIC MARGIN: B-EHAVIOR AND ENVIRONMENTAL SETTING

Ismar de Souza CARVALHO Departamento de Geologia, Instituto de Geociencias, UFRJ. Cidade Universitaria, Ilha do Fundao, 21949-900, RIO DE JANEIRO, RJ . BRASIL E-mail: [email protected]

Elizabete PEoRAo PETROBRAS/CENPES/DIVEXISEBIPE. Quadra 7, Predio 20, Cidade Universi!,;ria, 21949-900, RIO DE JANEIRO, RJ. BRASIL E-mail: [email protected]

ABSTRACT: The Sao Luis Basin, located on the equatorial coastal region of Brazil, shows a di­ versified Upper biota, The commonest vertebrate fossils and ichnofossils be­ long to a theropod dinosaurian fauna that is widespread over that geographic area,The theropod footprints and associated bone fragments are found in fine-grained quartzose sandstones, deposited in nearshore environments submitted to tidal currents. They are found in six localities of Sao Luis and Alcantara counties: Ponta da Guia, Ponta do Farol, Praia do Boqueirao, IIha do Medo, Praia da Baronesa and IIha do Cajual. There are trails and isolated footprints attributed to large and small theropods and ornithischians. The best pre­ served footprints are found at Ponta da Guia and Praia da Baronesa.The ichnocoenoses of Ponta da Guia and Praia da Baronesa, are discussed from the view point of dinosaurian so­ cial behavior. A gregarious behavior was observed among the Ponta da Guia theropods - a rare herding structure in this dinosaur group. The randomly oriented trackways and isolated footprints at Praia da Baronesa were interpreted as the record of a "foraging area" for thero­ pods. There they would search for fishes, turtles and other organisms, found in small la­ goons and channels of a tidal flat environment. The footprint-bearing strata of Sao Luis Basin are considered to compose a megatracksite alongside the early equatorial Atlantic ocean. Its geological context - a low-gradient coastal plain - allowed the establishment of specific dinosaur groups. There was a probable ecologic "segregation" of large-sized and small-sized theropods, in this way giving rise to a regional paleobiogeographic and pa­ laeoecologic distribution pattern of the theropod communities.

R ESUMO: A bacia de Sao Luis, localizada na regiao equatorial do Brasil, apresenta uma biota do Cretacico superior bastante diversificada. Trata-se de uma bacia tipo rifte cuja origem se relaciona com a abertura da margem atlantica no intervalo geocronologico compreendido entre 0 Aptiano e 0 Cenomaniano. Os fosseis e icnofosseis de vertebrados mais comuns nesta bacia pertencem a uma fauna de dinossaurios teropodomorfos, a qual esta distribui­ da numa am pia area geografica. As pegadas e fragmentos osseos de teropodes sao encon­ trados em arenitos quartzosos finos, depositados em ambientes litorais sujeitos a correntes de mare. Ocorrem em seis localidades dos municipios de Sao Luis e Alcantara (estado do Maranhao): Ponta da Guia, Ponta do Farol, Praia do Boqueirao, IIha do Medo, Praia da Baronesa e IIha do Cajual. As pistas e pegadas isoladas foram atribuidas a peque­ nos e grandes teropodes, alem de ornitisquios, sendo que as pegadas melhor preservadas sao oriundas da Ponta da Guia e Praia da Baronesa. Com base nas icnocenoses da Ponta da Guia e Praia da Baronesa, e discutido 0 comportamento social destes dinossaurios. Foi ob­ servado 0 habito gregario entre os teropodes da Ponta da Guia - uma estrutura organizacio­ nal rara neste grupo de dinossaurios. A orienta~ao aleatoria e as varias pegadas isoladas da Praia da Baronesa foram interpretadas como 0 registo de uma area de alimenta~ao. Os di-

369 artigos/papers I.S. CARVALHO & E. PEDRAO

nossaurios desta regiao poderiam procurar peixes, tartarugas e outros organismos em pe­ quenas lagoas e em canais da planicie de mare durante periodos de mare baixa, representando assim uma "area de alimenta!;ao" para teropodes de tamanho medio e pe­ queno. As camadas com pegadas fosseis na bacia de Sao Luis sao consideradas como par­ te de urn "megatracksite", localizado ao longo da linha de costa durante a fase inicial do oceano Atlantico equatorial. 0 contexte geologico deste "megatracksite" - uma planicie costeira de baixo gradiente - possibilitou 0 estabelecimento de grupos especificos de di­ nossauros. Existiu uma provavel segrega!;ao ecologica dos teropodes de grande e de pe­ queno tamanho, havendo assim uma distribui!;ao paleobiogeografica e paleoecologica das comunidades de teropodes.

INTRODUCTION theropod paleobiology, although uncommon, was already recorded by LEONARDI (1984, 1989) and During the opening of the Atlantic margin in the THULBORN & WADE (1979, 1984) from tracks of the equatorial region of Brazil (- Toro-Toro ichnofauna (EI Molino Formation, Maas­ time). tectonic action gave rise to numerous rift ba­ trichtian - Bolivia) and the Queensland ichnofauna sins. At the same time, structural reactivation of the (Winton Formation, -Cenomanian - Austra­ Precambrian basement in the interior of the conti­ lia). nent, allowed the subdivision of formerly wide sedi­ mentary areas into smaller new basins. The Sao This study presents a global view of theropod Luis basin (Fig. 1), located on the northern region of ichnofossil and fossil data from the equatorial Sao Maranhao State (Brazil), had its origin in this con­ Luis Basin. In addition, it discusses the results of text. This is the only basin in the equatorial Brazilian palynological analises that further contribute to a margin whose Cretaceous outcrops display sedi­ better understanding of the environment where this ments of this geological phase. In other equatorial dinosaurian fauna lived and respective age. basins, coeval deposits have submerged in the con­ tinental platform. GEOLOGY OF THE SAO Luis BASIN Tectonic settings at the end of the Early Creta­ The Sao Luis Basin is a Cretaceous rift basin of ceous, originated by the South America - African 18,000 km', whose evolution is related to the origin drifting gave rise to this basin. Intense faulting ofthe Brazilian equatorial margin. According to Ros­ through the present-day northern coast of Mara­ SETTI (1996a), the sedimentary framework of this nhao State originated thick sedimentary deposits. basin was strongly influenced by plate tectonics. During the Aptian, the simple shear stress associ­ The outcrop area of the Sao Luis Basin com­ ated with lithospheric thinning led to the initial rifting. prises Upper Cretaceous (Cenomanian) reddish The basin has an assymetrical profile and is siliciclastics (sandstones, siltstones, shales and bounded from the neighboring Parnaiba and Bar­ mudstones) and some carbonates. These litholo­ reirinha basins by the Ferrer-Urbano Santos gies are grouped into the , (south), Tocantins (west) and Rosario (east) struc­ which attains 2,000 m in thickness. Of total only 100 tural highs. Their pre-Cretaceous depositional his­ m of this unit are seen in outcrops. tory is linked with that of Parnaiba Basin, which Remains of a diversified paleobiota are found in altogether comprised a single, broad sedimentary this area, which include plants (angiosperms), mol­ area during the Paleozoic. lusks, fishes (bone fragments, scales, teeth) and In Figure 2 there is a summary of the lithostra­ reptiles (bones, teeth and ichnofossils). The com­ tigraphy of Sao Luis Basin , whose total sedimentary monest vertebrate fossils and ichnofossils belong to thickness attains 4,500 m (ARANHAeta/., 1990). The a theropod dinosaurian fauna that occurs over a outcrops of Cretaceous rocks are named as the wide geographic area. Environmental interpretation Itapecuru Formation. These rocks consist of reddish of the fossil-bearing lithofacies allows reconstruc­ sandstones, siltstones, shales and mudstones, with tion of a sandy tidal plain area, cut by freshwater and some interbedded carbonates composed of marls tidal channels, thus composing the scenary of a litto­ and limestones. The main sedimentary structures ral area submitted to a hot and dry climate. are channel and planar cross-stratification, ripple­ Of all ichnofossillocalities in the Sao Luis Basin, marks, fluidization structures, mud-cracks, herring­ two display the must abundant theropod tracks. The bone cross-stratification and hummocky cross­ best one is located at Ponta da Guia (Sao Luis stratification. The fossils found in these rocks are County) where it is possible to observe the parallel palynomorphs, plants (angiosperms), mollusks orientation of four large theropod trails, pointing out (Mytilidae, Inoceramidae, Pectinidae, Plicatulidae, to a possible gregarious behavior. This aspect of Limidae, Ostreidae, Trigonidae and Matricidae),

370 BRAZILIAN THEROPODS FROM THE EQUA TORIAL A TLANTIC MARGIN

Basin

POllia do FaroJ _____ ~-.r~-

o 2km =

Outcrops

Fig. 1 - Location map of Sao Luis Basin, Brazil, and its paleogeographical position during Cenomanian. fishes (Dipnoi, Elasmobranchia and Actinopterygii) , counties: Ponta da Guia, Ponta do Farol, Praia do reptiles (Dinosauria, Crocodylia and Chelonia). Boqueirao, IIha do Medo, Praia da Baronesa and There are also vertebrate (dinosaurian footprints) IIha do Cajual (CARVALHO & ARAUJO, 1995). There and invertebrate ichnofossils. are trails and isolated footprints attributed to large and small theropods, and ornithischians. The best The environmental interpretation of outcrop li­ preserved footprints localities are at Ponta da Guia thofacies points out to estuarine, nearshore and and Praia da Baronesa. shallow marine environments affected by both tidal and storm processes (KLE IN & FERRE IRA, 1979; The footprints found at Ponta da Guia are consid­ ROSSETTI, 1994, 1996a). According to ROSSETTI ered to have been produced by two different groups: (1996a), the architectural distribution of some de­ theropods and ornithopods. The ones attributed to posits of the Itapecuru Formation revealed a pro­ theropods are large-sized and show relationships grading, barred coast, probably in the distal with carnosaurs. Four trails present parallel orienta­ (seaward) portion of a wave-dominated estuarine tion, a possible evidence of a gregarious behavior. system. The ornithopod footprints were assigned to hadro­ saurians. THEROPOD FOOTPRINTS: EVIDENCE OF Dinosaurian social behavior was analysed by GREGARIOUS BEHAVIOR CURRIE (1983), LEONARDI (1980; 1989), LOCKLEY The theropod footprints and the associate bone (1986, 1991), LOCKLEY, HOUCK & PRINCE (1986), fragments in the Sao Luis Basin are found in fine­ LOCKLEY et a/. (1992) and THULBORN (1990). The in­ grained quartzose sandstones, with large scale ferences about herding among dinosaurs can be cross-stratification. RODRIGUES, LOVATO & CAYE supported upon ichnological analyses. The track­ (1990) considered such lithofacies as the result of ways in a preferred direction can be a proof of gre­ deposition in nearshore environments submitted to gariousness, although a physical feature on the tidal currents. These authors considered the possi­ environment could have controlled a series of indi­ bility of subaerial exposure of subaqueous dunes viduals that have passed on a same area at different with aeolian reworking. Alongside the coastline of a time intervals. A way to distinguish herd trackways shallow marine environment lived an abundantdino­ from physically controlled pathways is the presence saurian fauna. oftrackways with different moving direction from the ones that were considered as indicative of a gregari­ The dinosaurian footprints on Sao Luis Basin are ous behavior. The intertrackway spacing is another found in six localities of Sao Luis and Alcantara criterion in favor of herding. The regular space be-

371 I.S. CARVALHO & E. PEDRAO

sAo Luis BASIN Llll tOSffi. l.rrHQSTRATIQR .... PHy

e n. sep

.- I.F.G-I;ND­ ""0I!!- ~- __- n. ...,.•__ ..... _

--o::c 101 • .-. ~ T ___lr .. OIio . " ..3SA~ '",=: C1oMu>oI tfOOI _.... ' iI\oolioo ..... O ...... flfII'Ib . 1Il0010''''' 104 _ U .­ rI ·-

Fig. 2 - Stratigraphy summary of Sao Luis Basin.

tween adjacent trackways suggests animals walk­ ways from EI Molino Formation (Maastrichtian Toro­ ing in some kind of regular formation (LOCKLEY, Toro Basin, Bolivia). A mixed herding of ornithopods 1991). The gregariousness on dinosaur faunas was and coelurosaurs was recorded by THULBORN & already inferred from some Brazilian ichnofaunas. WADE (1979, 1984) from the Winton Formation (Al­ GODOY & LEONARDI (1985), LEON ARDI (1980, 1989), bian-Cenomanian - Queensland, Australia). The un­ CARVALHO & LEONARDI (1993) recognized this commonness of well documented evidence of a ethological aspect in Lower Cretaceous ichnofau­ gregarious behavior among theropods can be ex­ nas from Sousa Basin (Sousa Formation) and Par­ plained by the paleoecological analysis of FARLOW naiba Basin () at Northeastern (1976, apudTHuLBORN, 1990). He considered that Brazil. carnosaurs might have hunted singly or in small packs, what could explain the high frequen cy of indi­ The mapped trackways at Ponta da Guia show a vidual carnosaur tracks. group offour large theropods trackways that present clear morphological similarity (Fig. 3-4). The angular The other main theropod footprint assemblage is range of movement directions is only 20°, and the located at Praia da Baronesa. It is composed by ran­ maximum intertrackway spacing is 4 m. These facts domly oriented trackways and isolated footprints constitute good evidence to postulate the gregari­ (Fig. 6). They are always associated with fluidization ousness among the producers. Because there are structures and present superficial colour stains tracks in different directions, it is possible to consider (blue-gray, green or red). CARVALHO (1994) ex­ the absence of a physical barrier of the landscape plained the fluidization around the footprints as the configuration that could have controlled the move­ result of a "dinostatic pressure" in water-saturated ment direction of individuals (Fig. 5). and low coesive sediments. Such substrate aspect is corroborated by the metatarsal impressions in The herding evidence among theropods, al­ many footprints. KUBAN (1991 b) considered thatthis though rare, is also found in other ichnofaunas. preservational character cou ld be indicative of a be­ LEONARDI (1984, 1989)described a groupof60, and havior response to a soft substrate. The elongate another of 32, unidirectional carnosaurian track- plantigrade footprints would be explained by a low

372 BRAZILIAN THEROPODS FROM THE EQUA TOR/AL A TLANTIC MARGIN

ROS (1997) considered the theropod remains (iso­ lated teeth) as indicative of a group with dromeo­ saurid affinities. These fossils are found in fine­ grained sandstones deposited in a tidal-channel en­ vironment (Fig. 7). The erratic distribution of footprints at Praia da Baronesa could indicate a "foraging area" to the theropods. The theropods would search for fishes, turtles and other organisms, foraging food in the small lagoons of a tidal flat. During low-tide periods, subaerial exposure of the sediments allowed the di­ noturbation. This could be a good foraging area for the theropod dinosaurs, due to the presence_of aquatic animals caught in small water ponds along the exposed channels of the tidal plain.

ENVIRONMENTAL SETTING OF THEROPOD COMMUNITIES The environmental scenary during the Cenoma­ nian, in the Sao Luis Basin comprises many suben­ vironments associated with an estuary that occupied a low-gradient coastal plain. Distinct dino­ saur communities are found in this geological con­ text.

Fig. 3 - A theropod trackway from Ponta da Guia out­ crop, Sao Luis Basin.

posture assumed whenever a dinosaur foraged in mud flats or shallow water for small food items, stalk­ ing larger prey or while approaching other dino­ saurs. A common feature in the Praia da Baronesa foot­ prints is the contrasting colours from the surround­ ing substrate. There is a range from reddish to blue­ gray colours, contrasting with the light greenish hue of the substrate. KUBAN (1991 a) also observed this feature in dinosaur tracks of the Glen Rose Forma­ tion (Lower Cretaceous, Texas - USA). He explained this taphonomic aspect as the result of secondary sediment infilling on the original track depressions and oxidation of iron on the surface of infilling mate­ rial. The substrate where the theropod tracks of Praia da Baronesa are found also contain many skeletal remains of a diversified fauna. There are fishes from the families Myliobatidae, Semionontidae, Encho­ dontidae and Sparidae. Reptile remains include Pe­ Fig. 4 - An isolated theropod footprint from Ponta da lomedusidae (Testudines), Mosasauridae and Guia outcrop, Sao Luis Basin. Theropoda (EUGENIO, 1994). VILAS-BoAS & MEDEI-

373 I.S. CARVALHO & E. PEDRAO

tributed to channel, sand fiat, delta, and bay fill depo­ PONTA DA GUlA FOOTPRINTS a - SlPG-F{)30' ) sitional settings of an estuary. ESERTH & BRINKMAN b . SLPG· 29(HS') N ~ C • SLPG ·22(N. S) (1997) considered that portions of ancient estuarine d . SlPG· E(20' ) e . SL PG-A(l20' )I SLPQ-16 paleochannels have high theoretical potential for f - SL PQ· C(lW) burial and preservation of vertebrate skeletal re­ g • SLPG- B(l40' ) h . 5LPO-12(UO') mains. They described a mud-filled incised-valley ~, SLPQ -D( ISS' ) system in the Dinosaur Park Formation (Canada, k j 1 j SLPG-26{:-I · S) k . 5 LPO-17 ( US' ) Late Campanian) that shows this preservational po­ I . SLPG-2 S( 120' ) m _ SLPG-2 H 12S' ) tential. Much like in the deposits of Itapecuru Forma­ tion (Sao Luis Basin), there are sedimentological and paleontological features indicating mixed ma­ rine and non-marine infiuences. The fossil tracks and skeletal remains foundJn the fine-grained sandstones and siltstones of Praia da Baronesa are related to a tidal channel setting. During low-tide periods, subaerial exposure of the bedforms allowed them to suffer dinoturbation. The strata at Ponta da Guia were grouped by CARVALHO (1995) and CARVALHO & GON9ALVES (1994) into two facies associations. They were considered as the result of tidal flat and aeolian sedimentation. The track-bearing strata are fine-grained sandstones, \.

Fig. 5 - Footprints map distribution at Ponta da Guia. The diagram on the upper right corner shows the main movement directions of the dinosaurian fauna (Modified from CARVALHO, 1995 and CARVALHO & GON9ALVES, 1994).

ROSSEnl (1996b) recognized two depositional intervals (lower and upper successions) in outcrops of the Sao Luis Basin. The lower succession, ob­ served at IIha do Livramento, consists of a regres­ sive interval - an upward transition from seaward to landward settings. ROssEnl (1996a) grouped these strata into four facies associations, and attrib­ uted them to the following depositional settings: up­ per shoreface, foreshore, tidal channel , and lagoon­ washover. It is in the well sorted and fine-grained sandstones assigned to the upper shoreface facies that skeletal theropod remains are found, such as teeth and bone fragments (Fig. 8). Sandstones of this facies contain large-scale, low-angle cross­ beddings that are interpreted by RossEnl (1996a) to result from the drift of large-scale bedforms in a depositional setting characterized by the combined flows of storm-generated and tidal-generated cur­ rents. This author considered that such deposits re­ vealed a prograding, barred coast probably formed on the seaward portion of a wave-dominated estuar­ ine system. Fig. 6 - Theropod footprints from Praia da Baronesa The footprint bearing-strata are found in the up­ outcrop (Itapecuru Formation, Sao Luis Basin). There are per succession of RossEnl (1996b). The upper an abundant association of theropod footprints and teeth succession consists of tidal-dominated deposits at- on the same stratigraphic level.

374 BRAZILIAN THEROPODS FROM THE EQUA TORIAL A TLANTIC MARGIN

1962, Equisetosporites ambiguus HEDLUND, 1966, Equisetosporites spp. (DAUGHERTY, 1941) POCOCK, 1964, Steevesipollenites spp. STOVER, 1964), an­ giosperms (Afropollis jardinus DOYLE, JARDINE & DOERENKAMP, 1982, Hexaporotricolpites emilianovi BOLTENHAGEN, 1967, Cretacaeiporites polygona/is HERNGREEN, 1973, Cretacaeiporites mulleri HERN­ o o,s .... GREEN , 1973) and some taxons of doubtful botanical ~ affinity (Elaterop/icites africaensis HERNGREEN , 1973, Ga/eacornea causea B JARDINE, 1967, Elateroco/pites castalaini JARDINE, 1967, EJatero­ sporites aft. klaszi JARDINE , 1967 and Sofrepites le­ gouxae JARDINE, 1967). The main pollen group in this assemblage (Classopollis (PFLUG) REYRE , 1970) derives from gymnosperms ofthefamily Chei­ rolepideaceae. Secondarily, there occur Equiseto­ sporites and Steevesipollenites pollen grains. All of them are indicative of a hot climate. The angiosperm pollen grains are rare, although the presence of A. jardinus indicates an equatorial climate. The occur-

Fig. 7 - Theropod tooth with probable dromeosaurid af­ finities from Praia da Baronesa outcrop (Itapecuru Forma­ tion, Sao Luis Basin). interbedded with argillaceous siltstones, that show small-sized channel and tabular cross-stratification, ripple-marks, mud-cracks and clay-balls, laid down in a sand flat depositional environment. The thero­ pod footprints were probably produced in the supra­ tidal region of a low-gradient tidal flat, where the preservational potential is greater. ROSSETTI (1996b) considered thatthe lower and upper successions are part of two incised valleyfills. The lower succession was deposited at a time of slow rise in relative sea-level, during the highstand tract of an older incised valley. Meanwhile, the upper succession record the transition from the transgres­ sive to the highstand systems tract of a younger in­ cised valley.

PALYNOLOGY Through palynological analises (Fig. 9) it is pos­ sible to obtain a better understanding of some envi­ ronmental aspects under which the theropod fauna lived (PEDRAO, 1995). The palynological content of outcrops in the east portion of Sao Luis Basin include miospores shed by the local flora, protozoans and polychaets (PEDRAO et al., 1993; PEDRAo , 1995; PEDRAo et al., 1995). Continental palynomorphs are pteridophyte spores (Crybelosporites DETTMANN , 1963), gymnosperm Fig. 8 - Theropod tooth from Ilha do Uvramento out­ pollen grains (Classopollis major GROOT & GROOT, crop (Itapecuru Formation - Upper Cretaceous), Sao Luis Basin. Scale bar: 1 cm.

375 I.S. CARVALHO & E. PEDRAO

1

C. major E. ambiguus G. subtilis E. africaensis

• •10 ." - 7 8

A. jardinus 6 E. aff. klaszi G. causea S.legouxae

/

10 11 Subtilispl1aera cheit palynoforaminifer dinoflagellate

, , • "

13 14 scolecodont Oligospl1aeridiultl sp. Florentinia sp.

376 BRAZILIAN THEROPODS FROM THE EQUA TORIAL A TLANTIC MARGIN

rence of perisporate trilete spores in this assem­ ACKNOWLEDGEMENTS blage also points out to the same climate, and in The authors wish to thank Itapotiara Vilas-Boas addition, is indicative of a fluvial influence in the de­ forthe photographs of the theropod teeth; Francisco positional area. Jose Correa Martins, Francisco Rodrigues da Silva The Sao Luis assemblages include dinoflagel­ Jr. , Helena Pontes, Manoel Medeiros, Ronaldo An­ lates such as gonyaulacoids (Spiniferites (MANTELL, tonio Gon~alves, Sergio Frazao and Wilma dos 1850) SARJEANT, 1970), peridinioids (Subtilisphaera Santos Eugenio for field assistance; Jose Henrique cheit BELOW, 1981) and condensates (Florentinia Gon~alves de Melo for his helpful review of the spp. DAVEY & VERDIER, 1973, Oligosphaeridium aff. manuscript. This study was supported by Universi­ breviconispinum JAIN , 1977). The dinoflagellates dade Federal do Rio de Janeiro, Funda~ao Univer­ are brown and yellow unicelled algae referred to the sitaria Jose Bonifacio and PETROBRAS. It is a Division Pyrrophyta, that are found in the marine contribution to IGCP Project 381/UNESCO (South plankton. There are also chitinous remains in the Atlantic Mesozoic Correlations). palynological assemblage such as palynoforamini­ fera and scolecodonts. BIBLIOGRAPHY ARANHA, L.G.F.; liMA, H.P.; SOUZA, J.M.P.; MAKMO, R.K. & Fl. CONCLUSIONS GUEIRAS, J.M. (1990) - Evolugao tectonica e sedimentar das bacias de Braganga-Viseu, Sao Luis e Ilha Nova, in GABA­ The theropod fossils and ichnofossils of the Sao GlIA, G.P.R. & MILANI , E.J. (Eds.), Origem e evofw;ao das ba­ cias sedimentares, PETROsRAs, Rio de Janeiro, pp. 221- Luis Basin are a unique record of a dinosaurian 234. fauna which inhabited the Brazilian equatorial mar­ CARVALHO, I.S. & LEONARDI, G. (1993) - Geologia das bacias de gin during Cretaceous times. A gregarious behavior Pombal, Sousa , Uirauna-Brejo das Freiras e Vertentes (Nord­ is deduced from the analysis of some ichnocoe­ este do Brasil). Anais Acad. Brasileira C;lmcias, 64(3): 231- noses. The ones including randomly-oriented track­ 252. ways and isolated footprints were interpreted as the CARVALHO, I.S. (1994) - Contexto tafon6mico das pegadas de te­ r6podes da Praia da Baronesa (Cenomaniano , Bacia de Sao record of a "foraging area" for theropods. Luis). Boletim de Resumos Expandidos do 38° Congresso Palynological data is consistent with the infer­ Brasileiro de Geologia, Camboriu, Soc. Bras. GeoJ. , Dep. Nac. Produ<;ao Mineral/Centro Pesquisas Recursos Mine­ ence offluvial, lagoonal and shallow marine deposi­ rais, 3: 211-212. tional environments under dry and hot climate. The CARVALHO, I.S. & GONC;:ALVES, R.A. (1994) - Pegadas de dinos­ pollen grains and spores are of Cenomanian age. sauros neocretaceas da Forma9ao Itapecuru, Bacia de Sao Palynological evidence, the invertebrate fossils and Lu is (Maranhao, Brasil). Anais Acad. Brasileira Ci~ncias , 66(3): 279·292. the stratigraphic interpretation all point out to a tidal CARVALHO, I.S. (1995) - As pistas de dinossauros da Ponta da flat of a low-gradient coastal plain as the most likely Guia (Bacia de Sao Luis, Cretaceo Superior - Maranhao, Bra­ environment inhabited by the theropods. sil). Anais Acad. Brasileira Cilmcias, 67(4): 413-431. The discussed footprint-bearing strata of Sao CARVALHO, I.S. & ARAUJO, S.A.F. (1995) - A distribuigao geografi­ ca dos fasseis e icnof6sseis de Dinosauria na Bacia de Sao Luis Basin are considered a megatracksite. The Luis. Anais 47° Reuniao Anuaf Soc. Brasileira Progresso Ci­ dominance of large-sized theropod footprints is de­ encia, Sao Luis, 2: 439. tected in the southern area of the basin, which in­ CURRIE, P.J. (1983) - Hadrosaurtrackways from the Lower Creta­ cludes the Ponta da Guia region. To the north, ceous of Canada. Acta Pafaeonto/. Polon., 28(1-2): 63-73. ichnocoenoses such as that one of Praia da Baron­ EBERTH , D.A. & BRINKMAN, D.B. (1997) - Paleoecology of an es­ esa show medium- and small-sized theropod tracks. tuarine, incised-valley fill in the Dinosaur Park Formation (Ju­ dith Ri ver Group, Upper Cretaceous) of Southern Alberta, There was a probable ecologic "segregation" of Canada. Palaios, 12: 43-58. large and small-sized theropods. Its geological con­ E UG~ NI O, W.S. (1994) - Aspectos Paleontol6gicos do Cretaceo text - a low-gradient coastal plain - probably allowed da Baia de Sao Marcos, Maranhao, Brasil. Disserla<;ao de the establishment of specific dinosaur communities. Mestrado, Universidade Federal do Rio de Janeiro, Instituto de Geociencias, 77 pp. (unpublished). GODOY , L.C. & LEONARDI , G. (1985) - Dire90es e comportamento dos dinossauros da localidade Piau , Sousa, Paraiba (Brasil), Forma«8.o Sousa (Cretaceo Inferior). Brasil , Departamento Nacionat de Produ«8.o Mineral. Colet. Trabalhos Paleontol. Sor. "Gaol.", (Paleontol. Estral., 2), 27: 65-73. KLEIN, V.C. & FERREIRA, C.S. (1979) - Paleontologia e estratigra­ fia de uma facies estuarina da Forma«8.o Itapecuru, Estado do Maranhao. Anais Acad. Brasileira Ciencias, 51 (3): 523- f- previous page 533. Fig. 9 -The Cretaceous palynomorphs from Ponta do KUBAN , G.J. (1991a) - Color Distinctions and Other Curious Fea­ Farol (Itapecuru Formation - Lower Cenomanian), Sao tures of Dinosaur Tracks Near Glen Rose , Texas, in GILLETIE, D.O. & LOCKLEY, M.G. (Eds.), Dinosaur Tracks and Traces, Luis Basin. (Scale bar: 20 Il). Cambridge Univ. Press, Cambridge, pp. 427-440.

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