| Meraxes | |
|---|---|
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| Reconstructed skull | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Carcharodontosauridae |
| Tribe: | †Giganotosaurini |
| Genus: | †Meraxes Canale et al.,2022 |
| Species: | †M. gigas |
| Binomial name | |
| †Meraxes gigas Canale et al., 2022 | |
Meraxes is a genus of largecarcharodontosauridtheropod dinosaur from the Late CretaceousHuincul Formation ofPatagonia,Argentina. The genus contains a single species,Meraxes gigas.[1]
Theholotype ofMeraxes, MMCh-PV 65, was discovered in 2012. Known from a nearly completeskull,pectoral andpelvic elements, partialforelimbs, completehindlimbs, fragmentaryribs andcervical anddorsal vertebrae, asacrum, and several completecaudal vertebrae, it represents the most complete carcharodontosaurid skeleton known from the Southern Hemisphere.[1] The specimen was referred to as the "Campanas carcharodontosaurid" before its description as a new species in 2022.[2]
Meraxes gigas wasdescribed in 2022 by Canale et al. based on these remains. Thegeneric name, "Meraxes", honors a female dragon ridden byQueen Rhaenys Targaryen in theGeorge R. R. Martin novel series,A Song of Ice and Fire. The specific name, "gigas", means "giant" inGreek, in reference to its large size.[1]
Meraxes is one of the largest theropods, weighing approximately 4.26 metric tons (4.70 short tons).[1] Henderson (2023) listed a body length estimate of 9–10 metres (30–33 ft), referencing Canale et al. (2022), but also estimated a body length of 10.2–11.6 metres (33–38 ft) using the pelvic area.[3] Its skull is 1.27 m (4.2 ft) long, similar to that ofAcrocanthosaurus, which has a skull length of 1.23–1.29 m (4.0–4.2 ft).[1][4] The shapes and proportions of various bones, including the skull, scapula, metacarpals, ischial shaft, and foot, indicate thatMeraxes andAcrocanthosaurus had similar proportions and body size.Meraxes possessed reduced forelimbs, an instance ofconvergent evolution that occurred independently in four different lineages:Carcharodontosauridae,Abelisauridae,Tyrannosauridae, andAlvarezsauridae. Additionally, the second toes possess an enlarged claw, almost twice as long as the claw on the fourth toe.[1]
Osteohistological analysis of the holotype suggests the individual could have been between 39 and 53 years old when it died, having reached skeletal maturity approximately 4 years prior to its death (between 35 and 49 years old), making it the longest-lived non-avian theropod currently known.Meraxes was determined to have grown to large size by extending its growth period (hypermorphosis), rather than increasing its relative growth rate (acceleration) through development as inTyrannosaurus, to which it was compared.[1][2]
Canale et al. (2022) recoveredMeraxes as the earliest diverging member of the tribeGiganotosaurini within the Carcharodontosauridae. The results of theirphylogenetic analyses are displayed in thecladogram below:[1]
Cau (2024) also recovered similar relationships forMeraxes, but not in a clade withTyrannotitan,Giganotosaurus, andMapusaurus, as suggested by Canale et al. (2022).[5]
| Carcharodontosauridae |
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The fossil remains ofMeraxes were recovered from theHuincul Formation. A substantial number of taxa are known to have inhabited this paleoenvironment. Theropods from the formation include the paravianOveroraptor, the elaphrosaurineHuinculsaurus, the abelisaursSkorpiovenator,Tralkasaurus, andIlokelesia, the megaraptoranAoniraptor, and the fellow giant carcharodontosauridsMapusaurus andTaurovenator.[6][7]Meraxes was found in an older rock layer than eitherMapusaurus andTaurovenator, so it is unlikely they coexisted.[1][8] The herbivores of the area are represented by therebbachisaurid sauropodsCathartesaura andLimaysaurus, the titanosaursArgentinosaurus,Choconsaurus, andChucarosaurus, and indeterminateiguanodonts.[9][10][11]
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