Mapusaurus

''Mapusaurus'' () was a giant carcharodontosaurid carnosaurian dinosaur from the early Late Cretaceous (early Turonian stage), approximately 93.9 to 89.6 million years ago, of what is now Argentina.

Discovery

''Mapusaurus'' was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation (Rio Limay Subgroup, Cenomanian) at Cañadón del Gato. It was described and named by paleontologists Rodolfo Coria and Phil Currie in 2006.

The name ''Mapusaurus'' is derived from the Mapuche word ''Mapu'', meaning 'of the Land' or 'of the Earth' and the Greek ''sauros'', meaning 'lizard'. The type species, ''Mapusaurus 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.

The designated holotype for the genus and type species, ''Mapusaurus roseae'', is an isolated right nasal (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados, Plaza Huincul, Neuquén). Twelve paratypes have been designated, based on additional isolated skeletal elements. Taken together, the many individual elements recovered from the ''Mapusaurus'' bone bed represent most of the skeleton.

Description

''Mapusaurus'' was a large theropod, but smaller in size than its close relative ''Giganotosaurus'', reaching in length and in body mass. Some specimens noted by Coria and Currie may have belonged to an individual comparable in size to the ''Giganotosaurus'' holotype, reaching in length, but these dinosaurs may not have the exact same proportions, so this should be regarded as a "very rough" estimate.

It has been determined that ''Mapusaurus'' was diagnosed on autapomorphies, or unique traits, in regions of the skeleton that ''Giganotosaurus'' does not preserve. ''Mapusaurus'' only differs from ''Giganotosaurus'' in lacking a second opening on the middle quadrate, and in some details of the topology of the nasal rugosities.

Paleobiology

The fossil remains of ''Mapusaurus'' were discovered in a bone bed containing at least seven individuals of various growth stages. 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 ''Velociraptor'' and other dromaeosaurids around the planet, the ''Allosaurus''-dominated Cleveland-Lloyd Dinosaur Quarry of Utah, an '' Albertosaurus'' bone bed from Alberta and a ''Daspletosaurus'' bone bed from Montana, and even a ''Tyrannosaurus'' bone bed from ''Montana'', as well.

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''. If so, this would be the first substantive evidence of gregarious behavior by large theropods other than ''Tyrannosaurus'', although whether they might have hunted in organized packs (as wolves and lions do) or simply attacked in a mob, is unknown. The authors interpreted the depositional environment of the Huincul Formation at the Cañadón del Gato locality as a freshwater paleochannel deposit, "laid down by an ephemeral or seasonal stream in a region with arid or semi-arid climate". This bone bed is especially interesting, in light of the overall scarcity of fossilized bone within the Huincul Formation. An ontogenetic study by Canale ''et al.'' (2014) found that ''Mapusaurus'' displayed heterochrony, an evolutionary condition in which the animals may retain an ancestral characteristic during one stage of their life, but lose it as they develop. In ''Mapusaurus'', the maxillary fenestrae are present in younger individuals, but gradually disappear as they mature.

Classification

Cladistic analysis carried out by Coria and Currie definitively showed that ''Mapusaurus'' is nested within the clade Carcharodontosauridae. The authors noted that the structure of the femur suggests a closer relationship with ''Giganotosaurus'' than either taxon shares with ''Carcharodontosaurus''. They created a new monophyletic taxon based on this relationship, the subfamily Giganotosaurinae, defined as all carcharodontosaurids closer to ''Giganotosaurus'' and ''Mapusaurus'' than to ''Carcharodontosaurus''. They tentatively included the genus ''Tyrannotitan'' in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.

The following cladogram after Novas ''et al.'', 2013, shows the placement of ''Mapusaurus'' within Carcharodontosauridae.

Paleoecology

As previously mentioned, the Huincul Formation is thought to represent an arid environment with ephemeral or seasonal streams. The age of this formation is estimated at 97 to 93.5 Mya.Huincul Formation
at Fossilworks.org The dinosaur record is considered sparse here. ''Mapusaurus'' shared its environment with the sauropods '' Argentinosaurus'' (one of the largest sauropods, if not the largest), '' Choconsaurus'', and ''Cathartesaura''. Another carcharodontosaurid known as ''Meraxes'' was found in the same formation, but on older rocks than ''Mapusaurus'', so they probably didn't coexist. Abelisaurid theropods ''Skorpiovenator'' and ''Ilokelesia'' also lived in the region.

Fossilized pollen indicates a wide variety of plants was present in the Huincul Formation. A study of the El Zampal section of the formation found hornworts, liverworts, ferns, Selaginellales, possible Noeggerathiales, gymnosperms (including gnetophytes and conifers), and angiosperms (flowering plants), in addition to several pollen grains of unknown affinities. The Huincul Formation is among the richest Patagonian vertebrate associations, preserving fish including dipnoans and gar, chelid turtles, squamates, sphenodonts, neosuchian crocodilians, and a wide variety of dinosaurs. Vertebrates are most commonly found in the lower, and therefore older, part of the formation.

References

External links

Meat-Eating Dinosaur Was Bigger Than T. Rex.
National Geographic News
*

. Mike Taylor. The Dinosaur FAQ. August 27, 2002. (Named as Unnamed Argentinian Carcharodontosaurine)
* " nd the Largest Theropod is... http://dml.cmnh.org/2003Jul/msg00355.html. The Dinosaur Mailing List Archives. Retrieved March 21, 2010 (Named as Undescribed Carcharodontosaurine)

{{Taxonbar, from=Q131176

Apex predators
Carcharodontosaurids
Cenomanian life
Turonian life
Late Cretaceous dinosaurs of South America
Cretaceous Argentina
Fossils of Argentina
Huincul Formation
Fossil taxa described in 2006
Taxa named by Rodolfo Coria
Taxa named by Philip J. Currie