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GAlA N° 11, DEZEZEMBRO/DECEMBER 1995, pp. 13-33 (ISSN: O8715424)
REBBACHISAURUS TESSONEI SP. NOV. A NEW
SAUROPODA FROM THE ALBIAN-CENOMANIAN OF
ARGENTINA; NEW EVIDENCE ON THE ORIGIN OF
THE DIPLODOCIDAE
Jorge O. CALVO
Universidad Nacional del Comahue, Museo de Ciencias Naturales. Buenos Aires 1400, (8300) NEUQUÉN. ARGENTINA
Leonardo SALGADO
Universidad Nacional del Comahue, Museo de Ciencias Naturales. Buenos Aires 1400, (8300) NEUQUÉN. ARGENTINA
ABSTRACT: A new species of Albian -Cenomanian sauropods, Rebbachisaurus tessonei sp. nov., is
described. This new taxon is known from at least four specimens. One of them, the holotype is an
almost complete and articulated specimen from the Rio Limay Formation of Northwestern Patagonia,
and the most complete sauropod ever found in South America. Twelve autapomorphies support the
creation of this new taxon. Rebbachisaurus tessonei sp. nov. shares eleven cranial and postcranial
characters to support a close relationship to diplodocids; however, other ten postcranial characters,
which characterize the family Diplodocidae, are not present in R..tessonei sp. nov. Therefore, the eleven
synapomorphies allow the erection of a new lower taxon, Diplodocimorpha to include R. tessonei sp.
nov. as the sister group of Diplodocidae.
RESUMO: Descreve-se una nova espécie de saurópode do AIbiano-Cenomaniano, Rebbachisaurus
tessonei sp. nov., conhecida a partir de, pelo menos, quatro espécimes. Um destes exemplares, o
holótipo, provém da Formação do Rio Limay, no noroeste da Patagónia, e é o mais completo saurópode
encontrado na América do Sul. A definição deste movo táxone é apoiada por doze autopomorfias.
Rebbachisaurus tessonei sp. nov. apresenta onze características cranianas e pós-cranianas que susten-
tan uma proximidade aos diplodocídeos; no entanto, outras dez características pós-cranianas (que
caracterizam a família Diplodocidae) não estão presentes em R. tessonei sp. nov. Consequentemente,
as onze sinapomorfias permitem a formalização de um novo táxone de categoria inferior, Diplodoci-
morpha (que inclui R. tessonei sp. nov.), grupo irmão dos Diplodocidae.
INTRODUCTION
In 1988, during a field trip, of the Museo de Cien-
cias Naturales de la Universidad del Comahue and
the Museo de Ciencias Naturales “Bernardino Ri-
vadavia” of Buenos Aires, an almost complete and
articulated sauropod from the Albian-Cenomaian
beds of the Ezequiel Ramos Mexía lake in Neuquén
Province, Patagonia, Argentina was collected (Fig. 1).
It was briefly reported on by CALVO & BONAPARTE
(1988) and CALVO & SALGADO (1991), but no de-
tailed informtation was given.
Some bones of the new sauropod from Neuquén
resembled those of LAVOCAT (1954) from the
Aptian-Albian of Morocco, Africa. In the first paper
about the Morocco sauropod LAVOCAT (1951) listed
an incomplete scapula, eight vertebrae, a sacrum, and
seven ribs. ln his second paper LAVOCAT (1954)
erected Rebbachisaurus garasbae LAVOCAT describ-
ing the scapula, a mid-dorsal verlebra, the sacrum
and an anterior caudal, there Lavocat adds a
humerus. The species is characterized by the very
broad and racket-shaped blade of the scapula, a
unique character among the Sauropoda (MCINTOSH,
1990a);and very tall neural spine relative to the height
of the centra. The fragmentary nature of this material,
however, has resulted in several hypotheses on the
phylogenetic placement of R. garasbae.
Previous to Lavocat’s description of R. garasbae,
NOPCSA (1902) described and figured a dorsal ver-
tebra from the Neuquén Province, Patagonia, Argen-
tina.It strongly resembles that of R. garasbae and this
new material, based on the morphology of the neural
13 artigos/papers
J.O. CALVO & L. SALGADO
Fig. 1 - Map of Argentina (1) and Neuquén Province (2) detailing the area where Rebbachisaurus tessonei sp. nov. specimens
were collected (3).
spine. He provisionally referred this vertebra to Bo-
thriospondylus LYDEKKER. Later, HATCHER (1903)
found that the morphology of Nopcsa's dorsal verte-
bra is not generically distinguishable from that of
Haplocanthosaurus priscus HATCHER.
The deposits that yielded tile remains of Reb-
bachisaurus tessonei sp. nov. have also produced a di-
verse vertebrate fauna dominated by dinosaurs,
including the sauropod Andesaurus delgadoi (CALVO
& BONAPARTE, 1991), the theropod Giganotosaurus
carolinii (CALVO, 1990; CORIA & SALGADO, 1995),
frogs (BAEZ & CALVO, 1990),undescribed crocodiles,
and a rich dinosaurian ichnofauna (CALVO, 1989,
1991). The paleoenvironment of the Candeleros
Member was represented by a temperate climate with
alternate rainy and dry seasons (CALVO & GAZZERA,
1989). The age of the Rio Limay Formation in this
area of the basin has been interpreted as Albian-
Cenomanian (CALVO, 1991).
We present a detailed description of the new
sauropod and discuss the phylogenetic significance
of this new material. We also discuss the validity of
R. garasbae and the relationship between the
Nopcsa's vertebra, R. garasbae and this new species
in light of the present evidence.
SYSTEMATIC PALEONTOLOGY
DINOSAURIA OWEN
SAUROPODA MARSH
DIPLODOCIMORPHA new taxon
Etymology - Diplodoci, Diplodocus; morpha, with
morphology of Diplodocus.
Included taxa - Rebbachisaurus tessonei sp. nov.,
Diplodocidae, and all descendants of their common
ancestor.
Diagnosis - Sauropods with the following synapo-
morphies. (1) pencil like teeth, (2) anterior extension
of the quadratojugal placed beyond the anterior bor-
der of the orbit, (3) basipterygoid processes directed
forward, (4) quadrate inclined posterodorsally, (5) in-
frateniporal fenestra oval or slit-shaped, (6) narial
opening placed above the orbit, (7) whip-lash tail,
(8) tall neural arch in posterior dorsals being three
times higher than that of the centra, (9) tall neural
arch in caudals; at least 1.5 times higher than that of
the centra, (10) wing-like transverse process in
caudals, (11) humerus/femur ratio less than 0.70.
14
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
Genus Rebbachisaurus LAVOCAT, 1954
Type species - Rebbacisaurus garasbae LAVOCAT,
1954.
Remarks - LAVOCAT (1954) mentioned the differ-
ences of Rebbacisaurus garasbae with respect to
other sauropods, but he did not do an adequate
diagnosis for the genus.
Diagnosis - Paddle-like scapular blade, V-shape
angle between the acromion and the scapular blade,
absence of hyposphene-hypantrum in dorsals, tall
neural arch and, although it is a primitive character,
single neural spine, and parapophysis directed up-
ward at approximately 45°
Rebbachisaurus tessonei sp. nov.
(Fig. 3-17)
Assigned materials - Unnominated dorsal verte-
bra; NOPCSA, 1902: 21, fig. 1-3.
Holotype - MUCPv-205, articulated, well-pre-
served skeleton, including basicranium, disarticu-
lated cervical vertebrae, articulated vertebral column
in posterior dorsals and all caudals. Complete pelvis
and pectoral girdle, nearly complete hind and fore-
limbs lacking a manus. Gastric stones.
Assigned materials - MUCPv-206, a disarticulated
skeleton composed of two posteriors and two ante-
riors cervical vertebrae, and one posterior dorsal ver-
tebra, a sternal plate, four metacarpals, ribs and
gastric stones. MUCPv-153 a partial articulated
skeleton composed by two sacrals, the first six caudals,
pubis and ischium. Unnumbered dorsal vertebra de-
scribed by NOPCSA (1902).
Locality and horizon - Approximately 5 km South-
west of El Chocón locality, Neuquén Province,
Patagonia, Argentina (Fig. 2). Top of the Candeleros
Member (MUCPv-205 and 206) and base of the Huin-
cul Member (MUCPv-153) of the Rio Limay Forma-
tion, Neuquén Group. Albian-Cenomanian, Middle
Cretaceous.
Remains of the new sauropod were found in the
continental deposits of the Candeleros Member of
the Rio Liniay Formation, Neuquén Group (CAZAU
& ULIANA, 1973). The Rio Limay Formation is com-
posed of three Members, the lower one named Can-
deleros, the middle named Huincul and the upper
one named Lisandro (Fig. 2). The Candeleros Mem-
ber, in the southeastern sector of the Neuquén basin,
is represented by thick sequences of siliclastic red
beds. Silstones and fine sandstones are the most com-
mon component of this geological Member.
Diagnosis - Rebbachisaurus tessonei sp. nov. is
diagnosed as a Diplodocimorph sauropod (see
above). Rebbachisaurus tessonei sp. nov. has the fol-
lowing unique derived characters: basipterygoid
processes very thin and short. Posterior process of
the postorbital absent. Elongated anteroposteriorly
articular condyle of the quadrate. Tuberas veiy re-
duced. Paraoccipital processes not distally expanded.
Neural spine in posterior cervicals and dorsals with
an accessory lamina connected the diapopostzygapo-
physeal laminae and the supraprezygapophyseal
laminae. Anterior dorsals with both supraprezygapo-
physeal laminae contacting on the top of the spine.
Transverse process in anterior caudals formed by a
dorsal and ventral bar directed upward different to
R. garasbae that has a true wing-like transverse proc-
ess. Shaft of the pubis oval in cross section.
STRATIGRAPHIC SEQUENCE
OF THE NEUQUÉN GROUP
Age
Group
Formation
Member
Ana-
cleto
Bajo de
la
Plottier
Porte-
zuelo
Lisan-
dro
HuinculCandeleros
Bajada
Colorada
Fm
MUCPv-205 (Typ
e
MUCPV-206
Stratigraphic
position of the
Rebbachisaurus
specimens
Aptian Albian Cenomanian
N E U Q U E N
Allen Fm
RIO COLORAD
O
Campanian
Maastrichtian
Turonian Conician Santonian
MUCPv-153
RIO LIMAY RIO NEUQUEN
Fig. 2 – Scheme of the Neuquén Group sequence to show
the stratigraphic position of the Rebbachisaurus
specimens. MUCPv – Specimen collection number of
Rebbachisaurus tessonei sp. nov. at the Museum of the
University of Comahue-Patagonia, Argentina (data taken
From CAZAU & ULIANA, 1972; ULIANA &
DELLAPÉ, 1981; LEGARRETA & GULISANO, 1989;
BONAPARTE 1991, and CALVO, 1991).
15
J.O. CALVO & L. SALGADO
Etymology - This species is named in honor to Mr.
Lieto Tessone, discoverer of the Holotype.
DESCRIPTION
General remarks - The three specimens of Reb-
bachisaurus tessonei sp. nov. from El Chocón area
(MUCPv-153-205 and 206) are adults. Tue smallest
is MUCPv-153 and the largest is MUCPv-206. For
descriptions we have used the holotype (MUCPv-
205) except where pointed out where we have used
either MUCPv-153 or MUCPv-206.
Skull - The skull is represented by a basicranium
including the following bones: frontal, parietal, lac-
rimal squamosal, postorbital, prefrontal, supraoccipi-
tal, exoccipital, and basioccipital, laterosphenoids,
basisphenoids, basipterygoid processes, prootic, an-
thotic, opisthotic, nasals, quadratojugal, quadrate, ju-
gal. The skull is tall and somewhat elongated. It is
slightly deformed laterally by compression.
Dorsal skull roof - The nasals are poorly pre-
served, and the suture with the frontals is scarcely
visible (Fig. 3). Part of the posterolateral rim of the
nasal opening is present on the left side ; therefore
the narial opening above the orbit as in Diplo-
docidae. The sutural contacts of the prefrontals in-
clude the nasal (not visible), lacrimal and frontal. The
reduced prefrontals have a lenticular shape in dorsal
view, despite the fact that they are displaced ventrally
by postmortem deformation. The external margin in-
volves part of the orbital rim although its contribution
is reduced. In anterior view, the prefrontal overlaps
the lacrimal.
The lacrimals are complete except for its an-
teroventral portion (Fig. 3-4). The dorsal end en-
closes the prefrontal and contacts the poorly
preserved nasal. The lacrimal forms the anterior and
anteroventral rim of the orbit. The distal end of the
lacrimal has been slightly displaced backward by de-
formation. The jugal is poorly preserved, and part of
the anteroventral rim of the orbit could have be-
longed to it. The anterior rim of the lacrimal forms
the posterior margin of the antorbital fenestra.
The prefrontal contacts the nasal, lacrimal and
frontal (Fig.7).The contact with the nasal is obscured
by surface damage. The prefrontal has as a rhomboi-
dal shape in antero dorsal view. The bone has been
Fig. 3 - Rebbachisaurus tessonei sp. nov. Holotype. Skull roof in dorsal view. Abbreviatious: BO - basioccipital, BSD -
basioccipital depression, BTP - basipterygoid process, CP - crista prootica, EO - exoccipital, F - frontal, FM - foramen
magnum,J - jugal, L - lachrimal, LS - laterosphenoid, N - nasal, O - orbit, OS - orbitosphenoid, P - parietal, PF - prefrontal,
PTF - postemporal fenestra, PO - postorbital, PP - paraoocipital prooess, PS - parasphenoid, QJ - quadratojugal, SO –
supraoccipital, SQ -squamosal, STF -supratemporal fenestra, I to XII foramina for exit of nerves. Scale in centimeters.
16
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
Fig.4 - Rebbachisaurus tessonei sp.nov. Holotype.Skull in lateral view.Abbreviations as in Figure 3.Scale in centimeters
little deformed. It participates on the anterodorsal
rim of the orbit. The prefrontal overlaps the lacrimal
and frontal.
The frontals are paired bones as in all sauropods
except dicraeosaurids (Fig. 3). The frontal has a
trapezoidal shape, with the posterior side wider than
the anterior. and the lateral rim longer than the me-
dial rim. The prefrontal and postorbital overlap the
frontal. The frontal-parietal suture is well marked,
and it faces concave posteriorly. As in Amargasaurus
SALDAGO & BONAPARTE(SALGADO & CALVO,1992)
and Dicraeosaurus (JANENSCH, I935-36) the frontal
does not participate in the supratemporal opening
(Fig. 4). There is a marked depression at the contact
of both frontals with both parietals.
The paired parietals join the frontal anteriorly,
the postorbital and the supratemporal fenestra lat-
erally, the squamosal, supraoccipital and paraoccipi-
tal process posteriorly (Fig. 3). The parietal is
relatively wide and it presents a large depression near
its contact with the supraoccipital. The posterolateral
wing of the parietal twist into a vertical plane with
its ventral edge resting in the dorsal margin of the
squamosal (Fig. 4-5). There is no evidence of a me-
dian pineal foramen between the parietals. The su-
pratemporal fenestra is very small, similar to that in
Amargasaurus and Dicraeosaurus. It has a lenticular
shape and it is bordered by the lateral rim of the pa-
rietal and squamosal and the medial border of the
postorbital. The medial rim of the parietal contacts
the paraoccipital process proximally and the
squamosal distally. Between both bones the parietal
participates shortly in the dorsal rim of the postem-
poral fenestra. The postemporal fenestra is elongated
dorsoventrally. It is bordered by the paraoccipital
process internally and the squamosal laterally
(Fig. 5).
The postorbital is slender and curved. It does not
have a posterior process present in all other
sauropods, and it is considered an autapomorphic
character of Rebbachisaurus tessonei sp. nov. (Fig. 4).
The dorsal end contacts with the frontal. On the up-
permost portion of the supratemporal fossa the pa-
rietal shares a narrow contact with the postorbital.
On the ventral part of that fossa the postorbital has
an extensive Contact with the squamosal. The elon-
gated lenticular-shiaped supratemporal fenestra is
bordered by among these three bones. The dorsal
process of the postorbital is wedged between the pa-
rietal and frontal.
The squamosal twist downwardly 90° in such a
way that it is invisible in lateral view(Fig.4).The dorsal
end is fused to the parietal. Below the level of the
occipital condyle the squamosal twists 90°; so that,
the articular surface for the quadrate head faces ven-
trally (Fog. 5). The distal portion of the squamosal
extends widely foward and is fused to the quadra-
tojugal, wich is wide and extends foward. Although
17
J.O. CALVO & L. SALGADO
Fig. 5 - Rebbachisaurus tessonei sp. nov. Holotype. Skull in posteroventral view. Abbreviations as in Figure 3. Scale in
centimeters.
the skull is somewhat deformed, the infratemporal
opening is almost closed, with the squamosal and
quadratojugal very close to the postorbital (Fig. 4).
It is probably an autapomorphic character of Reb-
bachisaurus tessonei sp.nov. Anyway, the reduced slit-
shaped infratemporal opening resembles that oval
shape of Diplodocus MARSH, and it does not resemble
the triangular shape seen in either Camarasaurus
COPE or Brachiosaurus RIGGS.
The right quadrate is well preserved (Fig. 6). Its
triangular shape in lateral view is formed by dorsal,
ventral and anterior processes. The dorsal process has
a relatively slender shaft formed by lateral and medial
laminae, which form a "V' shape in cross section. In a
posterior view a deep fossa is present as that of
Camarasaurus and Brachiosaurus. The head is ex-
panded at the end. Its articulation with the squamosal
is large and triangular in shape. It is a rugose surface
for a muscle attachment. The body of the quadrate
angles anterodorsally in lateral view. The anterior
pterygoid process of the quadrate is a flattened sur-
face. The ventral process that articulates with the ar-
ticular on the lower jaw is longer than the dorsal
process. The articular condyle is four times longer
than wide, and it is expanded antero-posteriorly. We
consider this character an autapomorphy of Reb-
bachisaurus tessonei sp. nov. Although the quadrate
was found disarticulated from the skull, putting the
articular condyle horizontal to allow a normal move-
ment of the lower jaw, the distal end of the quadrate
inclines posterodorsally as in Diplodocus. The move-
ment of the lower jaw was probably fore and aft like
that of Diplodocus (CALVO, 1994a, 1994b).
Braincase - The small quadrangular supraoccipital
resembles those in Amargasaurus and Dicraeosau--
rus, and differ from the large ones present in
Diplodocus, Apatosaurus MARSH, Brachiosaurus and
Camarasaurus (Fig. 5). It contacts with the parietal
dorsally and dorsolaterally and the paraoccipital
process lateroventrally and ventrally.
The exposed contacts of the basioccipital include
the exoccipital and basisphenoid. The basioccipital
forms most of the occipital condyle. It is excluded
from the border of the foramen magnum by having
a medial process of the exoccipitals. The basal tuberas
are poorly developed.
The basisphenoid contacts the basioccipital. In
ventral view, a shallow central depression separates
the basipterygoid processes, which are shorter than
that in Diplodocus, and slender than that in Cama-
rasaurus, and oval in cross section (Fig. 5). In lateral
view, they project anteriorly as in diplodocids. The
parasphenoid contacts posteriorly with the basisphe-
noid. Its cultriform process is transversely compresed
(Fig. 7).
18
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
Fig. 6 - Rebbachisaurus tessonei sp. nov. Holotype. A-B - Rigth quadrate in posterior and lateral view. C - Tooth.
Abreviations: AC -articular condyle, H - head, PF - posterior fossa, PTP - pterygoid process. Scale in centimeters.
Fig. 7 - Rebbachisaurus tessonei sp. nov. Holotype. Skull in anterior view. Abbreviations as in Figure 3. Scale in
centimeters.
19
J.O. CALVO & L. SALGADO
The orbitosphenoids meet anteriorly (Fig. 7).
They overlap posteriorly the frontal and anteriorly
the laterosphenoid. The sutures are clearly seen in
lateral and anterior views. The orbitosphenoids do
not meet dorsally, leaving a large, subtriangular open-
ing from which the olfactory tract emerged as in other
sauropods. The sutural contact between the orbito-
sphenoid and the laterosphenoid is indicated by the
exit of the spinal nerves II and IV (Fig. 4).
Teeth - OnIy a few isolated teeth was preserved
(Fig.6C). The most complete is long, curved and slen-
der having a circular cross section. Another tooth pre-
serves the crown thaI is oval in cross section and it
is slightly compressed. All teeth have unworn crowns
ending in a very thin pencil-like tip. The crown tips
of Diplodocus are broader than those of this speci-
men.
Cervical vertebrae - There are 8 cervical vertebrae
preserved although probably 3 or 4 more vertebrae
could have been present. Anterior cervicals are 1.5
times higlier than long (Fig. 8A); this ratio increases
posteriorly reaching a value 2. The centra are strongly
opisthocoelous. The narrow and single neural spine,
placed in the middle of the centrum, is very tall, at
least 1.5 higher than longer; this high ratio is shared
with Amargasaurus and Dicraeosaurus. This is formed
by four laminae, two suprapostzygapophysials, and
two supraprezygapophysials, similar to those of
Haplocanthosaurus HATCHER. In anterior cervicals
the neural spine is inclined posteriorly as in Amar-
gasaurus while in medium and posterior ones they
are vertically placed (Fig. 8B). The centra bear two
deep oval pleurocentral cavities that extend for half
the length of the centrum. Cervical pleurocoelus are
divided by a thin vertical septum or pleurocentral
lamina. Tlie prezygapophysis are long and directed
dorsally and anteriorly. The oval articular facets are
flat with the longest axis directed anteroposteriorly.
The prezygapophysis are reinforced by supraprezy-
gapophyseal and diapoprezygapophyseal laminae.
An accessory lamina connects the diapopostzygapo-
physeal with the supraprezygapophyseal lamina at the
midway of each one and it is considered as an auta-
pomorphic character of Rebbachisaurus tessonei sp.
nov. (Fig. 8A-B). In posterior cervicals another ac-
cessory lamina is add; it is named a suprapostzygapo-
physeal accessory lamina and connects the
postzygapophysis with the supraprezygapophyseal
lamina at its distal end (Fig. 8B). This another ac-
cessory lamina is also considered an autapomorphic
character of Rebbachisaurus tessonei sp. nov. The cer-
vical ribs have short anterior branch and a longer pos-
terior one. The latter does not reach the posterior
face of the centrum. The postzygapophyses are pre-
served in medium and posterior cervicals, and they
are relatively large. Articular facets are flat directed
ventrally and internally. These articular facets are
connected to the diapophyses by oblique postdiapo-
physial laminae and to the neural spine by su-
prapostzygapophyseal laminae. In the middle of the
length of the infrapostzigapophyseal lamina is born
another lamina that is connected to the neural spine.
The short parapophyses are placed at the middle of
the centrum and in ventral position. In lateral view,
the diapophyses are reinforced by four laminae, two
infradiapophysials and two supradiapophysials.
Dorsal vertebrae - There are 12 dorsal vertebrae
preserved, four of them not complete. They are very
tal. Pleurocentral cavities are present in an dorsals.
The anterior ones have very small pleurocoels
(Fig. 8D). The neural arch is very high bearing long
transverse processes and a single neural spine
(Fig. 8C-D). Anterior dorsals are strongly opistho-
coelous with the centrum compressed latero and dor-
soventrally. The neural arch is taller than that of the
posterior cervicals, like those of Haplocanthosaurus.
The neural canal is large and oval with the longest
axis directed dorsoventrally. The neural arch, below
the beginning of the neural spine is very high, at least
twice as tall as the centrum.This height increases pos-
teriorly. The diapophyses are placed at a lower level
than the zygapophyses. Anterior dorsals lack hypo-
sphene-hypantrum. The prezygapophyses are short
with oval-shaped articular facets inclined axially.
They are placed almost over the diapophysis. They
are separated by a short diapoprezygapophyseal
lamina oriented horizontally. The prezygapophyses
are connected lo the neural spine through a su-
praprezygapophyseal lamina and to the centrum
through a infraprezygapophyseal lamina; therefore,
a long and deep channel is formed between laminae.
Moreover, a preespinal !amina is present in between
two supraprezygapophysial laminae.
The postzygapophyses are placed al a higher level
than the prezygapophyses. The articular facets are
large and oval in shape with the longest axis directed
downward and toward the axial plane. The postzy-
gapophyses are reinforced ventrally by a infrapostzy-
gapophyseal and a diapopostzygapophyseal lamina
(Fig. 8D). Dorsally they are reinforced by a su-
prapostzygapophyseal lamina and the suprapostzy-
gapophyseal accessory lamina already seen in
posterior cervicals. The suprapostzygapophyseal and
infrapostzygapophyseal laminae form a long and
deep channel. The four principal laminae that form
the spine are connected dorsally forming an arc.
Toward the middle dorsals, the postzygapophysis
are in contact with the neural spine and are closer
to each other. In midposterior dorsals they are fused,
as are the suprapostzygapophyseal laminae forming
the postespinal lamina (Fig. 9); This pattern of post-
espinal construction is present also in Apatosaurus
exceisus MARSH. The same occurs with both in-
frapostzigapophiseal laminae but they finally disap-
pear in most medial dorsal.
20
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
Fig. 8 - Rebbachisaurus tessonei sp. nov. Holotype. Cervical and anterior dorsal vertebra. A - Anterior cervical in lateral
view. B - Posterior cervical in lateral view. C, D - Anterior dorsal vertebra in anterior and lateral views. Abbreviations:
AL - accessory lamina, DPZL - diapopostzygapophyseal lamina, NC - Neural canal, P – parapophysis, PL - pleurocoel,
PRZ - prezygapophysis, PZ - postzygapophysis SPRZL - supraprezygapophyseal lamina, SPZAL -
suprapostzygapophyseal accesory lamina, TP - transverse process. Scale in centimeters.
21
J.O. CALVO & L. SALGADO
Fig. 9 - Rebbachisaurus tessonei sp. nov. MUCPv-206.
Mid-posterior dorsal vertebra in posterior view.
Abbreviations: DPZL- diapopostzygapophyseal larnina,
IDL- infradiapophyseal lamina, PL- postespinal larnina,
PZ- postzygapophysis, SDL- supradiapophyseal larnina,
SPZL - suprapostzygapophyseal lamina, TP - transverse
process. Scale in centimeters.
The neural spine of the posterior dorsal vertebrae
is formed by one prespinal, one postespinal and two
relatively wide supradiapophyseal laminae (Fig. 9).
Because the postzygapophyses are almost fused to
the neural arch, each diapopostzygapophyseal lamina
runs to close and parallel to the supradiapophyseal
lamina. Moreover, in posterior dorsals, the centra are
platicoelus as in Haplocanthosaurus, Diplodocidae
and Barapasaurus JAIN et al. The centra are longer
than in anterior dorsals. Pleurocoels are very large
occupying almost the entire Iength of the centrum.
The neural arch is higher than in anterior and medium
dorsals. The height of the neural arch is more than
three times higher than that of the centra in posterior
dorsaís similar to Diplodocidae and Andesaurus
CALVO & BONAPARTE.
Sacral vertebrae - Two small sacral fragments
were found in the holotype; but one complete sacral
centra was found in MUCPv-153 showing both end
amphyplatian.
Caudal vertebrae - Forty articulated caudal ver-
tebrae are preserved in the holotype. The vertebral
centra are platicoelous (Fig. 10B); the most anterior
centra are short and high. Posteriorly, the centrum
decrease in height but increase in length. The lateral
side is slightly concave. The ventral side in anterior
and middle caudals is flat, with a wide longitudinal
groove that disappears in posterior caudals. The most
anterior caudals present robust, short and relatively
wide transverse processes directed upward and for-
ward (Fig. 10A); although no true wing-like processes
are present, the dorsal component of the transverse
process is well developed as in diplodocids. In
MUCPv-153 the most anterior caudals were articu-
lated; the first three showed a perforated transverse
process, that is formed by a dorsal (diapophysis) and
a ventral (parapophysis) bar as in Apatosaurus
(Fig. l0C). This condition differs from that of R.
garasbae in which the transverse processes are typical
wing-like as in Diplodocidae.Therefore, we think that
the ancestral condition for Rebbachisaurus is the pres-
ence of wing-like transverse process. The condition
in R. tessonei sp. nov. is an autapomorphy. The neural
arch in anterior caudals is twice higher than the height
of the centra, as in Dicraeosaurus, and it is born on
the anterior border of the centrum. The neural spine
in these caudals is formed by a prespinal, postespinal
and two lateral laminae (Fig. 10A-B). Each lanima
becomes thicker and slightly wider ending in a bulky
bone. The neural arches in medium and posterior
caudals are placed on the middle of the centrum and
decrease in height (Fig. 11). In anterior view, the cen-
tra has a semilunar shape with the concavity ventrally
placed. The neural spines are triangular in shape be-
coming laterally compressed lacking the lateral lami-
nae present in the anterior ones. The spine extends
backward over the posterior border of the centrum
(Fig. 11A-B). The dorsal border of the spine is straight
in middle caudals (Fig. 11A). The prezygapophysis
are long extending anteriorly over the anterior border
of the centrum. The postzygapophysis are long and
well developed. The middle and posterior caudals
have a very short spine with the dorsal border inclined
foreward (Fig. 10B). The posterior caudal vertebrae
are long and very thin pencil-like (Fig. 1IC-D). The
tail is whip-lash like those in Diplodocus and Baro-
saurus MARSH.
Chevron - The tail is complete and only the an-
terior caudals bear chevrons. Anterior chevrons are
unforked and the proximal ramus are unfused as in
Haplocanthosaurus, brachiosaurids and cama-
rasaurids.
Scapula - Both scapula are preserved (Fig. 12A).
They are long and very wide, rectangular in shapes
with acute corners. Both distal and proximal ends are
22
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
Fig. 10 - Rebbachisaurus tessonei sp. nov. MUCPv-153. Anterior caudal vertebra. A - Fifth caudal vertebra in posterior
view. B - Caudals 1-5 in lateral view. C - Transverse process of caudal 3 in posterior and lateral views. Abbreviations: DB
- dorsal bar, LL – lateral lamina, NC - neural canal, PL - postespinal lamina, PRL - preespinal lamina, TP – transverse
process, VB - ventral bar. Scale in centimeters.
expanded. The former is paddle-like as in Reb-
bachisaurus garasbae and as broad as in Haplocan-
tosaurus priscus in which the maximum wide is three
times wider than the minimun ones. The proximal
end is thick in its contact with the coracoids. In dorsal
view, the scapula is slightly curved. In lateral view, a
ridge born froin its anteromedial border goes to the
posteroinferior border. The acromion is thick, acute
and directed upward.
Coracoid - Both coracoids are preserved
(Fig. 12A). Coracoids have trapezoidal shapes with
a robust glenoid articular surface for the humerus.
The glenoid cavity is thick, and it forms 1/3 of the
socket. The articulation with the scapula is a broad
and relatively long surface. The coracoid foramen is
closed and oval in shape.
Sternal plate - The sternal plate is very bad pre-
served in the holotype, but it is complete in MUCPv-
206. The sternal plate is a semilunar, laminar and thin
bone. The lateral border is concave while the medial
one is convex. This shape is also present in Ti-
tannosauridae, but we consider this character an au-
tapomorphy of Rebbachisaurus tessonei sp. nov.
Humerus – The left humerus and the proximal end
of the rigth one are preserved (Fig. 12B). The
humerus is robust, relatively short (90 cm in length).
The humerus/femur ratio is 0.62. It is less than 0.70
as in Diplodocids. The deltoid crest is placed near
the proxinial end. It is high with rounded corners,
and is inclined with respect to the humeral axis. The
internal tuberosity is well marked. The proximal cor-
ner is straight and slightly convex. The diaphysis is
robust and subcircular in section. The anterior de-
pression of the proximal end is wide and subtriangular
in shape. The distal end is smaller than the proximal
one. The entepicondyle and ectepicondyle are not
well marked.
UIna - Only the left ulna is preserved (Fig. 12C).
The ulna of 66 cm of length is straight and thin. The
robust proximal end is triradiate. The diaphysis is sub-
circular in cross section. The medial face is the widest;
the proximal half is concave forming sharp angles with
the other faces. The antero-lateral face is almost flat.
The distal articulation is thin, and a little expanded
posteriorly. The distal corner is convex with a small
depression in the anterolateral face. The Ulna/tibia
ratio is 0,78.
Radius - The left radius is preserved (Fig. 12 D).
The radius is elongated and it has 69 cm of length;
the diaphysis is straight and oval in cross section. The
expanded distal end is asymmetrical. The ulnar face
is slightly convex. It is marked by a ridge. It begins
on the posterior proximal end and lasts in the middle
of the diaphysis; from there, a bulge occurs in the
23
J.O. CALVO & L. SALGADO
middle of the distaI end of the sane ulnar face. The
proximal articulation is slightly concave and quad-
rangular in shape. The antiulnal face is flat.
Metacarpals - The holotype does not preserve
metacarpals but they are preserved in MUCPv- 206.
Despite that MUCPv-206 is a bigger animal than the
holotype, according to the cervical and dorsal verte-
bra sizes, the metacarpal III? of MUCPv-206 is only
a 30% of the radius length of the holotype. This com-
parative evidence shows that metacarpal II-III - ra-
dius length ratio in the holotype should have been
smaller than 0.45 as in other diplodocids and primitive
sauropods. Four metacarpals are preserved in the
Rebbachisaurus MUCPv-206. They were found dis-
articulated, so that the position of them is uncertain.
Metacarpais II-IV and V are well preserved but
slightly crushed. Metacarpal III is incomplete.
Metacarpal II? is long (20 cm) and much the wid-
est bone of the series, the proximal end is compressed,
Fig. 11 - Rebbachisaurus tessonei sp. nov. Holotype.
Caudal vertebrae. A - Middle caudal. B - Mid-posterior
caudal. C, D - Posterior caudals. Scale in centimeters.
the articular surface is rugose and oval in shape. It
has a notch on the medial side to articulate with meta-
carpal III. The anterior surface is relatively flat and
smooth. The distal end is expanded into a subacumi-
nate process on its infero-mesial margin. The distal
articular surface is rugose, concave latero-mesially.
The posterior surface is convex with a smooth ridge
coming from its upper-rnesial border to the lower-
lateral border. Metacarpal III? (20.5 cm) is the long-
est of the series. It is slender than Mc II. the proximal
portion is incomplete as well as a small portion of
the middle of the shaft. The anterior surface is convex
proximally and flattened distally. The distal articular
surface is wider than the proximal one, and it has a
subcuadrangular shape. The shaft is oval in cross sec-
tion. The posterior surface, not well preserved, has
a ridge in the middle of the medial side. Metacarpal
IV? (19 cm) is shorter than Mc II and III, and more
slender than Mc III. It is greatly constricted internally
making the shaft cross section of subtriangular shape.
The proximal articulation is very broad and subcir-
cular. The anterior view is flat proximally and convex
distally. The posterior view is convex proximally and
strongly convex distally. The distal articulation has a
subcircular shape. The medial border has a ridge in
its proximal half. Metacarpal V? (17 cm) is the
shorter of the series. It is wider than Mc III and more
Fig. 12 - Rebbachisaurus tessonei sp. nov. Holotype.
Pectoral girdle and fore limb. A - left scapulo-coracoid in
lateral view. B - Left humerus in anterior view. C - Left
ulna in lateral view. D - left radius in anterior view Scale
in centimeters.
24
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
robust than Mc II and III. The anterior surface is
convex with a twisted and smooth ridge coming from
its upper-lateral side to the lower-medial side. The
proximal end has a subcuadrangular shape and the
articulation has an oval shape. The posterior
side is smooth and flat. The widest portion is on the
proximal end.
Ilium - The left ilium is not well preserved; it is
short and low (Fig. 13). The ventral border, behind
of the acetabulum, is slightly convex forming a re-
duced preacetabular lamina. The postacetabular
process is also small. The pubic peduncle is wider
mediolaterally than anteroposteriorly. The ischial
peduncle is poorly exposed. The articular surface of
the acetabulum belongs mostly to the ilium, The an-
terior corner of the ilium is directed upward and for-
ward.
Pubis - Both pubes are preserved (Fig. 13). The
pubis is long (98 cm) and straight. The shaft is massive
and rounded in section a character not developed in
any other sauropod. The ischial and pubic peduncle
form an angle of more than 100°. The pubic foramen
is apparently open and oval in shape. The acetabular
surface of the pubis is small. Both the ischial and the
iliac articulation are reduced. The ambiens process
is not present as that of Diplodocus and Apatosaurus.
Ischium - Only the rigth ischium of the holotype
is preserved (Fig. 13-14). The ischium has smaller ar-
eas for articulation with the ilium and pubis; between
them there is a deep and well-marked concavity form-
ing part of the acetabulum. The ischium is long
(94 cm) with the ischionic shaft long and thin occu-
pying approximately the 80% of its length. It takes
the shape of a twisted shaft. The distal end is thin
and narrow; it has almost the same size as the shaft.
Fig. 13 - Rebbachisaurus tessonei sp. nov. Holotype.
Reconstruction of the pelvic girdle in lateral view. Scale in
centimeters.
Fig. 14 - Rebbachisaurus tessonei sp. nov. MUCPv-153. Ischia. A - in lateral view. B - dorsal views. Scale in centimeters.
25
J.O. CALVO & L. SALGADO
Both ischia contact side by side horizontally (articu-
lated in MUCPV-153) as in Brachiosaurus and Haplo-
canthosaurus priscus (Fig. 14). The pubic peduncle is
small but it is bigger than the iliac peduncle. The
proximal region has an apparently reduced ventral
keel (obturator process).
Femur - The complete Ieft femur and the distal
part of the right one are preserved (Fig. 15A). The
femur is robust, straight and long (144 cm). In a pos-
terior view the greater trochanter, placed on the up-
per third portion, is restricted lo a small longitudinal
bulge. Thus, the lateral projection of it is thin showing
sharp corners. In lateral view, the medial condyle is
better developed than the lateral one on the distal
end. The lateral bulge is not prominent. Distal con-
dyles are separated by a deep intercondylar groove.
Thr fourth trochanter is not well preserved, but ap-
pears to be poorly developed, above midlength of the
femur.
Tibia - Both tibiae are preserved (Fig. 15B). The
tibia of Rebbachisaurus tessonei sp. nov. (85 cm in
length) is considerably shorter than the femur. It has
suffered postmortem deformation. The distal end is
more broadly expanded transversely than the proxi-
mal one. The proximal end is much more developed
anteroposteriorly than the distal end. The articular
surface of the tibia is almost flat. The tibia/femur ratio
is 0.55.
Fibula - Both fibulae are preserved (Fig. 15C).
The fibula is much more slender than the tibia and
slightly exeeeds it in length (88 cm). In lateral view
it has a sigmoid shaped. The external face is convex
along its length and above its midlength is a vertically
ovale roughened tubercle for insertion of M. iliofibu-
laris. The internal face is flat except at the proximal
end where it is convex. The proximal end is slightly
expanded antero-posteriorly. The whole bone is flat-
tened transversely.
Astragalus - The left astragalus is partially pre-
served; only the distal end of the tongue is missing.
In proximal view it is triangular; a eoncavity deve-
loped on the posteromedial surface fits into the blunt
knob of the tibia. The convexity developed on the
anteromedial surface receives the concave arca of the
distal end of the tibia. Laterally, the astragalus is con-
cave to receive the expanded projection from the
mesiodistal end of the fibula. The distal surface of
the astragalus is broadly convex.
Metatarsals - Metatarsals are deformed by com-
pression and they were not found articulated. Meta-
tarsals II, IV and V were found in both feet, and
Metatarsal I of the right foot (Fig 16). Metatarsal I
is the shortest and stoutest bone of the series. It is
constricted medially. The proximal end is expanded
anteriorly and transversely. The distal end is ex-
panded anteriorly and compressed transversely. The
Fig. 15 - Rebbachisaurus tessonei sp. nov. Holotype. Hind
limb. A - Left femur in posterior view. B - Rigth tibia in
medial view. C - Left fibula in lateral view. Scale in
centimeters.
Fig. 16 - Rebbachisaurus tessonei sp. nov. Holotype. Rigth metatarsals. A - V. B - IV. C - II. D – I in anterior views. Scale
in centimeters.
26
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
proximal surface is nearly flat. The medial proximal
end is concave anteroposteriorly for articulation of
the Metatarsal II. Metatarsal II is stout and slightly
longer than metatarsal I. The proximal end is wider
than the distal one. A prominent ridge is developed
on the anterior surface from the distal end and ex-
tends diagonally up the middle of the proximal end.
The distal articular end presents a convex articular
surface anteroposteriorly but is concave transversely.
Metatarsal III is missing. Metatarsal IV is longer and
much more slender than Metatarsal II. There is a
prominent carina running dorsoventrally on the pos-
terior side. The proximal articular surface is flat.
Metatarsal V is the longest preserved; it is greatly
expanded proximally and little enlarged distally. The
distal end, in ventral view, has a quadrangular shape.
On the lateral distal end there is a prominent notch.
Both falanges I are preserved; they are short. The
proximal end is broader anteroposteriorly than trans-
versely, and it has an elongated oval curved shape.
In anterior view, falange I has a semilunar shape; both
the proximal and distal condyles have projections
from their posterolateral corners, and a deeply con-
cave rim unites both corners. The medial rim is
strongly convex.
Gastroliths - Gastric stones are rarely associated
to sauropod bones (CALVO 1994a; 1994c). However,
in the Rebbachisaurus tessonei sp. nov. holotype
(MUCPv-205), we have found six gastric stones to-
gether in an abdominal position; two of them were
adhered to the ribs. Five stones weighed from 350 to
375 g, but the other one weighed 850 g. The stones
are igneous rocks, some granties and some quarzitic.
They have rounded and rugose surfaces. The stones
are not highly colored. MUCPv-206 also preserved
six stones in between its ribs and dorsal vertebra they
weighed from 190 to 420 g.
DISCUSSION AND COMPARISONS
The discovery of the nearly complete sauropod
Rebbachisaurus tessonei sp. nov. has forced a recon-
sideration of the phylogenetic relationships of the ge-
nus Rebbachisaurus garasbae. Both R. tessonei sp.nov.
and R. garasbae are contemporary. R. garasbae is
represented by very few bones, which, though incom-
plete allows some comparison witlh the complete R.
tessonei sp. nov. The synapomorphic characters of
both genera are: 1) Broadly expanded scapular blade
with rounded distal rim paddle-like. The scapular
blade in Rebbachisaurus is very broad and racket-like
with the distal rim rounded. The major expansion of
the blade is at a half of its length. In prosauropods
and other diplodocids there are a small expansion
exactly on the distal end, but not in the complete
blade. The widest expansion is seen in HapIocan-
thosaurus (HATCHER, 1903;MCINTOSH & WILLIAMS,
1988) but this is fan-like. In Camarasaurus, and
Brachiosaurus only the third distal end of the scapular
a
blade is expanded, but lesser than that of Reb-
bachisaurus. Therefore, we consider this a sinapomor-
phy character for Rebbachisaurus. 2) V-shape angle
between the acromion and the scapular blade. 3) Ab-
sence of hyposphene-hypantrum in posterior dorsals.
The hyposphene-hypantrum is plesiomorphycally
present In all sauropods except in the most derived
genera of Titanosauridae. We consider this character
a sinapomorphy for Rebbachisaurus. 4) Tall neural
arch and, although it is a primitive character. 5) Single
neural spine. 6) Parapophysis directed upward at ap-
proximately 45°. Up to now only one autapomorphic
character in R. tessonei sp. nov., no true wing-Iike
transverse process in anterior caudals, differences it
from R. garasbae.
MCINTOSH (1990a) also recognized that a dorsal
vertebra described and illustrated by NOPCSA (1902)
resembles that of R. garasbae. Nopcsa's vertebra was
collected in the Alarcon Barda, 80 km southwest of
Neuquén City, Patagonia Argentina. Coincidentally
the type and other specimens described and illus-
trated here as Rebbachisaurus tessonei sp. nov. came
from the same area. Therefore, McIntosh's assign-
ment is certainly correct in including the Nopcsa's
vertebra as Rebbachisaurus, now Rebbachisaurus tes-
sonei sp. nov. Finally one more species of Reb-
bachisaurus was described and illustrated by
LAPPARENT (1960) as Rebbachisaurus tamesnensis.
However, such as MCINTOSH (1990a) recognized,
that species does not belong to Rebbachisaurus, at
least by having the following characters: presence of
spoon shaped teeth, slightly distal expansion of the
ischium and presence of Hyposphene-hypantrum in
dorsal vertebrae. R. tamesnensis is excluded in the
present analysis from belonging to the Diplodocimor-
pha. We believe “R. tamesnensis” is a camarasaurid
such as Lapparent proposed.
Several cranial and postcranial charaeters of Reb-
bachisaurus tessonei sp. nov. are not present in other
sauropods and are regarded here as autapomorphies
(see TABLE I an Appendix for character-state distri-
butions). 1) Basipterygoid processes very thin and
short. In Rebbachisaurus tessonei sp. nov. the short-
ness together with the extreme slenderness of the
basipterygoid processes is not seen in other
Sauropods. In prosauropods, Camarasaurus and
Titanosauridae, they are short but robust; in Diplo-
docus, Apatosaurus, Amargasaurus, and Dicraeosau-
rus they are long and relatively slender, although they
are more robust than in R. tessonei sp. nov. 2) In-
fratemporal fenestra almost closed. The quadratoju-
gal, squamosal, postorbital and jugal form a big
triangular infratemporal opening in Prosauropoda,
Camarasaurus, Brachiosaurus and Titanosauridae
(CALVO, 1994a, 1994b). It is oval and anteroposteri-
orly elongated in Diplodocus and Apatosaurus and
more reduced in Amargasaurus and Dicraeosaurus.
In R. tessonei sp. nov. the infratemporal fenestra is
27
J.O. CALVO & L. SALGADO
TABLE I
Character and taxon matrix.
CHARACTER
TAXON
5 10 15 20 25 30 35 40 45 49
PROSAUROPODA 00000 00000 00000 00000 ?0?00 ???00 00?00 00000 00000 0000
Barapasaurus tagorei ?00?? ????? ????0 00000 00?00 00000 ?0??? ????0 00000 ?0?0
Omeisaurus 00000 00000 00001 00000 01001 00000 00000 01000 00010 100?
Camarasaurus 00100 00000 00001 01010 01001 00000 00010 00100 10010 1001
Brachiosaurus 01100 00000 0?011 0000? ?1?01 11000 00011 00101 10110 1101
Andesaurus delgadoi ????? ????? ????? ????? ???11 11011 00?11 ?0??? 10011 1101
TITANOSAURIDAE 011?0 0000? 01011 00?00 01101 21012 00011 00011 10011 1101
Haplocantosaurus delfsi ????? ????? ????1 00001 01100 2?000 00010 ?0100 00000 10??
Haplocantosaurus priscus ????? ????? ????1 00001 01100 21000 00010 ?02?0 00110 10??
Rebbachisaurus tessonei 02101 11111 110?1 10101 11110 21000 02210 10210 00110 1010
Apatosaurus lousiae 12111 11010 10021 01011 01010 21001 01?00 1?0?0 01000 0010
Diplodocus 12111 11010 10021 01010 01010 21001 11100 11000 01000 0010
Barosaurus lentus ????? ????? ????1 ?1?10 01010 21001 11100 1100? ?10?? ?0??
Dicraeosaurus ?21?? 1???1 ?1120 11011 10010 21101 01200 110?0 01000 0010
Amargasaurus cazaui ????? 1?111 ?11?0 11111 10?10 21101 0??00 ??1?0 0???? ?01?
vestigial slit shaped. 3) Posterior process ol Postor-
bital absent. In R. tessonei sp. nov. the postorbital, in
lateral view, has the posterior and anterior border
perfectly curved; therefore, no trace of a postorbital
process is present. This condition has not been re-
ported elsewhere among dinosaurs. 4) The articular
condyle of the quadrate is elongated anteroposteri-
orly, the length is 4 times the width; in R. tessonei sp.
nov., it is elongated anteroposteriorly. In sauropod
outgroups, Camarasaurus, Brachiosaurus, Titano-
sauridae and in other diplodocids the articular con-
dyle, in ventral view, is of triangular shape. This shape
contrasts strongly with that of R. tessonei sp. nov. in
which it is rectangular. A similar articular condyle is
apparently present in Quaesitosaurus (KURZANOV &
BANIKOV, 1983), regarded as an advanced ti-
tanosaurid with a brachiosaurid-like skull (CALVO,
1994a, 1994b). In the context of all the evidence, we
think that this character was developed inde-
pendently both in Quaesitosaurus and R. tessonei sp.
nov. 5) Basal tuberas very reduced. In R. tessonei sp.
nov. the basal tuberas seem to have been very re-
duced. In other sauropoda and other dinosaura basal
tuberas are bulbous and welI developed. 6) Paraoc-
cipital process not distally expanded. The distal por-
tion of the paraoccipital process in R. tessonei sp. nov.
is narrow and straight. This configuration of the distal
part of the paraoccipital process is unknown among
diplodocids and sauropod outgroups. However, nar-
row distal end of the paraoccipital process is present
in derived Titanosauridae such as Antarctosaurus
(HUENE, 1929) and Saltasaurus BONAPARTE &
POWELL (POWELL, 1986). The difference between
the paraoccipital process in those Titanosauridae and
R. tessonei sp. nov. is that in the former they are curved
inward the skull plane axis. 7) Neural spine in cervi-
cals bears an accessory lamina connecting the
diapopostzygapophyseal with the supraprezygapo-
physeal lamina al midway of each one. Prosauropods
have simple neural spine without the neural spine
complexity present in sauropods. In Barapasaurus
(JAIN et al., 1979), some “cetiosaurids” such as
Patagosaurus (BONAPARTE,1979) Cetiosaurus medius
(MARTIN, 1987: fig. 1) we can only see the diapo-
postzygapophyseal and the suprapreziygapophysea1
laminae; in lateral view, a slight concavity is devel-
oped between these laminae. In other sauropods a
deep concavity is enclosed by the diapopostzygapo-
physeal, the supraprezygapophyseal and the su-
prapostzygapophyseal laminae. In R. tessonei sp. nov.
that deep concavity is divided by an accessory lamina
that connects the supraprezygapophyseal and the
diapopostzygapophyseal laminae. 8) Neural spine in
posterior cervicals and anterior dorsals present a
suprapostzygapophyseal accessory lamina that con-
nects the postzygapophysis with the supraprezygapo-
physeal lamina at its distal end. In other Sauropoda
the area enclosed, by the diapopostzygapophyseal,
the suprapostzygapophyseal and the supraprezygapo-
physeal, does not present any accessory lamina as
that. 9) Anterior dorsals with both supraprezygapo-
physeal laminae contacting on the top of the spine.
28
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
In sauropods with unforked neural spines, the su-
praprezygapophyseal lamina in anterior dorsals is
placed anterolaterally rising upward. These laminae
either disappear or form a massive bone on the top
of the spine. In R. tessonei sp. nov. both laminae reach
each other on the top of the spine following its cur-
vature. Therefore, both supraprezygapophyseal lami-
nae contact each other forming an arc. This character
is not seen in other sauropod. 10) Transverse proc-
cesses in anterior caudals formed by a dorsal (diapo-
physis) and a ventral (parapophysis) bar directed
upward. 11) Sternal plate of semilunar shape. This
condition is also present in derived Titanosauridae.
Th condition in R. tessonei sp. nov. is interpreted as
an autapomorphic character of this genus. 12) Shaft
of the pubis oval in cross section. The pubis is an
elongated bone in which the distal end is separated
from the proximal one by a long and slender shaft.
Tiis morphology is unknown atiiong otuer sauropods
in which the shaft of the pubis is somewhat platelike.
PHYLOGENETIC RELATIONSHIPS OF
REBBACHISAURUS TESSONEI SP. NOV.
The phylogenetic relationships of Rebbachisaurus
tessonei sp. nov. were investigated by a phylogenetic
analysis using the branch-and-bound option of PAUP
3.0.The taxa analyzed were 13 sauropod species, the
monophyletic Titanosauridae and the monophyletic
Prosauropoda. Characters were polarized using
Prosauropoda, Barapasaurus and Omeisaurus
YOUNG as outgroups. Camarasaurus, Brachiosaurus,
Andesaurus, Titanosauridae, Haplocanthosaurus pris-
cus, H. delfsi MCINTOSH & WILLIAMS and Reb-
bachisaurus tessonei sp. nov. were used as terminal
taxa.
For the analysis, 49 cranial and postcranial char-
acters were employed, none of which were autapo-
morphic for any terminal taxa. The analysis yielded
one parsimonious tree with 85 steps and a consistence
index of 0.655. The tree summarizing these results is
provided in Fig. 18. The present evidence suggests
that the genera within the family Diplodocidae:Apa-
tosaurus, Diplodocus, Amargasaurus, Dicraeosaurus
and Barosaurus form a monophyletic clade as has al-
ready been demonstrated by BERMAN & MCINTOSH
(1978), MCINTOSH (1990a) and YU (1993). We have
excluded from this family to Nemegtosaurus NOWIN-
SKY and Quaesitosaurus for belonging to Titanosauri-
dae (CALVO, 1994a, 1994b; SALGADO, CORIA &
CALVO, in press; SALGADO & CALVO, in press).
Several synapomorphies unite Rebbachisaurus tes-
sonei sp. nov. with Diplodocidae: (1) Pencil like teeth,
(2) Anterior extetision of tíle quadratojugal placed
beyond the anterior border of the orbit, (3) Anteriorly
directed basipterygoid processes, (4) Quadrate in-
clined posterodorsally, (5) Infratemporal fenestra
oval or slit shaped, (6) Narial opening placed above
Fig. 17 - Rebbachisaurus tesonei sp. nov. Holotype.
Reconstruction of the skeleton. Scale 1 m.
29
J.O. CALVO & L. SALGADO
Fig. 18 - Cladogram showing relationships of Rebbachisaurus tessonei sp. nov. among Sauropoda. Numbers refer to derived
characters usted in the Appendix (asterisked characters have ambiguous optimization).
the orbit, (7) Whip-lash tail, (8) Tall neural arch in
posterior dorsals being three times higher than that
of the centra, (9) Tall neural arch in caudals; at least
1.5 times higher than that of the centra, (10) Wing-like
transverse process, and (11) humerus/femur ratio
less than 0.70.
By contrast, other synapomorphies that charac-
terizes the Diplodocidae are not present in Reb-
bachisaurus tessonei sp. nov.: (12) Cervical neural
spine bifurcated, (13) Anterior dorsal neural spine
bifurcated, (14) Presence of Hyposphene-hypantrum
in anterior dorsals, (15) Slightly procoelous anterior
caudal vertebras, (16) Presence of rnidcaudal chev-
rons with fore and aft directed processes, (17) Closed
hemal canal in anterior caudals, (18) The ratio maxi-
mum width of the distal scapular blade/minumun
width of the scapular blade is 2, (19) Presence of the
prominent of the ambiens process in anterior part of
the pubis, (20) Expansion of the distal end of the is-
chia, (21) Wide dorsoventral contact of both distal
ends of ischia. Therefore, we have erected a new taxa
Diplodocimorpha to include Rebbachisaurus tessonei
sp. nov. and all other Diplodocidae presenting char-
acters 1 to 11. Diplodocidae is considered the sister
group of Rebbachisaurus tessonei sp. nov. presenting
characters 12-21.
The present analysis has shown that Haplocan-
thosaurus is a paraphyletic taxon. "H." delfsi shares
with "H." priscus + Diplodocimorpha the following
characters: 1) The high of the neural arch in anterior
dorsals is at least three times longer than the length
of the centra; 2) Dorsal centra in posterior dorsals
are amphyplatian or amphycoelus; and 3) Mid-
preespinal lamina in posterior dorsals occupy all the
length of the spine. "H."priscus, in turn, is considered
the sister gro up of the Diplodocimorpha by having a
distal scapular blade widely expanded (maximum
width/minimum width > 3). Unfortunately, no part
of the skull in "H." priscus and "H." delfsi is known;
therefore, several cranial characters here considered
diagnostic for Diplodocimorpha could be synapomor-
phies of a more inclusive group.
PALEOGEOGRAPHIC CONSIDERATIONS
The presence of R. garasbae in the Aptian-Albian
of Morocco and R. tessonei sp. nov. in the Albian-
Cenomanian? of Argentina increase our knowledge
about the Africa - South Anicrica faunal community
during mid-Cretaceous times (PATTERSON, 1975). It
also allows to establish a land bridge connection in
between both continents up to Albian times.
The Africa - South Anierica connection during
Aptian-Albian times is based by the presence of the
following vertebrates: The Mesosuchian crocodiles
Araripesuchus from the Aptian of Northeastern Brazil
and Niger (BUFFETAUT & TAQUET, 1979); the giant
crocodilian Sarcosuchus from the Aptian of Brazil
and Niger (BUFFETAUT & TAQUET, 1977); the turtles
Araripemyidae from the Aptian of Niger and Brazil
(DE BROIN, 1980) and the Coelacanths Mawsonia
from the Aptian-Albian of Brazil and Africa (WENZ,
1980).
30
REBBACHISAURUS TESSONEI SP. NOV.
A NEW SAUROPDA FROM THE ALBIAN-CENOMANIAN OF ARGENTINA
CONCLUSIONS
Rebbachisaurus tessonei sp. nov. a sauropod from
the Albian-Cenomanian of Patagonia is the most
complete species of Rebbachisaurus ever found.
Twelve autapomorphies support the erection of this
new taxa. Rebbachisaurus tessonei sp. nov. is the latest
diplodocimorph so far known. Rebbachisaurus tes-
sonei sp. nov. exhibits many synapomorphies that jus-
tify its position as the sister group of Diplodocidae,
and it also confirms the interpretation of this speci-
men as part of a large clade of Diplodocimorpha.
Eleven synapomorphies unite R. tessonei sp. nov. to
diplodocids: pencil like teeth; anterior extension of
the quadratojugal placed beyond the anterior border
of the orbit; quadrate inclined posterodorsally; narial
opening placed above the orbit; anteriorly directed
basipterygoid processes; infratemporal fenestra oval
or slit shaped; tall neural arch in posterior dorsals
being three times higher than that of the centra; tall
neural arch in caudals (at least 1.5 times higher that
that of the centra); whip-lash tail wing-like transverse
process in anterior caudals; humerus/femur ratio less
than 0.70. These characters allow us to recognize the
presence of a large clade that we call Diplodocimor-
pha.
Rebbachisaurus tessonei sp. nov. does not present
typical characters that support the monophyly of the
family Diplodocidae such as bifurcated cervical and
anterior dorsal neural spine, hyposphene-hypantrum
in anterior dorsals, prominent ambiens process on an-
terior part of the pubis, slightly procoelous anterior
caudal vertebra, closed hemal canal in anterior
caudals, midcaudal chevrons with fore and aft di-
rected processes, wide dorsoventral contact of both
distal ends of ischia, and expansion of the distal end
of the ischia. These characters are regarded as sy-
naponiorphies of the Diplodocidae. The genus Reb-
bachisaurus includes two species, R. garasbae from
Morocco and R. tessonei sp. nov. from Argentina; R.
tasmesnensis from Algeria is considered a cama-
rasaurid sauropod. The presence of the genus Reb-
bachisaurus in rocks of Argentina and Morocco
documents that an intercontinental land bridge be-
tween South America and Africa was present at least
up to the Albian age.
ACKNOWLEDGMENTS
We are grateful to Dr. Jose Bonaparte and his
team from the Museo Argentino de Ciencias Natu-
rales "Bernardino Rivadavia" who helped us to col-
lect the type of Rebbachisaurus tessonei sp. nov. We
thank to Paul Sereno and Jeff Wilson for their read-
ing, criticizing and English correcting of the manu-
script. We also thank to John McIntosh and Jose Luis
Sanz for their evaluations. We would like to express
our gratitude to the authorities of the University of
Comahue for funding our works and researching
through the proyect: Geology, Stratigraphy, Paleon-
tology and Geomorphology of the Neuquen province.
APPENDIX
List of 49 character and character status of
Sauropoda used for cladistic analysis (TABLE I).
Character codes: 0, primitive; 1,2, derived; ?, missing
or uncertain. Some sources for the character analysis
are: BERMAN & MCINTOSH,1978; GAUTHIER, 1986;
MCINTOSH, 1990b; YU, 1993; SALGADO et al. (in
press).
1) Fossa posterior in quadrate: present (0), absent
(1).
2) Tooth shape: spoon shaped (0), cone and pencil
chisel-like (1), pencil-like (2).
3) Serration in teeth: present (0), absent (1).
4) Angle lacrimal-parietal: posteriorly inclined
(0), vertical (1).
5) Quadrate position: vertical (0), inclined pos-
terodorsally (1).
6) Direction of the basipterygoid process: ven-
trally (0), anteriorly (1)
7) Narial opening position: in front of the orbit
(0), above the orbit (1).
8) Posterior rim of infratemporal fenestra: back of
the posterior rim of the orbit (0), well in front of the
posterior rim of the orbit (1).
9) Infratemporal fenestra shape: subtriangular (0),
oval / slit-shaped (1).
10) Supratemporal fenestra: big (0), small (1).
11) Anterior rim of the quadratojugal: placed be-
fore the anterior border of the orbit (0), beyond the
anterior border of the orbit (1).
12) Supraoccipital width: supraoccipital width
50% of skull width (0), supraoccipital width 30% of
skull width (1).
13) Frontals: unfused (0), fused (1).
14) Ascending process of the maxilla: placed in
the middle of it (0), placed posteriorly of it (1),
placed anteriorly of it (2).
15) Cervical centra: without pleurocoels (0), with
pleurocoels (1).
16) Height of the anterior cervical neural arch:
height of the neural arch > length of the centra (0),
height of the neural arch > length of the centra (1).
17) Shape of the neural spine in cervicals: undi-
vided (0), bifid (1).
18) Neural spine in anterior cervicals: directed up-
ward (0), directed backward (1).
31
J.O. CALVO & L. SALGADO
19) Neural spine in anterior dorsals: fused (0), un-
fused (1).
20) Neural arch on anterior dorsals: height of the
neural arch / length of the centra < 3 (0), height of
the neural arch / length of the centra > 3 (1).
21) Tall neural spine on anterior dorsals: height of
neural spine is less than 65% of height of the neural
arch (0), height of neural spine is more than 65% of
height of the neural arch (1).
22) Pleurocoels in dorsal centra: absent (0),
present (1).
23) Hyposphene-hypantrum on anterior dorsals:
present (0), absent (1).
24) Tall neural arch on posterior dorsals: neural
arch height / centra height < 3 (0), neural arch height
/ centra height > 3 (1).
25) Dorsal centra in posterior dorsals: amphipla-
tian-platicoelous (0), strongly opistocoelous (1).
26) Midpreespinal lamina on posterior dorsals:
absent (0), present on the superior part of the spine
(1), present over all the spine (2).
27) Postespinal lamina on posterior dorsals: ab-
sent (0), present (1).
28) Tall neural spine on posterior dorsals: neural
spine height is less than 75% of neural arch height
(0), neural spine height is more than 75% of neural
arch height (1).
29) Pleurocoels shape: no eye shaped (0), eye
shaped (1).
30) Centrum on anterior caudals: amphicoelous
(0), sligthtly procoelous (1), strongly procoelous (2).
31) Pleurocoelus on anterior caudals: absent (0),
present (1).
32) Wing-like process: absent (0), present well
developed (1), formed by a dorsal and ventral bar (2).
33) Neural arch on anterior caudals / height of 1.5
(0), 1.5 - 2 (1), > 2 (2).
34) Hemal canal on anterior caudals: closed (0),
open (1).
35) Neural arch on middle-posterior caudals:,
placed in the middle of the centra (0), anteriorly
placed (1).
36) Whip-lash tall: absent (0), present (1).
37) Forked midcaudal chevrons: absent (0), pre-
sent (1).
38) Width of the distal scapular blade: maximum
width / minimum width < 2 (0), maximum width /
mini- mum width 2 to 3 (1), maximum width /
minimum width > 3 (2).
39) Shape of sternal plate: oval (0). semilunar (1).
40) Lobe of the ilium: acute (0), expanded upward
41) Length of the articular surface of the pubis for
ischia: 30% or less length of pubis shaft (0), more
than 30% length of pubis shaft (1).
42) Prominent ambiens process on pubis: absent
(0), prominent (1).
43) Ventral rim of the distal end of ischium: V-
shaped (0), horizontal (1).
44) Distal end of ischium: expanded (0), narrow
(1).
45) Pubis / ischium lenglit ratio: pubis shorter
than ischium (0), pubis considerably longer than
ischium (1).
46) Dorsoventral contact of the distal end of is-
chium: higher than the dorsal exposition (0), shorter
than dorsal exposition (1).
47) Bulge in femur: absent (0), present (1).
48) Humeral proportion: less than 70% of femoral
length (0), more than 70% of femoral length (1).
49) Metacarpal proportion: less than 45% of the
radius length (0), more than 45% of the radius length
(1).
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Paper received: 17/07/1995
Paper accepted after revision: 10/11/1995
Reviewer's comment:
[This is] one of the most important papers I have read in recent
years, [...].
John S. McIntosh
Este artículo [...] tiene un gran interés para el conocimiento de la
historia evolutiva de los Saurópodos.
José Luis Sanz
33
