kellner et al, 2005b

1 Submitted on July 12, 2004. Accepted on August 22, 2005.2 Museu Nacional/UFRJ, Departamento de Geologia e Paleontologia. Quinta da Boa Vista, São Cristóvão, 20940-040, Rio de Janeiro, RJ, Brasil.3 E-mail: [email protected] Fellow of Conselho Nacional de Desenvolvimento Cientítico e Tecnológico (CNPq).5 Museu de Ciências da Terra, Departamento Nacional de Produção Mineral. Av. Pasteur, 404, Urca, 22290-240, Rio de Janeiro, RJ, Brazil. E-mail: [email protected] E-mail: [email protected].

Arquivos do Museu Nacional, Rio de Janeiro, v.63, n.3, p.529-564, jul./set.2005ISSN 0365-4508

DESCRIPTION OF A TITANOSAURID CAUDAL SERIES FROM THE BAURU

GROUP, LATE CRETACEOUS OF BRAZIL 1

(With 27 figures)

ALEXANDER WILHELM ARMIN KELLNER 2, 3, 4

DIOGENES DE ALMEIDA CAMPOS 4, 5

MARCELO N. F. TROTTA 2, 6

ABSTRACT: A new titanosaurid, Baurutitan britoi n. gen., n. sp., is described and compared with other taxaof that sauropod clade. The specimen (MCT 1490-R) consists of the last sacral followed by a sequence of 18caudal vertebrae that were found in the continental deposits of the Late Cretaceous Bauru Group thatoutcrop at the Peirópolis region, near the town of Uberaba, State of Minas Gerais, Brazil. This new taxon isdistinguished from other titanosaurians by several features, including subrectangular to square outline ofthe anterior articulation surface of the anterior and middle caudals, strongly pointed laterally directedprocess intercepting the spinoprezygapophyseal lamina in caudal 1; dorsal prezygapophyseal tuberosity onthe lateral margin of the prezygapophyses of caudals 2-4, that smoothens out in midcaudals. This materialdemonstrates that the horizontal ridge present in middle and posterior caudals of some titanosaurs, inBaurutitan britoi is homologous with a dorsal tuberosity and not with the transverse process.

Key words: Dinosauria. Sauropoda. Titanosauria. Titanosauridae. Cretaceous. Brazil.

RESUMO: Descrição da série caudal de um titanosaurídeo do Grupo Bauru, Cretáceo Superior do Brasil.

Um novo titanossaurídeo, Baurutitan britoi n. gen., n. sp., é descrito e comparado com outros membros desseclado de saurópodes. O espécime é composto por uma última vértebra sacral seguida de uma seqüência de 18vértebras caudais (MCT 1490-R) proveniente das cercanias do povoado de Peirópolis, no Município de Uberaba(Estado de Minas Gerais, Brasil), tendo sido encontrado nos depósitos continentais do Grupo Bauru (CretáceoSuperior). Entre as características que distinguem esse novo táxon dos demais Titanosauria estão a facesubretangular ou quadrada da articulação anterior das caudais, processo lateral bem desenvolvido interceptandoa lamina espinopré-zigapofisiária da caudal 1, tubérculo dorsal na margem lateral das pré-zigapófises das caudais2-4, que se torna em uma rugosidade que tende a se tornar menos pronunciada nas caudais médias. Estematerial também demonstra que em Baurutitan britoi n. gen., n. sp. a crista lateral nos centros das caudaismedianas é o resultado de uma diminuição de um processo dorsal e não é homólogo do processo transverso.

Palavras-chave: Dinosauria. Sauropoda. Titanosauria. Titanosauridae. Cretáceo. Brasil.

INTRODUCTION

Up to date the richest locality in Brazil withtitanosaur remains is Peirópolis (Fig.1). In the past,the most productive site was the Caieira quarrythat yielded hundreds of titanosaur bones(CAMPOS & KELLNER, 1999). Among the recoveredmaterial is a series of 19 vertebrae (the last sacraland 18 caudals) collected in 1957, housed in thecollection of the Earth Science Museum (MCT) ofthe Departamento Nacional de Produção Mineral

(DNPM, Rio de Janeiro) under the number MCT1490-R. This specimen was briefly described byPOWELL (1987) as the “Series C” and referred asTitanosaurus sp. It is one of the few articulatedtitanosaurid caudal sequences and has been usedseveral times to determine the place in the tail ofisolated or partially articulated caudals from otherdinosaurs (e.g., GONZÁLEZ RIGA, 2003;MARTÍNEZ et al., 2004).In this paper we redescribe MCT 1490-R andestablish a new titanosaurid taxon, Baurutitan britoi

530 A.W.A.KELLNER, D.A.CAMPOS & M.N.F.TROTTA

Arq. Mus. Nac., Rio de Janeiro, v.63, n.3, p.529-564, jul./set.2005

n. gen., n. sp. We also include a detailed descriptionof the chevrons that have not been studied before.This species is compared with the followingtitanosaurs: Aeolosaurus rionegrinus POWELL (2003);Aeolosaurus sp. SALGADO & CORIA (1993);Aeolosaurus sp. SALGADO, CORIA & CALVO,(1997b); Alamosaurus sanjuanensis GILMORE, 1922;Epachthosaurus sciuttoi POWELL, 1990 (MARTINEZet al., 2004); Gondwanatitan faustoi KELLNER &AZEVEDO, 1999; Mendozasaurus neguyelapGONZÁLEZ RIGA, 2003; Neuquensaurus australis(Lydekker 1893); Opisthocoelicaudia skarzynskiiBORSUK-BIALYNICKA, 1977; Pellegrinisaurus powelliSALGADO, 1996; Rinconsaurus caudamirus CALVO& GONZÁLEZ RIGA, 2003; Saltasaurus loricatusBONAPARTE & POWELL,1980; Titanosaurusaraukanicus (HUENE, 1929); Titanosaurus colbertiJAIN & BANDYOPADHYAY 1997 (renamed asIsisaurus colberti by WILSON & UPCHURCH, 2003);Lirainosaurus astibiae SANZ et al., 1999, and MCT1488-R/ MCT 1719-R (CAMPOS et al., 2005 - thisvolume). The data from most of the mentionedtitanosaur taxa was obtained from the originaldescription and complemented with other papersincluding CORIA et al. (1998), POWELL (1992, 2003),BONAPARTE (1996), and SALGADO, CORIA &CALVO, 1997a. The sedimentary rocks of this area

belong to the Marília Formation (BERTINI, 1993)from the Bauru Basin (FERNANDES & COIMBRA,1996). For a review of the paleontological contentof this and other stratigraphic units of the BauruBasin see BERTINI (1993) and BERTINI et al.(1993). Abbreviations as follows: (dtu) dorsaltuberosity, (nc) neural canal, (ns) neural spine,(posl) postspinal lamina, (poz) postzygapophysis,(prsl) prespinal lamina, (prz) prezygapophysis,(prztu) prezygapophyseal tuberosity, (tp) transverseprocess, (sprl) spinoprezygapophyseal lamina, (sri)sacral rib, (l) left, (r) right.

BRIEF HISTORY OF THE CAIEIRA QUARRY

In 1958, after several years working at oneparticular point in Peirópolis (the Caieira quarryof CAMPOS & KELLNER, 1999), L.I. Priceunderstood that this fossil deposit was moreextensive than he had anticipated and provided asummary of the activities done so far in his annualreport for the Geology and Mineralogy Division ofthe Departamento Nacional de Produção Mineral(DNPM). This report was published the next yearby the director of the DNPM, A.R. Lamego, withsome pictures of the quarry that are reproducedhere (Fig.2).

Fig.1- The Caieira site, near Uberaba, Minas Gerais State.

DESCRIPTION OF A TITANOSAURID CAUDAL SERIES FROM THE BAURU GROUP, LATE CRETACEOUS OF BRAZIL 531


According to PRICE (1955), he examined this regionin 1947 based on the information of JesuinoFelicissimo Junior, of the Instituto Geográfico eGeológico de São Paulo, who pointed out the presenceof fossil vertebrates in the Uberaba area. The nextyear (1948) he prepared the opening of a quarry which

was done only in 1949. Still according to Price’s reportof 1958, fossils have been collected in six differentoccasions (he did not precise the dates), with therecovery of several specimens, including turtles,crocodilomorphs, theropods (Coelurosauria - twospecies, “Carnosauria” - isolated teeth) and sauropod

Fig.2- Reproduction of the likely first published picture of the Peirópolis site, showing the Caieira quarry (on top) and thepelvis MCT 1488-R still in the field. This picture was reproduced from Price’s report published in LAMEGO (1959).



dinosaurs. Other fossils were also recovered such asfragments of fishes, freshwater invertebrates(gastropods, bivalves), ichnofossils (invertebratetubes), egg shale fragments, and plant remains(PRICE in LAMEGO, 1959:181-182). The overburdenthat had to be removed in order to reach the mainfossiliferous layer varied between 4 to 18 (!) meters,what was done manually. Extremely hardsedimentary rocks were removed occasionally bydynamite. Price also pointed out that until theexcavation of 1957, he regarded the titanosaur bonescollected belonging to three individuals of distinctsizes, all representing the same genus. However, in1957 he and his crew had found a series of 19vertebrae (at that point he though all were caudals)that clearly demonstrated the presence of a seconddistinct genus, making the re-evaluation of theassignment of all collected elements necessary.Although not published in his report, Price was alsoworking on a quarry map showing the mainspecimens recovered. A photo of this map waspublished by CAMPOS & KELLNER (1999) andshowed that the excavations at the Caieira quarrywere done in 1949, 1950, 1953, 1955, 1957, 1958,and 1959. A second copy of this picture was foundrecently and includes the year 1961 handwrittenby Price (Fig.3). Possible this was the last year ofexcavation at the Caieira quarry and apparently hasnot yielded any significant specimen.Examining the material collected by Price, POWELL(1987) described some remains of the Caieira quarry,including a partial vertebral column and pelvis (theseries “B”) and the articulated series of the last sacraland 18 caudals (the series “C”). This study waspartially reprinted recently (POWELL, 2003).Until 1999, none of those specimens were numbered.CAMPOS & KELLNER (1999) provided somenumbers of some important specimens collected inthe Peirópolis area (including the series B and Cfrom the Caieira quarry) and most elements havebeen numbered recently by one of the authors duringhis master dissertation (M.N.F. Trotta).

SYSTEMATIC PALEONTOLOGY

Saurischia Seeley, 1888Sauropodomorpha Huene, 1932

Sauropoda Marsh, 1878Titanosauria Bonaparte & Coria, 1993

Titanosauridae Lydekker, 1893

Baurutitan n.gen.

Type-species – Baurutitan britoi n.sp.

Etymology – The generic name is formed by Bauru,in allusion to the Bauru Group and titan, from thegiants of the Greek myths.

Diagnosis – The same as for the species.

Baurutitan britoi n.sp.

Holotype – Last sacral vertebrae articulated with asequence of 18 caudal vertebrae, belonging to asingle individual. This specimen (MCT 1490-R) ishoused at the Museu de Ciências da Terra - MCT(Earth Science Museum) of the DepartamentoNacional de Produção Mineral (DNPM), in Rio deJaneiro, Brazil (Figs.4-27).

Etymology – The specific name is given in honor ofIgnacio Aureliano Machado Brito (1938-2001), animportant Brazilian paleontologist, who advisedseveral students including two authors of this paper(DAC and AWAK).

Type-locality – MCT 1490-R was collected in thePeirópolis site, at the point known as “Caieira”which is an abandoned quarry at the São Luis Farmlocated at the Veadinho Hill. This point is situatedabout 2km North of Peirópolis, Municipality ofUberaba, Minas Gerais State, Southeastern Brazil.

Geological setting – As all specimens collected fromthe Caieira point, MCT 1490-R was found in fine tomedium grained white and yellow sandstones fromthe Marília Formation, Serra da Galga Member, ata height of 835m (BERTINI, 1993). The age of thisstratigraphic unit is regarded as Maastrichtian(GOBBO-RODRIGUES, PETRI & BERTINI, 1999).

Diagnosis – Titanosaurid dinosaur characterized bythe following potential autapomorphies: stronglypointed laterally directed process intercepting thespinoprezygapophyseal lamina on the caudal 1;anterolaterally directed spinoprezygapophyseallamina. It is further distinguished from othertitanosaurids by the following combination ofcharacters: first caudal biconvex; developed dorsaltuberosity on the neural arch that turns into a lateralridge in the middle caudals; neural spines in themost anterior caudals (1-4) inclined posteriorly,changing to a more vertical to subvertical inclinationin caudal 5 to 10; prezygapophyseal tuberosity onthe lateral margin of the prezygapophysis of caudals2-4, which becomes less developed in the posteriorelements, smoothing out in the midcaudals;subrectangular outline of anterior articulation of thecaudal centrum, getting more squared towards theend of the tail.



Fig.3- Map showing the position of the bones collected at the Caieira quarry made by L.I.Price. This figure reproduces a picture ofthe map taken by someone of Price’s crew. Note that the year 1961 was added by Price after this picture was taken, which is theonly difference of this map and the one published by CAMPOS & KELLNER (1999). Arrows indicate the main specimen recovered:(a) MCT 1488-R (see CAMPOS et al., 2005), (b) Baurutitan britoi n.gen., n.sp. (MCT 1490-R) and (c) MCT 1536-R.



DESCRIPTION AND COMPARISON

The material of Baurutitan britoi consists of 19vertebrae, starting with the last sacral andsubsequent caudals. All elements were foundart iculated (Fig.3) . The mater ial is wel lpreserved, lacking any major postmortemcompression, and is complete except for part ofthe left neural arch of the sacral and the righttransverse process of the 3rd and 7th caudal.The centra of the 7th and 8th caudal weredamaged possibly by a drilling instrumentduring the collecting process. After beingprepared (some decades ago) this sequence wasnumbered continuously starting with the lastpreserved sacral. Therefore, the numbers writtenon the caudals ( left on the specimen forhistor ical reasons) do not refer to theiranatomical position in the tail (e.g., caudalnumbered as 3 is, in fact, the 2nd caudal).For descriptive purposes, this vertebral series isdivided into sacral vertebrae (only the last onepreserved), first caudal, anterior caudals (2nd-7th), and middle caudals (8th-18th). Althoughadmittedly arbitrary, the distinction betweenanterior and middle caudals is made by thepresence of a well developed transverse process.In Baurutitan britoi, the first caudal where thisprocess starts to be vestigial is the 8th which ishere regarded as the beginning of the middlecaudal series. The nomenclature regardingdifferent lamina is based on WILSON (1999).

SACRAL VERTEBRA

The right side of the last sacral is complete,whereas the left side lacks the basal part of theneural spine, the neural arch, the diapophysis,parapophysis and prezygapophysis (Figs.4-7).The centrum is complete except for the mostanterior surface. Despite that, it is clear thatthe articulation with the preceding sacral wasslightly convex. The posterior articulationsurface is strongly concave, suggesting thatthis sacral had an opisthocoelous condition.Overall the centrum is rounded, slightly widerthan high at the posterior surface. Laterally,i t is longer than high, having a shallowdepression below the transverse process. Onthe right side, close to the dorsoanteriorcorner , the centrum is p ie rced by twoforamina. The centrum of the last sacral wasnot fused with the precedent element.

The neural arch is fused with the centrum andshows a complex morphology. The neural canalis not complete in anterior view but posteriorlyhas an oval shape, being higher than wide. Theneural spine is tall and transversally expandedwith a rectangular apex in dorsal view. Theanterior surface is irregular, showing shallowdepressions and ridges. On the right side of theneural arch (the left part is not preserved) thepresence of a prezygodiapophyseal lamina(partially broken) is observed. A bony ridge atthe anterior surface of the neural spine isconnected with the prezygodiapophyseal lamina,delimitating a subtriangular cavity with the apexsituated ventrally. Posteriorly the neural spinehas a deep cavity located between thepostzygapophyses. In lateral view, the neuralspine is inclined posteriorly, with the verticalprojection of the posterodorsal corner placedbehind the posterior margin of the centrum.Pre- and postspinal laminae are present. Theprespinal lamina is well developed and projectsanteriorly. In the middle part, it has a widthbetween 6 and 10mm. The lateral surface isirregular, with several shallow depressions. Atboth sides of the contact surface with theneura l sp ine there are i r regu lar anddorsoventrally elongated cavities which aredeeper at the right side. These cavities arepresent from the base of the neural spine untilat least two thirds of its length and do notreach the apex. The postspinal lamina is lessprojected than the prespinal lamina, keelsposteriorly with a wide base (~15mm) anddisappears near the postzygapophyses abovea concavity located at the base of the neuralsp ine . Latera l ly , the dorsa l part o f thepostspinal lamina is more developed gettinggradually lesser projected toward the base.Lateral to this lamina, a dorsoventral lyelongated depression is observed, bordered bya comparatively thick spinopostzygapophyseallamina. There are some depressions on thepostspinal lamina, as well as on the adjacentsurfaces of the neural spine.The spinodiapophyseal lamina is well developedand thick, covering the anterolateral margin ofthe neural spine until reaching its middleregion. The posterior surface shows twolaterally placed cavities. The dorsal one is ovaland deep. The ventral is much larger, has arounded shape and is deep too, being perforatedby several foramina.



Only the right prezygapophysis is preserved.I t is very short , having the art iculat ionsurface expanded anteroposteriorly. Thepostzygapophyses are located very close to theneural spine and show elongated articulationsurfaces for the first caudal. The parapophysisshows a pyramidal structure, with the ventralsurface being parallel to the horizontal plane,and a dorsal edge rising dorsally as a thickbony blade (proximal part of the sacral rib),

Fig.4- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), sacral vertebra in right lateral view. Scale bar = 50mm. See textfor abbreviations.

partially preserved on the right side. Unitingthe parapophysis and the centrum is a strongand thick bony bridge oriented anteriorly thatdoes not form a true lamina. A deepsubtriangular cavity is present on the dorsalsurface of this bridge.The sacral rib is partially preserved on the rightside. Although being fused to the centrum, thelimits can be observed particularly at the regioncorresponding to the parapophysis.



Comparisons with other titanosaurid taxa aredifficult since in most the last sacral is either notpresent or not described in detail. The degree offusion in the sacrals varies among titanosaurid orclosely related taxa. In Baurutitan britoi the last sacralwas not fused to the precedent sacral, similar toGondwanatitan faustoi (KELLNER & AZEVEDO,1999) but differing from Opisthocoelicaudiaskarzynskii, Isisaurus colberti, Neuquensaurusaustralis, and Saltasaurus loricatus where the sacrumis formed by six well coossified vertebrae (BORSUK-BIALYNICKA, 1977; JAIN & BANDYOPADHYAY,

1997; POWELL, 2003). Baurutitan britoi has theposterior articulation surface strongly concave,differing from the convex condition found in Isisauruscolberti, Saltasaurus loricatus, and Epachthosaurussciuttoi (JAIN & BANDYOPADHYAY, 1997; POWELL,2003; MARTÍNEZ, et al., 2004). The last sacral ofGondwanatitan faustoi is procoelous (KELLNER &AZEVEDO, 1999), differing from theopisthocoelous condition of Baurutitan britoi.Neuquensaurus australis has the posteriorarticulation of the last sacral slightly concave(POWELL, 2003), while in Baurutitan britoi the

Fig.5- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), sacral vertebra in anterior view. Scale bar = 50mm. See textfor abbreviations.



concavity is more pronounced. The posteriorarticulation of the last sacral of Opisthocoelicaudiaskarzynskii and Baurutitan britoi are stronglyconcave, but the former is flattened dorsoventrally(BORSUK-BIALYNICKA, 1977: plate 5, fig.4),contrasting to the more rounded condition foundin the latter. According to JAIN & BANDYOPADHYAY(1997), Isisaurus colberti has a longitudinaldepression on the ventral surface of the sacral centrathat is absent in Baurutitan britoi.

There are three almost complete sacra recovered fromthe Peirópolis region (CAMPOS & KELLNER, 1999)than can be compared with Baurutitan britoi. Two werecollected at the same point (Caieira) (MCT 1536-Rand MCT 1488-R/MCT 1719-R, the latter beingdiagnosed in this volume, see CAMPOS et al., 2005and the third one, collected at the Rodovia site (MCT1489-R). All were regarded as belonging to threedistinct species of Titanosauridae, respectively sp.A, B, and C of CAMPOS & KELLNER (1999). While

Fig.6- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), sacral vertebra in posterior view. Scale bar = 50mm. See text forabbreviations.



MCT 1536-R and MCT 1488-R have the last sacralunfused to the precedent element as observed inBaurutitan britoi, in MCT 1489-R all six elements ofthe sacrum are fused. The last sacral of Baurutitanbritoi differs from MCT 1536-R by having the centrumthe posterior articulation surface more set apart fromthe sacral ribs, whose ventral margin is comparativelythinner (e.g., more compressed anteroposteriorly). Thelast sacral of MCT 1536-R, that represents a smalleranimal (estimated length of the centrum ~ 80mm), isdorsoventrally flattened with the posterior articulationsurface less concave. The last sacral of MCT 1488-Rand MCT 1489-R also differs from Baurutitan britoiby having the centrum dorsoventrally flattened, theneural spine dorsally expanded and by having theposterior articulation surface strongly convex. MCT1488-R further differs by having the neural spinemore inclined posteriorly.

FIRST CAUDAL VERTEBRA

The first caudal is longer than the preceding sacral

and has a biconvex centrum with the posteriorarticulation more projected than the anterior one(Figs.8-11). The anterior articulation of the centrumis larger dorsoventrally (118,8mm) than theposterior articulation (108,6mm). In anterior viewthe centrum is oval, slightly wider (131,4mm) thanhigh (118,8mm), with the dorsal and ventralmargins flattened. The lateral surface and theventral margin are concave, giving the centrum thetypical spool-shaped appearance. In lateral viewthe centrum is longer than high, a result basicallydue to the expanded posterior condyle which isdisplaced dorsally (Fig.8). This condyle displays asagittal dorsoventrally oriented groove on the upperhalf of the centrum which does not appear to be oftaphonomic origin. The neural arch is placed onthe anterior half of the centrum. The neural canalis oval, higher than wide. The transverse processesare robust, compressed anteroposteriorly, directedlaterally and slightly posteriorly (Fig.11). Thoseprocesses are twisted so that the dorsal margin atthe distal end is displaced posteriorly.

Fig.7- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), sacral vertebra in dorsal view. Scale bar = 50mm. See text forabbreviations.



The neural spine is elongated and inclinedposteriorly, so that, in lateral view, the verticalprojection of the posterior corner is placed on thecondyle. The neural spine is transversallyexpanded, particularly at the apex, although ithas almost the same width. The prespinallamina is present and well developed, althoughless than in the sacral vertebra, and extendsfrom the base of the neural spine to the apex.The postspinal lamina is also present, beingthicker and shorter than the prespinal lamina.

Spinoprezygapophyseal laminae are present, welldeveloped, and run over the anterolateral cornerof the neural spine, disappearing before reachingthe apex. The prezygapophyses are short andhave elliptical articular facets which are longertransversally than anteroposteriorly. Behind eachprezygapophysis, but placed at a higher position,there is a pointed elevation named hereinprezygapophyseal tuberosity which is the meetingpoint of the spinoprezygapophyseal lamina andthe dorsal border of the transverse process. In

Fig.8- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 1 in right lateral view. Scale bar = 50mm. See text forabbreviations.



caudal 1 the prezygapophyseal tuberosityintercepts the spinoprezygapophyseal laminabefore it reaches the prezygapophysis. Thespinoprezygapophyseal lamina is well definedand directed anterolaterally connecting theneural spine and the prezygapophysealtuberosity. The postzygapophyses are positionedvery close to the neural spine and have long,lateroventrally directed articulation surfaces,with the major axis directed dorsoventrally.Spinopostzygapophyseal laminae are not verydeveloped, presented as blunt ridges.

Comparisons with some titanosaurid taxa arelimited since for most the first caudal is eitherunknown or only briefly described. As far ascomparisons are possible, Lirainosaurus astibiaediffers from Baurutitan britoi by having a procoelousfirst caudal and by having a comparatively smallercentrum and a dorsoventrally expanded neural arch(SANZ et al., 1999). Opisthocoelicaudia skarzynskiidiffers by having the first caudal opisthocoelous withbroader but shorter transverse processes. Althoughincomplete, the first caudal of Pellegrinisauruspowelli is also biconvex, but differs from Baurutitan

Fig.9- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 1 in anterior view. Scale bar = 50mm. See text for abbreviations.



britoi by having a comparatively shorter centrum anda marked depressed area under the transverseprocess (SALGADO, 1996: fig.3). Also incomplete,the first caudal of Gondwanatitan faustoi differs fromthe one of Baurutitan britoi by being procoelous andhaving a comparatively shorter centrum (KELLNER& AZEVEDO, 1999).Regarding Epachthosaurus sciuttoi, the first caudalis procoelous and shows longer and posteriorlymore developed transverse processes with a distallyexpanded bony blade (MARTÍNEZ et al., 2004)which is absent in Baurutitan britoi. Furthermore,the neural arch of the first caudal of Baurutitanbritoi is comparatively more set apart from thecentrum, giving the vertebrae a higher aspect.

Baurutitan britoi has a larger neural canal, the tipof the neural spine broader and the postspinallaminae more developed.The first caudal of Alamosaurus sanjuanensis alsohas a biconvex centrum but differs from Baurutitanbritoi by having the anterior articulation with asubrectangular outline that is higher than wide(GILMORE, 1946: pl.5, fig.1; pl.8, fig.1). In both theanterior articulation surface is larger than theposterior one, but in Alamosaurus sanjuanensis thisdifference is even bigger. Furthermore, Baurutitan britoihas the ventral margin of the centrum more concave,the neural spine inclined posteriorly with a strongerpostspinal lamina, and prezygapophyses facing lessinward than in Alamosaurus sanjuanensis.

Fig.10- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 1 in posterior view. Scale bar = 50mm. See text for abbreviations.



Regarding saltasaurines, the first caudal ofSaltasaurus loricatus is quite distinct from Baurutitanbritoi by being procoelous and dorsoventrallyflattened. Saltasaurus loricatus further differs byshowing long and robust transverse processes(similar to the last sacral) and the pre- and postspinallaminae comparatively thinner. The neural canal ofBaurutitan britoi is also comparatively larger and thepostzygapophyses are positioned closer to each otherwith the articulation surface displaced more laterally.Neuquensaurus australis has also a biconvex firstcaudal (HUENE, 1929: pl.3, fig.3), but in Baurutitanbritoi the neural spine is more inclined posteriorlyand the ventral margin is more concave.Besides the differences pointed out above, Baurutitanbritoi also shows a distinct prezygapophyseal tuberosity,

which intercepts the spinoprezygapophyseallamina. To our knowledge, such a projection was notreported (or illustrated) in this position and with thisshape and size in any titanosaurid first caudal before.Apparently Alamosaurus sanjuanensis has a similarprocess, but it is less developed and is not laterallyprojected as in Baurutitan britoi (GILMORE, 1946: pl.5,fig.1; pl.8, fig.1). Epachthosaurus sciuttoi also shows adistinct projection, but it is situated on the dorsal partof the transverse process and its relation with thespinoprezygapophyseal lamina cannot be determined(MARTÍNEZ et al., 2004: fig.6). In this context, thepresence of a prominent prezygapophyseal tuberosityunited with the neural spine by an anterolaterallyoriented spinoprezygapophyseal lamina is considereda potential autapomorphy of Baurutitan britoi.

Fig.11- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 1 in dorsal view. Scale bar = 50mm. See text for abbreviations.



ANTERIOR CAUDAL VERTEBRAE

Starting at caudal 2, all anterior caudals areprocoelous, having the posterior condyle welldeveloped in a medial position, except in caudal7 where it is slightly displaced dorsally (Figs.12-18). The longest caudal is the 4th, followed bythe 2nd, 5th, 3rd, 6th, and 7th (see Table 1). Themost anterior element has the widest centrumand all subsequent get gradually narrower.Starting on caudal 3 all have the ventral portioncompressed laterally, forming a flattened toslightly concave surface. In anterior view thecentrum has a subrectangular outline, beingwider than high with the dorsal and ventralmargins flattened. The posterior part of thecentrum changes from elliptical (e.g., wider thanhigh) in caudals 2 and 3, to a more “heart-shaped” condition of caudals 4-7 (and the caudal8, here considered to be the first middle caudal).The dorsal surface above the posterior end of thecentrum has a shallow concavity, limitedposteriorly by a thickening of the dorsal rim ofthe posterior articulation. The condyle of caudals4 to 6 shows a dorsoventrally oriented sagittalgroove (as observed in the last sacral) which getsshallow posteriorly and turns to a roundeddepression in the mid-caudals (see below). Incaudal 5 this groove is more developed than in

any other vertebrae. Starting at caudal 4 thecentrum bears two laterally placed and ventrallyoriented projections for the chevron which arelargest in caudal 5 and get gradually smallertowards the end of the series.

The neural arch is placed over the anterior halfof the centrum, near the rim of the anteriormargin. The neural canal is oval, higher thanwide, with the basal part slightly wider than theapex. The neural spine of caudal 2 is inclinedposteriorly, similar to the condition of caudal 1.The vertical projection of the anterior corner ofthe neural spine is placed behind the middle partof the centrum and the vertical projection of theposter ior corner rests over the distalarticulation, similar to the condition observedin caudal 1. Starting at caudal 3 the neural spineis less inclined, with the vertical projection ofthe anterior corner shifted towards the middlepart of the centrum and the vertical projectionof the posterior corner placed at the beginningof the distal articulation. Starting at caudal 4the neural spine is less inclined with the verticalprojection of the anterior (and posterior) cornerof the neural spine shifting gradually towardsthe anterior and middle part of the centrum,a condition present until the first middle caudalvertebra (caudal 8).

VERTEBRAE TOTAL LENGTH OF CENTRUM

MAXIMUM LENGTH OF CENTRUM (LEFT SIDE)

WITHOUT CONDYLE

MAXIMUM HEIGHT OF CENTRUM ANTERIOR

FACE

MAXIMUM WIDTH OF CENTRUM ANTERIOR

FACE sacral 6 128 128 117 115 caudal 1 175 93 119 131 caudal 2 134 89 118 141 caudal 3 129 95 109 132 caudal 4 136 102 101 121 caudal 5 133 95 97 111 caudal 6 127 96 90 108 caudal 7 124* 92 85 101 caudal 8 115 * 88* 79* 98* caudal 9 115 96 74 90 caudal 10 115 91 76 87 caudal 11 112 89 76 80 caudal 12 114 92 75 72 caudal 13 113 92 74 69 caudal 14 116 96 74 67 caudal 15 117 94 70 68 caudal 16 121 98 68 70 caudal 17 121 99 65 71 caudal 18 118 101 67 68

Obs.: (c.7*) preserved portion (articular condyle broken); (c.8*) preserved portion (anterior portion broken)

TABLE 1. Length of the vertebrae of Baurutitan britoi n.gen., n.sp. (in millimeters)



Pre- and postspinal laminae are well developed inall anterior caudals, with the postspinal laminaalways more robust. The prespinal lamina coversthe entire length of the neural spine (incompletelypreserved in caudal 7). The postspinal lamina tendsto be thicker at the apex, reducing gradually inventral direction, ending in the vacuity between thepostzygapophyses. In caudals 2 and 3, due to thegreat development of the postspinal lamina, thedorsal surface formed by the neural spine andpostspinal laminae is triangular, with the apexdirected posteriorly. Starting on caudal 4, thisdorsal surface gets gradually more elliptical withthe main axis directed anteroposteriorly. Somecavities are observed on the anterior surfaces ofthe neural spines in caudals 2 to 6, adjacent to theprespinal lamina. The position of those cavitiesvaries in number and size, being most of the timemore developed on one side.Spinoprezygapophyseal laminae are present andwell developed in caudal 2, running from the dorsalportion of the prezygapophyses, merging with theneural spine. The spinoprezygapophyseal lamina

of the right side bifurcates and sends adorsomedially projected subsidiary lamina thatends at the prespinal lamina. In caudals 3-5, thespinoprezygapophyseal laminae are gradually lessdeveloped. Subsidiary laminae are present incaudals 3 (at both sides); 4 (at the left side) and 5(at the right side), closer to the base of the neuralspine always ending at the prespinal lamina. Incaudals 6-7 the spinoprezygapophyseal laminae arereduced to ridges situated more closely to the baseof the neural spine.The prezygapophyses of the anterior caudals arewell developed, project dorsoanteriorly in caudal 2and become gradually more horizontal untilassuming a subhorizontal position in caudal 5, acondition kept by the remaining vertebrae. Theprezygapophyses of caudals 2 and 3 arecomparatively shorter and more robust than theother elements of the anterior series. The anteriortip of the prezygapophyses reaches the middle partof the preceding centrum. The articulation surfacesare large, roughly “D” shaped, and become smallerin the posterior elements.

Fig.12- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 5 in left lateral view. Scale bar = 50mm. See text forabbreviations.



There is a well developed rugose elevation placed onthe lateral surface of the prezygapophyseal process,close to the spinoprezygapophyseal lamina. Thisfeature corresponds to the prezygapophysealtuberosity of caudal 1 but differs here by being smallerand by not intercepting the spinoprezygapophyseallamina. It becomes gradually smaller and lessperceptive in caudals 3 and 4, until turning to asmall lateral rugosity that smoothens out incaudals 9 and 10 (see below).

The postzygapophyses are well developed in allanterior caudals, always positioned close to theneural spine. The postzygapophyseal articular facetsin caudal 2 are elliptical (with the largest axis orienteddorsoventrally) and become gradually smaller andmore oval in the posterior elements. Posteriorly thepostzygapophyses have a thick medial margin andform a “V” shaped interpostzygapophyseal opening.Spinopostzygapophyseal laminae are present in allanterior caudals, but vary in thickness and projection,being thick in caudal 2, more laminar in caudals 3-5, and reduced in caudals 6 and 7.

All anterior caudals have developed posterolaterallyoriented transverse processes that become graduallyshorter along the sequence until becoming vestigial(and eventually disappearing) in the middle caudalvertebrae. Those processes are compresseddorsoventrally and become more posteriorly orientedalong the sequence, until assuming a hook-shapeon caudals 5 to 7. Although in all caudals thetransverse processes are fused with the centrum andthe neural arch, their limits can be observed by rugosesurfaces, particularly visible on the more anteriorlyplaced elements.Starting at caudal 3, the dorsal tuberosity (situatedon the contact surface between the transverseprocesses and the neural arch) forms a rounded andthick bone projection that is present along allpreserved caudals and in the anterior series neversurpasses the extension of the transverse process(contrary to the middle caudals - see below).There are several differences between the supposedtitanosaurid Opisthocoelicaudia skarzynskii (e.g.,SALGADO, CORIA & CALVO, 1997a) and Baurutitan

Fig.13- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 5 in anterior view. Scale bar = 50mm. See text forabbreviations.



britoi. The most striking ones are the opisthocoelouscondition of the former (BORSUK-BIALYNICKA,1977) and the shorter centra which are rounded(BORSUK-BIALYNICKA, 1977: pl.5, figs.1b, 1c, 2c,3) and lack the quadrangular aspect observed inBaurutitan britoi. According to BORSUK-BIALYNICKA (1977, p.15), the centra ofOpisthocoelicaudia skarzynskii show a ventralconcavity bordered by ventrolateral ridgesthroughout the caudal series which are absent inBaurutitan britoi. The bases of the neural spines ofcaudal 2-7 of Opisthocoelicaudia skarzynskii are setover the distal half of the respective centra (BORSUK-BIALYNICKA, 1977: pl.4, figs.1b, 2a; pl.5, fig.2a)which in Baurutitan britoi are positioned in theanterior half. The prezygapophyses ofOpisthocoelicaudia skarzynskii are shorter anddorsoanteriorly oriented in caudals 2-7 (and caudal8, BORSUK-BIALYNICKA, 1977: pl.4, figs.1b, 2a;pl.5, fig.2a) which in caudals 4-7 of Baurutitan britoiare less dorsally oriented. Another difference is theposition of the postzygapophyses which inOpisthocoelicaudia skarzynskii are set closer to the

posterior margin, surpassing it in caudal 2(BORSUK-BIALYNICKA, 1977: pl.4, fig.1b). Thetransverse processes of Opisthocoelicaudiaskarzynskii are rudimentary, heavy blunt knobs,projecting outwards and backwards and decreasein size posteriorly (BORSUK-BIALYNICKA, 1977:15).In Baurutitan britoi the transverse processes are moredeveloped, being curved posteriorly until the lastanterior caudal (caudal 7).Epachthosaurus sciuttoi differs from Baurutitan britoiby the presence of hyposphene-hypantrumarticulations in the anterior (and middle) caudals,regarded by MARTÍNEZ et al., (2004) asautapomorphic for the Argentinean taxon. Basedon the illustration of the seventh caudal(MARTÍNEZ et al., 2004, fig.7), the centra ofEpachthosaurus sciuttoi are elliptical and do notshow the quadrangular outline present inBaurutitan britoi. The condyle is very large andslightly displaced dorsally and the articulationsurfaces for the chevrons more closely spaced thanin the Brazilian species. The neural spine in caudal7 of Epachthosaurus sciuttoi tends to be vertical to

Fig.14- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 5 in posterior view. Scale bar = 50mm. See text for abbreviations.



subvertical (what possible is also the condition inother anterior elements) and the prezygapophysesare shorter. The neural arch is lower compared toBaurutitan britoi and the postzygapophyses areconsequently placed closer to the dorsal margin ofthe centrum. No information is available regardingthe pre- and postspinal laminae, but based on thepublished illustrations they are comparatively lessdeveloped in Epachthosaurus sciuttoi compared toBaurutitan britoi.

Besides the biconvex condition observed in the firstcaudal, the anterior caudals of Alamosaurussanjuanensis resemble Baurutitan britoi by havingposteriorly oriented neural spines and a similarshape of the neural canal. Alamosaurussanjuanensis differ by having the centra of caudal2-7 higher than wide, comparatively shorterprezygapophyses (particularly in caudals 2-5)which tend do be more inclined anterodorsally(GILMORE, 1946). The prezygapophyses of somevertebrae have the ventral margin curved,contrasting to the straighter condition observed inBaurutitan britoi. Furthermore, Alamosaurus

sanjuanensis have the neural arches stronglydirected backward and high neural spines, featuresabsent in Baurutitan britoi.POWELL (2003) has referred a caudal series of ajuvenile t itanosaurid (MPCA 1501) toTitanosaurus araukanicus, but did only brieflydescribe it, what makes the comparison withBaurutitan britoi limited. Based on the figuredanterior caudals (POWELL, 2003: pl.6, Figs:1-5),MPCA 1501 lacks the quadrangular outline ofBaurutitan britoi. According to POWELL (2003:23),MPCA 1501 has almost vertical neural spines,contrasting to the more inclined conditionobserved in Baurutitan britoi.Based on the figured proximal caudals, Isisauruscolberti displays very high neural spine and shorterprezygapophyses compared to Baurutitan britoi.Furthermore, the posterior condyle of Isisauruscolberti displays a rounded outline, differing fromthe more quadrangular condition of Baurutitanbritoi. Ventral projections for the chevrons areapparently poorly developed in the anteriorelements of Isisaurus colberti.

Fig.15- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 5 in dorsal view. Scale bar = 50mm. See text for abbreviations.



The anterior caudals of Baurutitan britoi are differentfrom the holotype of Aeolosaurus rionegrinus(POWELL, 2003) and the specimens referred toAeolosaurus sp. from the Allen Formation(SALGADO & CORIA, 1993) and from the LosAlamitos Formation (SALGADO, CORIA & CALVO,1997b) by having neural spines posteriorly inclinedand not placed on the anterior half of the centrum,and comparatively shorter prezygapophyses. Thecondyle in all Aeolosaurus specimens tends to bedisplaced dorsally. The pre- and postspinal laminaeare not well developed (or were not described) inthe known elements (e.g., SALGADO & CORIA,1993). A pleurocoel-like depression is observed inone side of caudal 3 in Aeolosaurus rionegrinus(POWELL 2003) which is absent in Baurutitan britoi.The pre- and postspinal laminae that are preservedin both mentioned specimens of Aeolosaurus sp.are comparatively thinner than those of Baurutitan

britoi. The anterior caudal of Aeolosaurus sp. fromthe Allen Formation (MPCA 27174) apparently hasa dorsal tuberosity on the dorsal surface at thecontact region of the transverse process and theneural arch (SALGADO & CORIA, 1993: fig.2), butis less developed than in Baurutitan britoi.Judging from the preserved parts of the neuralspines of the anterior caudals of Gondwanatitanfaustoi, these were inclined dorsoanteriorly,differing from Baurutitan britoi. The caudal 3 ofGondwanatitan faustoi shows a well developedbony ridge on the ventral part of theprezygapophyses that terminates in aprotuberance directly in front of the anterolateralcorner of the centrum, and a second ridge,dorsoventrally directed which is connected to thisprotuberance (KELLNER & AZEVEDO, 1999:125and fig.11). Furthermore, caudal 3 ofGondwanatitan faustoi has a lateral elongated

Fig.16- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 1-7 in right lateral view. Scale bar = 100mm.



depression on the centrum that is absent inBaurutitan britoi. The “heart-shaped” posteriorsurface of the centrum is similar in both taxa, butin Gondwanatitan faustoi, the centrum tends tobe more flattened dorso-ventrally. Wherepreserved, the prezygapophyses of Gondwanatitanfaustoi are comparatively more gracile and thinnerand more laterally directed than in Baurutitanfaustoi, and there is no sign of a prezygapophysealtuberosity. The postzygapophyses tend to have alarger articulation surface, forming a dorsal rimthat is laterally directed, features absent inBaurutitan britoi. Gondwanatitan faustoi also lacksa tuberosity above the transverse process.

The anterior caudals of MCT 1719-R (new taxonthat is being described in this volume - see CAMPOSet al. 2005) differ from Baurutitan britoi by havingthe anterior outline of the centrum rounded (andnot quadrangular), a shorter centrum and theventral margin more concave. MCT 1719-R has thecondyle of the anteriormost preserved caudal(possible caudal 2) set apart from the centrumby a thick bony rim, being more rounded andhigher than in Baurutitan britoi. The neural spinein MCT 1719-R is very high, has a thinner baseand broadens towards the apex. It is furtherdirected anterodorsally and placed on the anteriorhalf of the centrum close to the anterior margin.

Fig.17- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 1-7 in anterior view. Scale bar = 100mm.



Where observed, the prespinal lamina is more developedthan the postspinal lamina in MCT 1719-R, contraryto the condition observed in Baurutitan britoi, wherethe postspinal lamina is very thick. Thepostzygapophyses of MCT 1719-R are moredeveloped, having a more concave articulation surfacewith the dorsal border projected laterally. Theinterpostzygapophyseal space is also “V” shaped butform a more acute angle than in Baurutitan britoi. MCT1719-R further differs from Baurutitan britoi by theabsence of a dorsal tuberosity on the contact regionbetween the transverse process and the neural arch.Among the caudal vertebrae of Mendozasaurusneguyelap there is an anterior caudal (IANIGLA-PV 065/1) regarded as a first or second caudal(GONZÁLEZ RIGA, 2003: fig.4D-E). The centrum

is procoelous and if this element is indeed the firstcaudal, differs from the biconvex caudal 1 ofBaurutitan britoi. As in Baurutitan britoi, some caudalvertebrae of the Argentinean species show strongpostspinal lamina, more developed than the prespinallamina on anterior caudals. The anterior caudals ofMendozasaurus neguyelap can be differentiated fromthe other anterior caudals of Baurutitan britoi byhaving a short centrum, a high and vertically orientedneural spine and the presence of a largeinterzygapophyseal cavity, which was regarded as aprobable autapomorphy of Mendozasaurus(GONZÁLEZ RIGA, 2003: p.160). IANIGLA-PV 065/1 displays a small depression on the distal articularcondyle which is distinct from the sagittal groove thatappears on the dorsal surface of the articular condyle

Fig.18- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 1-7 in posterior view. Scale bar = 100mm.



of caudal 1 of Baurutitan britoi. The following anteriorcaudals of Mendozasaurus neguyelap havesubcircular articular faces (GONZÁLEZ RIGA, 2003:p.160), differing from the quadrangular articular facesof Baurutitan britoi. The centra are stronglyprocoelous, with prominent posterior condyles up tothe 5th caudal (more pronounced than in the sameelements of Baurutitan britoi), but this procoelydecreases distally in the tail of Mendozasaurusneguyelap, while it persists in Baurutitan britoi.Ventral projections for the chevrons are absent orpoorly developed in Mendozasaurus (GONZÁLEZRIGA, 2003: fig.5E-F). The neural spines ofMendozasaurus neguyelap are laterally compressedin the base, but broaden distally (GONZÁLEZ RIGA,2003), differing from the transversely expanded neuralspines of Baurutitan britoi. The neural spines in theanterior caudals are slightly oriented posteriorly, so thatthe posterodorsal edges are placed posteriorly withrespect to the posterior margin of the postzygapophyses,a trait that, in Baurutitan britoi, appears only in middlecaudals (beginning in 12). Mendozasaurus neguyelapis also distinct from Baurutitan britoi by havingprezygapophyses with wide and dorsomedially projectedarticular facets of quadrangular contour. Finally, in theArgentinean taxon the anterior caudals have a reducedbony prominence - the prezygapophyseal tuberosity -over the spinoprezygapophyseal lamina, but differfrom Baurutitan britoi by being positioned on thedorsal margin of the prezygapophyseal processes.This feature is apparently absent in the first or secondcaudal of Mendozasaurus neguyelap (González Riga,pers. infor., 2005).

According to SALGADO (1996:358), the originalsequence of the anterior caudals of Pellegrinisauruspowelli was lost, the numeration given below beingestablished by comparison with hypodigm ofTitanosaurus araukanicus (MPCA 1501). Theanterior caudals of Pellegrinisaurus powelli displaya pleurocoel placed below the base of the transverseprocess (SALGADO, 1996; POWELL, 2003), afeature not present in any of the caudals ofBaurutitan britoi. The centrum of caudal 6 ofPellegrinisaurus powelli is more depressed, havinga posterior condyle which is more pointed andcomparatively wider than in Baurutitan britoi. Inposterior view, this condyle is not quadrangular,having instead convex ventral and lateral margins(SALGADO, 1996: fig.4). According to SALGADO(1996:358 and fig.4), there is a rounded ridgerunning obliquely from the base of the transverseprocess to almost the edge of the posteriorarticulation, a feature absent in Baurutitan britoi.

Caudal 7 of Pellegrinisaurus powelli shows a thinnerand taller neural spine, apparently with poorlydeveloped pre- and postspinal laminae (SALGADO,1996: fig. 5). This vertebra has a protuberance atboth sides of the centrum in the posteroventralcorner of the lateral surface (SALGADO, 1996:p.359 and fig.5 - LP), a feature not present inBaurutitan britoi. Caudals 6 and 7 of Pellegrinisauruspowelli have postzygapophyses placed at a lowerposition, closer to the centrum than thecorresponding elements of Baurutitan britoi.The centrum of the possible second caudal (MRS-Pv 23) of Rinconsaurus caudamirus has “pleurocoel-like” lateral depression (CALVO & GONZÁLEZRIGA, 2003:338), a feature not present in any ofthe anterior caudals of Baurutitan britoi. Besidesthe holotype (MRS-Pv 26), Rinconsaurus caudamirusis represented by several incomplete series ofanterior caudals (MRS-Pv 23, 24, 25) (CALVO &GONZÁLEZ RIGA, 2003), that have the centrahigher than wide, differing from Baurutitan britoi.At least in the holotype (MRS-Pv 26, CALVO &GONZÁLEZ RIGA, 2003: pl.2A), the ventral marginsof the centra are flat or comparatively less concavethan in Baurutitan britoi. Rinconsaurus caudamirusfurther shows a bony process separating thearticular facets of the postzygapophyses from theneural spine (CALVO & GONZÁLEZ RIGA, 2003).The anterior caudals of Saltasaurus loricatus havecentra which are comparatively more dorsoventrallydepressed than those of Baurutitan britoi. The centraalso have convex lateral walls, differing from thealmost vertical lateral walls of Baurutitan britoi. Thebases of the transverse processes are much moredorsoventrally developed in Saltasaurus loricatus thanin Baurutitan britoi. The ventral borders of thetransverse processes reach the middle of the centrumin the Argentinean species (POWELL, 2003: fig.33).The neural spine in the anterior caudals ofSaltasaurus loricatus is displaced in posteriordirection, the base of which is placed over theposterior half of the centrum (POWELL, 2003: fig.33),differing from the spines of Baurutitan britoi, the basesof which are placed over the anterior half of the centra.A further distinguishing feature of Baurutitan britoiis the well developed postspinal lamina, alwayslarger than the prespinal lamina, aprezygapophyseal tuberosity and a dorsaltuberosity at the base of the neural arch which iswell developed until the last anterior caudal (caudal7). Alamosaurus sanjuanensis apparently alsoshows a dorsal tuberosity (GILMORE, 1946: pl.5,pl.8), but smaller than in the Brazilian taxon.



MIDDLE CAUDAL VERTEBRAE

As the anterior caudals, all preserved elementsof the middle series (caudals 8-18) are procoelouswith a well developed posterior condyle andanterior cotyle (Figs.19-24). The size of thecentrum varies (Tab.1), with the vertebrae placedmore posteriorly slightly longer (caudals 14-18).There is some variation in the width of thecentrum, but overall the more posterior elementstend to be more compressed laterally. Theanterior surface of the centrum in middle caudalschanges from being wider than high in caudals8-10 to a more square outline from caudals 11to 15 and back to a more rectangular outline (i.e.,wider than high) in caudals 16-18. The lateralmargin of the anterior articulation surface variesfrom being almost vertical (e.g., caudals12-15)to slightly rounded (e.g., caudal 10). As in theanterior caudals, a shallow dorsal concavity ispresent on the posterior portion of the centrum,with the bony rim that limits the posterior endvery pronounced in most elements. Except for

caudals 8, 16 and 17, all show a shallow androunded depression at the condyle. Thisdepression can be slightly displaced ventrally(caudals 10-13) or is positioned at the mostposteriorly projected part. The posterior part ofthe centrum bears lateral ventrally orientedprojections for the chevron that get graduallyless developed posteriorly, disappearing incaudals 15-18.The neural arch is placed over the anterior half ofthe centrum. The neural canal is oval, but contraryto the anterior caudals, is wider than high in mostelements of the middle series. The neural spine getsgradually more inclined posteriorly, shifting thevertical projection of the anterior corner from theanterior part (caudal 8) to the middle part of thecentrum (remaining elements).At the same time, the tip of the neural spine tendsto get more elongated and a marked change isobserved from caudal 13 to 14, with the neuralspine getting more elongated with a broaderposterior end, a trend followed in the remainingpreserved elements.

Fig.19- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in right lateral view. Scale bar = 100mm.



Pre- and postspinal laminae can be individualizedin the first elements of the middle series, butgradually tend to merge with the neural spine.The prespinal lamina is individualized up tocaudal 13, being completely merged with theneural spine thereafter. The postspinal lamina,more robust than the prespinal lamina,completely merges with the neural spine startingon caudal 16.Spinoprezygapophyseal laminae are reduced,forming blunt ridges that run from the neuralspine to the dorsomedial portion of base of theprezygapophyses. A cavity is formed betweenthese ridges, del imited ventral ly by theintraprezygapophyseal lamina.The prezygapophyses are well developed, beingmore slender compared to those of the anteriorcaudals. The anterior margins of theprezygapophyses reach the middle part of thepreceding vertebrae, but gradually shift to theposterior half of the more posterior elements. Theprezygapophyses gradually assume a morehorizontal position, becoming subparallel to thehorizontal plane at caudal 14. The prezygapophysealarticulation surfaces are rounded and subverticallyoriented, becoming less marked posteriorly. Startingat caudal 16, the prezygapophyseal articulation

surfaces cannot be distinguished from theremaining part of the prezygapophyses. Caudals8 to 15 show a marked dorsal ridge above theprezygapophyseal articulation surfaces which tendto disappear in the more posterior elements thatlack distinct prezygapophyseal articulationsurfaces. This ridge does not connect with thespinoprezygapophyseal lamina.

The postzygapophyses are placed very closely tothe neural spine. They tend to be displacedposteriorly but in caudals 8 and 9 are stillpositioned above the middle part of the centrumwhereas from caudal 10 to 18 they arecompletely placed over the distal half of thecentrum. From caudals 8 to 14, there is a welldeveloped postzygapophyseal articulationsurface of oval shape which is present only onthe right side at caudal 15. Starting at caudal16, the postzygapophyses turn to a thickprojection at the posteroventral part of the neuralspine without any distinguishable articulationsurface. The “V” shaped interpostzygapophysealopening gets gradually smaller, disappearing atcaudal 15. Spinopostzygapophyseal laminaebecome reduced posteriorly, present as a bonyridge on caudal 8 and absent in the subsequentelements.

Fig.20- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in anterior view. Scale bar = 100mm.



In the elements of the middle caudal series, thetransverse processes are only observed (albeitreduced) in caudals 8 and 9 (on both sides) and 10(only on the right side), disappearing in theremaining elements. Where present, no limitsbetween the transverse process and the centrumor neural arch can be observed. The dorsaltuberosity is well developed in caudal 8, becominggradually smaller and more elongatedanteroposteriorly. It is clear that at least inBaurutitan britoi, the lateral extension seen in sometitanosaurids (e.g., Gondwanatitan), is not formedby the transverse process but by this independentdorsal tuberosity (see Discussion).As the anterior elements, the posterior caudals ofOpisthocoelicaudia skarzynskii differ fromBaurutitan britoi by being opisthocoelous untilcaudal 15, turning to amphiplatyan at caudal 16to 27 (BORSUK-BIALYNICKA, 1977). The centra areshorter and rounded (BORSUK-BIALYNICKA, 1977:pl.6, figs.4a, 5a), and not quadrangular as inBaurutitan britoi. The ventral concavity bordered byventrolateral ridges (absent in Baurutitan britoi) isstill present in the middle caudals ofOpisthocoelicaudia skarzynskii (BORSUK-BIALYNICKA (1977:15). The bases of the neural

spines of middle caudals of Opisthocoelicaudiaskarzynskii are set over the distal half of therespective centra (BORSUK-BIALYNICKA, 1977:pl.5, fig.5; pl.6, fig.7a), always more posteriorlyplaced than in the respective elements of Baurutitanbritoi. The prezygapophyses of Opisthocoelicaudiaskarzynskii are shorter (BORSUK-BIALYNICKA,1977: pl.4, figs.1b, 2a; pl.5, fig.2a), but show asimilar orientation as in Baurutitan britoi. Thepostzygapophyses of both species are placed on theposterior half of the centrum, but inOpisthocoelicaudia skarzynskii they are set closerto the posterior margin (BORSUK-BIALYNICKA,1977: pl.5, fig.5; pl.6, figs.1b, 7a). InOpisthocoelicaudia skarzynskii the caudals of themiddle series tend to have a more subverticallyoriented neural spine (BORSUK-BIALYNICKA,1977: pl.5, fig.5; pl.6, fig.7a).An important feature that distinguishes Baurutitanbritoi from Epachthosaurus sciuttoi is the presencein the latter of hyposphene-hypantrum articulationsin caudals 8-14 (MARTÍNEZ et al., 2004). Some ofthe middle elements show a ventral longitudinalgroove which is absent in Baurutitan britoi. Theneural spine in Epachthosaurus sciuttoi tend to bemore anteroposteriorly elongated, and the

Fig.21- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in posterior view. Scale bar = 100mm.



postzygapophyses are apparently not well delineated(“weak”, according to MARTÍNEZ et al., 2004).As in the anterior elements, the middle caudalvertebrae of Alamosaurus sanjuanensis also differ

from Baurutitan britoi by having the outline of thecentrum more rounded, lacking the quadrangularshape of the latter. The ventral projections for thechevrons are comparatively more developed in

Fig.22- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 9 in: (a) right lateral, (b) dorsal, (c) anterior, and (d) posteriorviews. Scale bar = 50mm. See text for abbreviations.

a b

c d



Alamosaurus sanjuanensis, particularly in caudals8-13, and the ventral margin of the centra are moreconcave. The prezygapophyses tend to becomparatively thinner and in caudals 8-10 show atuberosity which is absent in the correspondingvertebrae of Baurutitan britoi. Furthermore, inAlamosaurus sanjuanensis the neural spine getsmore elongated anteroposteriorly starting at thecaudal 11, while this happens only in caudal 14 inBaurutitan britoi.Midcaudals of Isisaurus colberti display high neuralspines and shorter prezygapophyses thanBaurutitan britoi. The outline of the posteriorarticulation is rounded contrasting to the morequadrangular condition observed in Baurutitanbritoi. The condyle in the Indian taxon is veryprojected anteroposteriorly (“cone-like”) anddisplaced dorsally. According to JAIN &BANDYOPADHYAY (1997) the mid- and distalcaudals of Isisaurus colberti show developedanterior and posterior facets for the chevrons whichin Baurutitan britoi tend to be reduced and presentonly on the ventral part of the posterior articulationsurface. Furthermore, Isisaurus colberti shows theventral surface of the centrum concave (JAIN &BANDYOPADHYAY, 1997: fig.12D), differing fromthe more flattened condition of Baurutitan britoi.As far as comparisons are possible, the main

difference from the middle caudals ofGondwanatitan faustoi and Baurutitan britoi is thepresence of a lateral anteroposteriorly elongatedridge that is more developed in the former. Asdemonstrated in Baurutitan britoi, this processcorresponds to the tuberosity present in moreanterior elements and not the transverse process.If this is also the case in Gondwanatitan faustoicannot be demonstrated and the questions if thosetwo lateral ridges of those taxa are homologousremains open.According to SANZ et al. (1999) only few caudalsare known from Lirainosaurus astibiae that, exceptfor the first (which is the holotype), are consideredparatypes. Comparing the last preserved caudal ofBaurutitan britoi with the middle caudal ofLirainosaurus astibiae figured by SANZ et al. (1999:pl.3, fig.A), the Spanish taxon differs by having theneural spine occupying a more central position,shorter prezygapophyses with a more expandedend, the postzygapophyses comparatively more setapart from the neural spine with more expandedarticulation surfaces, and the ventral margin of thecentrum more concave.The middle caudals of Mendozasaurus neguyelaphave centra with slightly procoelous, circularanterior faces (not rectangular or square as inBaurutitan britoi). The posterior faces have reduced

Fig.23- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), drawing of caudal 9 in (a) right lateral and (b) anterior views.Scale bar = 50mm. See text for abbreviations.

a b



condyles displaced dorsally, which is regarded as anautapomorphy of Mendozasaurus neguyelap(GONZÁLEZ RIGA, 2003). The neural spines aredepressed, flat and more elongated anteroposteriorlythan in Baurutitan britoi. The anterodorsal cornerof the neural spine in caudals 12-13 is higher andthicker than the posterodorsal one. This conditiondisappears in caudal 17, where the dorsal borderof the neural spine straightens and becomeshorizontal, with the anterodorsal corner forming aright angle (GONZÁLEZ RIGA, 2003, fig.5C). Thiscondition is not present in the distalmost preservedcaudals of Baurutitan britoi.Beginning in caudals 8-10, the middle caudalsof Pel legrinisaurus powell i d isplay acomparatively longer and lower centrum thanin the correspondent elements of Baurutitan britoi

(SALGADO, 1996:359). The midcaudal centra aredorsoventrally depressed, having convex lateralfaces, differing from the quadrangular shape of thecentra of Baurutitan britoi. Beyond the 15th vertebra,the centra of Pellegrinisaurus powelli, in anteriorview, become depressed, with convex lateral walls(SALGADO, 1996: fig.6C), contrasting with thequadrangular shape of caudals 15-18 of Baurutitanbritoi. In these distalmost elements, the neuralspines of Pellegrinisaurus powelli are lower and moreanteroposteriorly elongated than in Baurutitanbritoi. They reach the posterior end of the caudalcentrum, and have the anterodorsal corner of theneural spine set at a higher position in respect tothe posterodorsal corner (SALGADO, 1996: fig.6A),a condition present only in the last preservedcaudal of Baurutitan britoi.

Fig.24- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudal 18 in: (a) right lateral, (b) dorsal, (c) anterior, and (d) posteriorviews. Scale bar = 50mm. See text for abbreviations.

a b

c d



The middle caudals of Rinconsaurus caudamiruscan be distinguished from those of Baurutitanbritoi by the presence of bony processesseparating the articular faces of thepostzygapophyses from the neural spine, acharacter considered an autapomorphy ofRinconsaurus caudamirus (CALVO & GONZÁLEZRIGA, 2003). Among the distal caudals ofRinconsaurus caudamirus, there is a series (MRS-Pv 29) with unusual centra, showing a procoelousplus amphicoelous plus biconvex articulations(CALVO & GONZÁLEZ RIGA, 2003: pl.3, fig.A).Since the posterior part of Baurutitan britoi islacking, it is not possible to tell, in the presenttime, whether this condition was present in thistaxon. It should be noted, however, that a similarcondition has been reported in a caudal series(DGM 497-R) found in the same sedimentarydeposits, in a nearby quarry (TROTTA, CAMPOS& KELLNER, 2002).Regarding the Saltasaurinae Saltasaurus loricatusand Neuquensaurus australis, the main differenceis the anteroposteriorly elongated depression,

divided by a sagittal crest on the ventral surfaceof the centra (POWELL, 2003) which is absent fromBaurutitan britoi.

CHEVRONS

Fifteen chevrons of Baurutitan britoi wererecovered (Figs.25-27) . By the avai lableinformation, they were found articulated withthe caudal series (Fig.3). As the caudals, afterbeing prepared (some decades ago) they werenumbered according to the vertebrae to whichthey were connected. Therefore, the numberswritten on the chevrons (also left on thespecimen for historical reasons) do not refer tothe anatomical position of the caudals in thetail (e.g., chevron 4-5 was found connected tocaudals 3 and 4). The eight anteriormostchevrons show two numbers (e.g. 4-5; 5-6; 6-7), suggesting that they were probably in contactbetween two vertebrae. The last seven chevronsreceived single numbers and were possible moreclosely associated with one vertebra.

Fig.25- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), chevrons in left lateral view. The last chevron is figured in ventralview. Scale bar = 100mm.



Fig.26- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), chevrons arches in anterior view. Scale bar = 100mm.

Fig.27- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), chevrons arches in posterior view. Scale bar = 100mm.



All chevrons are well preserved and complete, withexception of the ventral tip of some elements. Thechevron series begins on caudal 3 and 4 and extendsuntil caudal 18. Therefore one chevron is missing(between the caudals 11-12). All chevrons are open,displaying a large haemal canal. The fouranteriormost chevrons (corresponding to the caudals3/4 - 6/7) are the largest (subequal in size) withlong ventral process. From the fifth chevron on, theirsizes gradually decrease, with the last preservedelement (corresponding to caudal 18) divided intotwo ossifications that do not fuse ventrally. In themore anterior elements, the ventral fused portion ofthe chevrons tend to very large (subequal or largerin size compared to the proximal processes), gettinggradually shorter in the more posteriorly placedelements. The depth from the haemal canal changesfrom being shorter than the whole chevron in theanterior elements until being much larger in themost posterior elements (corresponding to caudals13 to 18). The ventral portion corresponding to thefused part of the chevron is laterally compressed,forming an anteroposteriorly oriented blade-likelamina that gets gradually more reduced in the moreposteriorly situated elements.The anterior and posterior surface of this regionshows longitudinal ridges. The bone of the lateralsurface of the chevron corresponding to caudal 13is thickened, differing from the preceding elements.The posteriorly place chevrons also have a similarbut less developed thickened bone surface.Opisthocoelicaudia skarzynskii has chevrons startingat the last sacro-caudal as far back to caudal19, beyond which they were probably absent orquite rudimentary (BORSUK-BIALYNICKA,1977), differing from Baurutitan britoi (chevronsstarting at caudal 3). In the anterior caudals ofOpisthocoelicaudia skarzynskii, the haemal canal isabout one third of the chevrons length, differing fromthe anterior chevrons of Baurutitan britoi, which havehaemal canals equivalent to half of the chevronslength. The ventral projection of the chevrons 4 to 8in Opisthocoelicaudia skarzynskii is pointed, a featurenot present in any of the chevrons of Baurutitan britoiwhere they are rounded. The chevrons from 6 to 15of Opisthocoelicaudia skarzynskii are fused to thecentra, a condition not present in Baurutitan britoi.Furthermore, the chevrons of Opisthocoelicaudiaskarzynskii have comparatively larger and strongerarticular facets than those of Baurutitan britoi.The chevron of Aeolosaurus rionegrinus (POWELL,2003: pl.11, fig.3) is distinguished from those ofBaurutitan britoi by having a haemal canal more or

less equivalent to a third of the whole length of thebone, flanked by two well developed proximalprocesses both transversally and anteroposteriorlymore expanded than in the Brazilian taxon. Theproximal part of the ventral process is alsotransversally wider than in Baurutitan britoi.

Alamosaurus sanjuanensis has chevrons from thefirst caudal to the 25th (GILMORE, 1946). The armsof the chevrons in Alamosaurus sanjuanensis are setcloser to each other than in Baurutitan britoi, resultingin a more acute “V” shaped profile. The articular headsare more developed in being anteroposteriorly andlaterally more expanded than in the Brazilian taxon(GILMORE, 1946: fig.4).The chevron of Mendozasaurus neguyelap(GONZÁLEZ RIGA, 2003: fig.5D) has both arms setcloser to each other than in Baurutitan britoi,resulting is a more acute “V” shaped profile. Thearticular heads of the chevron are more expanded,both anteroposteriorly and laterally, in theArgentinean taxon. The ventral spine ofMendozasaurus neguyelap is thinner in anterior viewthan in Baurutitan britoi. The chevrons ofMendozasaurus neguyelap have double articularfacets in proximal ends (GONZÁLEZ RIGA, 2003:p.162), a trait not present in Baurutitan britoi.The haemal canal of an anterior chevron of Isisauruscolberti (JAIN & BANDYOPADHYAY, 1997: fig.17) isless deep than half of the length of the entire bone,thus differing from the corresponding deeper haemalcanals present in Baurutitan britoi. The bone is moreexpanded anteroposteriorly in the Indian taxon. Itshows also extremely developed articular facets, withclearly anterior and posterior articulating surfaces(JAIN & BANDYOPADHYAY, 1997: p.121), which areabsent in the Brazilian taxon. Below the canal, thehaemal arches of Isisaurus colberti have a roundedshape in cross section (JAIN & BANDYOPADHYAY,1997), differing from Baurutitan britoi, in which thehaemal arches have a more elliptical cross section,with the longest axis directed anteroposteriorly.The anterior chevrons of Saltasaurus loricatus aremore robust than the same elements of Baurutitanbritoi, being comparatively more expanded bothtransversally and anteroposteriorly, with welldeveloped articular heads (POWELL, 2003: fig.36a).Although the ventral spine of Saltasaurus loricatusalso displays an anterior ridge, it is thicker andrestricted to the distal portion of the spinecompared to Baurutitan britoi. The haemal canal isless deep in the Argentinean taxon, being less thana third of the entire length of the bone.



DISCUSSION

Dinosaurs in Brazil are known for a long time(KELLNER, 1996; 1998) and there are severallocalities where specimens have been recovered butfew have been actually named or studied properly(KELLNER & CAMPOS, 2000). Regardingsauropods, only three species have been describedso far: one diplodocid (CARVALHO, AVILLA &SALGADO, 2003) and two titanosaurids. The firsttitanosaurid, “Antarctosaurus brasiliensis” (ARID &VIZOTTO, 1971), is unfortunately based on materialthat cannot be diagnosed (e.g., KELLNER &CAMPOS, 2000). The second is Gondwanatitanfaustoi, which is closely related to Aeolosaurusrionegrinus (KELLNER & AZEVEDO, 1999). Fromall known localities with titanosaurid dinosaurs,Peirópolis was always regarded as the richest(CAMPOS & KELLNER, 1991; BERTINI et al., 1993;KELLNER & CAMPOS, 1997), showing somediversity (PRICE in LAMEGO, 1959; POWELL,1987; CAMPOS & KELLNER, 1999; TROTTA,CAMPOS, & KELLNER, 2001).From all specimens discovered at the Peirópolis site,the partially articulated vertebral columns known inthe literature as the sequences A (cervical vertebraeand three dorsals), B (cervical, dorsal and caudalvertebrae - see CAMPOS et al., 2005 - this volume),and C (last sacral and caudal vertebrae) were regardedas the most important ones (POWELL, 1987). Ofthose, the sequence C, here named Baurutitan britoi,is the most complete articulated caudal sequencefrom Brazil known to date (caudal 1 to 18), making itvery useful to place isolated anterior and middlecaudal elements in the tail. Based on comparisonswith MCT 1488-R (that has a partial neck, thecomplete dorsal series) and MCT 1719-R (incompletecaudal series), the length of Baurutitan britoi isestimated between 12 and 14 meters.One of the most outstanding features Baurutitanbritoi is the presence of a dorsal tuberosity situatedon the contact surface between the transverseprocesses and the neural arch. This process formsa rounded and thick bone projection that starts incaudal 2 and gets gradually smaller and moreelongated in the posterior elements, being presentin the last preserved caudal (caudal 18). Thetransverse process is present and well developed inall anterior elements, always larger than the dorsaltuberosity. In caudals 8 and 9, the transverseprocess is reduced, while in caudal 10 it isperceptible only on the right side as a tiny knoblikeprojection that completely disappears in caudal 11.

Starting on caudal 8, the dorsal tuberosity, however,despite getting gradually smaller in the posteriorelements, is always more projected than thetransverse process. This unequivocally shows thatthe lateral bony ridge present in the posteriorelements of the middle series is homologous withthe dorsal tuberosity and not with the transverseprocess. Alamosaurus sanjuanensis has thetransverse processes getting smaller posteriorly andaccording to GILMORE (1946), are replaced by“raised rectangular areas” which are replaced bylongitudinal ridges that disappear at caudal 27.Judging from the published pictures, Alamosaurussanjuanensis also bears a dorsal tuberosity (albeitless developed than in Baurutitan britoi) and the bonylateral ridges on the base of the neural arch, mightalso be homologous to the dorsal tuberosity insteadto the transverse processes.The presence of a lateral ridge in caudals from themiddle (and posterior) series has been observed inEpachthosaurus sciuttoi (MARTÍNEZ et al., 2004: fig.8a), where it was interpreted as the transverseprocess. Similar longitudinal ridges were observedin Gondwanatitan faustoi (KELLNER & AZEVEDO,1999). SALGADO, CORIA & CALVO (1997a) alsomention the presence of prominent lateral bony ridgesin the saltasaurines Neuquensaurus australis andSaltasaurus loricatus. Since those taxa apparently lacka dorsal tuberosity on the anterior caudals, thehomology of those bony ridges is not clear.Regarding the phylogenetic position of Baurutitanbritoi, the procoelous condition of anterior caudalsallows its allocation within Titanosauria(SALGADO, CORIA & CALVO, 1997a). The stronglyprocoelous condition of midcaudals indicates thatit is not a basal titanosaurid, such as Andesaurusdelgadoi Calvo & Bonaparte 1991 where the mid-and posterior caudals are amphiplatyan, a primitivefeature within Titanosauria (CALVO &BONAPARTE, 1991; SALGADO, CORIA & CALVO,1997a). The new Brazilian taxon also lacks severalcaudal traits found in the saltasaurines thatincludes strongly dorsoventrally flattened centrumof anterior caudals, with centrum significantlywider than high, and the position of the neuralspine, with the anterodorsal edge positionedposteriorly relative the anterior border of thepostzygapophyses. Baurutitan britoi is also not amember of the clade formed by Aeolosaurus +Gondwanatitan, lacking the strongly anterodorsallyoriented neural spine and the very anteriorlydisplaced neural arch. However, as inGondwanatitan faustoi and Aeolosaurus rionegrinus



(Kellner pers. obs. 1999), some of the anteriorcaudal vertebrae show the ventral part of thecentrum constricted, giving the posterior surfaceof the centrum a “heart-shaped” appearance, andpotentially could indicate some relationships ofthose mentioned taxa with Baurutitan britoi. Thenew species also shares some features withAlamosaurus sanjuanensis (e.g., dorsal tuberositythat continues in the posterior elements as aprominent lateral ridge).Concluding, Baurutitan britoi is a new titanosauridsauropod from Brazil, which is neither a basal (e.g.,Andesaurus) nor a derived (e.g., Saltasaurinae)taxon. It shows some similarities to Aeolosaurusrionegrinus and Gondwanatitan faustoi (“heart-shaped” centrum of some anterior caudals), also withAlamosaurus sanjuanensis. More information aboutits phylogenetic position can only be achieved by adetailed phylogenetic analysis of the Titanosauria.

ACKNOWLEDGMENTS

The authors wish to thank the following individualsand respective institutions, for assistance andaccess to specimens under their care: Jorge O.Calvo (Centro Paleontológico Lago Barreales,Universidad Nacional del Comahue, Neuquén), JoséF. Bonaparte (Museo Argentino de CienciasNaturales, Buenos Aires), Jaime E. Powell (Facultadde Ciencias Naturales, Universidad Nacional deTucumán, Tucumán), and Marcelo Reguero (Museode La Plata). We would also like to thank Luiz Júlioda Silva and Otávio da Silva Santos, formerpreparators at the Departamento Nacional deProdução Mineral, for the excellent work done onthis specimen, and Andrea Franco Saavedra(Colégio D. Pedro II, Rio de Janeiro) for preparingthe anterior part of the preserved sacral andcleaning the chevrons. Vanessa Dorneles Machado(Museu Nacional - Rio de Janeiro) is thanked forthe pictures that illustrate this paper and RitaC.T.Cassab (MCT/DNPM) for providing the paperof A.R.Lamego, where the report of L.I.Price aboutthe Peirópolis site was published.We have benefited from discussions with severalcolleagues, particularly Jaime E. Powell(Universidad Nacional de Tucuman, Tucuman),Jorge O. Calvo (Centro Paleontológico LagoBarreales, Universidad Nacional del Comahue,Neuquén), Reinaldo J. Bertini (UniversidadeEstatual Paulista, Rio Claro), Rodrigo MiloniSantucci (Universidade Estadual Paulista, Rio

Claro), Bernardo J. González Riga (Centro Regionalde Investigaciones Científicas y Tecnológicas,Mendoza) and Olga Giménez (Universidad Nacionalde la Patagonia “San Juan Bosco”, ComodoroRivadavia). Jorge O. Calvo (Centro PaleontológicoLago Barreales, Universidad Nacional del Comahue,Neuquén), Bernardo J. González Riga (CentroRegional de Investigaciones Científicas yTecnológicas, Mendoza), Douglas Riff (UniversidadeEstadual do Sudeste da Bahia, Vitória daConquista) and Jeffrey A. Wilson (University ofMichigan) are thanked for reviewing this paper. Thisproject was partially funded by FAPERJ (grant #E-26/152.442/2002-2005 to A.W.A. Kellner) andConselho Nacional de Desenvolvimento Científicoe Tecnológico - CNPq (grants to D.A. Campos andA.W.A. Kellner).

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