Mapusaurus ( 'earth lizard') is a genus of giant carcharodontosaurid dinosaur that lived in Argentina during the Cenomanian–Turonian ages of the Late Cretaceous. It is known from a bonebed of between seven and nine specimens, excavated from the Stratum of the Huincul Formation between 1997 and 2001 as part of the Argentinian-Canadian Dinosaur Project. In 2006, Rodolfo Coria and Philip J. Currie scientifically described Mapusaurus. Only one species of Mapusaurus, M. roseae, has been described, named after the rose-colored rocks in which it was discovered and sponsor Rose Letwin.
Mapusaurus was one of the largest carcharodontosaurids. Based on the biggest specimen known from the bonebed, represented by a left femur, it was originally estimated to have reached a maximum body length of and a mass of . Subsequent works have given maximum size estimates of and respectively. Mapusaurus generally resembled Giganotosaurus, though had a deeper skull, a more rugose maxilla, a rougher surface to its Lacrimal bone bone, differently proportioned neck vertebrae, and various other minor differences. The arms of Mapusaurus were very small, similar in terms of proportional size to those of Tyrannosauridae and Abelisauridae.
Discovery and naming
The first fossils of this taxon were discovered in 1995 by members of the Argentinian-Canadian Dinosaur Project
in an exposure of the Huincul Formation at Cañadón del Gato, a site south of
Plaza Huincul in Neuquén Province, Argentina.
In 1997, crews from the Project began excavating the fossils, which they believed to belong to a single skeleton of a large
Theropoda dinosaur.
However, during preparation of the remains it was realized that they came from several individuals of differing sizes and
Ontogeny. That same year, Argentine paleontologist
Rodolfo Coria and Canadian paleontologist Philip Currie, the leaders of the Project, announced the discovery of the theropod at a meeting of the
Society of Vertebrate Paleontology, stating that the team had unearthed a single skeleton of a new carcharodontosaurid theropod similar to
Giganotosaurus. By that time, an isolated
tooth, a , a (tail)
vertebra, a manual , an incomplete
pelvis,
Femur,
Tibia, a
fibula, a
Metatarsal bones, and several pedal (foot)
Phalanx bone had been collected,
however later digs would find more fossils.
Excavations of the fossils at Cañadón del Gato lasted from 1997 to 2001, wherein hundreds of fossils from at least seven to nine individuals of
Mapusaurus were discovered. These fossils were mentioned in conference abstracts in 2000 and 2001, which noted the possibility of pack behavior or gregariousness in large theropods based on the quantity and age range of the theropod fossils found.
In 2006, Coria and Currie scientifically described the remains, and identified them as belonging to a new genus and species of giant carcharodontosaurid theropod. Based on this material, they named them Mapusaurus roseae. The generic name Mapusaurus derives from the Mapuche word Mapu, meaning "Earth", and the Greek σαῦρος ( saûros), meaning "lizard", and thus "Earth lizard". The specific name roseae is named for both the rose-colored rocks, in which the fossils were found and for Rose Letwin, who sponsored the expeditions which recovered these fossils. Coria and Currie designated an isolated right (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados) as the holotype (name-bearing) specimen of M. roseae. Additionally, Coria and Currie assigned several Paratype to M. roseae, including portions of the skull, limbs, pelvis, and vertebrae. In total, Mapusaurus is known from parts of the skull and mandible, teeth, some cervical (neck), (back), and caudal vertebrae, much of the sacrum and pelvis, some Rib cage, parts of the , much of the Hindlimb, many pedal phalanges, and fragments of the forelimb and manus.
Taurovenator
In 2005, a right of a theropod dinosaur was unearthed by Argentine paleontologist
Matias Motta from a section of
sandstone Stratum in Violante Farm in Rio Negro Province, Argentina deriving from the lower member of the Huincul Formation.
The fossil was then transported to the Museo Provincial "Carlos Ameghino"
and cataloged under catalogue number MPCA-Pv 803.
In 2016. Motta and colleagues described the postorbital as the holotype of a new genus and species of carcharodontosaurid dinosaur,
Taurovenator violantei.
Taurovenator went largely unnoticed due to its fragmentary nature,
and Coria and colleagues (2019) suggested that
Taurovenator is synonymous with
Mapusaurus, considering both of the former's
Autapomorphy (distinguishing traits) were also found in
Mapusaurus.
Additionally, the authors considered that there was a high likelihood of them being .
However,
Taurovenator is actually from the lower unit of the Huincul Formation, while
Mapusaurus is from the upper unit of the formation, suggesting they could be distinct genera.
In 2022, another carcharodontosaurid from the Huincul Formation,
Meraxes, was named on the basis of a well-preserved skull and partial skeleton from the same strata as
Taurovenator. In their description of
Meraxes, the authors stated that
Taurovenator lacks sufficient diagnostic characters and may be coeval with
Meraxes.
In 2005, an associated skeleton (MPCA-Pv 803) including a partial skull and posterior (back portion) mandible, incomplete cervical (neck vertebrae) series, fragments of dorsal (back) vertebrae, several ribs, two partial forelimbs, a femur, a partial pes, gastralia, and a caudal vertebra was unearthed along with the Taurovenator. This specimen was regarded as belonging to an indeterminate carcharodontosaurid in the 2016 description of Taurovenator.
Description
In their paper describing
Mapusaurus, Coria and Currie estimated that the specimens found in the bonebed measured between in length, with the former being based on a left dentary (MCF PVPH-108.3) and the latter being based on a left femur (MCF-PVPH-108.203).
Subsequent maximum size estimates vary from around , and weight estimates range from .
Skull and dentition
The skull of
Mapusaurus was deeper and narrower than that of
Giganotosaurus, due to the comparative shortness of the
Maxilla and slenderness of the
Nasal bone.
The nasals were very rugose, as in
Carcharodontosaurus,
Giganotosaurus,
Meraxes, and
Tameryraptor. The lateral (external, or outer) surface of the maxilla in many carcharodontosaurids (i.e.
Carcharodontosaurus,
Giganotosaurus,
Meraxes, and
Tameryraptor) had a rough texture,
and the same is true of
Mapusaurus.
Whereas the
rugosity of
Giganotosaurus' maxilla stopped shortly posterior to (behind) the nasal opening, that of
Mapusaurus continued for most of the bone's length. The bar between the antorbital and , the so-called interfenestral strut, was fairly wide in comparison to other carcharodontosaurids. Whereas many derived carnosaurs had several openings in the maxilla anterior to (in front of) the antorbital fenestra, in
Mapusaurus, the maxillary fenestra was the only one,
and it disappeared with growth.
The antorbital fossa was about equal in size to that of
Carcharodontosaurus and
Giganotosaurus. The orbit, or eye socket, was partly divided into upper and lower sections by projections of the
Lacrimal bone and
postorbital bones.
Like in many derived carcharodontosaurids, such as
Meraxes, the lateral postorbital surface bore a robust brow horn.
The lacrimals and
Prefrontal bone bones were fused, as in many theropods, including
Giganotosaurus. The lacrimals of the two genera differed in that
Mapusaurus' lacrimal had a rugose dorsal (upper) surface, whereas that of
Giganotosaurus bore deep grooves.
Mapusaurus' teeth were similar to those of other carcharodontosaurids, being flat, narrow, and blade-like and bearing 10–12 denticles per , as opposed to 13–15 denticles per 5 mm in
Acrocanthosaurus. There were 12
Alveolus (tooth sockets) in each maxilla, as opposed to 14 in
Carcharodontosaurus.
The of Mapusaurus, the part of the lower jaw which bore teeth in life, was similar to that of Giganotosaurus in that it expanded anteriorly more than in most other theropods; this is contributed to by a ventral flange on the mandibular symphysis. While loosely similar expansions are seen in other groups and genera, such as Tyrannosaurus, in Mapusaurus (and by extension, presumably, other carcharodontosaurids), the presence of this distinctive flange in a juvenile suggests that it was not controlled by ontogeny. In both Mapusaurus and Giganotosaurus, the Meckelian groove is fairly shallow, though that of the former genus was positioned more dorsally. A partial surangular is known from a juvenile Mapusaurus specimen, which is identical to the corresponding bone in Giganotosaurus. The angular bone was strengthened by a thick ventral margin, which contributed to the ventral portion of the mandible. Each dentary appears to have had fifteen teeth.
Axial skeleton
The
Spinal column of
Mapusaurus closely resembled that of
Giganotosaurus. As in most carnosaurs, the neural arches, the masses of bone or
cartilage posterior to the main vertebral bodies, were inclined posterodorsally (rearward and upward). The
Vertebra (the tall projections at the top of each vertebra) of the axis, the second cervical (neck) vertebra, appears to have been longer and more gracile than those of
Mapusaurus. There were well-developed laminae between the neural spine and vertebral
epiphysis, which are not observed in more basal taxa such as
Acrocanthosaurus and
Allosaurus. Further back in the cervical column, the neck vertebrae were proportionally shorter and slimmer than those of
Giganotosaurus, more closely resembling
Abelisauridae in their proportions. The neural spines of the
Dorsal vertebra (back) vertebrae were relatively tall and were inclined posteriorly. The more posterior dorsal vertebrae were , meaning that both anterior and posterior surfaces were flat.
Mapusaurus' caudal (tail) vertebrae are well known from various specimens. The neural spines of the mid-caudal vertebrae were low and anteroposteriorly (from front-to-back) elongated. The most posterior one had a low regular neural spine and a second, accessory one anterior to it. The anatomy of the preserved
Rib cage, which resemble those of many other large theropods, suggests that the chest of
Mapusaurus would have been deeper than it was wide. Various fragmented
gastralia, the bones which would have supported the abdominal organs and served as muscle attachment points, are known, and do not seem to have meaningfully differed from those of other big theropods.
Appendicular skeleton
Mapusaurus'
scapula (shoulder blade) was long and gently curved, with a pronounced, sharply offset
Acromion, similar to other carnosaurs and tyrannosaurids. It is less robust than that of large
Ceratosauria and
Megalosauridae. The scapula and
coracoid were distinct bones, and did not co-ossify into a
scapulocoracoid. One partial coracoid is known. A possible
furcula is preserved, though there is a possibility that it is a fused pair of gastralia. What is known of the humerus (upper arm bone) based on a right humerus, MCF-PVPH-108.45, was fairly robust. The humerus was around a quarter of the length of the femur, and its arms were thus relatively short. The radius (one of the two forearm bones) was relatively massive. Little is preserved of the manus (hand). The second and third
Metacarpal bones (hand bones) appear to have been partly fused, though there is no indication that the first metacarpal had fused with the others. A single manual phalanx (finger bone) is known, as well as a probable
ungual phalanx (the bone which would have supported a
claw) which may be from the second digit.
The pelvis and hind limbs are very well preserved in comparison to the pectoral girdle and forelimbs. The ratio between the preacetabular and postacetabular lengths of the ilium (the parts before and after the acetabulum) is about the same as in the holotype of Giganotosaurus. At the back of the ilium, near the base of the peduncle where the ischium articulated, there were a series of shallow pits, likely attachment sites for the iliofemoralis and caudofemoralis muscles. Three femora (thigh bones) are known. Unlike most other carnosaurs, the fourth trochanter, one of the structures to which the caudofemoralis muscles would have attached, was prominent. It was similar in size to that of Giganotosaurus, though both were exceeded by that of Carcharodontosaurus. Like in Giganotosaurus, the lateral (outer) side of the tibia (one of the lower leg bones) of Mapusaurus extends further down than the medial (inner) side. The fibula, the other lower leg bone, was slightly more gracile than in the holotype of Giganotosaurus. The Metatarsal bones (foot bones) of Mapusaurus were fundamentally to those of other carnosaurs. Eight pedal (foot) phalanges are represented, though no pedal unguals are preserved.
Paleobiology
The
fossil remains of
Mapusaurus were discovered in a
bone bed containing at least seven to possibly up to nine individuals of various
Ontogeny.
Coria and Currie speculated that this may represent a long term, possibly coincidental accumulation of carcasses (some sort of
predator trap) and may provide clues about
Mapusaurus behavior.
Other known
theropod bone beds and fossil graveyards include those of
Dromaeosauridae Deinonychus and
Utahraptor,
[ ( abstract )] those of
Allosaurus from the Cleveland-Lloyd Dinosaur Quarry of
Utah,
and those of
tyrannosaurids Teratophoneus,
Albertosaurus and
Daspletosaurus.
Paleontologist Rodolfo Coria, of the Museo Carmen Funes, contrary to his published article, repeated in a press-conference earlier suggestions that this congregation of fossil bones may indicate that Mapusaurus like Giganotosaurus also hunted in groups and worked together to take down large prey, such as the immense sauropod Argentinosaurus.
A biomechanical model of Tyrannosaurus presented by William I. Sellers and colleagues in 2017 suggested that speeds above would probably have shattered the leg bones of Tyrannosaurus. The finding may mean that running was also not possible for other giant theropod dinosaurs like Giganotosaurus, Mapusaurus and Acrocanthosaurus.
Classification
Mapusaurus is a genus in the family Carcharodontosauridae,
subfamily Carcharodontosaurinae, and tribe Giganotosaurini.
Giganotosaurini contains
Mapusaurus itself in addition to the carcharodontosaurines
Meraxes, Giganotosaurus, and
Tyrannotitan, but excludes the African genus
Carcharodontosaurus. In their description of
Mapusaurus, Coria and Currie erected the subfamily (now tribe) Giganotosaurinae. They defined this subfamily as including all carcharodontosaurids closer to
Mapusaurus and
Giganotosaurus than
Carcharodontosaurus and as being united by the presence of a weak fourth trochanter and a broad groove on the distal end of the femur. They tentatively included the genus
Tyrannotitan in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.
Giganotosaurini is a tribe of giant carcharodontosaurines
Endemism to the Late Cretaceous of Argentina, with some members like
Giganotosaurus possibly being the largest theropods known, reaching sizes as large as in length and in mass.
American paleontologist Paul Sereno's description of Carcharodontosaurus fossils in 1996 led to the realization of a transcontinental clade of carcharodontosaurids. As more carcharodontosaurids were discovered, their interrelationships became even clearer. The group was defined as all allosauroids closer to Carcharodontosaurus than Allosaurus or Sinraptor by American paleontologist Thomas R. Holtz and colleagues in 2004.
In their 2022 description of the large carcharodontosaurine Meraxes, Juan I. Canale and colleagues recovered the following relationships for Mapusaurus and the Giganotosaurini.
In his 2024 review of theropod relationships, Cau recovered similar results, with Tyrannotitan as the sister taxon to the clade formed by Mapusaurus and Giganotosaurus. His results are displayed in the cladogram below:
Evolution
Argentine paleontologists Coria and
Leonardo Salgado suggested that the convergent evolution of gigantism in theropods could have been linked to common conditions in their environments or
ecosystems.
Sereno and colleagues found that the presence of carcharodontosaurids in Africa (
Carcharodontosaurus), North America (
Acrocanthosaurus), and South America (
Giganotosaurus), showed the group had a transcontinental distribution by the Early Cretaceous period. Dispersal routes between the northern and southern continents appear to have been severed by ocean barriers in the Late Cretaceous, which led to more distinct, provincial faunas, by preventing exchange.
Previously, it was thought that the Cretaceous world was biogeographically separated, with the northern continents being dominated by tyrannosaurids, South America by abelisaurids, and Africa by carcharodontosaurids.
The subfamily Carcharodontosaurinae, in which
Carcharodontosaurus belongs, appears to have been restricted to the southern continent of
Gondwana (formed by South America and Africa), where they were probably the
Apex predator.
The South American tribe Giganotosaurini may have been separated from their African relatives through
vicariance, when Gondwana broke up during the
Aptian–
Albian ages of the Early Cretaceous.
Paleoenvironment
Mapusaurus was discovered in the Argentine Province of Neuquén. It was found in the Huincul Formation, a rock formation bordering the Río Limay Subgroup, the latter of which is a subdivision of the Neuquén Group. This unit is located in the Neuquén Basin in
Patagonia. The Huincul Formation is composed of yellowish and greenish
Sandstone of fine-to-medium grain, some of which are
Tuff.
These deposits were laid down during the Upper Cretaceous, either in the middle
Cenomanian to early
Turonian stages
or the early Turonian to late
Santonian.
The deposits represent the drainage system of a
braided river.
Fossilised pollen indicates a wide variety of plants were present in the Huincul Formation. A study of the El Zampal section of the formation found Hornwort, Liverwort, Fern, Selaginellales, possible Noeggerathiales, Gymnosperm (including Gnetophyte and Conifer), and Angiosperm (flowering plants), in addition to several pollen grains of unknown affinities.
In addition to Mapusaurus, the theropods of the Huincul Formation are represented by the other giant carcharodontosaurids Meraxes and Taurovenator, Abelisaurid including Skorpiovenator,
External links
