Cathartesaura anaerobica gen. et sp. nov., a new rebbachisaurid (Dinosauria, Sauropoda) from the Huincul Formation (Upper Cretaceous), Río Negro, Argentina

Abstract

A new mid-sized sauropod from 'La Buitrera', Huincul Formation (Turonian-Coniacian), Río Negro Province, Cathartesaura anaerobica gen. et sp. nov. is described. It is known from an incomplete, but associated skeleton that includes diagnostic postcranial elements such as a posterior cervical, an anterior caudal, and a mid caudal vertebra, a left scapula, a left ilium and a right femur. Cathartesaura anaerobica gen. et sp. nov. exhibits several autapomorphies, such as a posterior cervical vertebra with an accessory lamina that arises from the mid length of the prezygodiapophysial lamina and reaches the centrum, a thin, wing-like transverse proc-esses on the anterior caudal vertebrae mostly supported by a ventral bony bar that frames a deep triangular fossa, and each anterior caudal neural spine with the lateral laminae composed of the spinoprezygapophyseal lamina, the lateral spinopostzygapophyseal lamina and the spinodiapophyseal lamina. The new taxon is related to Rebbachisaurus and Limaysaurus because of the presence of several synapomorphies, which support its inclusion in a separate clade of basal Diplodocoidea, the Rebbachisauridae. Aspects of rebbachisaurid vertebral anatomy including musculature and pneumaticity are briefly commented upon. A cladistic analysis is presented in an attempt to partially resolve basal diplodocoid phylogenetic relationships.

Full text

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 153
Rev. Mus. Argentino Cienc. Nat., n.s.
7(2): 153-166, 2005
Buenos Aires, ISSN 1514-5158
Cathartesaura anaerobica gen. et sp. nov., a new rebbachisaurid
(Dinosauria, Sauropoda) from the Huincul Formation
(Upper Cretaceous), Río Negro, Argentina
Pablo A. GALLINA1,3 & Sebastián APESTEGUIA2,3
1Facultad de Ciencias Naturales y Museo- Universidad Nacional de La Plata, 122 y 60, 1900, La Plata,
Argentina. E-mail: paleopol@yahoo.com.ar. 2Museo Argentino de Ciencias Naturales “B. Rivadavia”,
Av. Ángel Gallardo 470, (1405), Buenos Aires, Argentina. E-mail: paleoninja@yahoo.com.ar. 3Departamento
de Ciencias Naturales y Antropología (CEBBAD), Fundación de Historia Natural “Félix de Azara” -
Universidad Maimónides. V. Virasoro 732 (C1405BDB), Buenos Aires, Argentina.
Abstract: A new mid-sized sauropod from ‘La Buitrera’, Huincul Formation (Turonian-Coniacian), Río Negro
Province, Cathartesaura anaerobica gen. et sp. nov. is described. It is known from an incomplete, but associated
skeleton that includes diagnostic postcranial elements such as a posterior cervical, an anterior caudal, and a
mid caudal vertebra, a left scapula, a left ilium and a right femur. Cathartesaura anaerobica gen. et sp. nov.
exhibits several autapomorphies, such as a posterior cervical vertebra with an accessory lamina that arises from
the mid length of the prezygodiapophysial lamina and reaches the centrum, a thin, wing-like transverse proc-
esses on the anterior caudal vertebrae mostly supported by a ventral bony bar that frames a deep triangular
fossa, and each anterior caudal neural spine with the lateral laminae composed of the spinoprezygapophyseal
lamina, the lateral spinopostzygapophyseal lamina and the spinodiapophyseal lamina. The new taxon is related
to Rebbachisaurus and Limaysaurus because of the presence of several synapomorphies, which support its
inclusion in a separate clade of basal Diplodocoidea, the Rebbachisauridae. Aspects of rebbachisaurid vertebral
anatomy including musculature and pneumaticity are briefly commented upon. A cladistic analysis is presented
in an attempt to partially resolve basal diplodocoid phylogenetic relationships.
Key words: Dinosauria, Sauropoda, Rebbachisauridae, Upper Cretaceous, Río Negro, Argentina.
____________
The fossil record of the Cretaceous tetrapod
fauna from Río Negro Province, North Patagonia,
shows a high diversity of forms (Bonaparte, 1996;
Apesteguía, 2002). A good example of this diver-
sity is the locality known as ‘La Buitrera’, in
which the upper member of the Candeleros For-
mation (Cenomanian-Turonian) as well as the
basal member of the Huincul Formation
(Turonian-Coniacian) crop out. This locality has
provided rich faunas that include spheno-
dontians, snakes, araripesuchid crocodyliforms,
theropod and sauropod dinosaurs, mammals, and
ceratodontiform dipnoans (Apesteguía et al.,
2001). A new sauropod from the basal Huincul
Formation of ‘La Buitrera’ is described here. It
belongs to a monophyletic group of basal
Diplodocoidea, known as rebbachisaurids (Bona-
parte, 1997).
The presence of a monophyletic subgroup of
diplodocoids in the Cretaceous of Africa and
South America was first recognized by Bonaparte
(1996, 1997), who coined the family name
Rebbachisauridae for this clade. That name was
subsequently used by several authors (e.g.
Wilson, 1999; Sereno et al., 1999; Pereda-
Suberbiola et al., 2001, 2003; Carvalho et al.,
2003; Harris & Dodson, 2004), without a formal
diagnosis or valid definition until very recently
(Salgado et al., 2004; Upchurch et al., 2004;
Wilson, in press).
This group of moderately sized sauropods
survived until the Upper Cretaceous, sharing
environments with other sauropod lineages such
as basal titanosaurs. They are mostly known from
rather fragmentary remains, and many have not
been described in detail yet. Most specimens re-
main unpublished or are only partially described
(e.g. Nigersaurus taqueti), and only a few, such
as Limaysaurus tessonei (Calvo & Salgado, 1995)
are nearly complete. Therefore, the in-group re-
lationships of the Rebbachisauridae remain un-
clear.
Despite the dorsal vertebra described by
Nopcsa (1902) from Neuquén Province and the
materials from Morocco described by Lavocat
(1954), most materials referred to Rebbachi-

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
154
sauridae were only recognized as such in the last
decade. A growing number of genera were as-
signed to this family, including Rayososaurus
agrioensis Bonaparte 1996, from the Aptian of
Neuquén, Argentina; Rebbachisaurus garasbae
Lavocat 1954, from the Aptian-Albian of Mo-
rocco, Africa; Nigersaurus taqueti Sereno et al.,
1999, from the Aptian-Albian of Niger, Africa;
Rebbachisauridae indet. MPS-RV II Pereda-
Suberbiola et al. 2003, from the Lower Cretaceous
of Spain; and Limaysaurus tessonei (Calvo &
Salgado, 1995) from the Cenomanian of Neuquén,
Argentina.
The fossil record of the group was also ex-
panded by additional undescribed materials from
Cenomanian-Coniacian beds of Chubut Province,
Central Patagonia (Lamanna et al., 2001). Al-
though the higher-level systematic placement of
the group is complex, most authors interpret
them as basal diplodocoids (Calvo & Salgado,
1995; Wilson & Sereno, 1998; Wilson, 2002;
Upchurch et al., 2004). On the other hand, the
in-group relationships are still unclear. Further-
more, the still poor knowledge of their anatomy
invokes the risk of including other species that
were part of the wide radiation experienced by
basal diplocoids between the Late Jurassic and
Early Cretaceous among Rebbachisauridae, thus
rendering them a taxonomic ‘waste-basket’. A
cladistic analysis is presented here as an attempt
to partially resolve their phylogenetic relation-
ships.
Institutional abbrevations. MPCA- Museo
Provincial Carlos Ameghino, Cipolletti, Río Ne-
gro, Argentina. MCF- Museo Carmen Funes,
Plaza Huincul, Neuquén, Argentina. MPS-RV-II:
Museo de Dinosaurios – Paleontología, Salas de
los Infantes, Burgos, Spain. Pv-MOZ: Museo
“Profesor Dr. Juan Olsacher”, Zapala, Neuquén,
Argentina.
SYSTEMATIC PALEONTOLOGY
Saurischia Seeley, 1888
Sauropodomorpha Huene, 1932
Sauropoda Marsh, 1878
Diplodocoidea Upchurch, 1995
Rebbachisauridae Bonaparte, 1997
Cathartesaura gen. nov.
Type species. Cathartesaura anaerobica sp.
nov.
Diagnosis. Mid-sized sauropod dinosaur char-
acterized by the following derived features: pos-
terior cervical vertebra with an accessory lamina
that arises from the middle of the prezygodia-
pophysial lamina and reaches the centrum; thin
wing-like transverse processes of anterior cau-
dal mostly supported by the ventral bar forming
a deep triangular fossa, also framed by the
prezygodiapophyseal and centroprezyga-
pophyseal laminae; anterior caudal neural spine
with the lateral lamina composed of the
spinoprezygapophyseal lamina, the lateral
spinopostzygapophyseal lamina and the
spinodiapophyseal lamina.
Etymology. Cathartes, for the extant vultur
genera abundant in the quarry area; saura
(Greek), fem. lizard, reptile. Additionally, it im-
plies the combination of the generic and specifical
names of those vultures (Cathartes aura
Linnaeus, 1758).
Cathartesaura anaerobica, nov. sp.
Diagnosis. Same as for genus.
Etymology. Fem. for ANAEROBICOS S. A.,
an Argentine company of adhesives that provided
fieldwork and lab support in the extraction and
protection of the fossil materials.
Holotype. MPCA- 232, consisting of the fol-
lowing associated material from one quarry and
presumably from a single specimen: a posterior
cervical vertebra, a dorsal vertebra, an anterior
caudal, a mid caudal vertebra, left scapula, a left?
ilium, and a right femur. A dorsal vertebra, a
humerus and one metatarsal were also collected,
but they are poorly preserved.
Horizon and locality. Sandy to pelitic levels
of the lower section of the Huincul Formation,
regarded as Cenomanian (Leanza & Hugo, 2001)
to Coniacian (Corbella et al., 2004) at ‘La
Buitrera’, 80 km SW of Cipolletti, Río Negro
Province, Argentina (Fig. 1).
Fig. 1. Map showing the “La Buitrera” locality,
Río Negro Province, Northern Patagonia.

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 155
COMPARATIVE DESCRIPTION
Posterior cervical vertebra (Fig. 2A, B).
A complete posterior cervical vertebra (possibly
the eighth or ninth) was recovered. This verte-
bra is twice as tall as it is long. The neural arch
makes up approximately 2/3 of the total height.
The centrum is opisthocoelous, elongate and dor-
soventrally compressed, its length being three
times its height. The cervical system of pneu-
matic cavities consists of two independent and
successive foramina that connect to their respec-
tive internal camerae (Wedel et al., 2000). They
are oval in shape with an oblique long axis, and
are located on the lateral wall of the centrum
occupying at least 3/4 of its length. Both
“pleurocoels” (foramina and camerae) are sepa-
rated by a thin oblique septum (“pleurocentral”
lamina sensu Calvo & Salgado, 1995) that runs
parallel to the posterior centrodiapophyseal
lamina.
The first camera is slightly smaller than the
second and is placed above the parapophysis and
rostral to the level of the diapophysis. In contrast
to the second camera, the first camera is only a
shallow concavity with no internal divisions. The
second and larger camera is more complex, exca-
vating the interior of the centrum up to its pos-
terior end. Actually, this camera is separated from
the concave surface of the posterior articulation
of the centrum by a thin lamina of bone (Fig. 2B).
The neural canal is large with a horizontal
floor, and is developed as a wide arch that occu-
pies most of the neural arch base. In lateral view,
there are four main laminae that converge on the
diapophysis around the middle of the vertebral
length as in Haplocanthosaurus and diplodocoids.
A deep, posterior, and triangular fossa is framed
by the postzygodiapophysial and posterior
centrodiapophysial laminae. The centropostzy-
gapophysial lamina, which narrows upwards,
closes the triangle posteriorly. A similar, but shal-
lower and inverse triangle is framed by the
prezygodiapophysial and anterior centrodia-
pophysial laminae.
Two weaker accessory laminae are visible on
the lateral aspect of the neural arch. The first
connects the postzygodiapophysial and spino-
prezygapophysial laminae at the middle of their
spans (AL1). Originally proposed as an auta-
pomorphy for Limaysaurus tessonei, it certainly
represents a synapomorphy of a more inclusive
group (Gallina et al., 2002). The second acces-
sory lamina arises from the mid-length of the
prezygodiapophysial lamina and reaches the cen-
trum (AL2). It is here considered as an auta-
pomorphy of Cathartesaura. In posterior view,
two weak laminae run parallel to the spino-
postzygapophysial laminae. Their presence in
other rebbachisaurids is unknown.
The neural spine is square in cross-section at
its base, and becomes a thin lamina at the sum-
mit. The spine is obliquely inclined and oriented
forward, its origin being in the posterior half of
the centrum. It is buttressed anteriorly by the
spinoprezygapophysial laminae and posteriorly
by the spinopostzygapophysial laminae. There is
also a lateral column-like, robust lamina that
reaches two cm in width (probably the SPZAL of
Calvo & Salgado, 1995).
Anatomical comments. Most researchers (e.g.
McIntosh, 1990) consider that the system of cavi-
Fig. 2. Cathartesaura anaerobica gen. et sp. nov.
Posterior cervical vertebra. A, right lateral view;
B, detail of the centrum showing internal cavi-
ties. Abbreviations: acdl, anterior centrodiapo-
physeal lamina; al1, accesory lamina 1; al2,
accesory lamina 2; cam, camerae; cpol, centro-
postzygapophyseal lamina; di, diapophysis; ns,
neural spine; pa, parapophysis; pcdl, posterior
centrodiapophyseal lamina; podl, postzygodiapo-
physeal lamina; poz, postzygapophysis; prdl,
prezy-godiapophyseal lamina; prz, prezygapo-
physis; spol, spinopostzygapophyseal lamina;
sprl, spinoprezygapophyseal lamina; spzal,
suprapostzygapophyseal accesory lamina.

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
156
ties in the sauropod axial skeleton is profoundly
associated with the lightening of the skeleton.
Furthermore, Wedel et al. (2000) and Wedel
(2003a, b) proposed that the cavities are the re-
sult of pneumatic invasion by the pulmonary air
sac system. On the other hand, Bonaparte (1999)
suggested that the cavities and laminae in pre-
sacral vertebrae mostly served as attachment for
hyposomatic musculature which, for Wedel &
Sanders (2002), were developed in other anatomi-
cal structures.
In Cathartesaura, the development of tall,
distally widened neural spines, as well as strong
spinopostzygapophyseal and accesory laminae on
their posterior sides, indicates a strong develop-
ment of the epaxial musculature, most probably
the M. longus colli dorsalis, Mm. intercristales,
and Mm. interspinales of birds (see Wedel &
Sander, 2002). This important development of
dorsal structures also avoided an excessive
flexure of the neck. On the other hand, the lack
of the ansa costotransversia (bony bridge formed
by cervical rib + diapophysis + parapophysis) due
to taphonomy, precludes an analysis of the rela-
tive development of the hypaxial musculature.
The pneumaticity of the cervical vertebrae of
Cathartesaura anaerobica is well-developed and
provides an important source of anatomical in-
formation. Based on the morphological types of
Wedel et al. (2000), Cathartesaura bears camerate
vertebrae, with lateral foramina that open into a
large central camera that bifurcates into smaller
camerae as in Limaysaurus and Diplodocus.
Anterior caudal vertebra (Fig. 3A, B, C).
One complete anterior caudal vertebra has been
recovered, probably the second or third of the
caudal series. This vertebra is more than three
times taller than long. The centrum is
amphyplatian and subcircular in shape, with a
length / height ratio of about 1. 5. There is no
sign of pneumatic cavities in the centrum.
The tall neural arch is at least twice the cen-
trum height (a synapomorphy of Diplodocoidea,
reverted in Diplodocidae) as in Haplocan-
thosaurus, Losillasaurus, and the indeterminate
rebbachisaurid MPS-RV II. In the latter, as is the
case in the Titanosauriformes (Salgado et al.,
1997), the neural arch is located toward the an-
terior half of the centrum. Two deep fossae are
located laterally on the most anterior part of the
base of the neural arch. The neural canal is semi-
circular and well defined. The development of the
zygapophyses shows a significant reduction of
both prezygapophysis and postzygapophysis, a
condition also present in Dicraeosaurus,
Amazonsaurus and the isolated rebbachisaurid
neural arch MCF-PVPH-633. Moreover, the re-
duced prezygapophyses fit in narrow slits where
each postzygapophyses are dorsomedially lo-
cated. As in most diplodocoids, the transverse
processes are wing-like, but in Cathartesaura
they are thin laminae of bone mostly supported
by the ventral bar. They border a deep triangu-
lar fossa, also bounded by the diapoprezyga-
pophyseal and centroprezygapophyseal laminae,
which occupies the entire lateral face of the neu-
ral arch, and is here considered an autapomorphy
of Cathartesaura.
The neural spine is S-shaped in lateral view
as in Rebbachisauridae indet. MPS-RV-II, and it
is positioned at the most anterior part of the neu-
ral arch, its base being oriented backwards and
its summit forward. It is composed of the inter-
section of four conspicuous laminae, one each at
the anterior, posterior and lateral sides. These
laminae increase in thickness distally to end in
bulky borders. Both prespinal and postspinal
laminae reach the base of the neural arch.
The lateral lamina arises from the juncture
of three laminae (Fig. 3E): the spinoprezy-
gapophyseal (sprl), the lateral spinopostzy-
gapophyseal (lat. spol.), and the spinodia-
pophyseal laminae (spdl). This multiple juncture
is unique for Cathartesaura, whereas in other
diplodocoids the lateral lamina involves the fu-
sion of the spinodiapophyseal and lateral
spinopostzygapophyseal laminae (e.g., Apato-
saurus louisae, Limaysaurus sp. Pv-6722-MOZ),
or the spinoprezygapophyseal, and spino-
diapophyseal laminae (e.g., Amazonsaurus,
Dicraeosaurus hansemanni, MCF-PVPH-633).
The more conspicuous component to form this
lateral lamina in Amazonsaurus, Dicraeosaurus
hansemanni, and MCF-PVPH-633 is the anterior
one, arising from the prezygapophysis. Con-
versely, in Apatosaurus and Cathartesaura it is
the posterior one. However, whereas the former
originates from a single lamina (lat. spol.), the
latter includes the fusion of two laminae (lat.
spol. + spdl).
Mid caudal vertebra (Fig. 3F). One mid-cau-
dal vertebra has been recovered. The centrum is
amphyplatian and elongate. The lateral sides of
the centrum are concave and the ventral surface
is flat. In anterior view the centrum is triangular
(wide base) as in Limaysaurus and Amazonsaurus.
The neural arch makes up approximately half
the total height and is located at the middle of
the centrum. Neither the prezygapophysis nor
the postzygapophysis exceed the centrum length,
and the prezygapophysis is oriented horizontally.
Transverse processes are not developed. The neu-
ral spine is transversely compressed and directed
posteriorly.

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 157
Scapula (Fig. 4A). A left scapula was col-
lected, but its dorsal edge is poorly preserved. The
bone, 68 cm in length, is considerably expanded
distally, and the minimal width of the post-acro-
mial region reaches only 16 cm. Despite the poor
preservation, it can be said that it was racquet-
shaped as in other rebbachisaurids. The hook-
like acromial process is well defined, as in
Rayososaurus.
In ventral view the shaft exhibits a strong
curvature, developed medially with respect to the
level of the acromion. The glenoid border forms
a low angle with respect to the direction of the
shaft. The scapula-coracoid contact seems to be
rounded.
Ilium. The left ilium was recovered, but re-
mains mostly unprepared. The iliac blade is
slightly concave in lateral view, and the caudal
part is curved outwards. The dorsal edge of the
ilium is convex. The postacetabular process and
the ischial peduncle are poorly preserved. Al-
though incomplete, the pubic peduncle is devel-
Fig. 3. Cathartesaura anaerobica gen. et sp. nov. Caudal vertebrae. Anterior caudal
vertebra in A, right lateral view, B, right posterior detail and C, right anterior
detail. Main components of the lateral lamina in anterior caudal neural spine from
D, Apatosaurus louisae, and E, Cathartesaura anaerobica. F, mid-caudal vertebra
in right lateral view. Abbreviations: cpol, centropostzygapophyseal lamina; cprl,
centroprezigapophyseal lamina; di, diapophysis; fo, fossa; lat.spol, lateral
spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina; ns, neural
spine; posl, postspinal lamina; prsl, prespinal lamina; prz, prezygapophysis; poz,
postzygapophysis; prdl, prezygodiapophyseal lamina; spdl, spinodiapophiseal
lamina; tp, transverse processes.

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
158
oped perpendicular to the blade. This kind of
acetabular orientation is also present in
titanosauriforms and Amanzonsaurus ma-
ranhensis.
Femur (Fig. 4B). A right femur was recov-
ered. This bone is 1, 38 m long, similar in size to
that of Limaysaurus tessonei (1,41m long). This
femur is robust and anteroposteriorly com-
pressed. The distal end is poorly preserved so the
distal condyles are not observable. In posterior
view, the fourth trochanter is located on the up-
per mid-section and is developed as a lateral short
bulge in anterior view; this condition is also ob-
servable in Camarasaurus grandis, Haplocantho-
saurus priscus and Dicraeosaurus hansemanni.
The lateral margin of the femur is straight
and a lateral bulge (as present in titano-
sauriforms, see Salgado et al., 1997) is not devel-
oped.
PHYLOGENETIC RELATIONSHIPS OF
CATHARTESAURA
A cladistic analysis based on 77 characters in
19 taxa (see Appendix) was carried out in order
to clarify the phylogenetic relationships of
Cathartesaura within Sauropoda. The designated
outgroup in the analysis was Patagosaurus
fariasi (Bonaparte, 1979), whereas the ingroup
consisted of Losillasaurus giganteus (Casanovas
et al., 2001); Haplocanthosaurus priscus
(Hatcher, 1903); H. delfsi (McIntosh & Williams,
1988); Camarasaurus grandis (Cope, 1877);
Amargasaurus cazaui (Salgado & Bonaparte,
1991); Dicraeosaurus hansemannii (Janensch,
1914); D. sattleri (Janensch, 1914); Suuwassea
emilieae (Harris & Dodson, 2004); Apatosaurus
louisae (Marsh, 1877); Barosaurus lentus (Marsh,
1890); Diplodocus carnegii (Hatcher, 1901);
Limaysaurus tessonei; Limaysaurus sp. Pv-67/67-
MOZ (Salgado et al., 2004); Nigersaurus taqueti;
Rebbachisaurus garasbae; Rayososaurus agrioen-
sis; Rebbachisauridae indet. MPS-RV II; and
Cathartesaura anaerobica gen. et sp. nov. (this
paper).
Amazonsaurus maranhensis (Carvalho et al.,
2003), Histriasaurus boscariollii (Dalla Vecchia,
1998) and a caudal neural arch MCF-PVPH-633
were considered for comparisons, but were not
included in the cladistic analysis. Rayososaurus
and Limaysaurus are considered as separate gen-
era (contra Calvo & Salgado, 1996; Wilson &
Sereno, 1998). The only bones in common (sca-
pula and femur) are clearly different (Bonaparte,
1997) in morphology, and the taxa are temporally
separated. These distinctions are reflected in the
relative position of both taxa in the results of our
phylogenetic analysis.
Camarasaurus was included as representa-
tive of certain macronarians to avoid the phyloge-
netic problems caused by the recognised conver-
gences between derived macronarians (i.e.,
titanosaurs) and diplodocoids (Upchurch, 1999;
Apesteguía, 2004).
The data matrix was run using the program
NONA, version 2.0 (Goloboff, 1993), and the char-
acter polarity was determined by comparison
with the outgroup. Multi-state characters were
treated as unordered. Five most parsimonious
cladograms were obtained, with relatively high
indices (140 steps, consistency index: 0.66, reten-
tion index: 0.73) (Fig. 5A). The basal nodes 1, 2,
3, 4, and 5 (Neosauropoda, Macronaria, Diplo-
docoidea, Rebbachisauridae and Flagellicaudata)
and the more derived taxa (nodes 6 and 7,
Dicraeosauridae and Diplodocidae) are relatively
well supported. In contrast, the other nodes are
weaker due to missing data.
The cladogram shows some similarities with
previous studies (Wilson, 2002; Harris & Dodson,
2004), although it also shows some novel groups,
which add to our knowledge of rebbachisaurid
evolution and the phylogenetic position of con-
troversial taxa (i.e. Losillasaurus, Haplocantho-
saurus, Suuwassea). The strict consensus cla-
dogram shows an unresolved polytomy at the
base of Rebbachisauridae with the exception of
a node shared by L. tessonei and Nigersaurus
taqueti (Fig. 5C). Rebbachisauridae is here sup-
Fig. 4. Cathartesaura anaerobica gen. et sp. nov.
Pectoral girdle and hind limb. A, left scapula in
lateral view and B, right femur in anterior view.
Abbreviations: ap, acromial processes; fh, femo-
ral head; ft, fourth trochanter; scb, scapular
blade.

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 159
Fig. 5. Phylogenetic relationships of Cathartesaura anaerobica gen. et sp. nov. within Sauropoda. A,
One of the five most parsimonious tree; B, 50% majority-rule consensus tree and C, strict consensus
tree. Nodes: 1-Neosauropoda, 2-Macronaria, 3-Diplodocoidea, 4-Rebbachisauridae, 5-Flagellicaudata,
6-Dicraeosauridae and 7-Diplodocidae.

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
160
ported by six unambiguous synapomorphies:
Presence of a well developed accessory lateral
lamina connecting postzygodiapophyseal and
spinoprezygapophyseal laminae in posterior cer-
vical vertebrae (25.2); presence of anterior cau-
dal neural spines with the lateral border initially
flat but ending in a distally thickened bulky sum-
mit (53.1); wide-based, triangular mid-caudal
centra (60.2); racquet-shaped scapular blade
(63.2); and presence of a hook-like acromion proc-
ess (69.1).
Although the strict consensus of our analysis
retrieves Limaysaurus tessonei and Nigersaurus
taqueti as a monophyletic subclade, there is no
strong support for it.
In our analysis, Diplodocoidea is supported
by twenty unambiguous synapomorphies. The
recently described Suuwasea, considered as a
basal diplodocoid, is here considered a basal
diplodocid. Losillasaurus, which varies widely in
previous analyses from being a basal neosauropod
(Casanovas et al., 2001) to a basal eusauropod
(Harris & Dodson, 2004), is here considered a
basal macronarian or closely related to them.
Additionally, Haplocanthosaurus is again found
to be a paraphyletic taxon (Calvo & Salgado,
1995), but more closely related to basal macro-
narians (as in Wilson & Sereno, 1998; Casanovas
et al., 2001) than to diplodocoids.
DISCUSSION AND CONCLUSIONS
Diplodocoids were globally distributed
sauropods that evolved some lineages restricted
to northern landmasses (diplodocids) and south-
ern landmasses (dicraeosaurids). Their basal
forms, however, show a more ambiguous distri-
bution.
Although several Early Cretaceous dinosaurs
(e.g. basal neosauropods; basal neotetanurans;
basal neoceratosaurians; eurypodans and basal
iguanodontians) show a rather worldwide dis-
tribution since Late Pangean times, the incipi-
ent Laurasian - Gondwanan provincialism initi-
ated during the Late Jurassic (Bonaparte, 1979;
Rauhut, 2002) was certainly more evident by
Early Cretaceous times.
The Rebbachisauridae, abundant during the
Early Cretaceous, show a preferentially Gondwa-
nan distribution. However, recent findings in
Barremian to Aptian rocks of Spain (Pereda
Suberbiola et al., 2003) extend their distribution
northwards. Despite this undoubted presence on
a northern landmass, the paleogeographical re-
lationships between Iberia and Gondwana re-
main too complicated (Scotese et al., 1999;
Vrielynch & Bouysse, 2003; Scotese, 2004) to
depict a paleobiogeographical scenario for
rebbachisaurids. Furthermore, their absence in
the Wealden deposits and all North American
units supports a mostly southern distribution.
The Uppermost Cretaceous strata of the
Gondwanan landmasses are marked by the domi-
nance of abelisaurian theropods and titanosau-
rian sauropods. However, their faunal make-up
is more complicated in the earlier stages of the
Upper Cretaceous.
Southern Neuquén basin is, perhaps, the rich-
est fossiliferous area for Upper Cretaceous con-
tinental tetrapods. Its faunal content was re-
cently characterized in detail by Leanza et al.
(2004), and separated into four recognizable
faunal assemblages, in concordance with their
stratigraphic distribution: Limayan, Neuque-
nian, Coloradoan and Allenian assemblages.
The occurrence of rebbachisaurids in the
early Upper Cretaceous of Patagonia (Limayan
assemblage) is noteworthy, because they repre-
sent the only diplodocoids worldwide recorded
during this interval (Salgado et al., 1991; Calvo
& Salgado, 1995; Calvo & Salgado, 1998; Calvo,
1999; Apesteguía et al., 2001; Gallina et al., 2002).
Furthermore, their absence in rocks younger
than the “Mid” Cretaceous suggested to several
authors the presence of an extinction event that
involved these diplodocoids (Salgado, 2001;
Apesteguía, 2002; Leanza et al., 2004). Salgado
(2001) correlated this event with that responsi-
ble for the complete extinction of the Laurasian
sauropods, and the diversification of the narrow-
crowned titanosaurs, which Gallina et al. (2002)
related directly to the rise of saltasaurine
titanosaurs. Additionally, Apesteguía (2002) cor-
related the diplodocoid extinction to that of
carcharodontosaurid theropods, the rise of
coelurosaurian and abelisaurian theropods, and
the change in dominance from araripesuchid to
notosuchid mesoeucrocodylians, and from chelid
to podocnemidoid turtles. This occurred during
his Gondwanan Evolutionary Stage, between the
Early Gondwanan and the South American Do-
main for tetrapod faunas.
The youngest record of rebbachisaurids is
considered by most authors as those from the
Huincul Formation (Neuquén basin) and the Bajo
Barreal Formation (San Jorge basin). Although
the square-shaped mandible of the Coloradoan
titanosaur Antarctosaurus wichmannianus
(Huene, 1929) suggested some authors to con-
sider diplodocoids as present in Campanian times
(Jacobs et al. 1993; Upchurch 1999; Wilson &
Sereno, 1998), recent findings (Apesteguía, 2004)
demonstrated that titanosaurs also had square
jaws. Therefore, there is no compelling evidence

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 161
to support the presence of rebbachisaurids after
Coniacian times. This is apparently true for
Neuquén, San Jorge and Austral basins, from
North, Central and Southern Patagonia respec-
tively.
Late Cretaceous sauropod lineages are con-
sidered convergent (Salgado & Calvo, 1997;
Wilson, 2002) in their ‘horse-like’ skulls, restric-
tion of the cylindrical, narrow-crowned teeth to
the anterior part of the snout, comb-like denti-
tion (Coria & Chiappe, 2001), square mandibu-
lar symphyses, and nostrils retracted to the top
of the head. Both main lineages (titanosaurs and
rebbachisaurids) are convergent in the loss of
accessory articulations (i.e. hyposphene-
hypantrum complex). This trait would have pro-
vided a higher mobility and greater flexibility to
the vertebral column (Wilson & Carrano, 1999).
In this way, the rebbachisaurid anterior caudal
vertebrae show a marked reduction of the bony
elements related to the intervertebral contact
(zygapophyses), as well as the amphyplatian na-
ture of their vertebral centra. On the other hand,
these anterior caudal vertebrae show well-devel-
oped, wing-like transverse processes and tall neu-
ral spines (at least in Cathartesaura). All these
features together suggest an important develop-
ment of the musculature and elastic ligaments,
related to the pelvic girdle, and to the mid and
posterior caudal vertebrae respectively, the lat-
ter further evolving in relation to “whiplash”
mechanics of flagellicaudate diplodocoids.
The diversity, biogeography and ecological
importance of the Rebbachisauridae in the Late
Cretaceous terrestrial ecosystems is still far from
understood (Gallina et al., 2002). However, the
discovery of a new rebbachisaurid taxon has
broad implications in our comprehension of the
sauropod evolution in the Cretaceous of
Gondwana.
ACKNOWLEDGEMENTS
We thank the Avelás, Salinas and Pincheira
families, C. Muñoz, L. Fernández, and the
ENDEMAS and the Agencia Cultura of Río Ne-
gro for their valuable help in the field. Fieldwork
and specimen preparation was possible thanks
to J. A. and F. González, S. de Valais, A. Haro, A.
M. Forasiepi, M. L. Balarino, F. L. Agnolín, M.
Cárdenas, A. P. Carignano, A. Haluza, L. Gaetano,
S. Reuil, and A. Scanferla. H. Leanza, H. Corbella,
and R. R. Andreis are thanked for their geologi-
cal advice. Fieldwork and study were generously
supported by two projects to Fernando E. Novas,
granted by The National Geographic Society and
the Agencia Nacional de Promoción Científica y
Tecnológica. The Jurassic Foundation and The
Rotary Club granted S.A. projects. L. Salgado, J.
Wilson, José F. Bonaparte and an anonymous
reviewer substantially improved this work with
useful comments and/or critical review. P.
Makovicky improved the English version of the
original manuscript. Juan Canale, “Juje” Haluza,
Pablo Chiarelli and Federico Agnolín offered rich
discussions, and Jorge A. González made skillful
drawings.
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Recibido: 24-I-2005
Aceptado: 06-X-2005

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
164
APPENDIX II
List of Characters
1. Longitudinal grooves on lingual aspect of teeth. Wilson, 2002 (76): 0. absent; 1. present (weakly developed).
2. Number of replacement teeth per alveolus. Wilson, 2002 (74): 0. two or fewer; 1. more than four.
3. Occlusal pattern. Wilson, 2002 (68): 0. interlocking, V-shaped facets; 1. high-angled planar facets; 2. low
angled planar facets.
4. Tooth shape: 0. broad-crowned teeth; 1. slender cylindrical pencil-like teeth at about 10 mm in diameter; 2.
slender compressed wire-like teeth at about 5 mm in diameter.
5. Shape of anterior portion of tooth row. Modified from Wilson, 2002 (65): 0. V-shaped or U-shaped; 1. rectangu-
lar, tooth-bearing portion of jaw perpendicular to jaw rami.
6. Tooth row length. Modified from Wilson, 2002 (66): 0. extending to subnarial foramen; 1. restricted anterior
to subnarial foramen; 2. restricted anterior and laterally extended beyond the rami level.
7. Shape of the premaxillary anterior margin. Modified from Wilson, 2002 (2): 0. with marked step , skull sharply
demarcated; 1. without step.
8. Shape of the anteroventral margin of the dentary. Wilson, 2002 (56): 0. gently rounded; 1. sharply projecting
triangular process or “chin”.
9. Parietal contribution to post-temporal fenestra. Wilson, 2002 (22): 0. present; 1. absent.
10. Anteroposterior length of frontal. Modified from Wilson, 2002 (20): 0. less than the minimum transverse
breadth; 1. approximately twice the minimum transverse breadth.
11. Midline contact of frontals. Wilson, 2002 (19): 0. sutured; 1. fused in adult individuals.
12. Angle of divergence of the basipterygoid processes. Wilson, 2002 (47): 0. approximately 45°; 1. less than 30°.
13. Breadth of the basal tubera. Wilson, 2002 (49): 0. much broader than occipital condyle; 1. narrower than
occipital condyle.
14. Size of the crista prootica. Wilson, 2002 (45): 0. rudimentary; 1. expanded laterally into dorsolateral proc-
esses.
15. Position of the external nares in dorsal view. Modified from Wilson, 2002 (8): 0. retracted to level of orbits; 1.
retracted to a position between the orbits.
16. Maximum diameter of the antorbital fenestra. Wilson, 2002 (6): 0. much shorter than orbital maximum
diameter; 1. subequal to orbital maximum diameter.
17. Contribution to antorbital fenestra of jugal. Wilson, 2002 (13): 0. very reduced or absent; 1. large, bordering
approximately one-third its perimeter.
18. Anteroposterior length of ventral margin of the orbit. Modified from Wilson, 2002 (10): 0. reduced, with
acute orbital margin; 1. broad, with subcircular orbital margin.
19. Posterior process of postorbital. Wilson, 2002 (17): 0. present; 1. absent.
20. Supratemporal fenestra. Wilson, 2002 (25): 0. present; 1. absent.
21. Postparietal foramen. Wilson, 2002 (23): 0. absent; 1. present.
22. Shape of the presacral neural spines. Modified from Wilson, 2002 (89): 0. single; 1. bifid.
APPENDIX I
Data Matrix
Patagosaurus 0?000??0?? ????0???0? ?0?00-0010 ??1001100- 0-00000?00 00000????0 00?0000000 0011000
Losillasaurus ?????????? ?????????? ?0??00?01? ??000200?? ?0000?0?10 ?10-011300 ?????????? ??11???
H.priscus ?????????? ?????????? ?01010?020 1000?2?0?1 0000000000 010-000300 ?????????? ??00???
H.delfsi ?????????? ??0?????0? ?000010?20 10000200?? 00??000000 1?0-000001 1100011001 10?0???
Camarasaurus 0000000000 0000000000 0100000020 0000000000 0000000000 0100000000 111000000? 1000010
Amargasaurus 0?11?????0 1111????00 11001-0?01 ?110001122 0-1011??00 0000?????0 000??????0 ????00?
D.hansemanii 0?21111110 1111????00 1100000101 1010111102 1-10111000 0200111000 100??????0 0112?11
D.sattleri ?????????? ?????????? ?1??0-??01 ??10?1?102 1-?011???? ?-???????? ?????????? ???????
Suuwassea 00??0?1??? 00?0???0?0 11?1000?20 1?0??1?0?2 10?0?????0 0????????? ??0110110? ??????1
Apatosaurus ??21111?10 0000111000 ?111000??0 1100111012 0000011000 0001111110 0000011000 01111?1
Barosaurus ?????????? ?????????? ?1??001120 1100?110?1 00000?1110 100-011111 ?0???????? ??11???
Diplodocus 0121111110 0000111000 0111001120 11001110?2 0000011110 1000111111 000111110? 0112101
L. tessonei 1??2????11 0000???111 0000210?21 ?0100211?1 ?0?11?1000 0010101002 0121100211 1010?10
Nigersaurus 11121210?1 0?000??111 ?0????0??? 1?1??????? ?????????? ?-???????? ??21?001?? ???????
Rebbachisaurus 0????????? ?????????? ?0???????? ??110211?1 11111????? ?-???1???? ??2110011? 10?????
Rayososaurus ?????????? ?????????? ?????????? ?????????? ?????????? ?-???????? ??2110012? ????00?
Cathartesaura ?????????? ?????????? ?0?021?121 ?????????? ????1?1?00 0211111202 0?21100221 ?????10
Pv6718/67-MOZ ?????????? ?????????? ?0???????? ??01?????1 ?1?1?????1 0?1??0???2 ?1???????? ??10???
MPS-RV-II ?????????? ?????????? ?????????? ?????????? ??????1?01 0210101201 01???????? ????01?

Gallina & Apesteguia: Upper Cretaceous rebbachisaurid from Northern Patagonia 165
23. Number of cervical vertebrae. Modified from Wilson, 2002 (80): 0. 13 or fewer; 1. 15 or greater.
24. Shape of the centroprezygapophyseal lamina (cprl) in middle and posterior cervical vertebrae. Wilson, 2002
(88): 0. single; 1. divided.
25. Accessory lateral lamina connecting postzygodiapophyseal and spinoprezygapophyseal laminae in posterior
cervical vertebrae: 0. absent; 1. poorly developed; 2. present and well developed.
26. pneumatization of posterior cervical centra: 0. extended to the anterior half of the centrum; 1. extended to
the posterior half of the centrum.
27. Anteroposterior length/height of the posterior face, in mid-cervical centra. Wilson, 2002 (86): 0. 2.5-3.0; 1. >4.
28. Ventral surface of each cervical centrum. Casanovas et al., 2001 (4): 0. flat or lightly convex transversely; 1.
transversely concave.
29. Lateral surfaces of the cervical centra. Casanovas et al., 2001 (7): 0. lacking lateral excavations or with only
very weak depressions; 1. deeply excavated but without an oblique accessory lamina; 2. possessing a deep
excavation that is divided into cranial and caudal portions by oblique accessory lamina.
30. Cervical neural spine. Casanovas et al., 2001 (10): 0. low (the height of the vertebra does not exceed the
length of the centrum); 1. high (the height of the vertebra is at least 1.5 times the lenght of the centrum).
31. Length of the cervical ribs. Wilson, 2002 (140): 0. much longer than centrum, overlapping as many as three
subsequent vertebrae; 1. shorter than centrum, little or no overlap.
32. Number of dorsal vertebrae. Modified from Wilson, 2002 (91): 0. 11 or greater; 1. 10 or fewer.
33. Dorsal pleurocoels. Modified from Wilson, 2002 (78): 0. present; 1. absent.
34. Hyposphene-hypantrum articulation in dorsal vertebrae. Wilson, 2002 (106): 0. present; 1. absent.
35. Shape of the centropostzygapophyseal lamina (cpol), in middle and posterior dorsal vertebrae. Wilson, 2002
(95): 0. single; 1. divided.
36. Height of the neural arch pillars until the prezygapophyses in respect to the centrum height in middle and
posterior dorsal vertebrae: 0. low, lesser than the centrum height; 1. mid-sized, about the centrum height; 2.
tall, at least 1.5 times the centrum height.
37. Shape of middle and posterior dorsal neural spines. Modified from Wilson, 2002 (102): 0. flared distally, with
pendant , triangular lateral processes; 1. tapering or not flaring distally.
38. Length of dorsal neural spines. Wilson, 2002 (93): 0. approximately twice centrum length; 1. approximately
four times centrum length.
39. Orientation of the tuberculum in mid dorsal ribs: 0. spreading outside from rib shaft; 1. following straight
direction of rib shaft; 2. following medial bent of rib shaft.
40. Anterior axial lamina (sprl+prsl) in posterior dorsal vertebrae. Modified from Salgado et al., 2004 (34): 0.
absent, there are two independent and non-coalescent anterior laminae; 1. incompletely fused, both lami-
nae are individualized but form a double central structure; 2. present, the prespinal laminae is single and
well developed.
41. Well developed deep triangular cavity formed between centrodiapophyseal, centroprezygapophyseal and
prezygodiapophyseal laminae in posterior dorsal vertebrae: 0. absent; 1. present.
42. Pleurocoel size on posterior dorsal vertebrae: 0. small, occupying about one quarter to one third of the
centrum; 1. large, occupying almost all the upper half of the centrum.
43. Spinopostzygapophyseal laminae join the postspinal lamina over the diapophysis origin level in dorsal verte-
brae: 0. absent; 1. present.
44. Medial spinopostzygapophyseal lamina (sensu Salgado et al., 2004) in posterior dorsal vertebrae: 0. absent;
1. present.
45. Shape of posterior dorsal and anterior caudal neural spines. Modified from Wilson, 2002 (107): 0. rectangu-
lar through most of length; 1. “petal” shaped, expanding transversely through 75% of its length and then
tapering.
46. Length of the sacral neural spines. Wilson, 2002 (111): 0. approximately twice length of the centrum; 1. or
four times length of centrum.
47. “Dorsalization” of the neural spines of the proximal caudals. Casanovas et al., 2001 (35): 0. absent (spines ar
simple, laterally compressed, and lack laminae); 1. present (spines very similar to those of the dorsal verte-
brae).
48. Length of anterior caudal centra. Wilson, 2002 (120): 0. approximately the same over the first 20 vertebrae;
1. or doubling over the first 20 vertebrae.
49. Shape of the articular face of anterior caudal vertebrae. Modified from Wilson, 2002 (118): 0. flat; 1. procoelus.
50. Shape of the posterior articular face of anterior caudal vertebrae: 0. less or equal to the anterior articular
face; 1. more concave than the anterior articular face (i.e. slightly opisthocoelous).
51. Pneumatopores in anterior caudal centra. Wilson, 2002 (119): 0. absent; 1. present.
52. Lateral shape of the anterior caudal neural spine: 0. straight; 1. scimitar-shaped; 2. S-shaped.
53. Lateral lamina of the neural spine on anterior caudal vertebrae showing thick external borders: 0. absent; 1.
present.
54. Prespinal lamina of the neural spine on anterior caudal vertebrae with a thickened anterior rim: 0. absent;
1. present.
55. Height of the anterior caudal vertebrae spine: 0. low, subequal to the centrum height; 1. tall, more than 2
times the centrum height.

Revista del Museo Argentino de Ciencias Naturales, n. s. 7 (2), 2005
166
56. Shape of the anterior caudal transverse processes. Wilson, 2002 (128): 0. triangular distally; 1. “wing-like”,
not tapering distally.
57. Relative development of the ventral and dorsal components of the anterior caudal transverse processes.
Salgado et al., 2004 (42): 0. dorsal component poor; 1. well developed.
58. Components of the lateral marginal lamina in anterior caudal vertebrae neural spine. Modified from Wilson,
2002 (122): 0. only spinoprezygapophyseal. No contact with lateral postzygapophyseal lamina; 1.
spinoprezygapophyseal lamina (sprl) + lateral spinopostzygapophyseal lamina (lat. spol) contact in anterior
caudal vertebrae; 2. lat. spol is the main component of the lateral border of the neural spine; 3. the lateral
lamina of the neural spine in caudal vertebrae is not formed by neither sprl or lat. spol.
59. Shape of the anterior centrodiapophyseal lamina (acdl), in anterior caudal vertebrae. Wilson, 2002 (130): 0.
single; 1. divided.
60. Shape of the mid caudal centra. Modified from Wilson, 2002 (131): 0. cylindrical; 1. quadrangular, flat ventrally
and laterally; 2. triangle-shaped (wide base).
61. Orientation of prezygapophysis in mid caudal vertebrae: 0. horizontal; 1. upward.
62. Chevrons, “crus” bridging dorsal margin of haemal canal. Wilson, 2002 (145): 0. present; 1. absent.
63. Shape of the scapular blade. Wilson, 2002 (152): 0. acromial edge (or posterior process) not expanded; 1.
rounded expansion; 2. racquet-shaped.
64. Acromion dorsal margin of the scapula: 0. curved; 1. straight.
65. Posterior acromial axis of the scapula: 0. subvertical to the scapular diaphysis axis; 1. oblique to the scapular
diaphysis axis.
66. Scapular process located along the ventral margin at the level of the acromion origin: 0. absent; 1. present.
67. Scapular-coracoid articulation: 0. subvertical in respect to long axis of the scapula; 1. oblique.
68. Acromion length: 0. 1/3 or less the scapular length; 1. 1/2 to 1/3 scapular length; 2. approximately 1/2 scapu-
lar length.
69. Hook-like acromion process: 0. absent; 1. present; 2. extended as a finger..
70. Direction of the pubic peduncle relative to the ilium shaft: 0. oblique, and the ilium axis is horizontal; 1.
straight, and the ilium axis is oblique.
71. Shape of ischial shaft. Wilson, 2002 (195): 0. V shaped, nearly 50º; 1. flat, nearly coplanar.
72. Shape of ischial distal shaft. Modified from Wilson, 2002 (194): 0. medial and lateral depths subequal; 1.
depth of ischial shaft increase medially.
73. Relative length of iliac articular surface of pubis. Salgado et al., 2004 (49): 0. shorter than the acetabular
portion of the pubis; 1. longer than the acetabular portion of the pubis.
74. Development of ambiens process of pubis. Modified from Wilson, 2002 (189): 0. small, confluent, not differ-
entiated from the anterior border of the pubis; 1. evident, but not especially developed; 2. prominent, pro-
jecting anteriorly from anterior margin of pubis.
75. Posterior development of femoral tibial condyle in respect to the fibular condyle: 0. well developed; 1. poorly
developed.
76. Position of 4th trochanter in anterior view: 0. not visible (located on the posterior side); 1. visible (located
toward the medial side).
77. Posterolateral projection of metatarsal I distal condyle. Wilson, 2002 (220): 0. absent; 1. present.