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Description of a titanosaurid caudal series from the Bauru Group, Late Cretaceous of Brazil

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A new titanosaurid, Baurutitan britoi n. gen., n. sp., is described and compared with other taxa of that sauropod clade. The specimen (MCT 1490-R) consists of the last sacral followed by a sequence of 18 caudal vertebrae that were found in the continental deposits of the Late Cretaceous Bauru Group that outcrop at the Peirópolis region, near the town of Uberaba, State of Minas Gerais, Brazil. This new taxon is distinguished from other titanosaurians by several features, including subrectangular to square outline of the anterior articulation surface of the anterior and middle caudals, strongly pointed laterally directed process intercepting the spinoprezygapophyseal lamina in caudal 1; dorsal prezygapophyseal tuberosity on the lateral margin of the prezygapophyses of caudals 2-4, that smoothens out in midcaudals. This material demonstrates that the horizontal ridge present in middle and posterior caudals of some titanosaurs, in Baurutitan britoi is homologous with a dorsal tuberosity and not with the transverse process.
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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: kellner@mn.ufrj.br.
4
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: dac@abc.org.br.
6
E-mail: marcelotrotta@yahoo.com.br.
Arquivos do Museu Nacional, Rio de Janeiro, v.63, n.3, p.529-564, jul./set.2005
ISSN 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 taxa
of that sauropod clade. The specimen (MCT 1490-R) consists of the last sacral followed by a sequence of 18
caudal vertebrae that were found in the continental deposits of the Late Cretaceous Bauru Group that
outcrop at the Peirópolis region, near the town of Uberaba, State of Minas Gerais, Brazil. This new taxon is
distinguished from other titanosaurians by several features, including subrectangular to square outline of
the anterior articulation surface of the anterior and middle caudals, strongly pointed laterally directed
process intercepting the spinoprezygapophyseal lamina in caudal 1; dorsal prezygapophyseal tuberosity on
the lateral margin of the prezygapophyses of caudals 2-4, that smoothens out in midcaudals. This material
demonstrates that the horizontal ridge present in middle and posterior caudals of some titanosaurs, in
Baurutitan 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 desse
clado de saurópodes. O espécime é composto por uma última vértebra sacral seguida de uma seqüência de 18
vértebras 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 (Cretáceo
Superior). Entre as características que distinguem esse novo táxon dos demais Titanosauria estão a face
subretangular ou quadrada da articulação anterior das caudais, processo lateral bem desenvolvido interceptando
a lamina espinopré-zigapofisiária da caudal 1, tubérculo dorsal na margem lateral das pré-zigapófises das caudais
2-4, que se torna em uma rugosidade que tende a se tornar menos pronunciada nas caudais médias. Este
material também demonstra que em Baurutitan britoi n. gen., n. sp. a crista lateral nos centros das caudais
medianas 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 with
titanosaur remains is Peirópolis (Fig.1). In the past,
the most productive site was the Caieira quarry
that yielded hundreds of titanosaur bones
(CAMPOS & KELLNER, 1999). Among the recovered
material is a series of 19 vertebrae (the last sacral
and 18 caudals) collected in 1957, housed in the
collection of the Earth Science Museum (MCT) of
the Departamento Nacional de Produção Mineral
(DNPM, Rio de Janeiro) under the number MCT
1490-R. This specimen was briefly described by
POWELL (1987) as the “Series C” and referred as
Titanosaurus sp. It is one of the few articulated
titanosaurid caudal sequences and has been used
several times to determine the place in the tail of
isolated or partially articulated caudals from other
dinosaurs (e.g., GONZÁLEZ RIGA, 2003;
MARTÍNEZ et al., 2004).
In this paper we redescribe MCT 1490-R and
establish 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 description
of the chevrons that have not been studied before.
This species is compared with the following
titanosaurs: Aeolosaurus rionegrinus POWELL (2003);
Aeolosaurus sp. SALGADO & CORIA (1993);
Aeolosaurus sp. SALGADO, CORIA & CALVO,
(1997b); Alamosaurus sanjuanensis GILMORE, 1922;
Epachthosaurus sciuttoi POWELL, 1990 (MARTINEZ
et al., 2004); Gondwanatitan faustoi KELLNER &
AZEVEDO, 1999; Mendozasaurus neguyelap
GONZÁLEZ RIGA, 2003; Neuquensaurus australis
(Lydekker 1893); Opisthocoelicaudia skarzynskii
BORSUK-BIALYNICKA, 1977; Pellegrinisaurus powelli
SALGADO, 1996; Rinconsaurus caudamirus CALVO
& GONZÁLEZ RIGA, 2003; Saltasaurus loricatus
BONAPARTE & POWELL,1980; Titanosaurus
araukanicus (HUENE, 1929); Titanosaurus colberti
JAIN & BANDYOPADHYAY 1997 (renamed as
Isisaurus colberti by WILSON & UPCHURCH, 2003);
Lirainosaurus astibiae SANZ et al., 1999, and MCT
1488-R/ MCT 1719-R (CAMPOS et al., 2005 - this
volume). The data from most of the mentioned
titanosaur taxa was obtained from the original
description and complemented with other papers
including 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 content
of this and other stratigraphic units of the Bauru
Basin see BERTINI (1993) and BERTINI et al.
(1993). Abbreviations as follows: (dtu) dorsal
tuberosity, (nc) neural canal, (ns) neural spine,
(posl) postspinal lamina, (poz) postzygapophysis,
(prsl) prespinal lamina, (prz) prezygapophysis,
(prztu) prezygapophyseal tuberosity, (tp) transverse
process, (sprl) spinoprezygapophyseal lamina, (sri)
sacral rib, (l) left, (r) right.
BRIEF HISTORY OF THE CAIEIRA QUARRY
In 1958, after several years working at one
particular point in Peirópolis (the Caieira quarry
of CAMPOS & KELLNER, 1999), L.I. Price
understood that this fossil deposit was more
extensive than he had anticipated and provided a
summary of the activities done so far in his annual
report for the Geology and Mineralogy Division of
the Departamento Nacional de Produção Mineral
(DNPM). This report was published the next year
by the director of the DNPM, A.R. Lamego, with
some pictures of the quarry that are reproduced
here (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
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According to PRICE (1955), he examined this region
in 1947 based on the information of Jesuino
Felicissimo Junior, of the Instituto Geográfico e
Geológico de São Paulo, who pointed out the presence
of fossil vertebrates in the Uberaba area. The next
year (1948) he prepared the opening of a quarry which
was done only in 1949. Still according to Price’s report
of 1958, fossils have been collected in six different
occasions (he did not precise the dates), with the
recovery of several specimens, including turtles,
crocodilomorphs, theropods (Coelurosauria - two
species, “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 the
pelvis MCT 1488-R still in the field. This picture was reproduced from Price’s report published in LAMEGO (1959).
532 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
dinosaurs. Other fossils were also recovered such as
fragments of fishes, freshwater invertebrates
(gastropods, bivalves), ichnofossils (invertebrate
tubes), egg shale fragments, and plant remains
(PRICE in LAMEGO, 1959:181-182). The overburden
that had to be removed in order to reach the main
fossiliferous layer varied between 4 to 18 (!) meters,
what was done manually. Extremely hard
sedimentary rocks were removed occasionally by
dynamite. Price also pointed out that until the
excavation of 1957, he regarded the titanosaur bones
collected belonging to three individuals of distinct
sizes, all representing the same genus. However, in
1957 he and his crew had found a series of 19
vertebrae (at that point he though all were caudals)
that clearly demonstrated the presence of a second
distinct genus, making the re-evaluation of the
assignment of all collected elements necessary.
Although not published in his report, Price was also
working on a quarry map showing the main
specimens recovered. A photo of this map was
published by CAMPOS & KELLNER (1999) and
showed that the excavations at the Caieira quarry
were done in 1949, 1950, 1953, 1955, 1957, 1958,
and 1959. A second copy of this picture was found
recently and includes the year 1961 handwritten
by Price (Fig.3). Possible this was the last year of
excavation at the Caieira quarry and apparently has
not 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 (the
series “B”) and the articulated series of the last sacral
and 18 caudals (the series “C”). This study was
partially reprinted recently (POWELL, 2003).
Until 1999, none of those specimens were numbered.
CAMPOS & KELLNER (1999) provided some
numbers of some important specimens collected in
the Peirópolis area (including the series B and C
from the Caieira quarry) and most elements have
been numbered recently by one of the authors during
his master dissertation (M.N.F. Trotta).
SYSTEMATIC PALEONTOLOGY
Saurischia Seeley, 1888
Sauropodomorpha Huene, 1932
Sauropoda Marsh, 1878
Titanosauria 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 the
giants of the Greek myths.
Diagnosis – The same as for the species.
Baurutitan britoi n.sp.
Holotype – Last sacral vertebrae articulated with a
sequence of 18 caudal vertebrae, belonging to a
single individual. This specimen (MCT 1490-R) is
housed at the Museu de Ciências da Terra - MCT
(Earth Science Museum) of the Departamento
Nacional de Produção Mineral (DNPM), in Rio de
Janeiro, Brazil (Figs.4-27).
Etymology – The specific name is given in honor of
Ignacio Aureliano Machado Brito (1938-2001), an
important Brazilian paleontologist, who advised
several students including two authors of this paper
(DAC and AWAK).
Type-locality – MCT 1490-R was collected in the
Peirópolis site, at the point known as “Caieira”
which is an abandoned quarry at the São Luis Farm
located at the Veadinho Hill. This point is situated
about 2km North of Peirópolis, Municipality of
Uberaba, Minas Gerais State, Southeastern Brazil.
Geological setting – As all specimens collected from
the Caieira point, MCT 1490-R was found in fine to
medium grained white and yellow sandstones from
the Marília Formation, Serra da Galga Member, at
a height of 835m (BERTINI, 1993). The age of this
stratigraphic unit is regarded as Maastrichtian
(GOBBO-RODRIGUES, PETRI & BERTINI, 1999).
Diagnosis – Titanosaurid dinosaur characterized by
the following potential autapomorphies: strongly
pointed laterally directed process intercepting the
spinoprezygapophyseal lamina on the caudal 1;
anterolaterally directed spinoprezygapophyseal
lamina. It is further distinguished from other
titanosaurids by the following combination of
characters: first caudal biconvex; developed dorsal
tuberosity on the neural arch that turns into a lateral
ridge in the middle caudals; neural spines in the
most anterior caudals (1-4) inclined posteriorly,
changing to a more vertical to subvertical inclination
in caudal 5 to 10; prezygapophyseal tuberosity on
the lateral margin of the prezygapophysis of caudals
2-4, which becomes less developed in the posterior
elements, smoothing out in the midcaudals;
subrectangular outline of anterior articulation of the
caudal centrum, getting more squared towards the
end of the tail.
DESCRIPTION OF A TITANOSAURID CAUDAL SERIES FROM THE BAURU GROUP, LATE CRETACEOUS OF BRAZIL 533
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Fig.3- Map showing the position of the bones collected at the Caieira quarry made by L.I.Price. This figure reproduces a picture of
the map taken by someone of Price’s crew. Note that the year 1961 was added by Price after this picture was taken, which is the
only 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.
534 A.W.A.KELLNER, D.A.CAMPOS & M.N.F.TROTTA
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DESCRIPTION AND COMPARISON
The material of Baurutitan britoi consists of 19
vertebrae, starting with the last sacral and
subsequent caudals. All elements were found
articulated (Fig.3). The material is well
preserved, lacking any major postmortem
compression, and is complete except for part of
the left neural arch of the sacral and the right
transverse process of the 3rd and 7th caudal.
The centra of the 7th and 8th caudal were
damaged possibly by a drilling instrument
during the collecting process. After being
prepared (some decades ago) this sequence was
numbered continuously starting with the last
preserved sacral. Therefore, the numbers written
on the caudals (left on the specimen for
historical reasons) do not refer to their
anatomical position in the tail (e.g., caudal
numbered as 3 is, in fact, the 2nd caudal).
For descriptive purposes, this vertebral series is
divided into sacral vertebrae (only the last one
preserved), first caudal, anterior caudals (2nd-
7th), and middle caudals (8th-18th). Although
admittedly arbitrary, the distinction between
anterior and middle caudals is made by the
presence of a well developed transverse process.
In Baurutitan britoi, the first caudal where this
process starts to be vestigial is the 8th which is
here regarded as the beginning of the middle
caudal series. The nomenclature regarding
different lamina is based on WILSON (1999).
S
ACRAL VERTEBRA
The right side of the last sacral is complete,
whereas the left side lacks the basal part of the
neural spine, the neural arch, the diapophysis,
parapophysis and prezygapophysis (Figs.4-7).
The centrum is complete except for the most
anterior surface. Despite that, it is clear that
the articulation with the preceding sacral was
slightly convex. The posterior articulation
surface is strongly concave, suggesting that
this sacral had an opisthocoelous condition.
Overall the centrum is rounded, slightly wider
than high at the posterior surface. Laterally,
it is longer than high, having a shallow
depression below the transverse process. On
the right side, close to the dorsoanterior
corner, the centrum is pierced by two
foramina. The centrum of the last sacral was
not fused with the precedent element.
The neural arch is fused with the centrum and
shows a complex morphology. The neural canal
is not complete in anterior view but posteriorly
has an oval shape, being higher than wide. The
neural spine is tall and transversally expanded
with a rectangular apex in dorsal view. The
anterior surface is irregular, showing shallow
depressions and ridges. On the right side of the
neural arch (the left part is not preserved) the
presence of a prezygodiapophyseal lamina
(partially broken) is observed. A bony ridge at
the anterior surface of the neural spine is
connected with the prezygodiapophyseal lamina,
delimitating a subtriangular cavity with the apex
situated ventrally. Posteriorly the neural spine
has a deep cavity located between the
postzygapophyses. In lateral view, the neural
spine is inclined posteriorly, with the vertical
projection of the posterodorsal corner placed
behind the posterior margin of the centrum.
Pre- and postspinal laminae are present. The
prespinal lamina is well developed and projects
anteriorly. In the middle part, it has a width
between 6 and 10mm. The lateral surface is
irregular, with several shallow depressions. At
both sides of the contact surface with the
neural spine there are irregular and
dorsoventrally elongated cavities which are
deeper at the right side. These cavities are
present from the base of the neural spine until
at least two thirds of its length and do not
reach the apex. The postspinal lamina is less
projected than the prespinal lamina, keels
posteriorly with a wide base (~15mm) and
disappears near the postzygapophyses above
a concavity located at the base of the neural
spine. Laterally, the dorsal part of the
postspinal lamina is more developed getting
gradually lesser projected toward the base.
Lateral to this lamina, a dorsoventrally
elongated depression is observed, bordered by
a comparatively thick spinopostzygapophyseal
lamina. There are some depressions on the
postspinal lamina, as well as on the adjacent
surfaces of the neural spine.
The spinodiapophyseal lamina is well developed
and thick, covering the anterolateral margin of
the neural spine until reaching its middle
region. The posterior surface shows two
laterally placed cavities. The dorsal one is oval
and deep. The ventral is much larger, has a
rounded shape and is deep too, being perforated
by several foramina.
DESCRIPTION OF A TITANOSAURID CAUDAL SERIES FROM THE BAURU GROUP, LATE CRETACEOUS OF BRAZIL 535
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Only the right prezygapophysis is preserved.
It is very short, having the articulation
surface expanded anteroposteriorly. The
postzygapophyses are located very close to the
neural spine and show elongated articulation
surfaces for the first caudal. The parapophysis
shows a pyramidal structure, with the ventral
surface being parallel to the horizontal plane,
and a dorsal edge rising dorsally as a thick
bony 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 text
for abbreviations.
partially preserved on the right side. Uniting
the parapophysis and the centrum is a strong
and thick bony bridge oriented anteriorly that
does not form a true lamina. A deep
subtriangular cavity is present on the dorsal
surface of this bridge.
The sacral rib is partially preserved on the right
side. Although being fused to the centrum, the
limits can be observed particularly at the region
corresponding to the parapophysis.
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Comparisons with other titanosaurid taxa are
difficult since in most the last sacral is either not
present or not described in detail. The degree of
fusion in the sacrals varies among titanosaurid or
closely related taxa. In Baurutitan britoi the last sacral
was not fused to the precedent sacral, similar to
Gondwanatitan faustoi (KELLNER & AZEVEDO,
1999) but differing from Opisthocoelicaudia
skarzynskii, Isisaurus colberti, Neuquensaurus
australis, and Saltasaurus loricatus where the sacrum
is formed by six well coossified vertebrae (BORSUK-
BIALYNICKA, 1977; JAIN & BANDYOPADHYAY,
1997; POWELL, 2003). Baurutitan britoi has the
posterior articulation surface strongly concave,
differing from the convex condition found in Isisaurus
colberti, Saltasaurus loricatus, and Epachthosaurus
sciuttoi (JAIN & BANDYOPADHYAY, 1997; POWELL,
2003; MARTÍNEZ, et al., 2004). The last sacral of
Gondwanatitan faustoi is procoelous (KELLNER &
AZEVEDO, 1999), differing from the
opisthocoelous condition of Baurutitan britoi.
Neuquensaurus australis has the posterior
articulation 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 text
for abbreviations.
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concavity is more pronounced. The posterior
articulation of the last sacral of Opisthocoelicaudia
skarzynskii and Baurutitan britoi are strongly
concave, but the former is flattened dorsoventrally
(BORSUK-BIALYNICKA, 1977: plate 5, fig.4),
contrasting to the more rounded condition found
in the latter. According to JAIN & BANDYOPADHYAY
(1997), Isisaurus colberti has a longitudinal
depression on the ventral surface of the sacral centra
that is absent in Baurutitan britoi.
There are three almost complete sacra recovered from
the Peirópolis region (CAMPOS & KELLNER, 1999)
than can be compared with Baurutitan britoi. Two were
collected at the same point (Caieira) (MCT 1536-R
and MCT 1488-R/MCT 1719-R, the latter being
diagnosed in this volume, see CAMPOS et al., 2005
and the third one, collected at the Rodovia site (MCT
1489-R). All were regarded as belonging to three
distinct 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 for
abbreviations.
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MCT 1536-R and MCT 1488-R have the last sacral
unfused to the precedent element as observed in
Baurutitan britoi, in MCT 1489-R all six elements of
the sacrum are fused. The last sacral of Baurutitan
britoi differs from MCT 1536-R by having the centrum
the posterior articulation surface more set apart from
the sacral ribs, whose ventral margin is comparatively
thinner (e.g., more compressed anteroposteriorly). The
last sacral of MCT 1536-R, that represents a smaller
animal (estimated length of the centrum ~ 80mm), is
dorsoventrally flattened with the posterior articulation
surface less concave. The last sacral of MCT 1488-R
and MCT 1489-R also differs from Baurutitan britoi
by having the centrum dorsoventrally flattened, the
neural spine dorsally expanded and by having the
posterior articulation surface strongly convex. MCT
1488-R further differs by having the neural spine
more inclined posteriorly.
F
IRST CAUDAL VERTEBRA
The first caudal is longer than the preceding sacral
and has a biconvex centrum with the posterior
articulation more projected than the anterior one
(Figs.8-11). The anterior articulation of the centrum
is larger dorsoventrally (118,8mm) than the
posterior articulation (108,6mm). In anterior view
the centrum is oval, slightly wider (131,4mm) than
high (118,8mm), with the dorsal and ventral
margins flattened. The lateral surface and the
ventral margin are concave, giving the centrum the
typical spool-shaped appearance. In lateral view
the centrum is longer than high, a result basically
due to the expanded posterior condyle which is
displaced dorsally (Fig.8). This condyle displays a
sagittal dorsoventrally oriented groove on the upper
half of the centrum which does not appear to be of
taphonomic origin. The neural arch is placed on
the anterior half of the centrum. The neural canal
is oval, higher than wide. The transverse processes
are robust, compressed anteroposteriorly, directed
laterally and slightly posteriorly (Fig.11). Those
processes are twisted so that the dorsal margin at
the 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 for
abbreviations.
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The neural spine is elongated and inclined
posteriorly, so that, in lateral view, the vertical
projection of the posterior corner is placed on the
condyle. The neural spine is transversally
expanded, particularly at the apex, although it
has almost the same width. The prespinal
lamina is present and well developed, although
less than in the sacral vertebra, and extends
from the base of the neural spine to the apex.
The postspinal lamina is also present, being
thicker and shorter than the prespinal lamina.
Spinoprezygapophyseal laminae are present, well
developed, and run over the anterolateral corner
of the neural spine, disappearing before reaching
the apex. The prezygapophyses are short and
have elliptical articular facets which are longer
transversally than anteroposteriorly. Behind each
prezygapophysis, but placed at a higher position,
there is a pointed elevation named herein
prezygapophyseal tuberosity which is the meeting
point of the spinoprezygapophyseal lamina and
the 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 for
abbreviations.
540 A.W.A.KELLNER, D.A.CAMPOS & M.N.F.TROTTA
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caudal 1 the prezygapophyseal tuberosity
intercepts the spinoprezygapophyseal lamina
before it reaches the prezygapophysis. The
spinoprezygapophyseal lamina is well defined
and directed anterolaterally connecting the
neural spine and the prezygapophyseal
tuberosity. The postzygapophyses are positioned
very close to the neural spine and have long,
lateroventrally directed articulation surfaces,
with the major axis directed dorsoventrally.
Spinopostzygapophyseal laminae are not very
developed, presented as blunt ridges.
Comparisons with some titanosaurid taxa are
limited since for most the first caudal is either
unknown or only briefly described. As far as
comparisons are possible, Lirainosaurus astibiae
differs from Baurutitan britoi by having a procoelous
first caudal and by having a comparatively smaller
centrum and a dorsoventrally expanded neural arch
(SANZ et al., 1999). Opisthocoelicaudia skarzynskii
differs by having the first caudal opisthocoelous with
broader but shorter transverse processes. Although
incomplete, the first caudal of Pellegrinisaurus
powelli 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.
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britoi by having a comparatively shorter centrum and
a marked depressed area under the transverse
process (SALGADO, 1996: fig.3). Also incomplete,
the first caudal of Gondwanatitan faustoi differs from
the one of Baurutitan britoi by being procoelous and
having a comparatively shorter centrum (KELLNER
& AZEVEDO, 1999).
Regarding Epachthosaurus sciuttoi, the first caudal
is procoelous and shows longer and posteriorly
more developed transverse processes with a distally
expanded bony blade (MARTÍNEZ et al., 2004)
which is absent in Baurutitan britoi. Furthermore,
the neural arch of the first caudal of Baurutitan
britoi is comparatively more set apart from the
centrum, giving the vertebrae a higher aspect.
Baurutitan britoi has a larger neural canal, the tip
of the neural spine broader and the postspinal
laminae more developed.
The first caudal of Alamosaurus sanjuanensis also
has a biconvex centrum but differs from Baurutitan
britoi by having the anterior articulation with a
subrectangular outline that is higher than wide
(GILMORE, 1946: pl.5, fig.1; pl.8, fig.1). In both the
anterior articulation surface is larger than the
posterior one, but in Alamosaurus sanjuanensis this
difference is even bigger. Furthermore, Baurutitan britoi
has the ventral margin of the centrum more concave,
the neural spine inclined posteriorly with a stronger
postspinal lamina, and prezygapophyses facing less
inward 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.
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Regarding saltasaurines, the first caudal of
Saltasaurus loricatus is quite distinct from Baurutitan
britoi by being procoelous and dorsoventrally
flattened. Saltasaurus loricatus further differs by
showing long and robust transverse processes
(similar to the last sacral) and the pre- and postspinal
laminae comparatively thinner. The neural canal of
Baurutitan britoi is also comparatively larger and the
postzygapophyses are positioned closer to each other
with the articulation surface displaced more laterally.
Neuquensaurus australis has also a biconvex first
caudal (HUENE, 1929: pl.3, fig.3), but in Baurutitan
britoi the neural spine is more inclined posteriorly
and the ventral margin is more concave.
Besides the differences pointed out above, Baurutitan
britoi also shows a distinct prezygapophyseal tuberosity,
which intercepts the spinoprezygapophyseal
lamina. To our knowledge, such a projection was not
reported (or illustrated) in this position and with this
shape and size in any titanosaurid first caudal before.
Apparently Alamosaurus sanjuanensis has a similar
process, but it is less developed and is not laterally
projected as in Baurutitan britoi (GILMORE, 1946: pl.5,
fig.1; pl.8, fig.1). Epachthosaurus sciuttoi also shows a
distinct projection, but it is situated on the dorsal part
of the transverse process and its relation with the
spinoprezygapophyseal lamina cannot be determined
(MARTÍNEZ et al., 2004: fig.6). In this context, the
presence of a prominent prezygapophyseal tuberosity
united with the neural spine by an anterolaterally
oriented spinoprezygapophyseal lamina is considered
a 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.
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ANTERIOR CAUDAL VERTEBRAE
Starting at caudal 2, all anterior caudals are
procoelous, having the posterior condyle well
developed in a medial position, except in caudal
7 where it is slightly displaced dorsally (Figs.12-
18). The longest caudal is the 4th, followed by
the 2nd, 5th, 3rd, 6th, and 7th (see Table 1). The
most anterior element has the widest centrum
and all subsequent get gradually narrower.
Starting on caudal 3 all have the ventral portion
compressed laterally, forming a flattened to
slightly concave surface. In anterior view the
centrum has a subrectangular outline, being
wider than high with the dorsal and ventral
margins flattened. The posterior part of the
centrum changes from elliptical (e.g., wider than
high) in caudals 2 and 3, to a more “heart-
shaped” condition of caudals 4-7 (and the caudal
8, here considered to be the first middle caudal).
The dorsal surface above the posterior end of the
centrum has a shallow concavity, limited
posteriorly by a thickening of the dorsal rim of
the posterior articulation. The condyle of caudals
4 to 6 shows a dorsoventrally oriented sagittal
groove (as observed in the last sacral) which gets
shallow posteriorly and turns to a rounded
depression in the mid-caudals (see below). In
caudal 5 this groove is more developed than in
any other vertebrae. Starting at caudal 4 the
centrum bears two laterally placed and ventrally
oriented projections for the chevron which are
largest in caudal 5 and get gradually smaller
towards the end of the series.
The neural arch is placed over the anterior half
of the centrum, near the rim of the anterior
margin. The neural canal is oval, higher than
wide, with the basal part slightly wider than the
apex. The neural spine of caudal 2 is inclined
posteriorly, similar to the condition of caudal 1.
The vertical projection of the anterior corner of
the neural spine is placed behind the middle part
of the centrum and the vertical projection of the
posterior corner rests over the distal
articulation, similar to the condition observed
in caudal 1. Starting at caudal 3 the neural spine
is less inclined, with the vertical projection of
the anterior corner shifted towards the middle
part of the centrum and the vertical projection
of the posterior corner placed at the beginning
of the distal articulation. Starting at caudal 4
the neural spine is less inclined with the vertical
projection of the anterior (and posterior) corner
of the neural spine shifting gradually towards
the anterior and middle part of the centrum,
a condition present until the first middle caudal
vertebra (caudal 8).
VERTEBRAE TOTAL LENGTH OF
CENTRUM
M
AXIMUM LENGTH OF
CENTRUM
(LEFT SIDE)
WITHOUT CONDYLE
M
AXIMUM HEIGHT OF
CENTRUM ANTERIOR
FACE
M
AXIMUM 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)
544 A.W.A.KELLNER, D.A.CAMPOS & M.N.F.TROTTA
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Pre- and postspinal laminae are well developed in
all anterior caudals, with the postspinal lamina
always more robust. The prespinal lamina covers
the entire length of the neural spine (incompletely
preserved in caudal 7). The postspinal lamina tends
to be thicker at the apex, reducing gradually in
ventral direction, ending in the vacuity between the
postzygapophyses. In caudals 2 and 3, due to the
great development of the postspinal lamina, the
dorsal surface formed by the neural spine and
postspinal laminae is triangular, with the apex
directed posteriorly. Starting on caudal 4, this
dorsal surface gets gradually more elliptical with
the main axis directed anteroposteriorly. Some
cavities are observed on the anterior surfaces of
the neural spines in caudals 2 to 6, adjacent to the
prespinal lamina. The position of those cavities
varies in number and size, being most of the time
more developed on one side.
Spinoprezygapophyseal laminae are present and
well developed in caudal 2, running from the dorsal
portion of the prezygapophyses, merging with the
neural spine. The spinoprezygapophyseal lamina
of the right side bifurcates and sends a
dorsomedially projected subsidiary lamina that
ends at the prespinal lamina. In caudals 3-5, the
spinoprezygapophyseal laminae are gradually less
developed. Subsidiary laminae are present in
caudals 3 (at both sides); 4 (at the left side) and 5
(at the right side), closer to the base of the neural
spine always ending at the prespinal lamina. In
caudals 6-7 the spinoprezygapophyseal laminae are
reduced to ridges situated more closely to the base
of the neural spine.
The prezygapophyses of the anterior caudals are
well developed, project dorsoanteriorly in caudal 2
and become gradually more horizontal until
assuming a subhorizontal position in caudal 5, a
condition kept by the remaining vertebrae. The
prezygapophyses of caudals 2 and 3 are
comparatively shorter and more robust than the
other elements of the anterior series. The anterior
tip of the prezygapophyses reaches the middle part
of the preceding centrum. The articulation surfaces
are large, roughly “D” shaped, and become smaller
in 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 for
abbreviations.
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There is a well developed rugose elevation placed on
the lateral surface of the prezygapophyseal process,
close to the spinoprezygapophyseal lamina. This
feature corresponds to the prezygapophyseal
tuberosity of caudal 1 but differs here by being smaller
and by not intercepting the spinoprezygapophyseal
lamina. It becomes gradually smaller and less
perceptive in caudals 3 and 4, until turning to a
small lateral rugosity that smoothens out in
caudals 9 and 10 (see below).
The postzygapophyses are well developed in all
anterior caudals, always positioned close to the
neural spine. The postzygapophyseal articular facets
in caudal 2 are elliptical (with the largest axis oriented
dorsoventrally) and become gradually smaller and
more oval in the posterior elements. Posteriorly the
postzygapophyses have a thick medial margin and
form a “V” shaped interpostzygapophyseal opening.
Spinopostzygapophyseal laminae are present in all
anterior 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 posterolaterally
oriented transverse processes that become gradually
shorter along the sequence until becoming vestigial
(and eventually disappearing) in the middle caudal
vertebrae. Those processes are compressed
dorsoventrally and become more posteriorly oriented
along the sequence, until assuming a hook-shape
on caudals 5 to 7. Although in all caudals the
transverse processes are fused with the centrum and
the neural arch, their limits can be observed by rugose
surfaces, particularly visible on the more anteriorly
placed elements.
Starting at caudal 3, the dorsal tuberosity (situated
on the contact surface between the transverse
processes and the neural arch) forms a rounded and
thick bone projection that is present along all
preserved caudals and in the anterior series never
surpasses the extension of the transverse process
(contrary to the middle caudals - see below).
There are several differences between the supposed
titanosaurid 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 for
abbreviations.
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britoi. The most striking ones are the opisthocoelous
condition 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 in
Baurutitan britoi. According to BORSUK-
BIALYNICKA (1977, p.15), the centra of
Opisthocoelicaudia skarzynskii show a ventral
concavity bordered by ventrolateral ridges
throughout the caudal series which are absent in
Baurutitan britoi. The bases of the neural spines of
caudal 2-7 of Opisthocoelicaudia skarzynskii are set
over 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 the
anterior half. The prezygapophyses of
Opisthocoelicaudia skarzynskii are shorter and
dorsoanteriorly oriented in caudals 2-7 (and caudal
8, BORSUK-BIALYNICKA, 1977: pl.4, figs.1b, 2a;
pl.5, fig.2a) which in caudals 4-7 of Baurutitan britoi
are less dorsally oriented. Another difference is the
position of the postzygapophyses which in
Opisthocoelicaudia skarzynskii are set closer to the
posterior margin, surpassing it in caudal 2
(BORSUK-BIALYNICKA, 1977: pl.4, fig.1b). The
transverse processes of Opisthocoelicaudia
skarzynskii are rudimentary, heavy blunt knobs,
projecting outwards and backwards and decrease
in size posteriorly (BORSUK-BIALYNICKA, 1977:15).
In Baurutitan britoi the transverse processes are more
developed, being curved posteriorly until the last
anterior caudal (caudal 7).
Epachthosaurus sciuttoi differs from Baurutitan britoi
by the presence of hyposphene-hypantrum
articulations in the anterior (and middle) caudals,
regarded by MARTÍNEZ et al., (2004) as
autapomorphic for the Argentinean taxon. Based
on the illustration of the seventh caudal
(MARTÍNEZ et al., 2004, fig.7), the centra of
Epachthosaurus sciuttoi are elliptical and do not
show the quadrangular outline present in
Baurutitan britoi. The condyle is very large and
slightly displaced dorsally and the articulation
surfaces for the chevrons more closely spaced than
in the Brazilian species. The neural spine in caudal
7 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.
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subvertical (what possible is also the condition in
other anterior elements) and the prezygapophyses
are shorter. The neural arch is lower compared to
Baurutitan britoi and the postzygapophyses are
consequently placed closer to the dorsal margin of
the centrum. No information is available regarding
the pre- and postspinal laminae, but based on the
published illustrations they are comparatively less
developed in Epachthosaurus sciuttoi compared to
Baurutitan britoi.
Besides the biconvex condition observed in the first
caudal, the anterior caudals of Alamosaurus
sanjuanensis resemble Baurutitan britoi by having
posteriorly oriented neural spines and a similar
shape of the neural canal. Alamosaurus
sanjuanensis differ by having the centra of caudal
2-7 higher than wide, comparatively shorter
prezygapophyses (particularly in caudals 2-5)
which tend do be more inclined anterodorsally
(GILMORE, 1946). The prezygapophyses of some
vertebrae have the ventral margin curved,
contrasting to the straighter condition observed in
Baurutitan britoi. Furthermore, Alamosaurus
sanjuanensis have the neural arches strongly
directed backward and high neural spines, features
absent in Baurutitan britoi.
POWELL (2003) has referred a caudal series of a
juvenile titanosaurid (MPCA 1501) to
Titanosaurus araukanicus, but did only briefly
describe it, what makes the comparison with
Baurutitan britoi limited. Based on the figured
anterior caudals (POWELL, 2003: pl.6, Figs:1-5),
MPCA 1501 lacks the quadrangular outline of
Baurutitan britoi. According to POWELL (2003:23),
MPCA 1501 has almost vertical neural spines,
contrasting to the more inclined condition
observed in Baurutitan britoi.
Based on the figured proximal caudals, Isisaurus
colberti displays very high neural spine and shorter
prezygapophyses compared to Baurutitan britoi.
Furthermore, the posterior condyle of Isisaurus
colberti displays a rounded outline, differing from
the more quadrangular condition of Baurutitan
britoi. Ventral projections for the chevrons are
apparently poorly developed in the anterior
elements 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.
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The anterior caudals of Baurutitan britoi are different
from the holotype of Aeolosaurus rionegrinus
(POWELL, 2003) and the specimens referred to
Aeolosaurus sp. from the Allen Formation
(SALGADO & CORIA, 1993) and from the Los
Alamitos Formation (SALGADO, CORIA & CALVO,
1997b) by having neural spines posteriorly inclined
and not placed on the anterior half of the centrum,
and comparatively shorter prezygapophyses. The
condyle in all Aeolosaurus specimens tends to be
displaced dorsally. The pre- and postspinal laminae
are not well developed (or were not described) in
the known elements (e.g., SALGADO & CORIA,
1993). A pleurocoel-like depression is observed in
one side of caudal 3 in Aeolosaurus rionegrinus
(POWELL 2003) which is absent in Baurutitan britoi.
The pre- and postspinal laminae that are preserved
in both mentioned specimens of Aeolosaurus sp.
are comparatively thinner than those of Baurutitan
britoi. The anterior caudal of Aeolosaurus sp. from
the Allen Formation (MPCA 27174) apparently has
a dorsal tuberosity on the dorsal surface at the
contact region of the transverse process and the
neural arch (SALGADO & CORIA, 1993: fig.2), but
is less developed than in Baurutitan britoi.
Judging from the preserved parts of the neural
spines of the anterior caudals of Gondwanatitan
faustoi, these were inclined dorsoanteriorly,
differing from Baurutitan britoi. The caudal 3 of
Gondwanatitan faustoi shows a well developed
bony ridge on the ventral part of the
prezygapophyses that terminates in a
protuberance directly in front of the anterolateral
corner of the centrum, and a second ridge,
dorsoventrally directed which is connected to this
protuberance (KELLNER & AZEVEDO, 1999:125
and fig.11). Furthermore, caudal 3 of
Gondwanatitan 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.
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depression on the centrum that is absent in
Baurutitan britoi. The “heart-shaped” posterior
surface of the centrum is similar in both taxa, but
in Gondwanatitan faustoi, the centrum tends to
be more flattened dorso-ventrally. Where
preserved, the prezygapophyses of Gondwanatitan
faustoi are comparatively more gracile and thinner
and more laterally directed than in Baurutitan
faustoi, and there is no sign of a prezygapophyseal
tuberosity. The postzygapophyses tend to have a
larger articulation surface, forming a dorsal rim
that is laterally directed, features absent in
Baurutitan britoi. Gondwanatitan faustoi also lacks
a tuberosity above the transverse process.
The anterior caudals of MCT 1719-R (new taxon
that is being described in this volume - see CAMPOS
et al. 2005) differ from Baurutitan britoi by having
the anterior outline of the centrum rounded (and
not quadrangular), a shorter centrum and the
ventral margin more concave. MCT 1719-R has the
condyle of the anteriormost preserved caudal
(possible caudal 2) set apart from the centrum
by a thick bony rim, being more rounded and
higher than in Baurutitan britoi. The neural spine
in MCT 1719-R is very high, has a thinner base
and broadens towards the apex. It is further
directed anterodorsally and placed on the anterior
half 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.
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Where observed, the prespinal lamina is more developed
than the postspinal lamina in MCT 1719-R, contrary
to the condition observed in Baurutitan britoi, where
the postspinal lamina is very thick. The
postzygapophyses of MCT 1719-R are more
developed, having a more concave articulation surface
with the dorsal border projected laterally. The
interpostzygapophyseal space is also “V” shaped but
form a more acute angle than in Baurutitan britoi. MCT
1719-R further differs from Baurutitan britoi by the
absence of a dorsal tuberosity on the contact region
between the transverse process and the neural arch.
Among the caudal vertebrae of Mendozasaurus
neguyelap 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 first
caudal, differs from the biconvex caudal 1 of
Baurutitan britoi. As in Baurutitan britoi, some caudal
vertebrae of the Argentinean species show strong
postspinal lamina, more developed than the prespinal
lamina on anterior caudals. The anterior caudals of
Mendozasaurus neguyelap can be differentiated from
the other anterior caudals of Baurutitan britoi by
having a short centrum, a high and vertically oriented
neural spine and the presence of a large
interzygapophyseal cavity, which was regarded as a
probable autapomorphy of Mendozasaurus
(GONZÁLEZ RIGA, 2003: p.160). IANIGLA-PV 065/
1 displays a small depression on the distal articular
condyle which is distinct from the sagittal groove that
appears 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.
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of caudal 1 of Baurutitan britoi. The following anterior
caudals of Mendozasaurus neguyelap have
subcircular articular faces (GONZÁLEZ RIGA, 2003:
p.160), differing from the quadrangular articular faces
of Baurutitan britoi. The centra are strongly
procoelous, with prominent posterior condyles up to
the 5
th
caudal (more pronounced than in the same
elements of Baurutitan britoi), but this procoely
decreases distally in the tail of Mendozasaurus
neguyelap, while it persists in Baurutitan britoi.
Ventral projections for the chevrons are absent or
poorly developed in Mendozasaurus (GONZÁLEZ
RIGA, 2003: fig.5E-F). The neural spines of
Mendozasaurus neguyelap are laterally compressed
in the base, but broaden distally (GONZÁLEZ RIGA,
2003), differing from the transversely expanded neural
spines of Baurutitan britoi. The neural spines in the
anterior caudals are slightly oriented posteriorly, so that
the posterodorsal edges are placed posteriorly with
respect to the posterior margin of the postzygapophyses,
a trait that, in Baurutitan britoi, appears only in middle
caudals (beginning in 12). Mendozasaurus neguyelap
is also distinct from Baurutitan britoi by having
prezygapophyses with wide and dorsomedially projected
articular facets of quadrangular contour. Finally, in the
Argentinean taxon the anterior caudals have a reduced
bony prominence - the prezygapophyseal tuberosity -
over the spinoprezygapophyseal lamina, but differ
from Baurutitan britoi by being positioned on the
dorsal margin of the prezygapophyseal processes.
This feature is apparently absent in the first or second
caudal of Mendozasaurus neguyelap (González Riga,
pers. infor., 2005).
According to SALGADO (1996:358), the original
sequence of the anterior caudals of Pellegrinisaurus
powelli was lost, the numeration given below being
established by comparison with hypodigm of
Titanosaurus araukanicus (MPCA 1501). The
anterior caudals of Pellegrinisaurus powelli display
a pleurocoel placed below the base of the transverse
process (SALGADO, 1996; POWELL, 2003), a
feature not present in any of the caudals of
Baurutitan britoi. The centrum of caudal 6 of
Pellegrinisaurus powelli is more depressed, having
a posterior condyle which is more pointed and
comparatively wider than in Baurutitan britoi. In
posterior 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 ridge
running obliquely from the base of the transverse
process to almost the edge of the posterior
articulation, a feature absent in Baurutitan britoi.
Caudal 7 of Pellegrinisaurus powelli shows a thinner
and taller neural spine, apparently with poorly
developed pre- and postspinal laminae (SALGADO,
1996: fig. 5). This vertebra has a protuberance at
both sides of the centrum in the posteroventral
corner of the lateral surface (SALGADO, 1996:
p.359 and fig.5 - LP), a feature not present in
Baurutitan britoi. Caudals 6 and 7 of
Pellegrinisaurus
powelli have postzygapophyses placed at a lower
position, closer to the centrum than the
corresponding elements of Baurutitan britoi.
The centrum of the possible second caudal (MRS-
Pv 23) of Rinconsaurus caudamirus has “pleurocoel-
like” lateral depression (CALVO & GONZÁLEZ
RIGA, 2003:338), a feature not present in any of
the anterior caudals of Baurutitan britoi. Besides
the holotype (MRS-Pv 26), Rinconsaurus caudamirus
is represented by several incomplete series of
anterior caudals (MRS-Pv 23, 24, 25) (CALVO &
GONZÁLEZ RIGA, 2003), that have the centra
higher than wide, differing from Baurutitan britoi.
At least in the holotype (MRS-Pv 26, CALVO &
GONZÁLEZ RIGA, 2003: pl.2A), the ventral margins
of the centra are flat or comparatively less concave
than in Baurutitan britoi. Rinconsaurus caudamirus
further shows a bony process separating the
articular facets of the postzygapophyses from the
neural spine (CALVO & GONZÁLEZ RIGA, 2003).
The anterior caudals of Saltasaurus loricatus have
centra which are comparatively more dorsoventrally
depressed than those of Baurutitan britoi. The centra
also have convex lateral walls, differing from the
almost vertical lateral walls of Baurutitan britoi. The
bases of the transverse processes are much more
dorsoventrally developed in Saltasaurus loricatus than
in Baurutitan britoi. The ventral borders of the
transverse processes reach the middle of the centrum
in the Argentinean species (POWELL, 2003: fig.33).
The neural spine in the anterior caudals of
Saltasaurus loricatus is displaced in posterior
direction, the base of which is placed over the
posterior half of the centrum (POWELL, 2003: fig.33),
differing from the spines of Baurutitan britoi, the bases
of which are placed over the anterior half of the centra.
A further distinguishing feature of Baurutitan britoi
is the well developed postspinal lamina, always
larger than the prespinal lamina, a
prezygapophyseal tuberosity and a dorsal
tuberosity at the base of the neural arch which is
well developed until the last anterior caudal (caudal
7). Alamosaurus sanjuanensis apparently also
shows a dorsal tuberosity (GILMORE, 1946: pl.5,
pl.8), but smaller than in the Brazilian taxon.
552 A.W.A.KELLNER, D.A.CAMPOS & M.N.F.TROTTA
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MIDDLE CAUDAL VERTEBRAE
As the anterior caudals, all preserved elements
of the middle series (caudals 8-18) are procoelous
with a well developed posterior condyle and
anterior cotyle (Figs.19-24). The size of the
centrum varies (Tab.1), with the vertebrae placed
more posteriorly slightly longer (caudals 14-18).
There is some variation in the width of the
centrum, but overall the more posterior elements
tend to be more compressed laterally. The
anterior surface of the centrum in middle caudals
changes from being wider than high in caudals
8-10 to a more square outline from caudals 11
to 15 and back to a more rectangular outline (i.e.,
wider than high) in caudals 16-18. The lateral
margin of the anterior articulation surface varies
from being almost vertical (e.g., caudals12-15)
to slightly rounded (e.g., caudal 10). As in the
anterior caudals, a shallow dorsal concavity is
present on the posterior portion of the centrum,
with the bony rim that limits the posterior end
very pronounced in most elements. Except for
caudals 8, 16 and 17, all show a shallow and
rounded depression at the condyle. This
depression can be slightly displaced ventrally
(caudals 10-13) or is positioned at the most
posteriorly projected part. The posterior part of
the centrum bears lateral ventrally oriented
projections for the chevron that get gradually
less developed posteriorly, disappearing in
caudals 15-18.
The neural arch is placed over the anterior half of
the centrum. The neural canal is oval, but contrary
to the anterior caudals, is wider than high in most
elements of the middle series. The neural spine gets
gradually more inclined posteriorly, shifting the
vertical projection of the anterior corner from the
anterior part (caudal 8) to the middle part of the
centrum (remaining elements).
At the same time, the tip of the neural spine tends
to get more elongated and a marked change is
observed from caudal 13 to 14, with the neural
spine getting more elongated with a broader
posterior end, a trend followed in the remaining
preserved elements.
Fig.19- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in right lateral view. Scale bar = 100mm.
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Pre- and postspinal laminae can be individualized
in the first elements of the middle series, but
gradually tend to merge with the neural spine.
The prespinal lamina is individualized up to
caudal 13, being completely merged with the
neural spine thereafter. The postspinal lamina,
more robust than the prespinal lamina,
completely merges with the neural spine starting
on caudal 16.
Spinoprezygapophyseal laminae are reduced,
forming blunt ridges that run from the neural
spine to the dorsomedial portion of base of the
prezygapophyses. A cavity is formed between
these ridges, delimited ventrally by the
intraprezygapophyseal lamina.
The prezygapophyses are well developed, being
more slender compared to those of the anterior
caudals. The anterior margins of the
prezygapophyses reach the middle part of the
preceding vertebrae, but gradually shift to the
posterior half of the more posterior elements. The
prezygapophyses gradually assume a more
horizontal position, becoming subparallel to the
horizontal plane at caudal 14. The prezygapophyseal
articulation surfaces are rounded and subvertically
oriented, becoming less marked posteriorly. Starting
at caudal 16, the prezygapophyseal articulation
surfaces cannot be distinguished from the
remaining part of the prezygapophyses. Caudals
8 to 15 show a marked dorsal ridge above the
prezygapophyseal articulation surfaces which tend
to disappear in the more posterior elements that
lack distinct prezygapophyseal articulation
surfaces. This ridge does not connect with the
spinoprezygapophyseal lamina.
The postzygapophyses are placed very closely to
the neural spine. They tend to be displaced
posteriorly but in caudals 8 and 9 are still
positioned above the middle part of the centrum
whereas from caudal 10 to 18 they are
completely placed over the distal half of the
centrum. From caudals 8 to 14, there is a well
developed postzygapophyseal articulation
surface of oval shape which is present only on
the right side at caudal 15. Starting at caudal
16, the postzygapophyses turn to a thick
projection at the posteroventral part of the neural
spine without any distinguishable articulation
surface. The “V” shaped interpostzygapophyseal
opening gets gradually smaller, disappearing at
caudal 15. Spinopostzygapophyseal laminae
become reduced posteriorly, present as a bony
ridge on caudal 8 and absent in the subsequent
elements.
Fig.20- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in anterior view. Scale bar = 100mm.
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In the elements of the middle caudal series, the
transverse processes are only observed (albeit
reduced) in caudals 8 and 9 (on both sides) and 10
(only on the right side), disappearing in the
remaining elements. Where present, no limits
between the transverse process and the centrum
or neural arch can be observed. The dorsal
tuberosity is well developed in caudal 8, becoming
gradually smaller and more elongated
anteroposteriorly. It is clear that at least in
Baurutitan britoi, the lateral extension seen in some
titanosaurids (e.g., Gondwanatitan), is not formed
by the transverse process but by this independent
dorsal tuberosity (see Discussion).
As the anterior elements, the posterior caudals of
Opisthocoelicaudia skarzynskii differ from
Baurutitan britoi by being opisthocoelous until
caudal 15, turning to amphiplatyan at caudal 16
to 27 (BORSUK-BIALYNICKA, 1977). The centra are
shorter and rounded (BORSUK-BIALYNICKA, 1977:
pl.6, figs.4a, 5a), and not quadrangular as in
Baurutitan britoi. The ventral concavity bordered by
ventrolateral ridges (absent in Baurutitan britoi) is
still present in the middle caudals of
Opisthocoelicaudia skarzynskii (BORSUK-
BIALYNICKA (1977:15). The bases of the neural
spines of middle caudals of Opisthocoelicaudia
skarzynskii are set over the distal half of the
respective centra (BORSUK-BIALYNICKA, 1977:
pl.5, fig.5; pl.6, fig.7a), always more posteriorly
placed than in the respective elements of Baurutitan
britoi. The prezygapophyses of Opisthocoelicaudia
skarzynskii are shorter (BORSUK-BIALYNICKA,
1977: pl.4, figs.1b, 2a; pl.5, fig.2a), but show a
similar orientation as in Baurutitan britoi. The
postzygapophyses of both species are placed on the
posterior half of the centrum, but in
Opisthocoelicaudia skarzynskii they are set closer
to the posterior margin (BORSUK-BIALYNICKA,
1977: pl.5, fig.5; pl.6, figs.1b, 7a). In
Opisthocoelicaudia skarzynskii the caudals of the
middle series tend to have a more subvertically
oriented neural spine (BORSUK-BIALYNICKA,
1977: pl.5, fig.5; pl.6, fig.7a).
An important feature that distinguishes Baurutitan
britoi from Epachthosaurus sciuttoi is the presence
in the latter of hyposphene-hypantrum articulations
in caudals 8-14 (MARTÍNEZ et al., 2004). Some of
the middle elements show a ventral longitudinal
groove which is absent in Baurutitan britoi. The
neural spine in Epachthosaurus sciuttoi tend to be
more anteroposteriorly elongated, and the
Fig.21- Baurutitan britoi n.gen., n.sp. (MCT 1490-R), caudals 8-18 in posterior view. Scale bar = 100mm.
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postzygapophyses are apparently not well delineated
(“weak”, according to MARTÍNEZ et al., 2004).
As in the anterior elements, the middle caudal
vertebrae of Alamosaurus sanjuanensis also differ
from Baurutitan britoi by having the outline of the
centrum more rounded, lacking the quadrangular
shape of the latter. The ventral projections for the
chevrons 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) posterior
views. Scale bar = 50mm. See text for abbreviations.
a
b
cd
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Alamosaurus sanjuanensis, particularly in caudals
8-13, and the ventral margin of the centra are more
concave. The prezygapophyses tend to be
comparatively thinner and in caudals 8-10 show a
tuberosity which is absent in the corresponding
vertebrae of Baurutitan britoi. Furthermore, in
Alamosaurus sanjuanensis the neural spine gets
more elongated anteroposteriorly starting at the
caudal 11, while this happens only in caudal 14 in
Baurutitan britoi.
Midcaudals of Isisaurus colberti display high neural
spines and shorter prezygapophyses than
Baurutitan britoi. The outline of the posterior
articulation is rounded contrasting to the more
quadrangular condition observed in Baurutitan
britoi. The condyle in the Indian taxon is very
projected anteroposteriorly (“cone-like”) and
displaced dorsally. According to JAIN &
BANDYOPADHYAY (1997) the mid- and distal
caudals of Isisaurus colberti show developed
anterior and posterior facets for the chevrons which
in Baurutitan britoi tend to be reduced and present
only on the ventral part of the posterior articulation
surface. Furthermore, Isisaurus colberti shows the
ventral surface of the centrum concave (JAIN &
BANDYOPADHYAY, 1997: fig.12D), differing from
the more flattened condition of Baurutitan britoi.
As far as comparisons are possible, the main
difference from the middle caudals of
Gondwanatitan faustoi and Baurutitan britoi is the
presence of a lateral anteroposteriorly elongated
ridge that is more developed in the former. As
demonstrated in Baurutitan britoi, this process
corresponds to the tuberosity present in more
anterior elements and not the transverse process.
If this is also the case in Gondwanatitan faustoi
cannot be demonstrated and the questions if those
two lateral ridges of those taxa are homologous
remains open.
According to SANZ et al. (1999) only few caudals
are known from Lirainosaurus astibiae that, except
for the first (which is the holotype), are considered
paratypes. Comparing the last preserved caudal of
Baurutitan britoi with the middle caudal of
Lirainosaurus astibiae figured by SANZ et al. (1999:
pl.3, fig.A), the Spanish taxon differs by having the
neural spine occupying a more central position,
shorter prezygapophyses with a more expanded
end, the postzygapophyses comparatively more set
apart from the neural spine with more expanded
articulation surfaces, and the ventral margin of the
centrum more concave.
The middle caudals of Mendozasaurus neguyelap
have centra with slightly procoelous, circular
anterior faces (not rectangular or square as in
Baurutitan 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.
ab
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condyles displaced dorsally, which is regarded as an
autapomorphy of Mendozasaurus neguyelap
(GONZÁLEZ RIGA, 2003). The neural spines are
depressed, flat and more elongated anteroposteriorly
than in Baurutitan britoi. The anterodorsal corner
of the neural spine in caudals 12-13 is higher and
thicker than the posterodorsal one. This condition
disappears in caudal 17, where the dorsal border
of the neural spine straightens and becomes
horizontal, with the anterodorsal corner forming a
right angle (GONZÁLEZ RIGA, 2003, fig.5C). This
condition is not present in the distalmost preserved
caudals of Baurutitan britoi.
Beginning in caudals 8-10, the middle caudals
of Pellegrinisaurus powelli display a
comparatively longer and lower centrum than
in the correspondent elements of Baurutitan britoi
(SALGADO, 1996:359). The midcaudal centra are
dorsoventrally depressed, having convex lateral
faces, differing from the quadrangular shape of the
centra of Baurutitan britoi. Beyond the 15
th
vertebra,
the centra of Pellegrinisaurus powelli, in anterior
view, become depressed, with convex lateral walls
(SALGADO, 1996: fig.6C), contrasting with the
quadrangular shape of caudals 15-18 of Baurutitan
britoi. In these distalmost elements, the neural
spines of Pellegrinisaurus powelli are lower and more
anteroposteriorly elongated than in Baurutitan
britoi. They reach the posterior end of the caudal
centrum, and have the anterodorsal corner of the
neural spine set at a higher position in respect to
the posterodorsal corner (SALGADO, 1996: fig.6A),
a condition present only in the last preserved
caudal 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) posterior
views. Scale bar = 50mm. See text for abbreviations.
ab
c
d
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The middle caudals of Rinconsaurus caudamirus
can be distinguished from those of Baurutitan
britoi by the presence of bony processes
separating the articular faces of the
postzygapophyses from the neural spine, a
character considered an autapomorphy of
Rinconsaurus caudamirus (CALVO & GONZÁLEZ
RIGA, 2003). Among the distal caudals of
Rinconsaurus caudamirus, there is a series (MRS-
Pv 29) with unusual centra, showing a procoelous
plus amphicoelous plus biconvex articulations
(CALVO & GONZÁLEZ RIGA, 2003: pl.3, fig.A).
Since the posterior part of Baurutitan britoi is
lacking, it is not possible to tell, in the present
time, whether this condition was present in this
taxon. It should be noted, however, that a similar
condition has been reported in a caudal series
(DGM 497-R) found in the same sedimentary
deposits, in a nearby quarry (TROTTA, CAMPOS
& KELLNER, 2002).
Regarding the Saltasaurinae Saltasaurus loricatus
and Neuquensaurus australis, the main difference
is the anteroposteriorly elongated depression,
divided by a sagittal crest on the ventral surface
of the centra (POWELL, 2003) which is absent from
Baurutitan britoi.
C
HEVRONS
Fifteen chevrons of Baurutitan britoi were
recovered (Figs.25-27). By the available
information, they were found articulated with
the caudal series (Fig.3). As the caudals, after
being prepared (some decades ago) they were
numbered according to the vertebrae to which
they were connected. Therefore, the numbers
written on the chevrons (also left on the
specimen for historical reasons) do not refer to
the anatomical position of the caudals in the
tail (e.g., chevron 4-5 was found connected to
caudals 3 and 4). The eight anteriormost
chevrons show two numbers (e.g. 4-5; 5-6; 6-
7), suggesting that they were probably in contact
between two vertebrae. The last seven chevrons
received single numbers and were possible more
closely 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 ventral
view. Scale bar = 100mm.
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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.
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All chevrons are well preserved and complete, with
exception of the ventral tip of some elements. The
chevron series begins on caudal 3 and 4 and extends
until caudal 18. Therefore one chevron is missing
(between the caudals 11-12). All chevrons are open,
displaying a large haemal canal. The four
anteriormost chevrons (corresponding to the caudals
3/4 - 6/7) are the largest (subequal in size) with
long ventral process. From the fifth chevron on, their
sizes gradually decrease, with the last preserved
element (corresponding to caudal 18) divided into
two ossifications that do not fuse ventrally. In the
more anterior elements, the ventral fused portion of
the chevrons tend to very large (subequal or larger
in size compared to the proximal processes), getting
gradually shorter in the more posteriorly placed
elements. The depth from the haemal canal changes
from being shorter than the whole chevron in the
anterior elements until being much larger in the
most posterior elements (corresponding to caudals
13 to 18). The ventral portion corresponding to the
fused part of the chevron is laterally compressed,
forming an anteroposteriorly oriented blade-like
lamina that gets gradually more reduced in the more
posteriorly situated elements.
The anterior and posterior surface of this region
shows longitudinal ridges. The bone of the lateral
surface of the chevron corresponding to caudal 13
is thickened, differing from the preceding elements.
The posteriorly place chevrons also have a similar
but less developed thickened bone surface.
Opisthocoelicaudia skarzynskii has chevrons starting
at the last sacro-caudal as far back to caudal
19, beyond which they were probably absent or
quite rudimentary (BORSUK-BIALYNICKA,
1977), differing from Baurutitan britoi (chevrons
starting at caudal 3). In the anterior caudals of
Opisthocoelicaudia skarzynskii, the haemal canal is
about one third of the chevrons length, differing from
the anterior chevrons of Baurutitan britoi, which have
haemal canals equivalent to half of the chevrons
length. The ventral projection of the chevrons 4 to 8
in Opisthocoelicaudia skarzynskii is pointed, a feature
not present in any of the chevrons of Baurutitan britoi
where they are rounded. The chevrons from 6 to 15
of Opisthocoelicaudia skarzynskii are fused to the
centra, a condition not present in Baurutitan britoi.
Furthermore, the chevrons of Opisthocoelicaudia
skarzynskii have comparatively larger and stronger
articular facets than those of Baurutitan britoi.
The chevron of Aeolosaurus rionegrinus (POWELL,
2003: pl.11, fig.3) is distinguished from those of
Baurutitan britoi by having a haemal canal more or
less equivalent to a third of the whole length of the
bone, flanked by two well developed proximal
processes both transversally and anteroposteriorly
more expanded than in the Brazilian taxon. The
proximal part of the ventral process is also
transversally wider than in Baurutitan britoi.
Alamosaurus sanjuanensis has chevrons from the
first caudal to the 25
th
(GILMORE, 1946). The arms
of the chevrons in Alamosaurus sanjuanensis are set
closer to each other than in Baurutitan britoi, resulting
in a more acute “V” shaped profile. The articular heads
are more developed in being anteroposteriorly and
laterally more expanded than in the Brazilian taxon
(GILMORE, 1946: fig.4).
The chevron of Mendozasaurus neguyelap
(GONZÁLEZ RIGA, 2003: fig.5D) has both arms set
closer to each other than in Baurutitan britoi,
resulting is a more acute “V” shaped profile. The
articular heads of the chevron are more expanded,
both anteroposteriorly and laterally, in the
Argentinean taxon. The ventral spine of
Mendozasaurus neguyelap is thinner in anterior view
than in Baurutitan britoi. The chevrons of
Mendozasaurus neguyelap have double articular
facets in proximal ends (GONZÁLEZ RIGA, 2003:
p.162), a trait not present in Baurutitan britoi.
The haemal canal of an anterior chevron of Isisaurus
colberti (JAIN & BANDYOPADHYAY, 1997: fig.17) is
less deep than half of the length of the entire bone,
thus differing from the corresponding deeper haemal
canals present in Baurutitan britoi. The bone is more
expanded anteroposteriorly in the Indian taxon. It
shows also extremely developed articular facets, with
clearly anterior and posterior articulating surfaces
(JAIN & BANDYOPADHYAY, 1997: p.121), which are
absent in the Brazilian taxon. Below the canal, the
haemal arches of Isisaurus colberti have a rounded
shape in cross section (JAIN & BANDYOPADHYAY,
1997), differing from Baurutitan britoi, in which the
haemal arches have a more elliptical cross section,
with the longest axis directed anteroposteriorly.
The anterior chevrons of Saltasaurus loricatus are
more robust than the same elements of Baurutitan
britoi, being comparatively more expanded both
transversally and anteroposteriorly, with well
developed articular heads (POWELL, 2003: fig.36a).
Although the ventral spine of Saltasaurus loricatus
also displays an anterior ridge, it is thicker and
restricted to the distal portion of the spine
compared to Baurutitan britoi. The haemal canal is
less deep in the Argentinean taxon, being less than
a third of the entire length of the bone.
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DISCUSSION
Dinosaurs in Brazil are known for a long time
(KELLNER, 1996; 1998) and there are several
localities where specimens have been recovered but
few have been actually named or studied properly
(KELLNER & CAMPOS, 2000). Regarding
sauropods, only three species have been described
so far: one diplodocid (CARVALHO, AVILLA &
SALGADO, 2003) and two titanosaurids. The first
titanosaurid, “Antarctosaurus brasiliensis” (ARID &
VIZOTTO, 1971), is unfortunately based on material
that cannot be diagnosed (e.g., KELLNER &
CAMPOS, 2000). The second is Gondwanatitan
faustoi, which is closely related to Aeolosaurus
rionegrinus (KELLNER & AZEVEDO, 1999). From
all known localities with titanosaurid dinosaurs,
Peirópolis was always regarded as the richest
(CAMPOS & KELLNER, 1991; BERTINI et al., 1993;
KELLNER & CAMPOS, 1997), showing some
diversity (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 in
the literature as the sequences A (cervical vertebrae
and three dorsals), B (cervical, dorsal and caudal
vertebrae - see CAMPOS et al., 2005 - this volume),
and C (last sacral and caudal vertebrae) were regarded
as the most important ones (POWELL, 1987). Of
those, the sequence C, here named Baurutitan britoi,
is the most complete articulated caudal sequence
from Brazil known to date (caudal 1 to 18), making it
very useful to place isolated anterior and middle
caudal elements in the tail. Based on comparisons
with MCT 1488-R (that has a partial neck, the
complete dorsal series) and MCT 1719-R (incomplete
caudal series), the length of Baurutitan britoi is
estimated between 12 and 14 meters.
One of the most outstanding features Baurutitan
britoi is the presence of a dorsal tuberosity situated
on the contact surface between the transverse
processes and the neural arch. This process forms
a rounded and thick bone projection that starts in
caudal 2 and gets gradually smaller and more
elongated in the posterior elements, being present
in the last preserved caudal (caudal 18). The
transverse process is present and well developed in
all anterior elements, always larger than the dorsal
tuberosity. In caudals 8 and 9, the transverse
process is reduced, while in caudal 10 it is
perceptible only on the right side as a tiny knoblike
projection that completely disappears in caudal 11.
Starting on caudal 8, the dorsal tuberosity, however,
despite getting gradually smaller in the posterior
elements, is always more projected than the
transverse process. This unequivocally shows that
the lateral bony ridge present in the posterior
elements of the middle series is homologous with
the dorsal tuberosity and not with the transverse
process. Alamosaurus sanjuanensis has the
transverse processes getting smaller posteriorly and
according to GILMORE (1946), are replaced by
“raised rectangular areas” which are replaced by
longitudinal ridges that disappear at caudal 27.
Judging from the published pictures, Alamosaurus
sanjuanensis also bears a dorsal tuberosity (albeit
less developed than in Baurutitan britoi) and the bony
lateral ridges on the base of the neural arch, might
also be homologous to the dorsal tuberosity instead
to the transverse processes.
The presence of a lateral ridge in caudals from the
middle (and posterior) series has been observed in
Epachthosaurus sciuttoi (MARTÍNEZ et al., 2004: fig.
8a), where it was interpreted as the transverse
process. Similar longitudinal ridges were observed
in Gondwanatitan faustoi (KELLNER & AZEVEDO,
1999). SALGADO, CORIA & CALVO (1997a) also
mention the presence of prominent lateral bony ridges
in the saltasaurines Neuquensaurus australis and
Saltasaurus loricatus. Since those taxa apparently lack
a dorsal tuberosity on the anterior caudals, the
homology of those bony ridges is not clear.
Regarding the phylogenetic position of Baurutitan
britoi, the procoelous condition of anterior caudals
allows its allocation within Titanosauria
(SALGADO, CORIA & CALVO, 1997a). The strongly
procoelous condition of midcaudals indicates that
it is not a basal titanosaurid, such as Andesaurus
delgadoi Calvo & Bonaparte 1991 where the mid-
and posterior caudals are amphiplatyan, a primitive
feature within Titanosauria (CALVO &
BONAPARTE, 1991; SALGADO, CORIA & CALVO,
1997a). The new Brazilian taxon also lacks several
caudal traits found in the saltasaurines that
includes strongly dorsoventrally flattened centrum
of 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. Baurutitan britoi is also not a
member of the clade formed by Aeolosaurus +
Gondwanatitan, lacking the strongly anterodorsally
oriented neural spine and the very anteriorly
displaced neural arch. However, as in
Gondwanatitan faustoi and Aeolosaurus rionegrinus
562 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
(Kellner pers. obs. 1999), some of the anterior
caudal vertebrae show the ventral part of the
centrum constricted, giving the posterior surface
of the centrum a “heart-shaped” appearance, and
potentially could indicate some relationships of
those mentioned taxa with Baurutitan britoi. The
new species also shares some features with
Alamosaurus sanjuanensis (e.g., dorsal tuberosity
that continues in the posterior elements as a
prominent lateral ridge).
Concluding, Baurutitan britoi is a new titanosaurid
sauropod from Brazil, which is neither a basal (e.g.,
Andesaurus) nor a derived (e.g., Saltasaurinae)
taxon. It shows some similarities to Aeolosaurus
rionegrinus and Gondwanatitan faustoi (“heart-
shaped” centrum of some anterior caudals), also with
Alamosaurus sanjuanensis. More information about
its phylogenetic position can only be achieved by a
detailed phylogenetic analysis of the Titanosauria.
ACKNOWLEDGMENTS
The authors wish to thank the following individuals
and respective institutions, for assistance and
access to specimens under their care: Jorge O.
Calvo (Centro Paleontológico Lago Barreales,
Universidad Nacional del Comahue, Neuquén), 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 Luiz Júlio
da Silva and Otávio da Silva Santos, former
preparators at the Departamento Nacional de
Produção Mineral, for the excellent work done on
this specimen, and Andrea Franco Saavedra
(Colégio D. Pedro II, Rio de Janeiro) for preparing
the anterior part of the preserved sacral and
cleaning the chevrons. Vanessa Dorneles Machado
(Museu Nacional - Rio de Janeiro) is thanked for
the pictures that illustrate this paper and Rita
C.T.Cassab (MCT/DNPM) for providing the paper
of A.R.Lamego, where the report of L.I.Price about
the Peirópolis site was published.
We have benefited from discussions with several
colleagues, particularly Jaime E. Powell
(Universidad Nacional de Tucuman, Tucuman),
Jorge O. Calvo (Centro Paleontológico Lago
Barreales, Universidad Nacional del Comahue,
Neuquén), Reinaldo J. Bertini (Universidade
Estatual Paulista, Rio Claro), Rodrigo Miloni
Santucci (Universidade Estadual Paulista, Rio
Claro), Bernardo J. González Riga (Centro Regional
de Investigaciones Científicas y Tecnológicas,
Mendoza) and Olga Giménez (Universidad Nacional
de la Patagonia “San Juan Bosco”, Comodoro
Rivadavia). Jorge O. Calvo (Centro Paleontológico
Lago Barreales, Universidad Nacional del Comahue,
Neuquén), Bernardo J. González Riga (Centro
Regional de Investigaciones Científicas y
Tecnológicas, Mendoza), Douglas Riff (Universidade
Estadual do Sudeste da Bahia, Vitória da
Conquista) and Jeffrey A. Wilson (University of
Michigan) are thanked for reviewing this paper. This
project was partially funded by FAPERJ (grant #E-
26/152.442/2002-2005 to A.W.A. Kellner) and
Conselho Nacional de Desenvolvimento Científico
e Tecnológico - CNPq (grants to D.A. Campos and
A.W.A. Kellner).
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... Following previous works (e.g., Mannion et al., 2013;Carballido and Sander 2014) the classification of the caudal vertebrae in anterior, middle and posterior elements was based on anatomical features, as for example the presence of transverse processes, the development of neural spines, pre-and postzygapophysis, and the relative length of their centra. Additionally, and given the incomplete preservation of these structures in MPCA-Pv 1500 we also followed other more complete sequence known for other related titanosaurs (e.g., Baurutitan britoi; Kellner et al., 2005). For the present description and analysis, the caudal sequence of Pellegrinisaurus was divided in three sections: anterior (caudals 1-6), middle (caudals 7-16), and posterior (caudals 17-28) caudal vertebrae. ...
... There is a distinct lateral prominence at the level of the dorsal margin line of the neural canal ( Fig. 5A-C), which resembles the "dorsal tuberosity" described for other titanosaurians (e.g. Bonitasaura salgadoi, Baurutitan britoi; Kellner et al., 2005;Gallina and Apesteguía 2015). The bases of the neural arches are partially preserved and they occupy most of the anteroposterior length of the centrum (discounting the hemispherical posterior condyle). ...
... The first character is widely distributed amongst titanosaurs (e.g. Malawisaurus dixeyi Ophistocoelicaudia skarzynskii, Alamosaurus sanjuanensis, Baurutitan britoi; Gilmore 1946;Borsuk-Bialynicka 1977;Gomani 2005;Kellner et al., 2005), so we consider that this is not diagnostic of Pellegrinisaurus. The second character, which is always present in combination with the first one, is also present in at least two taxa: Alamosaurus sanjuanensis and Baurutitan britoi (Gilmore 1946;Kellner et al., 2005). ...
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Pellegrinisaurus powelli is a large titanosaurian sauropod from the Upper Cretaceous of northern Patagonia (Río Negro Province, Argentina). The holotype of this species comprises an incomplete femur, four dorsal and 26 caudal vertebrae collected from the Lago Pellegrini locality. A single middle caudal vertebra from the nearby Cinco Saltos locality has been more recently referred to Pellegrinisaurus. With the purpose of increasing our knowledge about the titanosaur faunas of the Upper Cretaceous of Patagonia, here we provide a detailed redescription of the holotype and referred specimens of Pellegrinisaurus, reviewing its diagnosis and phylogenetic position. A histological analysis of the femur of the holotype is also carried out. The diagnostic characters originally proposed for Pellegrinisaurus are here considered invalid because they either correspond with diagenetic deformations of the specimen or are present in other titanosaurs. The new diagnostic features are related with the presence of large lateral blind fossae with distinct dorsal rims in the anterior caudal centra and with a low longitudinal ridge on the posterior side of the femur shaft originated from the trochanteric shelf and extending to the distal third of the shaft. The phylogenetic analysis recovers Pellegrinisaurus as a non-saltasaurid lithostrotian, closely related with Alamosaurus sanjuanensis. The bone histology indicates that the holotype corresponds to a subadult (i.e. sexually mature but still growing) individual. Finally, the caudal vertebra previously attributed to Pellegrinisaurus cannot be referred to this genus and is here assigned to Titanosauria indet.
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The Late Cretaceous Marília Formation (Bauru Group, Bauru Basin) is a geological unit that occurs on São Paulo, Minas Gerais, Goiás, and Mato Grosso do Sul states, Brazil. This formation consists predominantly of paleosols developed in a semiarid/arid environment and recent reappraisal of its formerly known members reduced its lithological composition and geographical distribution. Hence, the Marília Formation has a very sparse vertebrate fossil record without named species so far. In this contribution we describe a new abelisaurid theropod (Dinosauria) from this unit, namely Kurupi itaata gen. et sp. nov., discovery in the Municipality of Monte Alto, western São Paulo State. The holotype MPMA 27-0001/02 consists of three caudal vertebrae and the partial pelvic girdle. Kurupi itaata gen. et sp. nov. shares with other South American abelisaurids fused ischia and caudal vertebrae with long and laterodorsally oriented transverse processes, with fan-shaped distal ends. Autapomorphies of the new theropod include the variation of ∼15º of the inclination of the transverse process between the first (C1) and seventh (C7) caudal vertebra; C1 with anterolaterally projected triangular process placed below the proximodistal mid-portion of the transverse process, and a notch at the anterodistal portion of the transverse process, between a shelf-like process and the anterodistal corner of the transverse process; and anterior caudal vertebrae (present in C1 and C7, inferred in the others) with a cuneiform process, anterodorsally projected, located on the dorsal surface of the transverse process. Phylogenetic analysis recovered Kurupi itaata gen. et sp. nov. among abelisaurid theropods, but was nested in an unresolved massive polytomy of the entire clade. Taphonomic traits on the studied specimens corroborate previous proposals for the paleoenvironmental context of the Marília Formation. Kurupi itaata gen. et sp. nov. was about 5 meters long, with a rigid tail, and cursorial locomotion as indicated by its a muscles attachment and bones anatomy. This new taxon contributes to the knowledge of the Maastrichtian continental fauna of Brazil and increases the diversity of medium-sized abelisaurids in western Gondwana.
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The record of unenlagiines in Brazil, except for one dorsal vertebra, is still under debate based on isolated teeth. Here, we describe Ypupiara lopai gen. et sp. nov., the first dromaeosaurid species from Brazil, from the Maastrichtian of the Bauru Group, Paraná Basin. The specimen consists of a partial right maxilla (with three teeth in loci) and a right dentary. Ypupiara is characterized by a restricted number of neurovascular foramina on the lateral surface of the maxilla, a rectangular and anteroposteriorly expanded interdental plate, and a labiolingual compression of the teeth, which have a labiolingual diameter more than 3/5 of the rostrocaudal diameter. Our phylogenetic analysis recovers Ypupiara as an unenlagiine based on the fluted teeth and places it as the sister taxon of Austroraptor due to the ratio of the labiolingual and mesiodistal diameters of the teeth being more than 3/5. We also erect the new group Unenlagiinia, which includes Unenlagiinae and Halszkaraptorinae. Ypupiara nests within Unenlagiinia based on the widely spaced teeth and the lack of mesial and distal carinae in the maxillary teeth. The morphology of the teeth is similar to Buitreraptor, although the proportions are markedly distinct. The teeth and comparisons with other Unenlagiinia also support fish being part of the diet for Ypupiara. We also performed a parsimony analysis of endemicity, which suggested that the presence of unenlagiines in Brazilian Upper Cretaceous outcrops is explained by dispersion or extinction events. The new species provides new information on the evolution of Gondwanan dromaeosaurids, and its preserved teeth provide new data to enable the assignment of isolated dromaeosaurid teeth from the Bauru Group.
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In the Neuquén Basin, the Portezuelo Formation (Turonian-Coniacian, Upper Cretaceous) is represented by extended fluvial outcrops that are well-known for yielding an abundant and diversified vertebrate fossil record. However, most of the sauropod fossil record is represented by incomplete specimens, and only two taxa are formally described for the upper Turonian–lower Santonian of the Neuquén Basin: Malarguesaurus and Futalognkosaurus. In this contribution we report new sauropod specimens composed of partially associated axial and appendicular elements coming from the upper section of the Portezuelo Formation of the Los Bastos locality, in the southern Neuquén Basin. The bones show a set of morphological features that allow us to refer them to a titanosaur sauropod: a “cone-chisel-like” tooth, procoelic caudal vertebrae, a dorsally expanded ulna olecranon, and a femur with a prominent lateral bulge and an elliptical diaphysis in cross-section. The phylogenetic analysis recovers the sauropod remains as an unstable colossosaurian within Titanosauria, an effect likely attributable to the incomplete condition of the specimens. Nevertheless, osteological and phylogenetic analyses, together with morphological comparisons with the sauropod fossil record of the Portezuelo Formation, suggest that the new specimens represent a titanosaur different to previously known taxa. Pending better preserved and more complete remains from Los Bastos, the new evidence allows us to improve our knowledge of sauropod diversity during the upper Turonian–lower Santonian, at least in the southern Neuquén Basin.
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One of the most fascinating research topics in the field of sauropod dinosaurs is the evolution of gigantism. In the particular case of Titanosauria, the record of multi-ton species (those exceeding 40 tons) comes mainly from Patagonia. The record of super-sized titanosaur sauropods has traditionally been extremely fragmentary, although recent discoveries of more complete taxa have revealed significant anatomical information previously unavailable due to preservation biases. In this contribution we present a giant titanosaur sauropod from the Candeleros Formation (Cenomanian, circa 98 Ma) of Neuquén Province, composed of an articulated sequence of 20 most anterior plus 4 posterior caudal vertebrae and several appendicular bones. This specimen clearly proves the presence of a second taxon from Candeleros Formation, in addition to Andesaurus, and is here considered one of the largest sauropods ever found, probably exceeding Patagotitan in size. While anatomical analysis does not currently allow us to regard it as a new species, the morphological disparity and the lack of equivalent elements with respect to coeval taxa also prevent us from assigning this new material to already known genera. A preliminary phylogenetic analysis places this new specimen at the base of the clade leading to Lognkosauria, in a polytomy with Bonitasaura. The specimen here reported strongly suggests the co-existence of the largest and middle-sized titanosaurs with small-sized rebbachisaurids at the beginning of the Late Cretaceous in Neuquén Province, indicating putative niche partitioning. This set of extremely large taxa from Patagonia has contributed to a better understanding of the phylogenetic relationships of titanosaurs, revealing the existence of a previously unknown lineage and shedding new light on body mass evolution.
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The Bauru Basin of SE Brazil is a large (ca. 370,000 km2) Upper Cretaceous intracratonic feature, important for its fossil remains and of particular value as a source of regional palaeoclimatic information. Historically, lithostratigraphic reconstructions have been performed mainly for successions of the central and southern parts of the basin, resulting in a lithostratigraphic scheme that is not applicable to the northernmost regions. In particular, the northeastern deposits of the Marília Formation (Serra da Galga and Ponte Alta members) reveal lithological, stratigraphic, and palaeontological differences from southeastern and northwestern counterparts (Echapor~a Member). Nevertheless, these deposits are considered as a single lithostratigraphic formation in the literature. To address this problem, this study demonstrates how the northeastern deposits of the Marília Formation do not show affinity to the rest of the unit. A more suitable lithostratigraphic model is proposed for the northeastern succession as a distinct and independent unit. Lithofacies and palaeopedological analysis, combined with lithostratigraphic mapping of the northeastern deposits, reveal 11 distinct lithofacies and three pedotypes over an area of _450 km2. Sedimentary facies and pedotypes were assigned to six interbedded architectural elements: (a) type 1 channel fill, (b) type 2 channel fill, (c) type 3 channel fill, (d) interchannels, (e) palaeosols, and (f) calcrete beds. The succession is interpreted as a distributive fluvial system with overall direction of flow to the NNW, and which developed under the influence of a semiarid climate regime. This contrasts with deposits of the southeastern and northwestern Marília Formation, previously suggested to be of fine-grained aeolian affinity with interbedded poorly channelised deposits assigned to an aeolian sand sheet environment. By revising the existing lithostratigraphic scheme for the northeastern deposits, and contrasting them with laterally equivalent strata, this work demonstrates how the previously named Serra da Galga and Ponte Alta members reveal a unique set of lithological, architectural, and genetic signatures that permits to separate them from the Marília Formation. Finally, a new lithostratigraphic classification for the unit is proposed: the Serra da Galga Formation, whose deposition relates to an ancient distributive fluvial system.
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Titanosaurian dinosaurs include some of the largest land-living animals that ever existed, and most were discovered in Cretaceous deposits of Argentina. Here we describe the first Brazilian gigantic titanosaur, Austroposeidon magnificus gen. et sp. nov., from the Late Cretaceous Presidente Prudente Formation (Bauru Group, Paraná Basin), São Paulo State, southeast Brazil. The size of this animal is estimated around 25 meters. It consists of a partial vertebral column composed by the last two cervical and the first dorsal vertebrae, all fairly complete and incomplete portions of at least one sacral and seven dorsal elements. The new species displays four autapomorphies: robust and tall centropostzygapophyseal laminae (cpol) in the last cervical vertebrae; last cervical vertebra bearing the posterior centrodiapophyseal lamina (pcdl) bifurcated; first dorsal vertebra with the anterior and posterior centrodiapophyseal laminae (acdl/pcdl) curved ventrolaterally, and the diapophysis reaching the dorsal margin of the centrum; posterior dorsal vertebra bearing forked spinoprezygapophyseal laminae (sprl). The phylogenetic analysis presented here reveals that Austroposeidon magnificus is the sister group of the Lognkosauria. CT scans reveal some new osteological internal features in the cervical vertebrae such as the intercalation of dense growth rings with camellae, reported for the first time in sauropods. The new taxon further shows that giant titanosaurs were also present in Brazil during the Late Cretaceous and provides new information about the evolution and internal osteological structures in the vertebrae of the Titanosauria clade.
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Remains assigned to Aeolosaurus Powell, 1986 from the Allen Formation are described. The specimen differs from the holotype of Aeolosaurus rionegrinus Powell, 1986 in the length of the prezigapophyses, relative position of the postzigapophyses, and radius and ischium morphology. Considerations on a specimen tentatively assigned to the type species, and modified diagnosis of genus are included. Association of dermal plates to the specimen here described is commented. -English summary
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The record of fossil reptiles in Brazil is comparatively poor. From deposits of Permian to Tertiary age only 83 forms have been described or were identified at a generic level. Surprisingly pterosaurs constitute the most diverse taxon (19 species), followed by crocodylomorphs (14 species), and turtles (13 species). Other groups such as Mesosauridae (Sauropsida), Pareiasauria, Procolophonidae, Squamata, Rhynchosauria, Proterochampsidae, Rauisuchidae, Stagonolepididae, and Aves are represented too. Remarkably, dinosaurs are confined to only 3 non-avian theropod and 1 sauropod species, which is incongruent with the extensive Mesozoic exposures of the country. The richest lithostratigraphic unit is the Santana Formation (24 species), followed by the Santa Maria Formation (17 species), and the upper units of the Bauru Group (12 species). The most important collections with fossil reptiles are housed at the Museu de Ciências da Terra (DNPM), Museu Nacional (UFRJ), and Department of Paleontology and Stratigraphy of the UFRGS. A brief survey of exhibitions, working conditions, job market, and publications shows that, despite some advances in the last two decades, a lot of work has to be done before the study of fossil reptiles (and Vertebrate Paleontology) in Brazil achieves the advanced conditions found in more developed countries.