The nameMapusaurus is derived from theMapuche wordMapu, meaning 'of the Land' or 'of the Earth' and theGreeksauros, meaning 'lizard'. Thetype species,Mapusaurus roseae, is named for both therose-colored rocks, in which the fossils were found and forRose Letwin, who sponsored the expeditions which recovered these fossils.[2]
The designatedholotype for thegenus andtype 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 theMapusaurus bone bed represent most of the skeleton.[2]
Mapusaurus was a large theropod, but slightly smaller in size than its close relativeGiganotosaurus, with the largest specimen measuring around 10.2–12.2 metres (33–40 ft) long and weighing up to 3–6 metric tons (3.3–6.6 short tons).[2][7][8][9]
It has been determined thatMapusaurus was diagnosed on autapomorphies, or unique traits, in regions of the skeleton thatGiganotosaurus does not preserve.Mapusaurus only differs fromGiganotosaurus in lacking a second opening on the middlequadrate, and in some details of the topology of the nasal rugosities.[10]
Paleontologist Rodolfo Coria, of theMuseo Carmen Funes, contrary to his published article, repeated in a press-conference earlier suggestions that this congregation of fossil bones may indicate thatMapusaurus likeGiganotosaurus also hunted in groups and worked together to take down large prey, such as the immensesauropodArgentinosaurus.[17] If so, this would be the first substantive evidence of gregarious behavior by large theropods other thanTyrannosaurus rex, 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 thedepositional 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".[2] 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)[12] found thatMapusaurus 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. InMapusaurus, the maxillary fenestrae are present in younger individuals, but gradually disappear as they mature.
Cladistic analysis carried out by Coria and Currie definitively showed thatMapusaurus is nested within thecladeCarcharodontosauridae. The authors noted that the structure of thefemur suggests a closer relationship withGiganotosaurus than eithertaxon shares withCarcharodontosaurus. They created a newmonophyletic taxon based on this relationship, thesubfamilyGiganotosaurinae, defined as all carcharodontosaurids closer toGiganotosaurus andMapusaurus than toCarcharodontosaurus. They tentatively included the genusTyrannotitan in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.[2]
In their 2022 description of the large carcharodontosaurineMeraxes, Canale et al. recovered the following relationships forMapusaurus and the Giganotosaurini.[18]
In his 2024 review of theropod relationships, Cau recovered similar results, withTyrannotitan as thesister taxon to the clade formed byMapusaurus andGiganotosaurus. His results are displayed in thecladogram below:[19]
Size comparison of several dinosaurs from theHuincul Formation,Mapusaurus in red
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.[20] The dinosaur record is considered sparse here.Mapusaurus shared its environment with thesauropodsArgentinosaurus (one of the largest sauropods, if not the largest),Choconsaurus,Chucarosaurus andCathartesaura. Two other giant carcharodontosaurids,Meraxes andTaurovenator, were found in the same formation, but in older rocks thanMapusaurus, so they likely were not coevals.[21][22] Theabelisaurid theropodsSkorpiovenator andIlokelesia also lived in the region.[23]
Fossilized pollen indicates a wide variety of plants was present in the Huincul Formation. A study of the El Zampal section of the formation foundhornworts,liverworts,ferns,Selaginellales, possibleNoeggerathiales,gymnosperms (includinggnetophytes andconifers), andangiosperms (flowering plants), in addition to several pollen grains of unknown affinities.[24] The Huincul Formation is among the richest Patagonian vertebrate associations, preserving fish includingdipnoans andgar,chelid turtles,squamates,sphenodonts,neosuchiancrocodilians, and a wide variety of dinosaurs.[25][26] Vertebrates are most commonly found in the lower, and therefore older, part of the formation.[27]
^Holtz, T. (2015).Paleontologists: Searching for Dinosaur Bones. Enslow Publishing, LLC. p. 54.ISBN978-0766069640.
^Paul, Gregory S. (2024).The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton, New Jersey: Princeton University Press. p. 116.ISBN9780691231570.
^Holtz, Thomas R. (2021). "Theropod guild structure and the tyrannosaurid niche assimilation hypothesis: implications for predatory dinosaur macroecology and ontogeny in later Late Cretaceous Asiamerica".Canadian Journal of Earth Sciences.58 (9): 778−795.doi:10.1139/cjes-2020-0174.hdl:1903/28566.
^abCanale, Juan Ignacio; Novas, Fernando Emilio; Salgado, Leonardo; Coria, Rodolfo Aníbal (December 1, 2015). "Cranial ontogenetic variation inMapusaurus roseae (Dinosauria: Theropoda) and the probable role of heterochrony in carcharodontosaurid evolution".Paläontologische Zeitschrift.89 (4):983–993.Bibcode:2015PalZ...89..983C.doi:10.1007/s12542-014-0251-3.hdl:11336/19258.ISSN0031-0220.S2CID133485236.
^Hunt, Adrian P; Lucas, Spencer G.; Krainer, Karl; Spielmann, Justin (2006). "The taphonomy of theCleveland-Lloyd Dinosaur Quarry, Upper Jurassic Morrison Formation, Utah: a re-evaluation". In Foster, John R.; Lucas, Spencer G. (eds.).Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin,36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 57–65.
^Bellardini, F.; Filippi, L.S. (2018). "New evidence of saurischian dinosaurs from the upper member of the Huincul Formation (Cenomanian) of Neuquén Province, Patagonia, Argentina".Reunión de Comunicaciones de la Asociación Paleontológica Argentina: 10.
"[And the Largest Theropod is...http://dml.cmnh.org/2003Jul/msg00355.html]". The Dinosaur Mailing List Archives. Retrieved March 21, 2010 (Named as Undescribed Carcharodontosaurine)
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