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Bonitasaura salgadoi gen. et sp. nov.: A beaked sauropod from the Late Cretaceous of Patagonia

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  • FUNDACION AZARA, UNIVERSIDAD MAIMONIDES, BUENOS AIRES, ARGENTINA

Abstract and Figures

Ornithischian and theropod dinosaurs were morphologically diverse during the Cretaceous. In contrast, sauropods were relatively more conservative. The anatomy of Bonitasaura salgadoi, a new 9-m titanosaurian sauropod from Upper Cretaceous beds of Patagonia, suggests that sauropod anatomical diversity would have included unexpected items. Its unusual, rectangular lower jaw possesses narrow, anteriorly restricted teeth and shows evidence of a sharp keratinous sheath over the nondentigerous region that probably worked to guillotine plant material. This discovery definitely demonstrates that titanosaurs acquired a mandibular configuration similar to that of some basal diplodocoids, as had already been suggested by the lower jaw of the controversial genus Antarctosaurus. This oral configuration, plus the beak-like structure and the skull shape, resemble some traits more commonly seen in Laurasian ornithischians, mostly unexpressed in southern continents. A high sauropod morphological diversity seems to be in agreement with the poorly represented ornithischian clades of the southern hemisphere.
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Naturwissenschaften (2004) 91:493–497
DOI 10.1007/s00114-004-0560-6
SHORT COMMUNICATION
Sebastin Apestegua
Bonitasaura salgadoi
gen. et sp. nov.: a beaked sauropod
from the Late Cretaceous of Patagonia
Received: 29 April 2004 / Accepted: 4 August 2004 / Published online: 10 September 2004
Springer-Verlag 2004
Abstract Ornithischian and theropod dinosaurs were
morphologically diverse during the Cretaceous. In con-
trast, sauropods were relatively more conservative. The
anatomy of Bonitasaura salgadoi, a new 9-m titano-
saurian sauropod from Upper Cretaceous beds of Patag-
onia, suggests that sauropod anatomical diversity would
have included unexpected items. Its unusual, rectangular
lower jaw possesses narrow, anteriorly restricted teeth and
shows evidence of a sharp keratinous sheath over the non-
dentigerous region that probably worked to guillotine
plant material. This discovery definitely demonstrates that
titanosaurs acquired a mandibular configuration similar
to that of some basal diplodocoids, as had already been
suggested by the lower jaw of the controversial genus
Antarctosaurus. This oral configuration, plus the beak-
like structure and the skull shape, resemble some traits
more commonly seen in Laurasian ornithischians, mostly
unexpressed in southern continents. A high sauropod
morphological diversity seems to be in agreement with
the poorly represented ornithischian clades of the south-
ern hemisphere.
Introduction
After the purported global extinction of diplodocoid
sauropod dinosaurs during the Cenomanian–Turonian
(Bakker 1986), titanosaurs became the sole surviving
latest Cretaceous sauropods. They successfully evolved in
southern continents by radiating in a wide range of forms
that later recolonized some Laurasian areas.
Derived titanosaurs are said to parallel diplodocoids
(Salgado and Calvo 1997; Wilson 2002) in their ‘horse-
like’ skulls, restriction of the cylindrical, narrow-crowned
teeth to the anterior part of the snout, comb-like dentition
(Coria and Chiappe 2001), squared symphysis, and nos-
trils retracted to the top of the head. The high femur/
humerus ratio (a reversal) and an incipient whiplash tail
could also be regarded as convergences. The lower jaw
seems also to be problematic in titanosaur anatomy.
Based on it, the Patagonian titanosaur Antarctosaurus
wichmannianus (von Huene 1929), was interpreted as a
chimera which included a diplodocoid lower jaw (Jacobs
et al. 1993; Wilson and Sereno 1998; Upchurch 1999),
and was later specified to be a rebbachisaurid (Sereno et
al. 1999).
A new partially articulated sauropod titanosaur
(Fig. 1c, d) was recovered in Santonian rocks of the Bajo
de la Carpa Formation top (Hugo and Leanza 1999) at Ro
Negro Province, Argentina. Among the collected bones, a
right dentary bearing several teeth provides new insights
into the morphology of Late Cretaceous herbivorous di-
nosaurs on southern continents.
Systematic paleontology
Saurischia Seeley 1888
Sauropoda Marsh 1878
Titanosauria Bonaparte and Coria 1993
Bonitasaura salgadoi gen. et. sp. nov.
Etymology
The generic name is derived from the “La Bonita” hill,
the name of the quarry, and saura, a female reptile. The
species, salgadoi, honors Leonardo Salgado, the Argen-
tinian paleontologist who gave new perspectives to sauro-
pod research.
Communicated by G. Mayr
S. Apestegua (
)
)
Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”,
Av. ngel Gallardo 470, 1405 Buenos Aires, Argentina
e-mail: paleoninja@yahoo.com.ar
Tel.: +54-11-49826595
Fax: +54-11-49826595
Holotype
MPCA 300 (Museo Provincial “Carlos Ameghino”,
Cipolletti, Ro Negro, Argentina), consists of a partially
articulated, subadult skeleton (Fig. 1a– c). The material
includes a left frontal, left parietal, right dentary with 15
teeth, lacking at least three or four alveoli distal to the
symphysis, two cervi cal, six dorsal, and 12 caudal ver-
tebrae, two chevrons, several cervical and dorsal ribs,
humerus, radius, two metacarpals, femur, tibia, two me-
tatarsals.
Locality and geological setting
“La Bonita” hill fossil quarry, Cerro Polica, Ro Negro
Province, NW Patagonia, Argentina. The specimen was
found in a fluvial sandstone (Hugo and Leanza 1999)
Fig. 1 A The ‘La Bonita’ hill, about 100 km south of Cipolletti,
Argentina. B Stratigraphic position (arrow) of the fossil discovery.
C Skeletal reconstruction and body shape of Bonitasaura. Pre-
served bones are indicated as dashed zones. The preserved dentary
is actually the right one. D Quarry map. Scale bars are 1 m in
length. Arrow in D points north. Skull bones are labelled as fr
(frontal), lj (lower jaw) and pa (parietal)
494
which belongs to the uppermost layers of the Bajo de la
Carpa Formation (Santonian; Hugo and Leanza 1999).
Diagnosis
Bonitasaura differs from other titanosaurs in the follow-
ing combination of features: dentary alveoli reduced in
number (three in the main ramus, one in the angle, and up
to seven in the anterior region); middle and posterior re-
gion of the dentary edentulous and forming a sharp dorsal
edge, with a profusely vascularized lateral side; very ro-
bust, diagonal neural arch pillars and bulging neural spine
summits on anterior dorsal vertebrae. More diagnostic
characters might emerge once all of the postcranial ma-
terial has been prepared.
Description
The preserved skull remains of Bonitasaura include right
frontal and parietal, and an incomplete lower jaw (Fig. 2a,
b). However, only the latter will be described here.
Bonitasaura (Fig. 2) bears an anteroposteriorly straight
mandibular ramus that turns medially at almost a right
angle to meet the opposite ramus in a transverse sym-
physis. The anteroventral margin of the dentary is vertical
and lacks a chin-like process, thus differing from diplo-
docoids (Salgado and Calvo 1997; Upchurch 1999; Wil-
son 2002). The depth of the dentary is fairly homogene-
ous except for the posteriormost preserved region, but it is
not possible to see whether it gradually deepens as in
Rapetosaurus (Curry Rogers and Forster 2004). As in the
latter, the lateral plate is substantially higher than the
medial one. Although only ten complete alveoli were
preserved, each ramus would have borne around 13 al-
veoli, which decrease in size posteriorly. All but the last
two alveoli are associated with large neurovascular fo-
ramina. The anteriormost preserved alveolus bears up
to three teeth, the same number as recorded for Antarc-
tosaurus and other titanosaurs (Powell 1979; Coria and
Chiappe 2001), whereas diplodocoids reached a higher
number, as in the rebbachisaurid Nigersaurus, where up
to seven narrow, striated replacement teeth are present
(Sereno et al. 1999).
Posterior to the tooth-bearing region, the dorsal border
of the jaw bears an abrupt elevation that terminates in a
long, thin, horizontal edge, only preserved for its first
65 mm (Fig. 2c, e). The jaw widens ventrally up to three
times. The upper 15 mm of this exquisitely preserved
surface, especially on the labial side, is profusely pierced
by small neurovascular foramina and furrows, as in the
regions on bird dentaries sheathed by the rhamphotheca
(Norell et al. 2001). This unusual morphology of the mid-
to posterior region of the dentary, where bite-forces are
higher, and its presumably keratinous cover, would have
provided a strong cropping device for cutting tough plant
material.
Fig. 2 Bonitasaura, MPCA
300, holotype. A Right frontal
in ventral and dorsal views. B
Left parietal in anterior, dorsal
and posterior views. C Labial
view of the cutting mandibular
crest on the posterior dentary
and its densely pitted lateral
surface. D Reconstruction of the
head of Bonitasaura showing
the position of the guillotine-
like mandibular crest covered
by a dark rhamphoteca. E Right
dentary in lingual and labial
(reversed) views. F Dentary in
ventral and dorsal views. Scale
bars: A, B, E, F 50 mm; C
30 mm. Abbreviations: fcb
frontal central “bump”; fpc
frontoparietal concavity; gc
guillotine crest; mg meckelian
groove; nvf neurovascular fo-
ramina; sr sculptured rim; vr
ventral ridge
495
In contrast with primitive titanosaurs (Martnez 1998),
which have broad-crowned, compressed cone-chisel-like
teeth, Bonitasaura bear narrow, pencil-chisel-like teeth
(Fig. 2), as in the derived titanosaurs Rapetosaurus (Curry
Rogers and Forster 2004), Antarctosaurus (von Huene
1929), Nemegtosaurus (Nowinski 1971), and undescribed
new forms from Patagonia. As in Antarctosaurus, Rin-
consaurus (Calvo and Gonzlez Riga 2003), and the
isolated Patagonian premaxilla MPCA 79 (Coria and
Chiappe 2001), these teeth have well-marked, non-den-
ticulated carinae on their mesial and lateral edges that
divide the labial and lingual sides. Although the teeth of
MPCA 79 are slightly larger in diameter, this difference is
expected to occur between upper and lower teeth in both
diplodocoids and titanosaurs (Nowinski 1971; Holland
1906). Rinconsaurus carinae are more primitive in being
larger and asymmetrically developed. These carinae fill a
morphological gap between the broad two-winged basal
macronarian teeth, the asymmetrically winged teeth of
basal titanosauriforms, and the completely cylindrical
teeth of advanced titanosaurs.
The abundant postcranial remains of Bonitasaura
(MPCA 300) will be described elsewhere. However,
Bonitasaura does not differ significantly in the postcra-
nium from other derived titanosaurs (Apestegua and
Gallina 2002). The dorsal vertebrae bear a well-developed
prespinal lamina. Both anterior and middle caudal verte-
brae are strongly procoelous, while the distalmost caudals
are long and biconvex. Metacarpals are relatively slender,
in contrast to the short metatarsals. Bonitasaura differs
from known titanosaur species in having anterior dorsals
with robust, bulging neural spine summits, which are
supported by remarkably robust bases.
Discussion
Although a detailed character analysis is beyond the scope
of this work, available information suggests that Boni-
tasaura is closely related to the Late Cretaceous Malagasy
titanosaur Rapetosaurus and the Mongolian taxa Nemeg-
tosaurus and Quaesitosaurus. These four sauropods share
sculptured frontal borders, a dentary symphysis that is
almost perpendicular to the mandibular rami, and narrow,
pencil-chisel-like teeth that are cylindrical in cross-sec-
tion and mostly restricted to the anteriormost portion of
the lower jaw. This set of characters may suggest that
Bonitasaura is related to the Nemegtosauridae (Wilson
2002), which is defined as including all titanosaurs more
closely related to Nemegtosaurus than to Saltasaurus.
Bonitasaura differs from Antarctosaurus in having the
guillotine crest, a less straight angle of symphysis, and a
rather flat instead sinuous posterior surface of the parietal.
Rapetosaurus substantially differs in having a dentigerous
region more extended backwards and an even more gently
curved symphysis (Curry Rogers and Forster 2004). The
presence in Antarctosaurus of an extensive edentulous
region (although devoid of a tall crest) and the Rapeto-
saurus short, rugose postalveolar ridge and the bizarre
post-dentigerous corner of the maxilla, suggest that in-
cipient guillotine-like structures could have been devel-
oped in other titanosaurs.
The unresolved phylogenetic relationships of Antarc-
tosaurus, and the fact that the record of Late Cretaceous
sauropods is only composed of derived titanosaurs and
basal diplodocoids (i.e., Rebbachisauridae), led Upchurch
(1999) to propose two possibilities for the status and
evolutionary relationships of this species: a chimera of
bones from different lineages, or a diplodocoid that ac-
quired a postcranium largely convergent with that of
derived titanosaurs. The discovery of Bonitasaura has
shed light on the systematic affinities of Antarctosaurus,
showing that its bizarre lower jaw features are not unusual
in advanced titanosaurs, which can bear a squared snout
convergent to that of diplodocoids, as originally proposed
(see von Huene 1929; Calvo 1994; Salgado 2001). This is
also supported by the clear titanosaur affinities of the
remaining Antarctosaurus bones.
Wilson (2002) remarked on the morphological diver-
sity acquired by sauropod dinosaurs. However, it is clear
that their lineages were morphologically far less disparate
than other dinosaurs (e.g., theropods include Tyran-
nosaurus rex and hummingbirds; ornithischians include
large frilled ceratopsians as well as small and fast runners
like Othnielia). Sauropod morphological variation is lim-
ited to changes in relative neck and limb proportions, loss
of manual phalanges, muscular and pneumatic variation
(inferred), armor, weapons and tail mobility, wide or nar-
row hip and limb gauges (Wilson and Carrano 1999), and
some craniodental configurations. Several workers (e.g.,
Paul 1984) have already noted the possible possession of
both beaks and teeth in prosauropods, their sister-group; a
combination that is common in ornithischians, occasion-
ally present in theropods, but was never suspected for
derived sauropods.
The feeding mechanism proposed for derived ti-
tanosaurs (Calvo 1994) involves cutting and cropping of
selected soft vegetation with the anteriormost teeth. The
device exhibited by Bonitasaura, novel for sauropods,
with the non-dentigerous zone of the dentary (and perhaps
the maxilla) developed into a cutting surface, would
have permitted effective slicing of tougher vegetation and
minimized tooth wear. On the other hand, comb-like
dental replacements have already been reported for ad-
vanced diplodocoids and purported titanosaurs (Coria and
Chiappe 2001; Powell 1979; Holland 1906).
Most nemegtosaur ids had a long, square-sno uted,
shoe-shaped, hadrosaur-like head (Curry Rogers and
Forst er 2004; Nowinski 1971), which could be present
also in the Late Cretaceous reb bachisaurid diplodocoids.
The new titanosaur Bonitasaura constitutes the first
sauro pod dinosaur yet recorded that not only possesses
squared jaws, with narrow-crowned teeth arranged in
continuous series that include at least three replacement
elements per alveolus, but additionally also a keratinous
beak to aid in cutting plant material. A keratinous cutting
structure in addition to the aforeme ntioned nemeg-
tosaurid features has previously been reporte d only in
496
Late Cretaceous orni thischians, particularly hadrosaurs
(Morris 1970), and has been proposed as an adapt ive
response to the rise and diversi fication of flowering
plants (Bakker 1986; Salgado and Calvo 1997). How-
ever, the beak of ornithischians differs from that of
Bonit asaura in that it is at the tip of the mouth, and there
are teeth in the cheeks. Functional anatomical studies are
necessary in order to evaluate how these differences re-
flect different ways of living in the two taxa. Further-
more, the dental mechanism seems to be less complex by
far. The configuration shown by Bonitas aura is thus
unique in having a poste riorly placed beak.
Interestingly, the similarities in mouth configuration
and corporal mobility (i.e., loss of the hyposphene–hy-
pantrum complex) among rebbachisaurid sauropods and
derived titanosaurs suggest probable constraints on sauro-
pod morphology that conditioned them to take advantage
of a determinate resource. These constraints could be
related to genetical or morphological limitations, envi-
ronmental stasis, or the dominance of a particular vege-
tational food source.
Late Cretaceous sauropods in the southern he misphere
apparently entered new adaptative zones that were pre-
viously believed to have been oc cupied exclusively by
ornithischians (Powell 2003). The unusual features ex-
hibited by titanosaurs and rebbachisaurids suggest that
some Lat e Cretaceous sauropods acquired a disparate
morphological diversity. Although several ornithischian
lineages were prese nt at the same time, they were re-
stricted to rare and small-sized forms when compared
with other regions. This panorama changed when North
American ornithischians entered South America by
Late Campanian t imes. The morphological diversit y o f
Late Cretaceous southern hemisphere sauropods and thei r
adaptative capabilities may help to explain their persis-
tence into the latest Cretaceous.
Acknowledgements The work was supported by the Jurassic
Foundation and Paleogenesis. I gratefully acknowledge the assis-
tance of the Pincheira and vila families and thank them for their
kind help. Thanks to Mr. Parodi for guiding us to the fossil site and
to Marcos Zffliga and the Salinas family for logistics. P.A. Gallina,
F.L. Agnolin, G. Lio, L. Gaetano, M. Cardenas, M. de la Fuente, L.
Ballarino, F. Pose, are thanked for field support. Thanks to the
geologists Hugo Corbela and Hector Leanza for the stratigraphic
position of the specimen. I am grateful to J.A. Gonzlez for illus-
trations and M. Isasi for preparation. M. Lamanna, J.F. Bonaparte
and P.J. Makovicky substantially improved this work with useful
comments and critical reviews.
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... The fossil remains of Bonitasaura salgadoi were discovered in the Santonian-Campanian Bajo de la Carpa Formation, at La Bonita site in the Río Negro Province (Apesteguía 2004). Taphonomic and sedimentary analyses concluded that the dinosaur died close to a river margin and was rapidly incorporated into the fluvial sediments that buried the bones in successive events (Pérez et al. 2009). ...
... Amazonsaurus maranhensis (Carvalho et al. 2013); Tapuiasaurus macedoi (Zaher et al. 2011); Laplatasaurus araukanicus (Huene 1929); Amargasaurus cazaui (Salgado and Bonaparte 1991); Amargatitanis macni (Apesteguía 2007); Rinconsaurus caudamirus (Calvo and González Riga 2003); Muyelensaurus pecheni (Calvo et al. 2007a, b, c); Sarmientosaurus musacchioi (Martínez et al. 2016); Saltasaurus loricatus (Bonaparte and Powell 1980); Rocasaurus muniozi (Salgado and Azpilicueta 2000); Brasilotitan nemophagus (Machado et al. 2013) Overosaurus paradasorum (Coria et al. 2013); Trigonosaurus pricei (Bonaparte 1996(Bonaparte , 1997; Comahuesaurus windhauseni (Carballido et al. 2012); Bonitasaura salgadoi (Apesteguía 2004); Panamericansaurus schroederi (Calvo and Porfiri 2010); Narambuenatitan palomoi (Filippi et al. 2011); Epachthosaurus sciuttoi (Powell 1990); Pitekunsaurus macayai (Filippi and Garrido 2008); Ligabuesaurus leanzai (Bonaparte et al. 2006); Kaijutitan maui (Filippi et al. 2019); Elaltitan lilloi (Mannion and Otero 2012); Drusilasaura deseadensis (Navarrete et al. 2011); ...
Chapter
Most taphonomy studies of South American sauropodomorphs have addressed extrinsic factors such as sedimentary environments, bone dispersal, and mineralogical processes that occurred during fossil diagenesis. These studies provide important data on the taphonomic modes which are associated with bone accumulations in different paleoenvironmental contexts. However, these analyses have generally not considered intrinsic factors like the shape, size, and structural integrity of the skeletal elements, variables that can produce some taphonomic bias. Sauropodomorphs include dinosaurs of highly varied sizes, ranging from small (less than 8 m long) to remarkably giant forms (around 30 m long). In the largest sauropods, such as the huge titanosaurs, very incomplete skeletons are commonly found and most notably skull and articulated pedes rarely are preserved. We focus here on some intrinsic anatomical factors as they relate to articulation in some key parts of the skeletons. Further, this study suggests that the preservation of fragile portions of sauropodomorph skeletons was possible only under specific combinations of sedimentological and biological processes.
... Por otro lado, es relevante mencionar que Argentina presenta una oportunidadúnica para realizar este tipo de estudio debido a, como se mencionó anteriormente, la gran cantidad de fósiles de titanosaurios (incluyendo material craneano) hallados en el país. Es por esto que la mayoría de los especímenes de Titanosauria utilizados en esta tesis provienen de yacimientos argentinos (Huene, 1929;Bonaparte y Powell, 1980;Chiappe et al., 1998;Chiappe et al., 2001;Apesteguía, 2004;Martinelli y Forasiepi, 2004;Paulina Carabajal y Salgado, 2007;Filippi et al., 2011;Martínez et al., 2016). A pesar de contar con este muestreo geográfico restringido, los titanosaurios argentinos utilizados en esta tesis permiten que distintos subclados de Titanosauria estén representados (e.g., Powell, 1992;Salgado et al., 2014;Martínez et al., 2016). ...
Thesis
Full-text available
Cranial material from several titanosaurs was examined qualitatively and quantitatively for ontogenetic changes in the width/length ratio and general morphology of the frontals, the width/length ratio of the endocranium's anterior portion, and the position of the external nares. The frontals and cerebral hemispheres' width/length ratios were also compared between different sauropodomorphs in a phylogenetic context. The only modifications these traits went through in titanosaurs occurred during the first stages of ontogeny, before the juvenile stage. These involved an increase in the width to length ratio of the frontals and the retraction of the external nares. Additionally, in several species the lateral margin of the frontals seemed to go from being concave to convex or straight, and ornamentation formed on it over time. On the other hand, the frontals, cerebral hemispheres and external nares remained relatively constant in their morphology and position from the juvenile to the adult stage. Finally, there is a strong evolutionary increase in the width/length ratio of the frontals and cerebral hemispheres from non-eusauropod sauropodomorphs to eusauropods, and a small decrease in the width/length ratio of the cerebral hemispheres within Titanosaurs.
... Entre los dinosaurios terópodos se encuentran representados los alvarezsáuridos, abelisáuridos y megaraptores, como Achillesaurus manazzonei , Alvarezsaurus calvoi , Velocisaurus unicus Brisson Egli et al., 2016), Viavenator exxonei (Filippi et al., 2016) y Tratayenia rosalesi (Porfiri et al., 2018). En cuanto a los dinosaurios saurópodos, sólo se encuentran representados por los ejemplares holotípicos de Bonitasaura salgadoi (Apesteguía, 2004) y Traukutitan eocaudata (Juárez Valieri y Calvo, 2011). Entre los restos de aves enanthiornites se encuentra Neuquenornis volans y Patagopteryx deferrariisi (Alvarenga y Bonaparte, 1992). ...
Thesis
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
... Entre los dinosaurios herbívoros se descubrieron y describieron al saurópodo rebaquisáurido Cathartesaura anaerobica, en La Buitrera (Gallina y Apesteguía, 2005), y el titanosaurio Bonitasaura salgadoi (Fig. 6.5), descubierto en rocas del Cretácico Superior (Apesteguía, 2004). Cóndor sobre el valle medio del río Chubut, que permitió reforzar la visión de un linaje gondwánico de esfenodontes para el Jurásico . ...
... De la zona de Cerro Policía, en el sector más septentrional del ANP Valle Cretácico, S. Apesteguía y su equipo co-lectaron materiales de dinosaurios saurópodos, entre ellos el de la especie Bonitasaura salgadoi (Apesteguía, 2004;Gallina y Apesteguía, 2011 El actual museo, creado a partir de la iniciativa de Héctor Plata en el marco de proyectos y campañas sistemáticas a cargo de Zulma Brandoni de Gasparini (Gasparini et al., 2003(Gasparini et al., , 2005(Gasparini et al., , 2007 ...
... The Bajo de la Carpa Formation (Santonian, Upper Cretaceous) is a continental unit belonging to the Neuqu en Group of the Neuqu en Basin, which presents a wide distribution throughout northwestern Patagonia (Garrido, 2010(Garrido, , 2011. This geological unit has yielded a large diversity of terrestrial tetrapods, mainly dominated by dinosaurs (e.g., Woodward, 1896;Bonaparte, 1991;Caldwell and Albino, 2001;Apesteguía, 2004;Gianechini et al., 2011;Filippi et al., 2016;Porfiri et al., 2018;Cruzado-Caballero et al., 2019;Gianechini et al., 2020). Particularly, the theropod fauna from these deposits has a major role in our understanding of the evolution as a whole of the theropod lineage history in South America (see Novas et al., 2013;Holtz, 2021). ...
Article
The abundant record of theropods from Bajo de La Carpa Formation (Neuquén Group, Santonian), known from the end of the nineteenth century, come from numerous locations within the Neuquén Basin. During the excavation of the titanosaur Bonitasaura salgadoi at the La Bonita fossiliferous site, northwest of Río Negro province Argentina, were recovered three isolated teeth assignable to non-avian theropod dinosaurs. Previous studies of these dental materials suggested that MPCA-Pv-247 corresponds to an indeterminate tetanure possibly related to Orkoraptor, a taxon of uncertain phylogenetic position at that moment, and MPCA-Pv-249 and 251 as possible abelisauroids. Three methods were carried out, namely, a cladistic analysis performed on a dentition-based data matrix, and a discriminant and cluster analyses performed in a large dataset including measurements of non-avian theropod teeth. The results assign for the first time a confidently phylogenetic position to the described dental material. The analysis shows that MPCA-Pv 247 belongs to Megaraptoridae, whereas MPCA-Pv 249 and 251 were recovered as belonging to Abelisauridae, supporting in a reliable way the previous assignments. The results show the presence of Megaraptoridae at La Bonita and, additionally, they represent an evidence of the first direct association of megaraptorids and abelisaurids at the same locality of the Bajo de La Carpa Formation, according to similar associations from other units of the Neuquén Group.
Book
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En esta obra se listan un total de 161 nuevas especies, 94 fósiles y 67 vivientes, dadas a conocer a lo largo de dos décadas por investigadores de la Fundación Azara —en varios casos conjuntamente con colegas de otras instituciones— que al momento de la publicación continuaban siendo consideradas válidas para la ciencia.
Article
Rinconsaurus caudamirus, from the Bajo de la Carpa Formation (Santonian), Río Negro, Argentina, is represented by several axial and appendicular elements from, at least, four specimens. The axial skeleton of this taxon was described in detail in a recent contribution, pending a complete analysis and description of its appendicular skeleton. This contribution focuses on the description of the appendicular skeleton of Rinconsaurus and its phylogenetic relationships, considering the new information provided here. Rinconsaurus clearly differs from other titanosaurs for the presence of several autapomorphic characters and for a unique association of characters, some of which are also present in lognkosaurians, aeolosaurines and saltasaurines titanosaurs, and by having a scapula with a scapular blade angled 65° with respect to the coracoid articulation, similar to that of Bellusaurus, Dreadnoughtus and Muyelensaurus. Equations for estimating body mass in sauropods based on long bone circumference suggest a body mass of at least 3-5 tonnes for the largest individuals of Rinconsaurus, being lighter than saltasaurines, but heavier than aeolosaurines. Rinconsaurus was incorporated into an expanded version of a phylogenetic data matrix along with several ontemporary South American titanosaurs. The resulting data matrix comprises 102 taxa scored for 431 characters, and our phylogenetic analysis retrieves Rinconsaurus as a member of the clade Rinconsauria. For its part, the clade Rinconsauria, in which Aeolosaurini is nested, is recovered within a diverse Lognkosauria. When the resulting trees are time calibrated and taking into account the position of Ninjatitan within Rinconsauria, there results that the possible origin of the clades Lognkosauria and Rinconsauria (among other titanosaur clades) could have occurred towards the beginning of the Early Cretaceous.
Article
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Titanosaurian sauropods are known to exhibit remarkable body size disparity, with some taxa famed for nearing the zenith of terrestrial vertebrate body size. Here, we describe a new titanosaurian – Ibirania parva gen. et sp. nov. – from the Upper Cretaceous (Santonian– Campanian) São José do Rio Preto Formation of Bauru Basin, in which represents one of the smallest sauropods known to date. The new taxon is diagnosed by seven autapomorphies and had an estimated body length of 5.7 m. Histological and μCT scan analyses showed that this new taxon is represented by skeletally mature individuals, which had attained somatic maturity prior to death. Phylogenetic analyses recovered the new taxon deeply nested within Saltasaurinae, a clade previously known by small-sized forms. Ibirania parva gen. et sp. nov. brings new information indicating that the body size reduction in some titanosaurians could be driven by recurrent ecophysiographical settings, present in South America prior to the diversity peak attained by the group during the Campanian–Maastrichtian.
Chapter
Titanosaurian sauropods were the most diverse and successful group of large-bodied terrestrial herbivores. Two aspects regarding their evolutionary history stand out, namely their great morphological diversity and their extensive record from various continental masses. In South America, and particularly in Argentina, the group has the richest record worldwide. This is mainly due to the conjunction of two factors: the extensive paleontological investigation carried out by South American researchers since the beginning of the twentieth century and the well-exposed outcrops of Cretaceous continental strata. With the exception of Tapuiasaurus from Brazil, the entire record of South American named titanosaurs discovered in the Berriasian–Santonian interval comes from Argentina, specifically from Patagonia, including the south of Mendoza, Neuquén, Río Negro, and Chubut Provinces. With a number of 22 valid taxa, the Early and ‘Mid’-Cretaceous titanosaur record of South America includes basally branching (‘basal’) forms (e.g., Andesaurus, Ninjatitan), basal and derived lithostrotians (e.g., Sarmientosaurus, Tapuiasaurus, and Epachthosaurus), and most of the colossosaurs (mainly the giant lognkosaurs Mendozasaurus, Futalognkosaurus, Patagotitan, and Notocolossus). After their origin in the Early Cretaceous, titanosaurians experienced a rapid increase in taxonomic diversity, which is maintained toward the Late Cretaceous. However, during the Berriasian–Santonian interval, the size of titanosaurs reached its climax, representing the largest vertebrate animals ever to inhabit the earth. Some South American titanosaurs from this time have been widely used to define new clades (e.g., Colossosauria, Lognkosauria, Rinconsauria) that clarified the main phylogenetic relationships at lower level. Moreover, studies in some key paleobiological aspects related with the estimation of size contributed to better understanding the biology of some species in the context of the process of gigantism.
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Rapetosaurus krausei (Sauropoda: Titanosauria) from the Upper Cretaceous Maevarano Formation of Madagascar is the best-preserved and most complete titanosaur yet described. The skull of Rapetosaurus is particularly significant because most titanosaurs are diagnosed solely on the basis of fragmentary postcranial material, and knowledge of the titanosaur skull has remained incomplete. Material referred to Rapetosaurus includes the type skull from an adult that preserves the basicranium, rostrum, mandible, and palate. A second, juvenile skull preserves most of the braincase and cranial vault, as well as some of the palate and lower jaw. Here we provide a detailed description of Ropetosaurus cranial anatomy and highlight comparative relationships among known titanosaur and other neosauropod skulls. The Rapetosaurus skull is similar to those of diplodocoids in its overall shape, with retracted external nares and an elongated snout. However, extensive tooth distribution and bone articulations surrounding the external narial region and orbit are more similar to those of macronarians like Camarasaurus and Brachiosaurus. The maxilla, basicranium, paroccipital process, and pterygoid are among the most diagnostic elements of the Rapetosaurus skull, along with the enlarged antorbital fenestra, anteroventrally oriented braincase, and mandible. Titanosaur crania exhibit a greater diversity than previously recognized and, in light of Rapetosaurus, it is apparent that there is not a narrowly constrained bauplan for the skull of titanosaurs. Broad generalizations about evolution based on previously known, fragmentary fossils require re-evaluation. Ultimately, Rapetosaurus will be key in resolving titanosaur higher-level and ingroup phylogeny.
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The titanosaurid skull is interpreted as Camarasaurus-like, but with "peg-like" teeth restricted to the extremity of the jaws, which exhibit wear facets sharply inclined with respect to the labio-lingual axis. The last character is shared with Brachiosaurus Riggs and Pleurocoelus Marsh, and it is considered a probable synapomorphy of Titanosauriformes. Several cranial characters are considered synapomorphies of Titanosauria or a less inclusive group (long recurved paraoccipital processes, becoming slender downwards; reduced, narrow supratemporal fenestra), or synapomorphies within Titanosauridae ("peg-like" teeth; teeth restricted to the anterior region of the snout and mandibular symphysis perpendicular to the long axis of the lower jaw). Several characters, such as "peg-like" teeth restricted to the anterior region of the snout, wear facets sharply inclined with respect to the labiolingual looth axis, and mandibular symphysis perpendicular to the long axis of the lower jaw, suggest that Nemegtosaurus mongoliensis Nowinski and Quaesitosaurus orientalis Kurzanov and Banikov are related to the Titanosauridae. "Pleurocoelus" sp., from the Lower Cretaceous of Texas and Utah, is considered a basal titanosaur by having procoelous anterior caudals, teeth with an intermediate morphology between Brachiosaurus and titanosaurids, and dorsal verterbrae with centro-parapophyseal lamina and ventrally widened, sligthly forked infradiapophyseal lamina. Basal titanosaurs and other titanosaur-related sauropods had a wide distribution during the Early Cretaceous. The hypothesis that Alamosaums sanjuanensis Gilmore is a Late Cretaceous inmigrant from South America is consistent with its phylogenetic position. The Saltasaurinae, in turn, represent an endemic group of South America.
Article
Two major ichnotypes of sauropod trackways have been described: "narrow-gauge," in which both manus and pes prints approach or intersect the trackway midline, and "wide-gauge," in which these prints are well apart from the midline. This gauge disparity could be the result of differences in behavior, body size, or morphology between the respective trackmakers. However, the biomechanics of locomotion in large terrestrial vertebrates suggest that sauropods were probably restricted in locomotor behavior, and the lack of systematic size differences between footprint gauges argues against body-size-related influences. We argue that skeletal morphology is responsible for gauge differences and integrate data from locomotor biomechanics and systematics with the track record to predict the hindlimb morphology of wide-gauge trackmakers. Broader foot stances in large, graviportal animals entail predictable mechanical consequences and hindlimb modifications. These could include outwardly angled femora, offset knee condyles, and a more eccentric femoral midshaft cross-section. A survey of sauropod hindlimb morphology reveals that these features are synapomorphies of titanosaurs, suggesting that they were the makers of wide-gauge trackways. The temporal and geographic distribution of titanosaurs is consistent with this hypothesis because wide-gauge trackways predominate during the Cretaceous and are found worldwide. Additional appendicular synapomorphies of titanosaurs are interpreted in light of identifying these animals as wide-gauge trackmakers. We suggest that titanosaurs may have used a bipedal stance more frequently than did other sauropods. These correlations between ichnology, biomechanics, and systematics imply that titanosaurs were unique among sauropods in having a more varied repertoire of locomotor habits.