Arquivos do Museu Nacional, Rio de Janeiro, v.63, n.3, p.565-593, jul./set.2005 
ISSN 0365-4508 

ON A TITANOSAURID (DINOSAURIA, SAUROPODA) VERTEBRAL COLUMN 
FROM THE BAURU GROUP, LATE CRETACEOUS OF BRAZIL 1 
(With 39 figures) 


DIOGENES DE ALMEIDA CAMPOS 2, 3 
ALEXANDER W. A. KELLNER 3, 4 
REINALDO J. BERTINI 5 
RODRIGO M. SANTUCCI 5 

ABSTRACT: A new titanosaurid dinosaur from the Late Cretaceous continental deposits of the Bauru Group 
is described. Trigonosaurus pricei n.gen., n.sp., is based on two specimens, both collected at the Caieira 
Quarry near Peirópolis, Minas Gerais. The holotype consists of the five most posterior cervical vertebrae, 10 
dorsals, six sacrals and the left ilium (MCT 1488-R). The second specimen (paratype) consists of 10 caudal 
vertebrae that according to a quarry map, were found isolated but show a similar morphology and compatible 
size suggesting that they belonged to one individual (MCT 1719-R). Trigonosaurus pricei is diagnosed by a 
combination of characters such as elongated cervicals and middorsals, dorsal vertebrae 9 and 10 with 
incipient postzygodiapophyseal lamina and transverse processes well developed throughout the sequence 
formed by anterior and medial caudals. The occurrence of this new taxon indicates a higher diversity of 
titanosaurids in the Brazil during the Cretaceous period. 

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

RESUMO: Sobre uma coluna vertebral de um titanossaurídeo (Dinosauria, Sauropoda) do grupo Bauru, 

Neocretáceo do Brasil. 
Um novo titanossaurídeo procedente dos depósitos continentais do grupo Bauru (Neocretáceo) é descrito. 
Trigonosaurus pricei n.gen., n.sp. é baseado em dois exemplares coletados na localidade Caieira na região de 
Peirópolis, Minas Gerais. O holótipo é composto das últimas cinco vértebras cervicais, 10 vértebras dorsais, 
seis sacrais e o ílio esquerdo (MCT 1488-R). O segundo exemplar (parátipo) é formado por 10 vértebras 
caudais que, de acordo com um mapa da escavação, foram encontradas isoladas, mas apresentam o mesmo 
padrão morfológico e um tamanho compatível, sendo, deste modo, consideradas como pertencentes a um 
mesmo indivíduo (MCT 1719-R). Trigonosaurus pricei é diagnosticado por uma combinação de caracteres 
tais como vértebras cervicais e dorsais médias alongadas, vértebras dorsais 9 e 10 com uma incipiente 
lâmina diapopós-zigapofisiária e processos transversos bem desenvolvidos por toda seqüência anterior e 
média da série caudal. A ocorrência deste novo táxon demonstra a existência de uma maior diversidade de 
titanosaurídeos no Brasil durante o período Cretáceo. 

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

INTRODUCTION and São Paulo (BERTINI, 1993; KELLNER & 

CAMPOS, 2000). Despite being numerous, most 
The most abundant dinosaur group in Brazil is records of titanosaurids from Brazil consist of 
the Sauropoda, particularly those belonging to the undescribed isolated elements. Up to date, the 
clade Titanosauria from the Bauru Group most complete specimens are the holotype of 
(BERTINI et al., 1993; KELLNER, 1998). Remains Gondwanatitan faustoi Kellner & Azevedo, 1999 
of those sauropods have been found in several and the so called “Series B” (POWELL, 1987, 
localities, particularly in the states of Minas Gerais 2003). The latter was collected at the quarry 

1 Submitted on May 2, 2005. Accepted on August 22, 2005. 
2 Museu de Ciências da Terra, Departamento Nacional de Produção Mineral. Av. Pasteur, 404, Urca, 22290-240, Rio de Janeiro, RJ, Brasil. 


E-mail: dac@abc.org.br. 
3 Fellow of Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). 
4 Museu Nacional/UFRJ, Departamento de Geologia e Paleontologia. Quinta da Boa Vista, São Cristóvão, 20940-040, Rio de Janeiro, RJ, Brasil. 

E-mail: kellner@mn.ufrj.br. 
5 NEPV - DGA - IGCE - UNESP, Rio Claro, Brasil. 


 D.A.CAMPOS, A.W.A.KELLNER, R.J.BERTINI & R.M.SANTUCCI 

known as “Caieira” in Peirópolis by Llewellyn Ivor 
Price, where strata of the Bauru group have 
yielded several titanosaurid bones (e.g., CAMPOS 
& KELLNER, 1999; Fig.1). This vertebral sequence 
is housed at the Museu de Ciências da Terra of 
the Departamento Nacional de Produção Mineral 
(MCT/DNPM) in Rio de Janeiro, under the 
numbers MCT 1488-R and MCT 1719-R (see 
comments below). Although recognized as perhaps 
the best specimen recovered from the Peirópolis 
region (PRICE in LAMEGO, 1959) and representing 
a new taxon (e.g. POWELL, 1987; BERTINI, 1993; 
CAMPOS & KELLNER, 1999), this dinosaur still 
remained unnamed and undiagnosed. The main 
purpose of this paper is to diagnose this new 
titanosaurid taxon, here named Trigonosaurus 
pricei n.gen., n.sp., and compare it with members 
of the Titanosauria. Since several details of this 
new taxon were already published (POWELL, 
1987; 2003; CAMPOS & KELLNER, 1999), we 
opted to provide a general morphological review 
and repeat only the main features that make 
Trigonosaurus 
pricei distinct from other 
titanosaurids. We also provided illustrations and 
detailed descriptions of the caudal vertebrae (MCT 
1719-R) which were neither described nor 
illustrated before. We also illustrate the cervical 

series of this species that except for cervicals 12 

and 13 were also not figured before. 
Abbreviations as follows: (ac) acetabulum, (dia) 
diapophysis, (il) ilium, (isped) ischiatic peduncle, (nc) 
neural canal, (ns) neural spine, (podl) 
postzygodiapophyseal lamina, (posl) postspinal 
lamina, (poz) postzygapophysis, (pped) pubic 
peduncle, (prsl) prespinal lamina, (prz) 
prezygapophysis, (s) sacral vertebra, (sri) sacral rib, 
(tp) transverse process, (l) left, (r) right. 

COMMENTS ON THE “SERIES B” 

The “Series B” is composed of a partial vertebral 
column with cervicals, dorsals, sacrals, caudals, 
and the left ilium, all previously treated as 
belonging to the same individual (e.g, POWELL, 
1987). As CAMPOS & KELLNER (1999) pointed out, 
the main problem of this association is the fact 
that the 10 caudals referred to this series were not 
found articulated or in close contact with the 
remaining parts of the specimen. Actually, several 
caudal elements have been found isolated at the 
Caieira quarry and the association of those 10 
caudals among themselves and with the remaining 
part of the “Series B” was probably done by Price, 
likely based on the similar morphology and 


Fig.1- The map of South America showing the distribution of the Bauru Basin. In detail the location of the Caieira Quarry, 
near Peirópolis, where Trigonosaurus 
pricei n.gen., n.sp. was collected. 

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compatible size. According to his 1958 report, 
PRICE (in LAMEGO, 1959) mentioned that he 
previously believed that all titanosaurid specimens 
recovered from this quarry belonged to three 
individuals of different sizes of the same genus, 
but with the discovery of an articulated series of 
caudal vertebrae in 1957, he understood that there 
was more taxonomic diversity in this collection than 
he had assumed (see also KELLNER, CAMPOS & 
TROTTA, 2005, this volume). 

Examining the material it is clear to us that those 
caudal vertebrae show a similar morphology and differ 
in size, which is consistent with their probable different 
position in the tail. Compared to the articulated caudal 
series represented by MCT 1490-R, some elements 
appear to articulate, but most belong to different parts 
of the tail. Their size is compatible with the sacral 
elements and therefore we cannot preclude the 
possibility that they belong to the same individual 
represented by MCT 1488-R, as has been apparently 
assumed by Price (and followed by POWELL, 1987; 
2003). Nevertheless, since they were found neither 
articulated nor in close contact with the remaining 
part of the “Series B”, we opted to regard them as 
belonging to a different individual but representing 
the same species as MCT 1488-R. Therefore the 
caudals received a distinct number (MCT 1719-R). 

Observing Price’s quarry map in detail (CAMPOS & 
KELLNER, 1999; KELLNER, CAMPOS & TROTTA, 
2005, this volume), the number of vertebrae 
individualized on the map differs from the elements 
that are present in MCT 1488-R. On the map there 
are five sacral vertebrae and 13 presacral elements 
instead of the six sacrals and 15 presacral vertebrae. 
We believe that those discrepancies indicate that 
this map was made when the specimen was still in 
the field and before all elements had been fully 
prepared, with sediment possible obscuring the 
limits of some bones. 

SYSTEMATIC PALAEONTOLOGY 


Saurischia Seeley, 1888 
Sauropodomorpha Huene, 1932 
Sauropoda Marsh, 1878 
Titanosauriformes Salgado, Coria & Calvo, 1997 
Titanosauria Bonaparte & Coria, 1993 
Titanosauridae Lydekker, 1893 


Trigonosaurus n.gen. 

Type- species – Trigonosaurus pricei n.sp. 

Etymology – from the Greek language trigónos 
(triângulo) in allusion to the region known as 
“Triângulo Mineiro” from the Minas Gerais State, 
where the specimen was collected, and saurus 
meaning reptile. 

Diagnosis – the same as for the species. 

Trigonosaurus pricei n.sp. 

Holotype – incomplete vertebral column formed 
by five cervical vertebrae, ten dorsals (last 
cervical and all dorsals articulated), sacrum and 
ilium (MCT 1488-R) housed at the Museu de 
Ciências da Terra (Departamento Nacional de 
Produção Mineral). 

Paratype – ten caudals (MCT 1719-R) housed at 
the Museu de Ciências da Terra (Departamento 
Nacional de Produção Mineral). 

Etymology – the specific name is given in honor of 
Llewellyn Ivor Price, a very important vertebrate 
paleontologist, whose birth day centenary is 
celebrated in 2005. L.I. Price collected this and 
several other specimens and inspired the authors 
of this paper, some of which had the pleasure to 
work with him (DAC and RJB). 

Type-locality – MCT 1488-R and MCT 1719-R 
were collected at the quarry known as “Caieira” 
(locality 120 of BERTINI, 1993), an abandoned 
quarry from the São Luís Farm, Veadinho Hill, 
situated about 2km north of Peirópolis, 
Municipality of Uberaba, State of Minas Gerais, 
Southeastern Brazil (BERTINI, 1993; CAMPOS & 
KELLNER, 1999). 

Geological setting – the specimen was found in fine 
to medium grained white and yellow sandstones, 
with conspicuous siltic-argillaceous matrix, and 
some disseminated small argilitic pellets from the 
Bauru Group, Marília Formation, Serra da Galga 
Member, height 835m. The age of this stratigraphic 
unit is regarded as Maastrichtian (GOBBORODRIGUES, 
PETRI & BERTINI, 1999). 

Diagnosis – titanosaurid dinosaur characterized 
by the following combination of characters: 
elongated midcervical vertebrae, with low neural 
spine and concave ventral margin; elongated 
middorsal vertebrae with strongly posteriorly 
inclined neural spine; dorsal vertebrae 9 and 10 
with incipient postzygodiapophyseal lamina; 
anterior caudal vertebrae with thin base 
broadening towards the top; anteriormost 

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caudals (2-5), with two and middle caudals with 
one pronounced dorsal depression on the 
transverse process; prezygapophyses on the 
caudal vertebrae extended forward (but not to the 
same degree as Aeolosaurus rionegrinus and 
Gondwanatitan faustoi), with wide articular faces; 
articulation surfaces for haemal arches strongly 
developed starting on caudal 3 until the last 
preserved element (caudal 20); transverse 
processes well developed throughout the 
sequence formed by anterior and medial caudals 
(until at least caudal 20). 

DESCRIPTION AND COMPARISONS 

The preserved part of the vertebral column of 
Trigonosaurus pricei is formed by five cervical 
vertebrae, 10 dorsals, six sacrals and the right 
ilium (MCT 1488-R), and 10 caudals (MCT 1719R). 
The last cervical vertebra, the dorsals and the 
pelvis were found articulated, as was also 
indicated on the quarry map made by Price 
(CAMPOS & KELLNER, 1999; KELLNER, 
CAMPOS & TROTTA, 2005, this volume). The 
bones of Trigonosaurus pricei have a whitish 
colour and are well preserved, a common feature 
of the fossils found in the Peirópolis region. 
Except for the neural spine of the sixth dorsal 
vertebra, no sign of strong distortion is observed. 
Parts of some vertebrae were broken, particularly 
the cervicals and some of the neural spines of 
the caudals. The nomenclature regarding 
different lamina is based on WILSON (1999). 

CERVICAL VERTEBRAE 

Five cervical vertebrae of Trigonosaurus pricei are 
known. Based on Price’s quarry map (CAMPOS & 
KELLNER, 1999), those elements were not 
articulated but closely associated, although not 
all could be recognized or distinguished from the 
dorsal vertebrae in the map. Their sizes are 
compatible and as far as comparisons are possible 
they articulate suggesting that they formed a 
continuous sequence (Figs.2-14). The last cervical 
was found articulated with the first dorsal and 
both were not separated (Figs.2, 5). Based on an 
almost complete cervical series from another point 
of Peirópolis (Mombuca quarry, according to 
CAMPOS & KELLNER, 1999), POWELL (1987) 
established that the titanosaur neck was formed 
by 13 elements (including atlas and axis). 

Therefore the five cervicals of Trigonosaurus pricei 

are here regarded to represent cervicals 9 to 13. 
Overall none of the cervical vertebrae of 
Trigonosaurus pricei is complete. Except for 
cervical 9, all lack to most dorsal part of the neural 
spine. Cervicals 9 and 10 have part of the right 
lateral side broken particularly the region of the 
cervical rib. Cervicals 12 and 13 also have the 
cervical ribs broken on the right side. All posterior 
ends of the remaining cervical ribs were broken 
possible prior to fossilization or during the 
collecting of the specimen. 

In general, the anterior cervical tend to be more 
elongated (cervicals 9 and 10) while the posterior 
ones tend to be shorter and laterally expanded 
giving them a more robust appearance (Tab.1). 
All are opisthocoelous, with the lateral margin of 
the centrum concave, and lack pleurocoels. 
Ventrally the anterior surface of the centrum 
shows a deep depression between the 
parapophyses and turns to a convex surface close 
to the posterior articulation surface. Pre- and 
postzygapophyses are short and project anteriorly 
and posteriorly, showing well developed articular 
facets. The neural spine in cervical 9 is low, has 
the dorsal portion laterally expanded and tends 
to be more elongated compared to the more 
posterior elements (e.g., cervicals 12 and 13). The 
spinoprezygapophyseal lamina is very thick and 
is more developed in the more anteriorly 
positioned cervicals. There is a shallow depression 
on the medial surface of the prezygapophyses 
(medial to the spinoprezygapophyseal lamina) that 
is displaced medially in cervical 9 but gets 
gradually more horizontal in the posterior 
cervicals. The spinopostzygapophyseal lamina 
tends to be more developed running on the medial 
surfaces of the neural spine and the 
postzygapophyses. Deep pre- and postspinal 
fossae are present. The last cervical vertebra has 
a relatively thick vertebral centrum, wider than 
tall, with a wide and laterally expanded neural 
arch. The diapophyses of this cervical are strong 
and they have downward and backward orientated 
articulation surfaces. 

The cervical ribs are not complete in any of the 
elements, lacking the posterior projection. They 
are double-headed and are fused with the 
diapophysis and the parapophysis, and are 
placed parallel to the axis of the vertebral column. 
The anterior projection is well developed, 
surpassing the centrum and (in lateral view) level 
with the prezygaphophysis. 

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TABLE 1. Measurements of the cervical vertebrae of 
Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R) 

Cervical vertebrae Total length of centrum 
(mm) 

cervical 9 280 
cervical 10 282 
cervical 11 277 
cervical 12 258 
cervical 13 202 

The comparisons of the cervical vertebrae of 
Trigonosaurus pricei are restricted since the neck 
is known in only a few titanosaur species. Only 
one cervical of Malawisaurus dixeyi (Haughton, 
1928) is figured (JACOBS et al., 1993) and possible 
comes from the middle-posterior part of the neck. 
It is also an elongated element and differs from 
Trigonosaurus pricei mainly by having a higher 
neural spine and the ventral margin of the centrum 
straighter. The cervicals of Isisaurus colberti (JAIN 
& BANDYOPADHYAY, 1997; WILSON & 
UPCHURCH, 2003) are quite different from 
Trigonosaurus pricei (and other titanosaurids) by 
being much shorter, showing a higher neural spine 
and showing pleurocoels. Trigonosaurus pricei 

further differs from this species by having the 
anterior and posterior projection of the cervical ribs 
more developed. Gondwanatitan faustoi has only 
an incomplete centrum of a possible posterior 
cervical that is remarkably different from 
Trigonosaurus pricei by showing the anterior 
condyle smaller and by having two ventral 
depressions separated by a bony ridge (KELLNER 
& AZEVEDO, 1999). According to CALVO & 
GONZÁLEZ RIGA (2003), Rinconsaurus caudamirus 
has a long anterioposterior depression with small 
pleurocoels on the lateral surface of the cervical 
centrum, which is absent in Trigonosaurus pricei. 

The cervicals of Saltasaurus loricatus are also quite 
distinct from Trigonosaurus pricei by being 
comparatively shorter, presenting deep pleurocoels 
and a very low neural spine. Furthermore, 
Saltasaurus loricatus has a straighter ventral 
margin and peculiar long and posteriorly projected 
postzygapophyses (POWELL, 2003: 114). The 
lateral tuberosity of the neural spine observed in 
some cervicals of Saltasaurus loricatus is absent in 
Trigonosaurus pricei. Furthermore, Trigonosaurus 
pricei does not show the short prezygapophyses 
with the articular facets positioned near the level 
of the diapophysis, which is regarded a diagnostic 
feature of the Saltasaurinae (SALGADO, CORIA & 
CALVO, 1997). 


Fig.2-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical vertebrae (9-13) and first dorsal in left lateral view. 
Scale bar = 100mm. 

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Fig.3-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical vertebrae (9-13) in anterior view. Scale bar = 100mm. 


Fig.4-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical vertebrae (9-12) in posterior view. Scale bar = 100mm. 

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Fig.5-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical vertebrae and first dorsal in dorsal view. Scale bar = 100mm. 


Fig.6-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 9 in left lateral view. Scale bar = 100mm. 

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Fig.7-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 9 in anterior view. Scale bar = 100mm. 


Fig.8-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 9 in posterior view. Scale bar = 100mm. 

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Fig.9-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 9 in dorsal view. Scale bar = 100mm. 


Fig.10-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 9 in ventral view. Scale bar = 100mm. 

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Fig.11-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 11 in anterior view. Scale bar = 100mm. 


Fig.12-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 11 in posterior view. Scale bar = 100mm. 

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Fig.13-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 11 in dorsal view. Scale bar = 100mm. 


Fig.14-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), cervical 11 in ventral view. Scale bar = 100mm. 

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DORSAL VERTEBRAE 

The dorsal vertebral sequence of Trigonosaurus 
pricei is complete and was already described in 
some detail by POWELL (1987, 2003) and a 
summary with the main features is presented 
below (Figs.15-20; Tab.2). All elements are 
strongly opisthocoelous, a common feature among 
titanosaurids. The anterior surfaces are 
hemispherical and convex, while the posterior 
surfaces are larger and concave. All dorsals bear 
a deep pleurocoel marked by sharp borders 
positioned on the lateral surface of the centrum, 
below the neural arches. This pleurocoel is 
smallest in the dorsal 2, getting gradually more 
elongated (“eye shaped”) in the remaining 
elements. The size of the centrum varies, being 
relatively longer in the middle part of the series. 
No hyposphene-hypantrum is present. The neural 
arches have a broad lateral base that occupies 
over 50% of the centrum length. The neural spine 
of the first dorsal is incomplete but the preserved 
portion indicates it was low and undivided. 
Starting at dorsal 3, the neural spine gets 

elongated and gradually more inclined posteriorly 
extending above the anterior part of the 
subsequent vertebra. In the last dorsal (the 10th) 
the neural spine changes abruptly to a vertical 
position. Dorsal 5 shows a pair of accessory 

TABLE 2. Measurements of the dorsal vertebrae (MCT 
1488-R) of Trigonosaurus pricei n.gen., n.sp. 

Dorsal vertebrae Total length of centrum 
(mm) 

dorsal 1 ~148 
dorsal 2 ~ 128 
dorsal 3 ~ 110 
dorsal 4 ~155 
dorsal 5 ~150 
dorsal 6 ~ 170 
dorsal 7 ~ 155 
dorsal 8 ~ 150 
dorsal 9 ~ 148 
dorsal 10 ~ 140 


Fig.15-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), dorsals 4 and 5 in left lateral view. Scale bar = 100mm. 

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diapophyseal laminae (Fig.18) which are also well 
developed in dorsal 7. At dorsal 1, the 
parapophysis are located on the lateral part of the 
anterior half of the centrum, but gradually 
migrates to a more dorsal position in the 
subsequent elements, reaching almost the same 
height of the diapophysis at dorsal 6. On dorsals 
9 and 10 the parapophysis migrates again to a 
more ventral position relative to the diapophysis. 
The prezygapophysis does not project very much 
anteriorly. The postzygapophysis is always located 
very close to the neural spine. A prespinal lamina 
is present in all dorsals and gets gradually more 
developed and thicker in the more posteriorly 
elements until dorsal 9. 

Overall the dorsal vertebrae of Trigonosaurus 
pricei differ from most other titanosaurid taxa 
by being proportionally longer (similar to 
Gondwanatitan faustoi and Saltasaurus 
loricatus), with large pleurocoels (smaller than 
in Gondwanatitan faustoi and Epachthosaurus 
sciuttoi). The neural spines of the middorsals 
are inclined, apparently more than in any other 
titanosaurid. Trigonosaurus pricei lacks 

hyposphene-hypantrum, which is observed in 
the more basal titanosaurid Andesaurus 
delgadoi and in Epachthosaurus. A 
postzygodiapophyseal lamina linking the 
diapophysis and the postzygapophysis is 
incipiently developed in dorsals 9 and 10 of 
Trigonosaurus pricei (Fig.20). Such a lamina is 
absent in Opisthocoelicaudia skarzynskii. The 
difference in size of the anterior and posterior 
articulation surface is more strongly developed 
in Gondwanatitan faustoi (KELLNER & 
AZEVEDO, 1999) compared with Trigonosaurus 
pricei. Opisthocoelicaudia skarzynskii bears a 
neural spine bifurcated into two “low 
metapophyses” (BORSUK-BIALYNICKA, 1977), 
absent in Trigonosaurus pricei. The dorsal 
vertebrae of Opisthocoelicaudia skarzynskii, and 
the few incomplete remains of Pellegrinisaurus 
powelli, have the centra twice as wide than high 
(BORSUK-BIALYNICKA, 1977; SALGADO, 
1996), also differing from Trigonosaurus pricei. 
The few dorsal vertebrae known from 
Malawisaurus dixeyi bear wide and more robust 
transverse processes (JACOBS et al., 1993), 


Fig.16-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), dorsal 4 in anterior view. Scale bar = 100mm. 

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differing from Trigonosaurus pricei. Based on 
the illustrations presented by CORIA et al. 
(1998: Fig.61) of the dorsals of Argentinosaurus 
huinculensis, Trigonosaurus pricei shows a 
larger size variation within the dorsal vertebral 
elements. 

SACRUM 

The sacrum of Trigonosaurus pricei is composed of 
six vertebrae (total length 583mm), which are well 
preserved, except for the right transverse process 
of the third sacral vertebra (Figs.21-24). Except for 
the last sacral, all centra are fused. The first sacral 
vertebra was incorporated from the dorsal vertebral 
series and the last from the caudal series (CAMPOS 
& KELLNER, 1999). As far as observations are 
possible, sacrals 1 to 5 are opisthocoelous, while 
the last sacral is either procoelous or biconvex, with 
a convex posterior articulation for the first caudal 

(not preserved). Pre- and postspinal laminae, 
forming a sagittal bony surface, uniting the neural 
spines of adjacent sacrals, are present. The 
spinodiapophyseal, postzygodiapophyseal and 
prezygodiapophyseal laminae are observed, which 
tend to be more reduced in the last three sacrals. 

Sacral ribs tend to be robust and directed laterally. 
The first sacral rib is very long and contacts the 
anterior margin of the ilium blade. The left ilium 
is connected to the sacrum and has the 
preacetabular lobe elongated and laterally 
projected. More details of sacrum and pelvis, 
including comparisons, were provided by CAMPOS 
& KELLNER (1999). 

CAUDAL VERTEBRAE 

There are 10 caudal vertebrae known of 
Trigonosaurus pricei (Figs.25-39). Compared to the 
articulated caudal series MCT 1490-R (see 


Fig.17-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), dorsal 5 in posterior view. Scale bar = 100mm. 

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KELLNER, CAMPOS & TROTTA, 2005, this 
volume), they are tentatively interpreted as being 
the 2nd, 3rd, 5th, 6th, 9th, 12th, 14th, 16th, 
18th, and 20th (Table 3). Overall they show a 
very similar morphology. All are procoelous, with 
the posterior condyle slightly displaced dorsally 
and a strongly concave cotyle. The condyle is 
separated from the centrum by a bony ridge that 
is developed in all preserved elements. The lateral 
surface is concave. The anterior surface of the 
centrum is always wider than high, with an oval 
outline that gets more subrectangular in the more 
posterior elements. The posterior part of the 
centrum changes from elliptical (e.g., wider than 
high) in caudals 2 and 3, to a more rectangular 
shape condition (e.g., higher than wide) from 

caudals 5, 6 and 9 and to a more oval shape in 
remaining elements. A shallow groove or 
depression is observed in the posterior condyle 
of some elements (caudals 2, 9, 12 and 14). The 
articulation for the haemal arches are strongly 
developed starting on caudal 3 and are present 
until the last preserved element. 

As in several titanosaurid dinosaurs, the neural 
arch is placed over the anterior half of the centrum, 
near the rim of the anterior margin. The neural 
spine is inclined anteriorly until caudal 18 and gets 
more vertical in caudal 20. From anterior and 
posterior views it is possible to observe that the 
base of the neural spine is laterally compressed 
and the dorsal part slightly expanded laterally, 
what is more visible in the anterior elements but is 


Fig.18-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), dorsals 4 and 5 in dorsal view. Scale bar = 100mm. 

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still perceptible in caudal 14. Pre- and postspinal 
laminae are present, with the prespinal lamina more 
developed. Spinoprezygapophyseal laminae are 
present and well developed particularly in caudal 
2, running from the anterolateral margin of the 
neural spine until the prezygapophysis. In caudal 
3, the spinoprezygapophyseal lamina is reduced, 
migrates posteriorly, and bifurcates, sending one 
additional lamina (accessory spinoprezygapophyseal 
lamina) to the anterolateral portion of the neural 
spine. The decrease of the spinoprezygapophyseal 
laminae continues until it is no more perceptible in 
caudal 6. The accessory lamina, however, is well 
developed in caudal 5 contacting the prespinal 
lamina, merging with the lateral margin of the neural 
spine in the posterior elements. 

The prezygapophyses of caudal 2 are short and 
projected dorsoanteriorly. In the remaining 

caudals, prezygapophyses get longer and 
gradually get less inclined, assuming a 
subhorizontal position starting at caudal 9. A 
tuberosity is observed in the dorsolateral margin 
of the articulation surface of the prezygapophyses. 
It is very well developed in caudals 3 to 6 and 
smoothens out in the more posteriorly positioned 
elements. The articular faces of the 
prezygapophysis are strongly inclined, forming a 
very acute angle in respect to the sagittal plane in 
the anterior caudals, getting gradually less 
inclined in the posterior elements. 

The postzygapophyses are placed very closely to 
the neural spine and are well developed in all 
preserved elements, having large articulation 
surfaces (caudal 20). In the more anteriorly 
positioned elements (caudals 2-5), the 
postzygapophyseal articular surface forms a 


Fig.19-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), dorsals 9 and 10 in left lateral view. Scale bar = 100mm. 

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flattened and inclined surface, but starting in 
caudal 6, this surface gets gradually more concave 
with the dorsal margin becoming directed laterally. 
All preserved caudals show well developed 
lateroposteriorly oriented transverse processes 
that get reduced only in the more posteriorly 
situated elements (caudal 14) and are still present 
as clearly distinct processes in caudal 20 (the last 
preserved one attributed to Trigonosaurus pricei). 
Among the most interesting features of those 
elements is the presence of two dorsal depressions 

on the transverse processes of caudals 2-5, with 
the most laterally placed one smoothing out in 
caudal 6. The second depression, however, is 
perceptible until caudal 12. At the contact surface 
between the transverse process and the neural 
arch, the bone is rugose but no dorsal tuberosity 
as in MCT 1490-R is observed in the anterior 
elements. Caudals 16 and 18, however, have the 
bone surface in this part thickened, forming a 
ridge displaced to the anterolateral surface of the 
transverse process. 


Fig.20-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), detail of dorsal 10 in lateroposterior view. Scale bar = 100mm. See 
text for abbreviations. 

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From all known titanosaurid dinosaurs, the caudal 
vertebrae of Trigonosaurus pricei are more similar 
to the ones reported for Aeolosaurus rionegrinus 
and Gondwanatitan faustoi, sharing with those taxa 
the anterodorsally directed neural spine and 
prezygapophyses. Differing from Aeolosaurus 
rionegrinus, the prezygapophyses of Trigonosaurus 
pricei are comparatively shorter. Furthermore, 
Trigonosaurus pricei does not show the “heart-
shaped” condition found in Gondwanatitan faustoi 
(KELLNER & AZEVEDO, 1999), Aeolosaurus 
rionegrinus (Kellner, pers. obs.) and in caudals 4-8 
of MCT 1490-R (KELLNER, CAMPOS & TROTTA, 
2005, this volume). Trigonosaurus pricei also differs 
from MCT 1490-R by having the prespinal lamina 

more developed than the postspinal lamina and by 

having the transverse process more developed. 
Furthermore, Trigonosaurus pricei shows 
depressions on the dorsal surface of the transverse 
process, which, as far as we know, were not 
recorded in any other titanosaurid dinosaur of 
which large parts of the tail are known such as 
Epachthosaurus sciuttoi (MARTÍNEZ et al., 2004), 
Alamosaurus sanjuanensis (GILMORE, 1946), 
Titanosaurus araukanicus (POWELL, 2003), 
Gondwanatitan faustoi (KELLNER & AZEVEDO, 
1999), MCT 1490-R (KELLNER, CAMPOS & 
TROTTA, 2005, this volume), Pellegrinisaurus 
powelli (SALGADO, 1996), and Rinconsaurus 
caudamirus (CALVO & GONZÁLEZ RIGA, 2003). 


Fig.21-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), sacrum and left ilium in dorsal view. Scale bar = 100mm. 

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TABLE 3. Measurements of the caudal vertebrae of Trigonosaurus pricei n.gen., n.sp. - paratype (MCT 1719-R) 

Caudal vertebrae* Total length Maximum length Maximum height Maximum width 
of centrum of centrum (left side) of centrum of centrum 
without condyle - anterior face - anterior face 
caudal 2 94.5 77.8 ~87.0 105.0 
caudal 3 96.0 72.8 86.2 99.8 
caudal 5 90.5 75.2 76.7 93.6 
caudal 6 96.0 78.4 71.9 82.1 
caudal 9 89.5 77.0 ~64.5 72.1 
caudal 12 85.7 71.0 61.0 68.3 
caudal 14 79.5 68.5 58.5 71.6 
caudal 16 72.5 ~62.0 51.6 64.6 
caudal 18 76.0 63.8 54.7 67.0 
caudal 20 75.1 65.0 48.0 ~59.0 

* Note that the number of the caudals regarding their position in the tail is tentative. 
Fig.22-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), detail of the sacrum and left ilium. Scale bar = 100mm. 

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Fig.23-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), pelvis in posterior view. Scale bar = 100mm. 


Fig.24-Trigonosaurus pricei n.gen., n.sp. (MCT 1488-R), drawing of pelvis in ventral view (from CAMPOS & KELLNER, 
1999). Scale bar = 100mm. See text for abbreviations. 

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Fig.25-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), anterior caudal vertebrae in right lateral view. Scale bar = 100mm. 


Fig.26-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), middle caudal vertebrae in right lateral view. Scale bar = 100mm. 


Fig.27-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), anterior caudal vertebrae in anterior view. Scale bar = 100mm. 

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Fig.28-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), middle caudal vertebrae anterior view. Scale bar = 100mm. 


Fig.29-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), anterior caudal vertebrae in posterior view. Scale bar = 100mm. 


Fig.30-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), middle caudal vertebrae in posterior view. Scale bar = 100mm. 

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Fig.31-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), anterior caudal vertebrae in dorsal view. Scale bar = 100mm. 


Fig.32-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), middle caudal vertebrae in dorsal view. Scale bar = 100mm. 


Fig.33-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 2 in right lateral view. Scale bar = 
50mm. See text for abbreviations. 

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Fig.34-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 2 in anterior view. Scale bar = 50mm. 
See text for abbreviations. 


Fig.35-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 2 in posterior view. Scale bar = 50mm. 
See text for abbreviations. 

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Fig.36-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 2 in dorsal view. Scale bar = 50mm. 
See text for abbreviations. 


Fig.37-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 9 in right lateral view. Scale bar = 
50mm. See text for abbreviations. 

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Fig.38-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 9 in anterior view. Scale bar = 50mm. 
See text for abbreviations. 


Fig.39-Trigonosaurus pricei n.gen., n.sp. (MCT 1719-R), possible caudal vertebrae 9 in posterior view. Scale bar = 50mm. 
See text for abbreviations. 

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DISCUSSION AND CONCLUSION 

From the hundreds of sauropod bones found in 
the Peirópolis region, all attributed to the 
Titanosauridae (PRICE, 1955; BERTINI, 1993; 
CAMPOS & KELLNER, 1999), the most important 
specimens are the informally known “A, B and C 
Series” (POWELL, 1987; 2003). They consist of an 
almost complete series of cervical vertebrae and 
three dorsals (Series A), the last five cervicals, 
complete dorsal series, sacrum and caudal 
vertebrae (Series B), and the last sacral and a 
sequence of 18 articulated caudal vertebrae (Series 
C, see KELLNER, CAMPOS & TROTTA, 2005, this 
volume). As pointed out, the “Series B” (here 
described as Trigonosaurus pricei n.gen., n.sp.) was 
already mentioned several times in the literature, 
even used in phylogenetic studies (e.g., SALGADO, 
CORIA & CALVO, 1997). Its importance was 
recognized by Price (in LAMEGO, 1959), who always 
regarded this specimen representing a new 
titanosaurid taxon, here named Trigonosaurus 
pricei n.gen., n.sp. Based on comparisons with the 
cervical sequence also collected in the Peirópolis 
region (MCT 1487-R) the holotype of this species 
had an estimated length of about 9.5 meters 

While the dorsal vertebrae and the sacrum (with 
the ilium articulated) were described in some detail 
(POWELL, 1987; CAMPOS & KELLNER, 1999), the 
cervical and caudal vertebrae have not received the 
same attention. POWELL (2003) provided more 
information on this material, but some are probably 
mistaken. For example, POWELL (2003:62) 
presented measurements for 15 caudals of the 
“Series B”, but there are only 10 preserved elements 
(POWELL, 1987; CAMPOS & KELLNER, 1999). 
Furthermore, cervical 12 of Trigonosaurus pricei 
was illustrated as belonging to the Series A 
(POWELL, 2003: pl. 13, fig.12), what is incorrect. 

SALGADO, CORIA & CALVO (1997) regarded 
Trigonosaurus pricei as a member of the 
Titanosauridae, closely related to the Asian 
Opisthocoelicaudia skarzynskii. The sole character 
shared by those taxa is the absence of a 
postzygodiapophyseal lamina in the posterior 
dorsals. However, a close examination indicates that 
an incipient lamina uniting the postzygapophysis 
and the diapophysis is observed in dorsals 9 and 
10, corresponding to the horizontal lamina of 
POWELL (2003). In any case, this phylogenetic 
relationship is somewhat unexpected and has to 
be further evaluated. 

Still regarding the phylogenetic position of 
Trigonosaurus pricei, it is not a member of the more 
derived titanosaurs (Saltasaurinae) lacking features 
such as a strongly dorsoventrally flattened centrum 
of the anterior caudals with centrum significantly 
wider than high, and the position of the neural spine, 
with the anterodorsal edge positioned posteriorly 
relative the anterior border of the postzygapophyses. 
This new species does not occupy a more basal 
position within Titanosauria, showing strongly 
procoelous caudal vertebra in all preserved elements, 
different from Andesaurus delgadoi and 
Malawisaurus dixeyi (CALVO & BONAPARTE, 1991; 
JACOBS et al., 1993). It also lacks the hyposphenehypantrum 
articulation observed in more basal 
titanosaurids and in Epachthosaurus sciuttoi 
(MARTÍNEZ et al., 2004). The anteriorly displaced 
neural arch and the anterodorsally projected neural 
spine of Trigonosaurus pricei suggest some affinities 
with Aeolosaurus rionegrinus and Gondwanatitan 
faustoi. However, none of the preserved elements of 
the new taxon shows the ventral part of the centrum 
constricted, giving the posterior surface of the 
centrum a “heart-shaped” appearance. 

To conclude, Trigonosaurus pricei confirms the 
supposition that more than one taxon was present 
in the Caieira Quarry, as pointed out by Price (in 
LAMEGO, 1959), indicating a higher diversity of 
titanosaurids in Brazil during the Cretaceous, 
presently represented by only two taxa -
Gondwanatitan faustoi and MCT 1490-R (KELLNER, 
CAMPOS & TROTTA, 2005, this volume). 

ACKNOWLEDGMENTS 

The authors wish to thank the following individuals 
and respective institutions, for assistance and access 
to specimens under their care: José F. Bonaparte 
(Museo Argentino de Ciencias Naturales, Buenos 
Aires), Jaime E. Powell (Facultad de Ciencias 
Naturales, Universidad Nacional de Tucumán, 
Tucumán), and Marcelo Reguero (Museo de La 
Plata). We would also like to thank Otávio da Silva 
Santos and Luiz Júlio da Silva, former preparators 
at the Departamento Nacional de Produção Mineral, 
for the excellent work done on the this specimen. 

We have benefited from discussions with several 
colleagues, particularly Jaime E. Powell (Universidad 
Nacional de Tucumán), Jorge Calvo (Universidad 
Nacional del Comahue) and Marcelo N.F. Trotta 
(Museu Nacional). Vanessa Dorneles Machado, 

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 D.A.CAMPOS, A.W.A.KELLNER, R.J.BERTINI & R.M.SANTUCCI 

Maurílio Oliveira and Uiara Gomes Cabral (Museu 
Nacional) are thanked for preparing some of the 
photos that illustrate this paper. We would also like 
to thank Marcelo N.F. Trotta and Juliana Manso 
Sayão (Museu Nacional) for reviewing earlier 
versions of this paper. This project was partially 
funded by CNPq (grants to D.A.Campos and A.W.A. 
Kellner), FAPERJ (grant #E-26/152.442/2002-2005 
to A.W.A.Kellner) and FAPESP (grant #02/00574-2 
to R. M. Santucci). 

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