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Mapusaurus

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Mapusaurus
Temporal range: Late Cretaceous (Cenomanian to Turonian), ~97–93.5 Ma
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Reconstructed skeletons of an adult and a juvenile (left)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Carcharodontosauridae
Subfamily: †Carcharodontosaurinae
Tribe: †Giganotosaurini
Genus: †Mapusaurus
Coria & Currie, 2006
Type species
†Mapusaurus roseae
Coria & Currie, 2006

Mapusaurus (meaning "Earth lizard") was a giant carcharodontosaurid carnosaurian dinosaur from the early Late Cretaceous (late Cenomanian to early Turonian stage), approximately 97 to 93 million years ago, of what is now Argentina.

Discovery

Reconstructed skull

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.[1]

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.[1]

Description

Size of a few specimens compared to a human

Mapusaurus was a large theropod, and was roughly similar in size to its close relative Giganotosaurus, with the largest known individuals estimated as about 11.5 meters (38 ft) to 12.6 meters (41 ft) in length or more and weighing about 3 metric tons (3.3 short tons) to 5 metric tons (5.5 short tons).[1] The longest individual for which Coria and Currie (2006) provided a concrete estimate in Table 1 (appendix lll) is the animal to which femur MCF-PVPH-208.203 belonged; this individual is estimated as 10.2 meters (33 ft) long.

Coria and Currie note the presence of isolated bones from at least one longer individual, but do not provide a figure, instead finding the larger bones coherent with an individual of comparable size to Giganotosaurus holotype estimated at 12.2 meters (40 ft) in length,[1] although not with the same exact proportions, having taller and wider neural spines, a more elongate fibula (86 centimeters (34 in) compared to 83.5 centimeters (32.9 in)) but more slender (81–89% the width as in Giganotosaurus)[1] as well as a wider pubic shaft in minimal dimensions (10% wider as indicated by a 7.8 centimeters (3.1 in) long fragment catalogued as MCF-PVPH-108.145), and with a differently proportioned skull, shorter in length than Giganotosaurus because the maxilla is not elongated (12 teeth compared to 14 in Carcharodontosaurus), but deeper in proportion due to this, as well as narrower (due to the narrow nasals). Considering this, a fragmentary maxilla is coherent with the size of the Giganotosaurus-sized individual (MCF-PVPH-108.169). A neural arch from an axis (MCF-PVPH-108.83) and a scapular blade fragment are also the same exact size as the same elements in Giganotosaurus. The weight estimate of 3,000 kilograms (6,600 lb) is from a 1,300 millimeters (51 in) long femur with a 455 millimeters (17.9 in) circumference (MCF-PVPH-208.234).[1]

Holtz estimated the maximum size of the animal at 12.6 meters (41 ft).[2] This estimate has been cited in Drew Eddy and Julia Clarke (2011),[3] and cited again in a phylogenetic table in a 2014 analysis by Canale et al..[4] Gregory Paul gave a lower estimation of 11.5 meters (37.7 ft) and 5 metric tons (5.5 short tons).[5]

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.[6]

Paleobiology

Restoration

The fossil remains of Mapusaurus were discovered in a bone bed containing at least seven individuals of various growth stages.[4][3] 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.[1] Other known theropod bone beds include the Allosaurus-dominated Cleveland-Lloyd Dinosaur Quarry of Utah, an Albertosaurus bone bed from Alberta and a Daspletosaurus bone bed from Montana.

Mapusaurus bones with pathologies

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 hunted in groups and worked together to take down large prey, such as the immense sauropod Argentinosaurus.[7] 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 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".[1] 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)[4] 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

Comparison of two Mapusaurus roseae skulls

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.[1]

The following cladogram after Novas et al., 2013, shows the placement of Mapusaurus within Carcharodontosauridae.[8]

Paleoecology

Silhouettes of dinosaurs from the Huincul Formation as size comparison
Size comparison of several dinosaurs from the Huincul 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.[2] 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. Abelisaurid theropods Skorpiovenator and Ilokelesia also lived in the region.[9]

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.[10] 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.[11][12] Vertebrates are most commonly found in the lower, and therefore older, part of the formation.[13]

References

  1. ^ a b c d e f g h i Coria, R. A.; Currie, P. J. (2006). "A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina". Geodiversitas. 28 (1): 71–118. ISSN 1280-9659. CiteSeerx: 10.1.1.624.2450 – via ResearchGate.
  2. ^ a b Holtz, Thomas R., Jr. (2012). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages (PDF). Genus List.{{cite book}}: CS1 maint: multiple names: authors list (link)
  3. ^ a b Eddy, Drew R.; Clarke, Julia A. (March 21, 2011). "New Information on the Cranial Anatomy of Acrocanthosaurus atokensis and Its Implications for the Phylogeny of Allosauroidea (Dinosauria: Theropoda)". PLOS ONE. 6 (3): e17932. Bibcode:2011PLoSO...617932E. doi:10.1371/journal.pone.0017932. ISSN 1932-6203. PMC 3061882. PMID 21445312.
  4. ^ a b c Canale, Juan Ignacio; Novas, Fernando Emilio; Salgado, Leonardo; Coria, Rodolfo Aníbal (December 1, 2015). "Cranial ontogenetic variation in Mapusaurus roseae (Dinosauria: Theropoda) and the probable role of heterochrony in carcharodontosaurid evolution". Paläontologische Zeitschrift. 89 (4): 983–993. doi:10.1007/s12542-014-0251-3. ISSN 0031-0220. S2CID 133485236.
  5. ^ Paul, Gregory S (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 98.
  6. ^ Carrano, Matthew T.; Benson, Roger B. J.; Sampson, Scott D. (June 1, 2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. doi:10.1080/14772019.2011.630927. ISSN 1477-2019. S2CID 85354215.
  7. ^ "Details Revealed About Huge Dinosaurs". ABC News US. Associated Press. 2006.[dead link‍]
  8. ^ Novas, Fernando E. (2013). "Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia". Cretaceous Research. 45: 174–215. doi:10.1016/j.cretres.2013.04.001.
  9. ^ Sánchez, Maria Lidia; Heredia, Susana; Calvo, Jorge O. (2006). "Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén" [Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group), Confluencia, Neuquén]. Revista de la Asociación Geológica Argentina. 61 (1): 3–18 – via ResearchGate.
  10. ^ Vallati, P. (2001). "Middle cretaceous microflora from the Huincul Formation ("Dinosaurian Beds") in the Neuquén Basin, Patagonia, Argentina". Palynology. 25 (1): 179–197. doi:10.2113/0250179.
  11. ^ Motta, M.J.; Aranciaga Rolando, A.M.; Rozadilla, S.; Agnolín, F.E.; Chimento, N.R.; Egli, F.B.; Novas, F.E. (2016). "New theropod fauna from the upper cretaceous (Huincul Formation) of Northwestern Patagonia, Argentina". New Mexico Museum of Natural History and Science Bulletin. 71: 231–253.
  12. ^ Motta, M.J.; Brissón Egli, F.; Aranciaga Rolando, A.M.; Rozadilla, S.; Gentil, A. R.; Lio, G.; Cerroni, M.; Garcia Marsà, J.; Agnolín, F. L.; D'Angelo, J. S.; Álvarez-Herrera, G. P.; Alsina, C.H.; Novas, F.E. (2019). "New vertebrate remains from the Huincul Formation (Cenomanian–Turonian;Upper Cretaceous) in Río Negro, Argentina". Publicación Electrónica de la Asociación Paleontológica Argentina. 19 (1): R26. doi:10.5710/PEAPA.15.04.2019.29 (inactive May 31, 2021). Archived from the original on December 14, 2019. Retrieved December 14, 2019.{{cite journal}}: CS1 maint: DOI inactive as of May 2021 (link)
  13. ^ 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.
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