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Barrosasaurus Casamiquelai Gen. Et Sp. Nov., A New Titanosaur (Dinosauria, Sauropoda) From The Anacleto Formation (Late Cretaceous: Early Campanian) Of Sierra Barrosa (Neuquén, Argentina)

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Abstract

A new Late Cretaceous titanosaurian sauropod from the Sierra Barrosa locality (Anacleto Formation, Late Cretaceous, early Campanian) of Neuquén Province, Argentina, Barrosasaurus casamiquelai gen. et sp. nov., is described. The holotype of this species consists of three large and incomplete, although well-preserved, dorsal vertebrae (one probably the third, the next the seventh or eighth, and the last the ninth or tenth). The arrangement of neural arch laminae in the dorsal vertebrae of this titanosaur differs from that present in other genera in the following ways: the spinoprezygapophyseal laminae are well developed in the third vertebra, and relictual in the seventh or eighth vertebra; two spinodiapophyseal laminae are present in the seventh or eighth and in the ninth or tenth vertebrae, the anterior spinodiapophyseal lamina being more strongly developed than the posterior spinodiapophyseal lamina in the ninth or tenth vertebra. These characters, among others, allow the ecognition of this individual as a new species of Titanosauria, which increases knowledge of the diversity of titanosaurs in the Late Cretaceous of Patagonia.
Accepted by R. Butler: 20 Aug. 2009; published: 7 Sept. 2009 1
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2009 · Magnolia Press
Zootaxa 2222: 116 (2009)
www.mapress.com/zootaxa/Article
Barrosasaurus casamiquelai gen. et sp. nov., a new titanosaur (Dinosauria,
Sauropoda) from the Anacleto Formation (Late Cretaceous: early Campanian)
of Sierra Barrosa (Neuquén, Argentina)
LEONARDO SALGADO1 & RODOLFO A. CORIA2
1Conicet-Inibioma, Museo de Geología y Paleontología de la Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén,
Argentina. E-mail: lsalgado@uncoma.edu.ar
2Conicet, Museo “Carmen Funes”, 8318 Plaza Huincul, Neuquén, Argentina. E-mail: coriarod@copelnet.com.ar
Abstract
A new Late Cretaceous titanosaurian sauropod from the Sierra Barrosa locality (Anacleto Formation, Late Cretaceous,
early Campanian) of Neuquén Province, Argentina, Barrosasaurus casamiquelai gen. et sp. nov., is described. The
holotype of this species consists of three large and incomplete, although well-preserved, dorsal vertebrae (one probably
the third, the next the seventh or eighth, and the last the ninth or tenth). The arrangement of neural arch laminae in the
dorsal vertebrae of this titanosaur differs from that present in other genera in the following ways: the
spinoprezygapophyseal laminae are well developed in the third vertebra, and relictual in the seventh or eighth vertebra;
two spinodiapophyseal laminae are present in the seventh or eighth and in the ninth or tenth vertebrae, the anterior
spinodiapophyseal lamina being more strongly developed than the posterior spinodiapophyseal lamina in the ninth or
tenth vertebra. These characters, among others, allow the recognition of this individual as a new species of Titanosauria,
which increases knowledge of the diversity of titanosaurs in the Late Cretaceous of Patagonia.
Key words: Sauropoda, Titanosauria, new species, Sierra Barrosa, Neuquén, Patagonia, Argentina, Upper Cretaceous,
Anacleto Formation
Introduction
The record of sauropod dinosaurs from the Anacleto Formation (Neuquén Group, Upper Cretaceous, lower
Campanian), which crops out widely in both Río Negro and Neuquén provinces of Patagonia, Argentina
(Ramos 1981; Coria et al. 2000, Dingus et al. 2000), currently comprises the species Laplatasaurus
araukanicus Huene, 1929, Pellegrinisaurus powelli Salgado, 1996, and Neuquensaurus australis (Lydekker,
1893). This record also includes the beautifully preserved titanosaur embryos from the exceptional locality of
Auca Mahuevo, in the north of Neuquén province (Chiappe et al. 1998, 2001). Although isolated and
fragmentary material of titanosaurian sauropods is common in the Anacleto Formation, examples of
associated and well-preserved remains belonging to a single individual are rare.
In the locality of Sierra Barrosa (Fig. 1) the Neuquén Group, including the Portezuelo, Plottier, Bajo de la
Carpa and Anacleto formations, crops out extensively. Abundant terrestrial vertebrates, including saurischian
dinosaurs, crocodiles and turtles, have been recovered from multiple stratigraphic levels (Coria et al. 2000,
2001, 2004; Coria & Currie 2002). Here, we describe a new species of Titanosauria, Barrosasaurus
casamiquelai gen. et sp. nov., from the Sierra Barrosa locality. The remains of this new taxon were collected
from a single horizon, and were deeply embedded in reddish fluvial sandstones, positioned close to one
another (Fig. 2). We therefore infer that they belong to a single individual. They exhibit an exceptional state of
preservation that makes possible the examination of the delicate laminar architecture of the dorsal neural
SALGADO & CORIA2 · Zootaxa 2222 © 2009 Magnolia Press
arches, which is usually lost as a result of weathering. These laminae have been considered to be
phylogenetically significant (e.g. Bonaparte 1999; Wilson 1999; Salgado et al. 2006). The information
provided by this new taxon improves our knowledge of the complex evolutionary history of South American
titanosaurs.
Institutional abbreviations. CPP, Centro de Pesquisas Paleontológicas Llewellyn Ivor Price, Peirópolis,
Minas Gerais, Brasil. IANIGLA-PV, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales,
Colección Paleontología de Vertebrados, Mendoza, Argentina. MACN-CH, Museo Argentino de Ciencias
Naturales “Bernardino Rivadavia”, Colección Chubut, Buenos Aires, Argentina. MAU-Pv-CO, Museo
“Argentino Urquiza”, Colección Paleontología de Vertebrados, Cerro Overo, Rincón de los Sauces, Neuquén,
Argentina. MCF-PVPH, Museo “Carmen Funes”, Colección Paleontología de Vertebrados, Plaza Huincul,
Neuquén, Argentina. MCS, Museo de Cinco Saltos, Río Negro, Argentina.
MCT, Museu de Ciencias da Terra (Departamento Nacional de Produçao Mineral), Río de Janeiro, Brazil.
PVL, Fundación “Miguel Lillo”, Colección Paleontología de Vertebrados, Tucumán, Argentina. UNPSJB-Pv,
Universidad Nacional de la Patagonia “San Juan Bosco”, Colección Paleontología de Vertebrados, Comodoro
Rivadavia, Chubut, Argentina.
FIGURE 1. Location map.
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A NEW TITANOSAURIAN SAUROPOD FROM ARGENTINA
FIGURE 2. A) Photograph of the holotype material of Barrosasaurus casamiquelai gen. et sp. nov. during excavation.
B) Map showing the original positions of the specimens. The grid is composed of 10 x 10 cm quadrats.
Systematic Paleontology
Dinosauria Owen, 1842
Saurischia Seeley, 1887
Sauropoda Marsh, 1878
Titanosauriformes Salgado, Coria & Calvo, 1997
Titanosauria Bonaparte & Coria, 1993
Genus Barrosasaurus gen. nov.
Type species. Barrosasaurus casamiquelai sp. nov.
Etymology. In reference to Sierra Barrosa, the locality where the holotype of the type species was found, and
sauros (Greek term for lizard or reptile).
Diagnosis. As for type and only known species.
Barrosasaurus casamiquelai sp. nov.
Figures 3–6
Holotype. MCF-PVPH-447/1–3, one anterior dorsal (MCF-PVPH-447/3) and two posterior dorsal vertebrae
(MCF-PVPH-447/1 and MCF-PVPH-447/2) belonging to a single individual.
Etymology. In honor of the late Rodolfo Casamiquela (1932–2008) for his important contributions to the
development of Argentinean Earth Sciences.
Type locality and horizon. Sierra Barrosa (locality coordinates: 38° 50’ 27’’ S, 68° 50’ 28’’ W; Neuquén
Province, Argentina; Fig. 1), lower Anacleto Formation (Upper Cretaceous, lower Campanian; Ramos 1981;
Dingus et al. 2000). In general, the Anacleto Formation is characterized in this area by the presence of
stacked, massive, medium-to-coarse-grained sandstone bodies with locally occurring extraformational
particles, pebbles and cobbles. Sandstone bodies are typically sheet-shaped, but lenticular bodies occur
SALGADO & CORIA4 · Zootaxa 2222 © 2009 Magnolia Press
locally. Sediments are almost uniformly red in color, but some gray to yellow sandstones also occur.
Sandstones are heavily bioturbated with localized occurrences of decimeter-scale, “lumpy” to vertically
oriented calcareous concretions that preferentially cement Planolites burrow-fills, and a variety of more
complex burrow/dwelling structures of unknown origin (Coria et al. 2000).
FIGURE 3. Barrosasaurus casamiquelai gen. et sp. nov., holotype (MCF-PVPH-447/3). Anterior dorsal vertebra in
anterior (A) and left lateral (B) views. Abbreviations: acpl, anterior centroparapophyseal lamina; al, accesory lamina;
apcdl, accesory posterior centrodiapophyseal lamina; d, diapophysis; nc, neural canal; p, pleurocoel; pcdl, posterior
centrodiapophyseal lamina; pcpl, posterior centroparapophyseal lamina; pp, parapophysis; ppdl, paradiapophyseal
lamina; prsl, prespinal lamina; prz, prezygapophysis; sf, small fossa; sprl, spinoprezygapophyseal lamina; tprl,
intraprezygapophyseal lamina. Scale bar equals 10 cm.
Diagnosis. Large titanosaurian sauropod characterized by the following autapomorphies: 1) posterior
dorsal vertebrae bearing paired, short spinal laminae, nearly parallel to the prespinal lamina; 2) well-
developed anterior spinodiapophyseal laminae in posterior dorsal vertebrae; 3) anterior spinodiapophyseal
laminae divided into at least two, and up to three, branches in posteriormost dorsal vertebrae; 4) aliform
processes with broad, planar and rugose laterodorsal surfaces; 5) portion of neural spine distal to the aliform
process is longer than the portion of the spine that is proximal to the aliform process, at least in the posterior
dorsals.
Description. MCF-PVPH-447/3 (Figs 3, 6A). This vertebra is identified as an anterior dorsal, probably
the third dorsal, based on the relative position of the parapophysis and comparison to the complete dorsal
series of Trigonosaurus pricei Campos, Kellner, Bertini & Santucci, 2005 and other unpublished specimens
(e.g. MAU-Pv-CO-439). Only the anterior half of the vertebra is preserved, and all parts of the specimen
positioned posterior to the diapophysis are missing, including most of the neural spine (Fig. 3A, B).
The centrum is opisthocoelous, and notably wider than high. The anterior articular surface is convex and has
an elliptical outline (Fig. 3A). In lateral view, the lateral surfaces of the centrum are strongly excavated and
anteroposteriorly concave, and the pleurocoels are placed on the anterior part of the centrum, close to the
ventral margin (Fig. 3B). Unlike the condition in the posterior dorsals, the pleurocoels open directly onto the
lateral surfaces of the centrum, and are not set in the bottom of a fossa enclosed by sharp borders. The
posterior articular face of the centrum is not preserved, although the element is likely to have been relatively
short anteroposteriorly. The ventral surface of the centrum is dominated by a thick, longitudinal keel (Fig.
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A NEW TITANOSAURIAN SAUROPOD FROM ARGENTINA
6A), a character noted by Upchurch et al. (2004: their character 126) as present in other sauropods, such as
Diplodocus Marsh, 1878 and Haplocanthosaurus Hatcher, 1903.
FIGURE 4. Barrosasaurus casamiquelai gen. et sp. nov., holotype (MCF-PVPH-447/1). Posterior dorsal (seventh or
eighth) vertebra in anterior (A), right lateral (B) and posterior (C) views. Abbreviations:acpl, anterior
centroparapophyseal lamina; alp, aliform process; apcdl, accessory posterior centrodiapophyseal lamina; aspdl, anterior
spinodiapophyseal lamina; d, diapophysis; nc, neural canal; pcdl, posterior centrodiapophyseal lamina; pcpl, posterior
centroparapophyseal lamina; posl, postspinal lamina; pp, parapophysis; ppdl, paradiapophyseal lamina; prsl, prespinal
lamina; prz, prezygapophysis; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina; tprl,
intraprezygapophyseal lamina. Scale bar equals 10 cm.
In anterior view the neural arch is transversely wide. The transverse processes are dorsoventrally
flattened. The diapophyses project laterally and slightly dorsally (Fig. 3A). The anterior surface of the neural
arch is slightly concave. The centroprezygapophyseal laminae are absent. The neural canal is nearly circular.
A short segment of the base of the prespinal lamina is preserved and extends dorsal to a small fossa that is
located above the neural canal (Fig. 3A, sf). The small fossa is bordered ventrally by a prominent, shelf-like,
supraneural structure, which corresponds to the fused left and right intraprezygapophyseal laminae (Fig. 3A,
tprl). The bases of both spinoprezygapophyseal laminae are clearly visible in anterior view (Fig. 3A, sprl).
Several titanosaurs preserve relatively complete dorsal sequences, including Trigonosaurus pricei,
Argyrosaurus superbus Lydekker, 1893, Neuquensaurus australis, and Argentinosaurus huinculensis
Bonaparte & Coria, 1993. In general, the spinoprezygapophyseal laminae are absent or extremely reduced in
the anterior dorsals of these taxa (Huene 1929; Bonaparte & Coria 1993; Campos et al. 2005; Powell 2003).
Because the neural spine is missing, it is not possible to determine if the spinoprezygapophyseal laminae were
confluent at some point on the element. The prezygapophyses are well separated from one another (Fig. 3A,
prz), and are placed posterior to the parapophyses, at a point approximately level with the diapophyses. The
articular facets of the prezygapophyses have an oval outline, with their longest diameter transversely oriented
(Fig. 3A). The articular faces of the prezygapophyses face dorsomedially, at an angle of approximately 30° to
the horizontal. The parapophyses project laterally, with their articular facets dorsoventrally elongated and
slightly concave.
SALGADO & CORIA6 · Zootaxa 2222 © 2009 Magnolia Press
FIGURE 5. Barrosasaurus casamiquelai gen. et sp. nov., holotype (MCF-PVPH-447/2). Posterior dorsal (ninth or
tenth) vertebra in anterior (A), posterior (B), left (C), and right lateral (D) views. Abbreviations: acpl, anterior
centroparapophyseal lamina; alp, aliform process; apcdl, accesory posterior centrodiapophyseal lamina; aspdl, anterior
spinodiapophyseal lamina; f, fossa; nc, neural canal; p, pleurocoel; pcdl, posterior centrodiapophyseal lamina; pcpl,
posterior centroparapophyseal lamina; podl, postzygodiapophyseal lamina; posl, postspinal lamina; prsl, prespinal
lamina; prz, prezygapophysis; pz, postzygapophysis; r, rib; spol, spinoposztzygapophyseal lamina; sprl,
spinoprezygapophyseal lamina; tl, transverse lamina. Scale bar equals 10 cm.
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FIGURE 6. Barrosasaurus casamiquelai gen. et sp. nov., holotype. Dorsal centra in ventral view: A, MCF-PVPH-447/
3; B, MCF-PVPH-447/1; MCF-PVPH-447/2. Abbreviation: vk, ventral keel. Scale bar equals 10 cm.
FIGURE 7. Comparison of anterior dorsal vertebrae of some selected titanosaurs, in anterior view. A, Barrosasaurus
casamiquelai gen. et sp. nov. (holotype, MCF-PVPH-447/3). B, Argentinosaurus huinculensis (holotype, MCF-PVPH-
1). C, Mendozasaurus neguyelap (paratype, IANIGLA-PV 066). Scale bar equals 10 cm.
In lateral view, the neural arch is anteroposteriorly short (Fig. 3B). The parapophyses are placed
approximately at the midpoint between the dorsal border of the centrum and the diapophyses (Fig. 3A, B, pp).
A well developed anterior centroparapophyseal lamina is present (Fig. 3B, acpl), whereas the posterior
centroparapophyseal lamina is poorly developed (Fig. 3B, pcpl). The paradiapophyseal lamina, which links
the parapophysis with the anterior face of the diapophysis, is well-developed (Fig. 3A, B, ppdl). Posterior to
the paradiapophyseal lamina, there is another, shorter, lamina that extends to the ventral border of the
diapophysis (Fig. 3B, al). Between this short accessory lamina and the paradiapophyseal lamina there is a
shallow fossa. A robust posterior centrodiapophyseal lamina extends from the ventral face of the diapophysis
(Fig. 3B, pcdl). In addition, an accessory posterior centrodiapophyseal lamina extends anteroventrally from
the ventral face of the diapophysis (Fig. 3B, apcdl). This accessory posterior centrodiapophyseal lamina
subdivides a fossa that is positioned posterior to the parapophysis: the infradiapophyseal fossa (Fig. 3B). On
the left side, the base of a spinodiapophyseal lamina is present.
MCF-PVPH-447/1 (Figs 4A–C, 6B). This vertebra is from the posterior part of the series, and is possibly
the seventh or eighth. This positional identification is based on the relative position of the parapophysis,
comparison to the complete dorsal series of Trigonosaurus pricei (Campos et al. 2005), and the fact that
MCF-PVPH-447/2 (see below) is clearly positioned more posteriorly within the vertebral column with respect
to MCF-PVPH-447/1 (MCF-PVPH-447/2 is probably the ninth or tenth dorsal, assuming a total count of ten
dorsals as in most titanosaurs [Powell 2003]). The vertebral centrum possesses a convex anterior articular
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face, a concave posterior articular face that is wider than high, and dorsoventrally convex and
anteroposteriorly concave lateral surfaces (Fig 4A–C). The elliptical pleurocoels are obliquely oriented such
that their anterior halves are positioned more dorsally on the centrum that the posterior halves (Fig. 4B). A
prominent longitudinal keel-like ridge is present on the ventral surface of the centrum (Fig. 6B).
FIGURE 8. Comparison among posterior dorsal vertebrae of some selected titanosaurs. A, B, Barrosasaurus
casamiquelai gen. et. sp. nov. (holotype, MCF-PVPH-447/2), ninth or tenth dorsal in posterior (A) and right lateral (B)
views. C, D, Neuquensaurus australis (MCS-5), dorsal 9? in posterior (C) and right lateral (D) views. E, F, Argyrosaurus
superbus (PVL 4628, MACN-CH 217), dorsal 10? in anterior (E) and right lateral (F) views. G, Trigonosaurus pricei
(holotype, MCT-1488-R), dorsals 9 and 10 in left lateral view. Scale bar equals 10 cm.
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The neural arch is relatively short anteroposteriorly, and placed mostly on the anterior half of the centrum
(Fig. 4A–C). At the base of the prespinal lamina (Fig. 4A, B, prsl), on both sides, a short and delicate
ventrolaterally extending lamina is present, which ends near the medial border of the prezygapophyses (Fig.
4A, sprl?). These laminae may represent subdivisions of the prespinal lamina, vestiges of the
spinoprezygapophyseal lamina, or both.
In anterior view, the prezygapophyses are transversely broad and anteroposteriorly short processes, and
their articular facets face dorsomedially and converge ventrally (Fig. 4A, prz). Ventral to a well-developed
intraprezygapophyseal lamina (Fig. 4A, tprl), a median septum separates two deep cavities. The parapophyses
are almost level with the prezygapophyses and are connected by a short and horizontal prezygoparapophyseal
lamina (Fig. 4A, prpl).
In both anterior and posterior views, distal to the union of the posterior spinodiapophyseal with the
spinopostzygapophyseal laminae (Fig. 4B, pspdl, spol), small lateral expansions of the neural spine are
present (Fig. 4, alp). These are probably homologous to the aliform processes of Epachthosaurus sciuttoi
Powell, 1990 (Martínez et al. 2004) (Fig. 4A, C). In Barrosasaurus, the posterior spinodiapophyseal lamina of
MCF-PVPH-447/1 is more strongly expanded laterally than the anterior spinodiapophyseal lamina (Fig. 4A).
The surfaces of these aliform processes are subrectangular in lateral view (Fig. 4B, alp), and are oriented in
planes that converge dorsally in both anterior and posterior views (Fig. 4A, C). Lateral to the point where the
anterior and posterior spinodiapophyseal laminae adjoin (Fig. 4B, aspdl, pspdl), on the dorsal surface of the
diapophysis, a series of laterally diverging laminae is present.
TABLE 1. Measurements of the holotype specimen, MCF-PVPH-447 of Barrosasaurus casamiquelai gen. et sp nov.
Measurements in mm.
The paradiapophyseal lamina is short (Fig. 4A, B, ppdl). An anterior centroparapophyseal lamina and a
well-developed and obliquely oriented posterior centroparapophyseal lamina are present (Fig. 4, acpl, pcpl).
Ventral to the diapophysis, the posterior centrodiapophyseal lamina is present (Fig. 4B, C, pcdl), and is
slightly thinner than the posterior centroparapophyseal lamina. The nearly vertical accessory posterior
centrodiapophyseal lamina (Fig. 4B, apcdl) divides the infradiapophyseal fossa and connects to the posterior
centroparapophyseal lamina. The area between the anterior and posterior centroparapophyseal laminae is a
shallow, triangular depression. The centropostzygapophyseal (Fig. 4B, C, cpol), spinopostzygapophyseal,
posterior centrodiapophyseal, and the posterior spinodiapophyseal laminae enclose a deep, rhomboidal and
dorsoventrally elongated fossa (Fig. 4B) that extends onto the posterior face of the transverse process.
MCF-PVPH-447/3 MCF-PVPH-447/1 MCF-PVPH-447/2
Centrum length (including condyle) 170 270 230
Anterior centrum height 160 180 185
Posterior centrum height -- 200 200
Posterior centrum width -- 270 280
Height from iintraprezygapophyseal laminae to the
spine apex 80 380 320
External width between prezygapophyses 300 250 170
Length of the neural arch base 75 (preserved) 120 110
Anterior centrum width 255 150 (estimated)| 240 (estimated)
Spine maximum width (from aliform processes) -- 160 180 (estimated)
Distal neural spine height (from aliform process to
top of neural spine) -- 180 (preserved) 90 (preserved)
Total heigth 290
(without neural spine) 640 630
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In posterior view (Fig. 4C), ventral to the postzygapophyses, the robust centropostzygapophyseal laminae
enclose a deep depression that contains the neural canal (Fig. 4C, nc), which is roofed by a well developed
intrapostzygapophyseal lamina (Fig. 4C, tpol). There are no postzygodiapophyseal laminae.
The neural spine is tall, nearly vertical and transversely expanded. Because the distal end of the neural
spine is missing, it is not possible to estimate its total height (see Table 1). In anterior view, the prespinal
lamina is well-developed in its basal and mid segments (Fig. 4A, prsl). Towards the distal end of the preserved
neural spine, the prespinal lamina splits into multiple low crests, which diverge distally. In posterior view
(Fig. 4C, posl), the postspinal lamina is clearly less well-developed than is the prespinal lamina. The area
bounded by the spinopostzygapophyseal and the postspinal laminae bears a series of short and robust, rib-like,
nearly transversely extending laminae that converge laterally towards the postzygapophyses.
In lateral view, a short and robust spinopostzygapophyseal lamina is well-developed (Fig. 4B, spol). Two
spinodiapophyseal laminae are also present, and converge ventrally at their bases (Fig. 4B, aspdl, pspdl). The
posterior spinodiapophyseal lamina contacts the spinopostzygapophyseal lamina at the mid height of the
spine, whereas the anterior spinodiapophyseal lamina extends further dorsally, probably reaching the distal
end of the spine. Between both spinodiapophyseal laminae, there is a deep, elongated fossa, which is deeper at
the base of the spine than more distally (Fig. 4B).
MCF-PVPH-447/2 (Fig. 5A–D). This is a posterior dorsal vertebra, possibly the ninth or the tenth of the
column, based on comparison to dorsals nine and ten of Trigonosaurus pricei, which, unlike the immediately
preceding vertebrae, have postzygodiapophyseal laminae (Campos et al. 2005). This vertebra is almost
complete, lacking only the distal end of the neural spine and the left postzygapophysis. In this specimen, the
head of the right rib is preserved fused to the transverse process, in contact with the corresponding
diapophysis and parapophysis.
The centrum of MCF-PVPH-447/2 is strongly opistocoelous and wider than high. The lateral faces are
anteroposteriorly excavated, bearing deep pleurocoels (Fig. 5C, D), although these pleurocoels are slightly
shorter anteroposteriorly than those of MCF-PVPH-447/3. Unlike the other vertebrae, the centrum of MCF-
PVPH-447/2 does not possess a ventral keel (Fig. 6C).
The neural arch is anteroposteriorly short, and more strongly inclined anteriorly than those of the
preceding vertebrae (Fig. 5C, D). The posterior centrodiapophyseal lamina is weakly developed (Fig. 5C, D,
pcdl), as are the anterior and posterior centroparapophyseal laminae (Fig. 5C, D, acpl, pcpl). MCF-PVPH-
447/2 shows asymmetries in the pattern of laminae at the base of the neural arch. On the left side, on the
lateral surface of the neural arch ventral to the diapophysis, several poorly developed laminae are present (Fig.
5C), which are absent on the right side (Fig. 5D). One of these laminae corresponds to the accessory posterior
centrodiapophyseal lamina (Fig. 5C, apcdl?). Another lamina oriented perpendicular to the putative accesory
posterior centrodiapophyseal lamina is interpreted as the posterior centroparapophyseal lamina. In addition,
MCF-PVPH-447/2 possesses a conspicuous postzygodiapophyseal lamina (Fig. 5D, podl), which is
laterodorsally and anteriorly oriented, and which extends from the lateral margin of the postzygapophysis to
the posterior margin of the diapophysis. Unlike MCF-PVPH-447/1, the articular facets of the
postzygapophyses face ventrally (Fig. 5B). The transverse processes are laterodorsally directed, and placed in
a higher position than the postzygapophyses.
The neural spine is noticeably shorter anteroposteriorly than in MCF-PVPH-447/1. In anterior view, the
prespinal lamina is well developed (Fig. 5A, prsl). On the left side of the base of the prespinal lamina, a small
oblique lamina is present, similar to that observed in MCF-PVPH-447/1. This probably corresponds to a
vestige of a spinoprezygapophyseal lamina (Fig. 5A, sprl?). In addition, in the middle of the neural spine, a
conspicuous lamina is observed extending perpendicular to the prespinal lamina (Fig. 5A, tl). Further rib-like
transversely extending laminae, parallel to, and shorter than, the former, are placed at different levels on the
anterior surface of the neural spine (Fig. 5A).
In lateral view, a robust, anterior spinodiapophyseal lamina is present (Fig. 5D, aspdl), which is bifurcated
at both dorsal (spinal) and ventral (diapophyseal) ends. The posterior spinodiapophyseal lamina (Fig. 5B, D,
pspdl) is laterally less strongly developed than the anterior spinodiapophyseal lamina. Consequently, the
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aliform process is only partially visible in anterior view (Fig. 5A, alp). The greater development of the
anterior spinodiapophyseal lamina prevents the fossa enclosed by these laminae from being visible in anterior
view (Fig. 5B, D).
In posterior view, both the spinopostzygapophyseal and postspinal laminae are well-developed (Fig. 5B,
spol, posl). The spinopostzygapophyseal laminae have convex outlines in lateral view, unlike those of MCF-
PVPH-447/1, which have a concave outline. Moreover, MCF-PVPH-447/2 lacks rib-like transverse laminae
between the postspinal lamina and the spinopostzygapophyseal lamina.
Discussion
Comparisons. Despite being known only from fragmentary remains, Barrosasaurus casamiquelai exhibits a
series of autapomorphic characters that justify its recognition as a new species of sauropod. These characters
are discussed below:
1. Presence of short laminae, lateral to the base of the prespinal lamina, in the posterior dorsals. As discussed
above, these laminae (also well-developed in the anterior dorsal vertebra, MCF-PVPH-447/3) may
represent relicts of spinoprezygapophyseal laminae. In Trigonosaurus pricei (Campos et al. 2005),
Neuquensaurus australis (Salgado et al. 2005), and Saltasaurus loricatus Bonaparte & Powell, 1980
(Powell 2003), as well as in some unpublished titanosaur specimens (MAU-Pv-CO-439, MCF-PVPH-
109), the spinoprezygapophyseal laminae are present in the anterior dorsal vertebrae (although less well-
developed than in Barrosasaurus casamiquelai), and absent posteriorly from the fourth or fifth dorsal
vertebra onwards. In Uberabatitan ribeiroi Salgado & Carvalho, 2008, and in another specimen from
Brazil, CPP-494 (Santucci & Bertini 2006), two laminae nearly parallel to the prespinal lamina are
present, somewhat resembling the condition existing in Barrosasaurus casamiquelai.
2. Posterior dorsal vertebrae with well-developed anterior spinodiapophyseal laminae, which are, in the last
dorsal, much more developed than the posterior spinodiapophyseal laminae. In most titanosaurs, including
Trigonosaurus pricei (Campos et al. 2005), Epachthosaurus sciuttoi (Martínez et al. 2004),
Argentinosaurus huinculensis (Bonaparte & Coria 1993) and Argyrosaurus superbus (PVL 4628, MACN-
CH 217), the anterior spinodiapophyseal laminae are poorly developed or totally reduced relative to the
posterior spinodiapophyseal laminae. In other taxa, such as Neuquensaurus australis (MCS-5) and
Saltasaurus loricatus (PVL 4017-13, 4017-135, 4017-137, 4017-15) the anterior spinodiapophyseal
laminae are probably the only spinodiapophyseal lamina present in the posterior dorsals. In Barrosasaurus
casamiquelai, the anterior spinodiapophyseal lamina is more robust than the posterior spinodiapophyseal
lamina, and it extends almost to the tip of the spine, extending beyond the aliform process.
3. Posteriormost dorsal vertebrae with the anterior spinodiapophyseal lamina divided into at least two, and
up to three, subsidiary laminae. In those titanosaurs in which the anterior spinodiapophyseal lamina is
well-developed (Saltasaurus loricatus, PVL 4017-13, 4017-135, 4017-137, 4017-15; Neuquensaurus
australis, MCS-5), this structure is never divided.
4. Aliform processes with broad, planar and rugose laterodorsal surfaces. As in Epachthosaurus sciuttoi
(Martínez et al. 2004), and other titanosaurs such as Argentinosaurus huinculensis (Bonaparte & Coria
1993), Barrosasaurus casamiquelai possesses lateral expansions known as aliform processes in the
posterolateral borders of the neural spines of the dorsal vertebrae (Martínez et al. 2004). In
Epachthosaurus sciuttoi, the laterodorsal margin of each lateral expansion is a stout lamina that connects
it with the apex of the spine (Martínez et al. 2004, fig. 3). In contrast, Barrosasaurus casamiquelai
possesses a wide, flat, rugose structure in an equivalent position.
5. The part of the neural spine that is distal to the aliform process (or lateral expansion), is equal to, or is
longer than, the part of the neural spine which is ventral to this structure (in MCF-PVPH-447/1). In most
titanosaurs such as Argentinosaurus huinculensis (Coria & Bonaparte 1993), Trigonosaurus pricei
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(Campos et al. 2005), CPP-494 (Santucci & Bertini 2006), Opisthocoelicaudia skarzynskii Borsuk-
Byalinicka, 1977, and Rapetosaurus krausei Curry-Rogers & Forster, 2001, with the possible exception of
Epachthosaurus sciuttoi (Martínez et al. 2004), the section of the spine between the lateral expansion and
the apex is short, and is shorter than the section of the spine below these expansions. In contrast, in
Barrosasaurus casamiquelai the part of the neural spine that is distal to the aliform process occupies at
least 50% of the height of the neural spine, measured from the base of the transverse process to the top of
the spine.
In comparison with other titanosaurs from the Anacleto Formation, Barrosasaurus casamiquelai
represents a significantly larger taxon than Neuquensaurus australis (from the locality of Cinco Saltos, Río
Negro, Argentina; Lydekker 1893), which also differs in other ways, including a distinctive pattern of
vertebral laminae. The posterior dorsal neural arch and spine of Neuquensaurus australis is slightly inclined
posteriorly (Salgado et al. 2005; Fig. 8C, D), which contrasts with the anteriorly inclined arch and spine of
Barrosasaurus casamiquelai (MCF-PVPH-447/2). Neuquensaurus australis has a single spinodiapophyseal
lamina in its posterior dorsal vertebrae (Salgado et al. 2005; this lamina is probably the anterior
spinodiapophyseal lamina, pers. obs. of MCS-5), unlike the double spinodiapophyseal lamina present in
Barrosasaurus casamiquelai. Finally, the transverse processes of the posterior dorsals of Neuquensaurus
australis typically project dorsolaterally (Salgado et al. 2005), instead of projecting laterally as in
Barrosasaurus casamiquelai (Fig. 8A–D).
Barrosasaurus casamiquelai markedly differs from Pellegrinisaurus powelli (from the locality of Lago
Pellegrini, Río Negro, Argentina) in the proportions of the dorsal centra. In Pellegrinisaurus, the posterior
dorsal centra are two times wider than high, a diagnostic character for the genus (Salgado 1996), whereas in
Barrosasaurus the centrum width is only 25 % greater than the centrum height (Table 1).
The dorsal vertebrae of Laplatasaurus araukanicus (locality of Cinco Saltos, Cerro Policía, and other
localities of Río Negro, Argentina) are virtually unknown, as well as most of its skeleton. However, there is a
partial neural arch referred to Laplatasaurus araukanicus by Huene (1929, plate XXII 2), which exhibits a
single spinodiapophyseal lamina as in Neuquensaurus australis; by contrast, as noted above, in
Barrosasaurus casamiquelai the spinodiapophyseal lamina is double. In that vertebra, the
spinopostzygapophyseal laminae are clearly visible in anterior view, and the surface existing between the
prezygapophyses and the neural canal is more reduced (Huene 1929, plate XXII 2a) when compared with the
condition in Barrosasaurus casamiquelai. Laplatasaurus araukanicus, which comes from the uppermost
levels of the Anacleto Formation (unlike Barrosasaurus casamiquelai, which comes from the base of the
unit), is clearly a smaller species than Barrosasaurus casamiquelai. All the appendicular bones assigned to
Laplatasaurus araukanicus (figured by Powell [2003, plate 5]), including the lectotype, belong to mid-sized
individuals. These specimens are presumably adults (although perhaps not fully grown), because of the well-
marked rugosities for muscular attachments.
The dorsal vertebrae of the probable nemegtosaurid Antarctosaurus wichmannianus Huene, 1929, from
the overlying Allen Formation (middle Campanian–lower Maastrichtian, Ballent 1980), are unknown.
However, in nemegtosaurids recorded from other continents, such as Rapetosaurus krausei, these elements
are markadedly different from Barrosasaurus casamiquelai (Curry Rogers & Forster 2001). Curry Rogers
(2005) listed a series of synapomorphies of her “Rapetosaurus clade”, which included middle and posterior
dorsal neural spines posteriorly directed, middle and posterior dorsal neural spines that comprise less than
50% of total vertebral height, and middle and posterior dorsal neural spines distally flared and transverse
processes of posterior dorsals lying vertically above parapophyses. None of those synapomorphies are
observed in Barrosasaurus casamiquelai.
With respect to titanosaurs from other formations and geographical areas, Barrosasaurus casamiquelai
differs from Epachthosaurus sciuttoi (UNPSJB-Pv 920; early Late Cretaceous, Bajo Barreal Formation,
Chubut Province, Argentina) in having lower posterior dorsal neural arches relative to the centrum length. In
the ninth dorsal of Epachthosaurus sciuttoi, for example, the centrum length is nearly 50% the height of the
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A NEW TITANOSAURIAN SAUROPOD FROM ARGENTINA
entire vertebra (Martínez et al. 2004), whereas in Barrosasaurus casamiquelai the centrum of the ninth or
tenth dorsal is, at most, 36% of the height of the entire vertebra. In addition, the following differences are
observed: the dorsal neural arches of Epachthosaurus sciuttoi are either vertically oriented or posteriorly
inclined (Martínez et al. 2004), and are never anteriorly inclined as occurs in Barrosasaurus casamiquelai.;
the hyposphene-hypantrum complex is present on the posterior face of the posterior dorsal neural arches of
Epachthosaurus sciuttoi (Martínez et al. 2004), whereas these structures are absent in Barrosasaurus
casamiquelai; the postzygodiapophyseal lamina is present in the posterior dorsal vertebrae of Epachthosaurus
sciuttoi (Martínez et al. 2004), unlike Barrosasaurus casamiquelai where this lamina is only present in the
posteriormost dorsal (MCF-PVPH-447/2).
Barrosasaurus casamiquelai also exhibits notable differences to Argentinosaurus huinculensis (early Late
Cretaceous, Huincul Formation, Neuquén Province, Argentina) (Fig. 7A, B). The prezygapophyses of the
anterior dorsals of Argentinosaurus huinculensis are closer to each other than in Barrosasaurus casamiquelai
(Bonaparte & Coria 1993; MCF-PVPH 1; Fig. 7B); the transverse processes of the anterior dorsals of
Argentinosaurus huinculensis are laterally projected (Bonaparte & Coria 1993; MCF-PVPH 1), whereas in
Barrosasaurus casamiquelai these project dorsolaterally (Fig. 7A, B); the spinoprezygapophyseal laminae are
absent in the anterior dorsals of Argentinosaurus huinculensis (Bonaparte & Coria 1993; MCF-PVPH 1),
unlike the condition in Barrosasaurus casamiquelai, where they are present.
Barrosasaurus casamiquelai differs from Argyrosaurus superbus (early Late Cretaceous, Bajo Barreal
Formation, Chubut Province, Argentina) (PVL 4628, MACN-CH 217; Fig. 8E, F). In this sauropod, the neural
arch of the tenth dorsal vertebrae is vertical (Bonaparte 1999; PVL 4628, MACN-CH 217), not anteriorly
inclined as in the corresponding vertebra of Barrosasaurus casamiquelai (MCF-PVPH-447/2). In addition, in
Barrosasaurus casamiquelai the base of the posterior dorsal neural arch is anteroposteriorly shorter (relative
to the centrum length) than in Argyrosaurus superbus (PVL 4628, MACN-CH 217). In Barrosasaurus
casamiquelai the length of the base of the posterior dorsal neural arch is less than 50% of the centrum length,
whereas in Argyrosaurus superbus (PVL 4628, MACN-CH 217) that ratio is greater (PVL 4628, MACN-CH
217). The short and robust, rib-like transverse laminae of the anterior face of the neural spine observed in the
posterior dorsal vertebra (MCF-PVPH-447/2) of Barrosasaurus casamiquelai are not present in the posterior
dorsals of Argyrosaurus superbus (PVL 4628, MACN-CH 217; Bonaparte 1999). The deep fossa between the
anterior and posterior spinodiapophyseal laminae observed in Barrosasaurus casamiquelai is not present in
the posterior dorsals of Argyrosaurus superbus, where the anterior spinodiapophyseal lamina seems to be
poorly developed (PVL 4628, MACN-CH 217).
Compared with Mendozasaurus neguyelap González Riga, 2003 (Late Cretaceous, Río Neuquén
Formation, Mendoza Province, Argentina) (paratype, IANIGLA-PV 066), Barrosasaurus casamiquelai
differs in many ways. The transverse processes of the anterior dorsal vertebra of Mendozasaurus neguyelap
are nearly laterally projected and anteroposteriorly compressed (González Riga 2003; IANIGLA-PV 066; Fig.
7C), unlike those of Barrosasaurus casamiquelai, where they are rather dorsolaterally projected and
dorsoventrally depressed. Moreover, the only preserved anterior dorsal of Mendozasaurus neguyelap has well
developed prezygoparapophyseal laminae (González Riga 2003), unlike the condition in Barrosasaurus
casamiquelai (MCF-PVPH-447/3), where these lamina are absent.
Compared with Barrosasaurus casamiquelai, Trigonosaurus pricei (Late Cretaceous, Marilia Formation,
Uberaba, Brazil) (MCT-1488-R, holotype; Fig. 8G) has longer posterior dorsal centra. The centrum of the
tenth dorsal of Trigonosaurus pricei (Campos et al. 2005; MCT-1488-R) is nearly 60 % of the total height of
the vertebra, whereas in Barrosasaurus casamiquelai the centrum of the ninth or tenth dorsal (MCF-PVPH-
447/2) is, at most, 36% the height of the whole vertebra (Table 1). Trigonosaurus pricei possesses posterior
dorsals with dorsolaterally projected transverse processes (Campos et al. 2005; MCT-1488-R), unlike the
laterally projected transverse processes of Barrosasaurus casamiquelai. Finally, the base of the neural arch of
the posterior dorsals of Trigonosaurus pricei occupies almost the entire dorsal border of the centrum (Campos
et al. 2005; MCT-1488-R), unlike the condition in Barrosasaurus casamiquelai where the base of the neural
arches is anteroposteriorly short (Fig. 8A, B, G).
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Phylogenetic position. Barrosasaurus casamiquelai displays a combination of characters that confirm its
referral to Camarasauromorpha, Titanosauriformes and Titanosauria, including opithocoelous dorsal centra
(Salgado et al. 1997, character 9, a synapomorphy of Camarasauromorpha; Wilson 2002, character 105,
synapomorphy of Macronaria), middle and posterior dorsal neural arches that lack fossa between the neural
canal and prezygapophyses (Curry Rogers 2005, character 173, synapomorphy of Titanosauriformes), eye-
shaped pleurocoels in dorsal vertebrae (Salgado et al. 1997, character 20, synapomorphy of Titanosauria;
Upchurch et al. 2004, synapomorphy of Camarasauromorpha), presence of an accessory posterior
centrodiapophyseal lamina in dorsal vertebrae (modified from Salgado et al. 1997, character 21,
synapomorphy of Titanosauria), and absence of hyposphene-hypantrum articulations in dorsal vertebrae
(Salgado et al. 1997, character 25, synapomorphy of “Titanosauridae”; Wilson 2002, character 106,
synapomorphy of Titanosauria).
The phylogenetic relationships of Titanosauria have been analyzed in recent years by Wilson (2002),
Upchurch et al. (2004), Curry Rogers (2005), and Calvo et al. (2007), among others. Divergent results are
recovered by these analyses; however, some taxa, for instance Saltasaurini, are commonly better supported
than others. It is not possible to score any of the diagnostic characters proposed for Saltasaurini by Calvo et al.
(2007, their characters 14, 19, 20, 35, 40) for Barrosasaurus casamiquelai. Barrosasaurus casamiquelai bears
two well-developed spinodiapophyseal laminae, the anterior and posterior spinodiapophyseal laminae, which
are also present in some basal titanosaurs, such as Epachthosaurus sciuttoi (UNPSJB-Pv-920), as well as the
accessory or relictual spinoprezygapophyseal lamina, present in Epachthosaurus sciuttoi (Martínez et al.
2004) and Uberabatitan ribeiroi, but absent in Saltasaurini and Trigonosaurus pricei (Campos et al. 2005).
In summary, the exact relationships of Barrosasaurus casamiquelai are yet to be established, but the presence
of unique features allows not only the recognition of a new taxon, increasing our knowledge of the diversity of
Titanosauria during the Late Cretaceous, but also, given the wealth of new taxa described recently (e.g.
Apesteguía 2004; Calvo et al. 2007; Filippi & Garrido 2008), emphasizes the need to revisit titanosaurian
phylogeny.
Acknowledgments
We thank A. Arcucci, J. Porfiri and C. Verali for assistance with fieldwork, and A. Garrido for finding the
specimen and providing geological data. Thanks to the principal of School # 291 of Sierra Barrosa, Prof.
Dardo Domínguez, and to the teachers and pupil of the school, for their hospitality during our field-work. A.
Geréz (MCF) prepared all illustrations except figures 2 and 6. We thank the referees Philip Mannion and Mike
D’Emic, and the editors, especially Richard Butler, who provided very useful comments for improving the
manuscript. We thank COPELCO Cooperativa Ltd. for their technical support. Fieldwork and research were
funded by the National Geographic Society (CRE grant 6526-99 to R.A.C).
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... Sierra Barrosa, Neuquén Province, Argentina (Fig. 1). Neuquén Group (Upper Cretaceous), Río Colorado Subgroup, Anacleto Formation (lowermiddle Campanian) (Salgado and Coria 2009). Diagnosis Large titanosaur characterized by the following autapomorphies: (1) posterior dorsal vertebrae bearing paired and short spinal laminae, nearly parallel to the prespinal lamina; (2) well-developed anterior spinodiapophyseal laminae in posterior dorsal vertebrae; (3) anterior spinodiapophyseal laminae divided into at least two, and up to three, branches in posteriormost dorsal vertebrae; (4) aliform processes with broad, planar and rugose laterodorsal surfaces; (5) portion of neural spine distal to the aliform process is longer than the portion of the spine that is proximal to the aliform process, at least in the posterior dorsals (Salgado and Coria 2009). ...
... Neuquén Group (Upper Cretaceous), Río Colorado Subgroup, Anacleto Formation (lowermiddle Campanian) (Salgado and Coria 2009). Diagnosis Large titanosaur characterized by the following autapomorphies: (1) posterior dorsal vertebrae bearing paired and short spinal laminae, nearly parallel to the prespinal lamina; (2) well-developed anterior spinodiapophyseal laminae in posterior dorsal vertebrae; (3) anterior spinodiapophyseal laminae divided into at least two, and up to three, branches in posteriormost dorsal vertebrae; (4) aliform processes with broad, planar and rugose laterodorsal surfaces; (5) portion of neural spine distal to the aliform process is longer than the portion of the spine that is proximal to the aliform process, at least in the posterior dorsals (Salgado and Coria 2009). ...
... Although the exact phylogenetic relationships of B. casamiquelai have not yet been established, Salgado and Coria (2009) considered this species as a Titanosauria based on opisthocoelous dorsal centra, middle and posterior dorsal neural arches that lack fossa between the neural canal and prezygapophyses, eye-shaped pleurocoels in dorsal vertebrae, presence of an accessory posterior centrodiapophyseal lamina in dorsal vertebrae, and absence of hyposphene-hypantrum articulations in dorsal vertebrae. ...
Chapter
Titanosaurian sauropods were the most diverse and successful group of large-bodied terrestrial herbivores. Two aspects regarding their evolutionary history stand out, namely their great morphological diversity and their extensive record from various continental masses. In South America, and particularly in Argentina, the group has the richest record worldwide. This is mainly due to the conjunction of two factors: the extensive paleontological investigation carried out by South American researchers since the beginning of the twentieth century and the well-exposed outcrops of Cretaceous continental strata. With the exception of Tapuiasaurus from Brazil, the entire record of South American named titanosaurs discovered in the Berriasian–Santonian interval comes from Argentina, specifically from Patagonia, including the south of Mendoza, Neuquén, Río Negro, and Chubut Provinces. With a number of 22 valid taxa, the Early and ‘Mid’-Cretaceous titanosaur record of South America includes basally branching (‘basal’) forms (e.g., Andesaurus, Ninjatitan), basal and derived lithostrotians (e.g., Sarmientosaurus, Tapuiasaurus, and Epachthosaurus), and most of the colossosaurs (mainly the giant lognkosaurs Mendozasaurus, Futalognkosaurus, Patagotitan, and Notocolossus). After their origin in the Early Cretaceous, titanosaurians experienced a rapid increase in taxonomic diversity, which is maintained toward the Late Cretaceous. However, during the Berriasian–Santonian interval, the size of titanosaurs reached its climax, representing the largest vertebrate animals ever to inhabit the earth. Some South American titanosaurs from this time have been widely used to define new clades (e.g., Colossosauria, Lognkosauria, Rinconsauria) that clarified the main phylogenetic relationships at lower level. Moreover, studies in some key paleobiological aspects related with the estimation of size contributed to better understanding the biology of some species in the context of the process of gigantism.
... Aeolosaurus maximus (Santucci and Arruda-Campos 2011); Katepensaurus goicoecheai (Ibiricu et al. 2013); Choconsaurus baileywillisi (Simón et al. 2017); Zapalasaurus bonapartei (Salgado et al. 2006); Agustinia ligabuei. Bonaparte (1999b); Nullotitan glaciaris (Novas et al. 2019); Atacamatitan chilensis (Kellner et al. 2011); Punatitan coughlini (Hechenleitner et al. 2020); Limaysaurus tessonei (Calvo and Salgado 1995;Salgado et al. 2004); Quetecsaurus rusconii (González Riga and Ortiz David 2014); Barrosasaurus casamiquelai (Salgado and Coria 2009); Maxakalisaurus topai (Kellner et al. 2006); Adamantisaurus mezzalirai (Santucci and Bertini 2006); Baurutitan britoi ; Aeolosaurus rionegrinus rionegrinus (Powell 1987); Aeolosaurus colhuehuapensis (Casal et al. 2007); Andesaurus delgadoi (Calvo and Bonaparte 1991); Triunfosaurus leonardii (Carvalho et al. 2017); Pellegrinisaurus powelli (Salgado 1996); Cathartesaura anaerobica (Gallina and Apesteguía 2005); Padillasaurus leivaensis (Carballido et al. 2015); Baalsaurus mansillai (Calvo and González Riga 2018); Nopcsaspondylus alarconensis (Apesteguía 2007). Antarctosaurus wichmanianus (Huene 1929). ...
Chapter
Most taphonomy studies of South American sauropodomorphs have addressed extrinsic factors such as sedimentary environments, bone dispersal, and mineralogical processes that occurred during fossil diagenesis. These studies provide important data on the taphonomic modes which are associated with bone accumulations in different paleoenvironmental contexts. However, these analyses have generally not considered intrinsic factors like the shape, size, and structural integrity of the skeletal elements, variables that can produce some taphonomic bias. Sauropodomorphs include dinosaurs of highly varied sizes, ranging from small (less than 8 m long) to remarkably giant forms (around 30 m long). In the largest sauropods, such as the huge titanosaurs, very incomplete skeletons are commonly found and most notably skull and articulated pedes rarely are preserved. We focus here on some intrinsic anatomical factors as they relate to articulation in some key parts of the skeletons. Further, this study suggests that the preservation of fragile portions of sauropodomorph skeletons was possible only under specific combinations of sedimentological and biological processes.
... The trackmaker of Teratopodus could be some of any of the species recorded in Anacleto Formation, such as Antarctosaurus wichmanianus (Huene, 1929), Barrosasaurus casamiquelai (Salgado and Coria, 2009), Laplatasaurus araukanicus (Huene, 1929), Narambuenatitan palomoi (Filippi et al., 2011), Neuquensaurus australis (Powell, 1986), Overosaurus paradasorum (Coria et al., 2013); Pitekunsaurus macayai (Filippi and Garrido, 2008), and Rinconsaurus caudamirus (Calvo and Gonz alez Riga, 2003). ...
Article
A new titanosaur sauropod ichnotaxon named Teratopodus malarguensis gen. et sp. nov is erected based on a unique association of 10 characters. It is represented by new tracks discovered in the upper section of the Anacleto Formation outcropping in the southern Mendoza Province (middle Campanian, Neuquén Basin). Teratopodus diagnosis includes pes tracks with suboval shaped, with a slightly obtuse ‘V-shaped’ heel and three large claws impressions laterally deflected corresponding to the digits I, II and III; and symmetrical kidney-shaped manus tracks with a slightly concave posterior border. Teratopodus has a medium-gauge trackway and a medium degree of heteropody (∼1/3). In addition, a new characterization of the heels impressions in sauropod tracks is proposed here including the postero-latero-medial angle (PLM°); according to this, Teratopodus pes track can be classified into slightly ‘V-shaped’ heel (PLM° = 95°–100°). The trackmakers are two titanosaurs specimens of relatively small-medium sized of ca. 11 m and 14 m length. These tracks are preserved in a poorly drained floodplain deposits with ephemeral channels controlled by flash flood episodes. In this context, the trackmakers walked from a humid ground to a more flooded one, leaving behind one of the best-preserved pes tracks ever recorded in South America.
... The fossil-bearing level belongs to the Campanian Anacleto Formation (Neuquén Group, Rio Colorado Subgroup) (Hugo and Leanza, 1999;Dingus et al., 2000), and consisting of a 1.5-2 m thick layer of grey-green clayey sandstone (Finotti and Landini, 2009;Finotti et al., 2013;Gianechini et al., 2015). This litostratigraphic unit has yielded ichnofossils and a rich amount of vertebrate fossils, among them several dinosaur taxa that include the sauropods Antarctosaurus wichmannianus (von Huene, 1929), Barrosasaurus casamiquelai (Salgado and Coria, 2009), Narambuenatitan palomoi (Filippi et al., 2011), Neuquensaurus australis (Lydekker, 1893;Salgado et al., 2005;D'Emic and Wilson, 2011), Pellegrinisaurus powelli (Salgado, 1996), Pitekunsaurus macayai (Filippi and Garrido, 2008), and Laplatasaurus araukanicus (von Huene, 1929;Gallina and Otero, 2015); the theropods Aerosteon riocoloradensis (Sereno et al., 2008) and Aucasaurus garridoi (Coria et al., 2002), the ornithopod Gasparinisaura cincosaltensis (Coria and Salgado, 1996), and sauropod nests (Chiappe et al., 1998(Chiappe et al., , 2001(Chiappe et al., , 2001Chiappe and Coria, 2004). Gianechini et al. (2015) mentioned the presence of sauropod remains in the same quarry of MPCN-PV-69, which could be identified as Laplatasaurus araukanicus (von Huene, 1929) or Bonitasaura salgadoi (Apesteguía, 2004). ...
Article
Abelisauridae is a theropod clade with a wide distribution in the Late Cretaceous of Gondwana. Some of the best preserved abelisaurid specimens were recovered from Patagonia (Argentina) such as Skorpiovenator, Ilokelesia, Carnotaurus and Aucasaurus. Here we describe a dorsal part of a neural spine; a middle caudal vertebra; a distal part of a left metatarsal IV; a complete right phalanx IV-1; left phalanges IV-1, 2 and 3; and a pedal ungual phalanx. These materials were recovered from the same quarry of a recently published indeterminate abelisaurid specimen (MPCN-PV-69). The most distinctive characters are a triangular shape of the distal end of metatarsal IV (present in other abelisauroids); phalanx IV-1 with the proximal surface dorsoventrally tall and the ventral surface wider than the dorsal one causing a medial tilting of bone (set of features considered autapomorphic in Velocisaurus, although is also present in different abelisaurids); phalanx IV-1 and 2 with a ridge which spans from the proximodorsal projection, splits in two branch and surrounds a laterally displaced and obliquely oriented oval hyperextensor pit; a pedal ungual phalanx with two medial and lateral vascular grooves, and lacking a flexor tubercle (abelisauroids synapomorphies). The mentioned feature of phalanges IV-1 and 2 is only found among abelisaurids and is here considered as a possible new synapomorphy of Abelisauridae. Thus, besides they constitute new abelisaurid remains from Patagonia, the new materials provide valuable morphological data that could expand the diagnosis of Abelisauridae.
... There are anterior and posterior spinodiapophyseal laminae (aspdl and pspdl) crossing the lateral surface of the neural spine (Figs. 6 and 7) and delimit an interlaminar fossa that we propose to be named spdl-f, Fig. 7D. These two laminae are present in the dicraeosaurid Brachytrachelopan and in titanosaurians (González Riga, 2003;Martínez et al., 2004;Rauhut et al., 2005;Salgado & Coria, 2009;Salgado & Powell, 2010). The right aspdl and pspdl laminae are in contact with one another by means of an accessory lamina that divides the fossa situated between the two spinodiapophyseal laminae (spdl), (Figs. ...
Article
Full-text available
The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian–early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian–early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event.
... There are anterior and posterior spinodiapophyseal laminae (aspdl and pspdl) crossing the lateral surface of the neural spine (Figs. 6 and 7) and delimit an interlaminar fossa that we propose to be named spdl-f, Fig. 7D. These two laminae are present in the dicraeosaurid Brachytrachelopan and in titanosaurians (González Riga, 2003;Martínez et al., 2004;Rauhut et al., 2005;Salgado & Coria, 2009;Salgado & Powell, 2010). The right aspdl and pspdl laminae are in contact with one another by means of an accessory lamina that divides the fossa situated between the two spinodiapophyseal laminae (spdl), (Figs. ...
Article
Full-text available
The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian–early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian–early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event.
... In 2001, the Argentinean-Canadian Dinosaur Project team collected fossils on Sierra Barrosa, 30 km northeast of Plaza Huincul, Neuquén Province, Argentina. The rocks of this locality represent the last stratigraphic sequence of Upper Cretaceous beds of the Neuquén Group, and yield a unique association of terrestrial vertebrates including skeletons of turtles, crocodiles, saurischian dinosaurs, mammals and footprints of birds [21][22][23][24]. During the course of that expedition, a partial skeleton of a meat-eating dinosaur was recovered. ...
Article
Full-text available
A skeleton discovered in the Upper Cretaceous Sierra Barrosa Formation (Turonian-Coniacian) of Neuquén Province, Argentina represents a new species of theropod dinosaur related to the long snouted, highly pneumatized Megaraptoridae. The holotype specimen of Murusraptor barrosaensis n.gen et n.sp. (MCF-PVPH-411) includes much of the skull, axial skeleton, pelvis and tibia. Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary. Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp.include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. In spite being immature, it is a larger but more gracile animal than existing specimens of Megaraptor, and is comparable in size with Aerosteon and Orkoraptor. The controversial phylogeny of the Megaraptoridae as members of the Allosauroidea or a clade of Coelurosauria is considered analyzing two alternative data sets.
Article
Rinconsaurus caudamirus, from the Bajo de la Carpa Formation (Santonian), Río Negro, Argentina, is represented by several axial and appendicular elements from, at least, four specimens. The axial skeleton of this taxon was described in detail in a recent contribution, pending a complete analysis and description of its appendicular skeleton. This contribution focuses on the description of the appendicular skeleton of Rinconsaurus and its phylogenetic relationships, considering the new information provided here. Rinconsaurus clearly differs from other titanosaurs for the presence of several autapomorphic characters and for a unique association of characters, some of which are also present in lognkosaurians, aeolosaurines and saltasaurines titanosaurs, and by having a scapula with a scapular blade angled 65° with respect to the coracoid articulation, similar to that of Bellusaurus, Dreadnoughtus and Muyelensaurus. Equations for estimating body mass in sauropods based on long bone circumference suggest a body mass of at least 3-5 tonnes for the largest individuals of Rinconsaurus, being lighter than saltasaurines, but heavier than aeolosaurines. Rinconsaurus was incorporated into an expanded version of a phylogenetic data matrix along with several ontemporary South American titanosaurs. The resulting data matrix comprises 102 taxa scored for 431 characters, and our phylogenetic analysis retrieves Rinconsaurus as a member of the clade Rinconsauria. For its part, the clade Rinconsauria, in which Aeolosaurini is nested, is recovered within a diverse Lognkosauria. When the resulting trees are time calibrated and taking into account the position of Ninjatitan within Rinconsauria, there results that the possible origin of the clades Lognkosauria and Rinconsauria (among other titanosaur clades) could have occurred towards the beginning of the Early Cretaceous.
Article
The record of sauropods in the Upper Cretaceous of Patagonia is rich. However, there are still several blanks on this record. Here it is described a new sauropod assemblage coming from the Salitral Ojo de Agua Area, Río Negro province, northern Patagonia, Argentina (Allen Formation; Maastrichtian). Remains of indeterminate saltasaurines, aeolosaurines, as well as new specimens of the small saltasaurine Rocasaurus muniozi and the new eutitanosaur Menucocelsior arriagadai gen. et sp. nov., are described.. The new eutitanosaur is represented by an incomplete caudal series and some appendicular bones that indicate that it does not belong to any previously recognized eutitanosaur clade (e.g, Colossosauria, Saltasaurinae, Aeolosaurini). The co-occurrence of several roughly coeval titanosaurs in a restricted area (as occur in Bajo de Santa Rosa, Salitral Moreno and Salitral Ojo de Agua sites) with different body plans, indicates that they probably occupied particular ecological niches and that probably competition for resources was limited, allowing the connivance of several taxa in a single locality and age. This pattern is not observed in other sites of the world. Based on these records and on the high diversity of osteoderm morphotypes recovered, it appears to be certain that palaeoecological conditions in the area were able to sustain and promote the flourishing of many species of titanosaurs.
Article
Titanosaurs are the most common vertebrates found in the Bauru Group deposits. However, their record is rather fragmentary generally not allowing a detailed comparative study. In this contribution new titanosaur remains from Peirópolis (Serra da Galga Member, Marília Formation) are described. An isolated but complete large dorsal vertebra with an interesting combination of characteristics (e.g. mid-posterior dorsal vertebrae with diapopostzygapophyseal laminae; well-developed prespinal lamina with two accessory laminae; centrodiapophyseal laminae not widened ventrally, and a large area for muscular attachment on the dorsal aspect of the diapophyses) is compared with other titanosaurs. Comments regarding left-right asymmetry in this material are also made.
Article
The holotype of Pellegrinisaurus powelli nov. gen. et sp., recovered from levels of Alien Formation at lago Pellegrini (Province of Río Negro, Argentina) is described. Previous reference of this specimen to c. Epachthosaurus sp. is discarded, as it does not share derived features with the holotype of Epachthosaurus sciuttoi Powell. Probable autapomorphies of Pellegrinisaurus powelli are: (1) transverse width of the centrum of the posterior dorsal vertebrae approximately twice the maximum dorsoventral depth, and (2) mid-posterior and posterior caudal vertebrae with anteroposteriorly elongated and dorsoventrally depressed neural spines, the anterior ends of which are higher anteriorly than posteriorly. Pellegrinisaurus powelli is considered a probable sister taxon of the Saltasaurinae on account of low vertebral centra in the medial and posterior caudals, with dorso-ventrally convex lateral faces.