Meraxes

Genus of carcharodontosaurid dinosaurs

Meraxes

Temporal range: Late Cretaceous (Cenomanian), ~95–93.9 Ma

PreꞒ

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 large carcharodontosaurid theropod dinosaur from the Late Cretaceous Huincul Formation of Patagonia, Argentina. The genus contains a single species, Meraxes gigas.[1]

## Discovery and naming

[edit]

The holotype of Meraxes, MMCh-PV 65, was discovered in 2012. Known from a nearly complete skull, pectoral and pelvic elements, partial forelimbs, complete hindlimbs, fragmentary ribs and cervical and dorsal vertebrae, a sacrum, and several complete caudal 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 was described in 2022 by Canale et al. based on these remains. The generic name, "Meraxes", honors a female dragon ridden by Queen Rhaenys Targaryen in the George R. R. Martin novel series, A Song of Ice and Fire. The specific name, "gigas", means "giant" in Greek, in reference to its large size.[1]

## Description

[edit]

Size compared to a human

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 of Acrocanthosaurus, 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 that Meraxes and Acrocanthosaurus had similar proportions and body size. Meraxes possessed reduced forelimbs, an instance of convergent evolution that occurred independently in four different lineages: Carcharodontosauridae, Abelisauridae, Tyrannosauridae, and Alvarezsauridae. Additionally, the second toes possess an enlarged claw, almost twice as long as the claw on the fourth toe.[1]

Life restoration

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 in Tyrannosaurus, to which it was compared.[1][2]

## Classification

[edit]

Canale et al. (2022) recovered Meraxes as the earliest diverging member of the tribe Giganotosaurini within the Carcharodontosauridae. The results of their phylogenetic analyses are displayed in the cladogram below:[1]

Carcharodontosauridae |

|  |  Neovenator

|

|  |

Concavenator

|

|  Eocarcharia

Lajasvenator

Lusovenator

|  |  Acrocanthosaurus

|

|  |  Shaochilong

|

Carcharodontosaurinae |

|  |  Carcharodontosaurus spp.

|

Giganotosaurini |

|  |  Meraxes

|

|  |

Tyrannotitan

|

|  |  Giganotosaurus

|

|  Mapusaurus

## Paleoenvironment

[edit]

Several dinosaurs from the Huincul Formation (Meraxes in dark blue, left)

The fossil remains of Meraxes were recovered from the Huincul Formation. A substantial number of taxa are known to have inhabited this paleoenvironment. Theropods from the formation include the paravian Overoraptor, the elaphrosaurine Huinculsaurus, the abelisaurs Skorpiovenator, Tralkasaurus, and Ilokelesia, the megaraptoran Aoniraptor, and the fellow giant carcharodontosaurids Mapusaurus and Taurovenator.[5][6] Meraxes was found in an older rock layer than either Mapusaurus and Taurovenator, so it is unlikely they coexisted.[1][7] The herbivores of the area are represented by the rebbachisaurid sauropods Cathartesaura and Limaysaurus, the titanosaurs Argentinosaurus, Choconsaurus, and Chucarosaurus, and indeterminate iguanodonts.[8][9][10]

## References

[edit]

1. ^ a b c d e f g h i Canale, Juan I.; Apesteguía, Sebastián; Gallina, Pablo A.; Mitchell, Jonathan; Smith, Nathan D.; Cullen, Thomas M.; Shinya, Akiko; Haluza, Alejandro; Gianechini, Federico A.; Makovicky, Peter J. (July 2022). "New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction". Current Biology. 32 (14): 3195–3202.e5. Bibcode:2022CBio...32E3195C. doi:10.1016/j.cub.2022.05.057. PMID 35803271. S2CID 250343124.
2. ^ a b Cullen, Thomas M.; Canale, Juan I.; Apesteguía, Sebastián; Smith, Nathan D.; Hu, Dongyu; Makovicky, Peter J. (25 November 2020). "Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size evolution". Proceedings of the Royal Society B: Biological Sciences. 287 (1939): 20202258. doi:10.1098/rspb.2020.2258. PMC 7739506. PMID 33234083. S2CID 227154091.
3. ^ Henderson, Donald M. (2023). "Growth constraints set an upper limit to theropod dinosaur body size". The Science of Nature. 110 (1). 4. Bibcode:2023SciNa.110....4H. doi:10.1007/s00114-023-01832-1. PMID 36715746.
4. ^ Currie, Philip J.; Carpenter, Kenneth (2000). "A new specimen of Acrocanthosaurus atokensis (Theropoda, Dinosauria) from the Lower Cretaceous Antlers Formation (Lower Cretaceous, Aptian) of Oklahoma, USA". Geodiversitas. 22 (2): 207–246.
5. ^ Matías J. Motta; Federico L. Agnolín; Federico Brissón Egli; Fernando E. Novas (2020). "New theropod dinosaur from the Upper Cretaceous of Patagonia sheds light on the paravian radiation in Gondwana". The Science of Nature. 107 (3): Article number 24. Bibcode:2020SciNa.107...24M. doi:10.1007/s00114-020-01682-1. hdl:11336/135530. PMID 32468191. S2CID 218913199.
6. ^ Cerroni, M.A.; Motta, M.J.; Agnolín, F.L.; Aranciaga Rolando, A.M.; Brissón Egli, F.; Novas, F.E. (2020). "A new abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro province, Argentina". Journal of South American Earth Sciences. 98: 102445. Bibcode:2020JSAES..9802445C. doi:10.1016/j.jsames.2019.102445. S2CID 213781725.
7. ^ Rolando, Alexis M. Aranciaga; Motta, Matías J.; Agnolín, Federico L.; Tsuihiji, Takanobu; Miner, Santiago; Brissón-Egli, Federico; Novas, Fernando E. (9 October 2024). "A new carcharodontosaurid specimen sheds light on the anatomy of South American giant predatory dinosaurs". The Science of Nature. 111 (6): 56. Bibcode:2024SciNa.111...56R. doi:10.1007/s00114-024-01942-4. ISSN 1432-1904. PMID 39382666.
8. ^ Calvo, Jorge O.; Salgado, Leonardo (1995). "Rebbachisaurus tessonei sp. nov. a new Sauropoda from the Albian-Cenomanian of Argentina; new evidence on the origin of the Diplodocidae" (PDF). Gaia. 11: 13–33\. Archived from the original (PDF) on 23 September 2021.
9. ^ Baiano, Mattia A.; Coria, Rodolfo A.; Cau, Andrea (June 2020). "A new abelisauroid (Dinosauria: Theropoda) from the Huincul Formation (lower Upper Cretaceous, Neuquén Basin) of Patagonia, Argentina". Cretaceous Research. 110: 104408. Bibcode:2020CrRes.11004408B. doi:10.1016/j.cretres.2020.104408. S2CID 214118853.
10. ^ Agnolin, Federico L.; Gonzalez Riga, Bernardo J.; Aranciaga Rolando, Alexis M.; Rozadilla, Sebastián; Motta, Matías J.; Chimento, Nicolás R.; Novas, Fernando E. (2 February 2023). "A new giant titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous of Northwestern Patagonia, Argentina". Cretaceous Research. 146: 105487. Bibcode:2023CrRes.14605487A. doi:10.1016/j.cretres.2023.105487. ISSN 0195-6671.

* v
* t
* e

Theropoda

* Kingdom: Animalia
* Phylum: Chordata
* Class: Sauropsida
* Clade: Avemetatarsalia
* Clade: Dinosauria

| Avemetatarsalia|

*     * see Avemetatarsalia

Theropoda|

*     * see below↓

Theropoda

Theropoda

* Chindesaurus?
* Daemonosaurus?
* Eodromaeus?
* Erythrovenator
* Guaibasaurus?
* Nhandumirim?
* Tawa?
* Herrerasauria?

Neotheropoda

* Dilophosaurus
* Dolichosuchus?
* Dracovenator
* Gojirasaurus
* Lepidus
* Liliensternus
* Lophostropheus
* Notatesseraeraptor
* Sarcosaurus
* Shuangbaisaurus
* Sinosaurus
* Tachiraptor
* Velocipes?
* Zupaysaurus

Coelophysoidea|

* Dracoraptor?
* Panguraptor
* Pendraig
* Podokesaurus
* Powellvenator

Coelophysidae|

* Camposaurus
* Coelophysis
* Lucianovenator
* Megapnosaurus?
* Panguraptor?
* Procompsognathus
* Pterospondylus?
* Segisaurus

Averostra|

*     * see below↓

Dubious neotheropods|

* Teinurosaurus
* Halticosaurus

Averostra

Averostra

* Dornraptor
* Lophostropheus?

Ceratosauria

* Berberosaurus
* Camarillasaurus?
* Dandakosaurus?
* Fosterovenator
* Ostafrikasaurus?
* Saltriovenator
* Sarcosaurus?
* Spinostropheus?

Neoceratosauria

| Ceratosauridae|

* Ceratosaurus
* Genyodectes

|

Abelisauroidea|

* Bahariasaurus?
* Betasuchus
* Dahalokely
* Deltadromeus?
* Eoabelisaurus?
* Genusaurus
* Gualicho?
* Ligabueino

Noasauridae|

* Afromimus?
* Austrocheirus?
* Berthasaura
* Compsosuchus?
* Dahalokely?
* Genusaurus?
* Kiyacursor
* Ligabueino
* Spinostropheus

Elaphrosaurinae|

* Elaphrosaurus
* Huinculsaurus
* Limusaurus

Noasaurinae|

* Laevisuchus
* Masiakasaurus
* Noasaurus
* Velocisaurus
* Vespersaurus

Abelisauridae|

* Chenanisaurus
* Dryptosauroides?
* Eoabelisaurus
* Indosuchus
* Kryptops
* Kurupi
* Rugops
* Spectrovenator
* Tarascosaurus
* Tralkasaurus
* Xenotarsosaurus

Majungasaurinae|

* Arcovenator
* Dahalokely?
* Genusaurus
* Indosaurus
* Majungasaurus
* Rahiolisaurus?
* Rajasaurus

Carnotaurinae|

* Majungasaurinae?

| Brachyrostra|

* Dahalokely?
* Ekrixinatosaurus
* Elemgasem
* Guemesia
* Ilokelesia
* Llukalkan
* Niebla
* Rahiolisaurus?
* Skorpiovenator
* Thanos

Furileusauria|

* Abelisaurus
* Aucasaurus
* Caletodraco
* Carnotaurus
* Elemgasem?
* Koleken
* Pycnonemosaurus
* Quilmesaurus
* Viavenator

| Tetanurae|

*     * see below↓

|

Tetanurae

Tetanurae

* Calamospondylus?
* Chienkosaurus?
* Chilesaurus?
* Chuandongocoelurus
* Cruxicheiros?
* Cryolophosaurus
* Kaijiangosaurus
* Kayentavenator
* Monolophosaurus
* Pandoravenator
* Sinosaurus?
* Szechuanosaurus
* Vectaerovenator

Orionides

Megalosauroidea

* Yunyangosaurus

Piatnitzkysauridae|

* Condorraptor
* Marshosaurus
* Piatnitzkysaurus
* Xuanhanosaurus?

Megalosauria

* Streptospondylus?

Megalosauridae|

* Eustreptospondylus

Megalosaurinae|

* Duriavenator
* Megalosaurus
* Torvosaurus
* Wiehenvenator

Afrovenatorinae|

* Afrovenator
* Dubreuillosaurus
* Leshansaurus
* Magnosaurus
* Piveteausaurus
* Poekilopleuron?

Spinosauridae

* Camarillasaurus?
* Cristatusaurus
* Iberospinus
* Ostafrikasaurus?

Baryonychinae|

* Baryonyx
* Protathlitis
* Riojavenatrix
* Suchosaurus?
* Vallibonavenatrix?

Ceratosuchopsini|

* Ceratosuchops
* Eocarcharia?
* Riparovenator
* Suchomimus

Spinosaurinae|

* Camarillasaurus?
* Ichthyovenator
* Irritator
* Oxalaia
* Siamosaurus

Spinosaurini|

* Sigilmassasaurus
* Spinosaurus

| Avetheropoda|

*     * see below↓

|

Avetheropoda

Avetheropoda

* Gasosaurus?
* Lourinhanosaurus?

Carnosauria

* Altispinax
* Monolophosaurus?
* Megalosauridae?
* Spinosauridae?

Allosauroidea

* Asfaltovenator
* Erectopus
* Xuanhanosaurus?
* Piatnitzkysauridae?

Metriacanthosauridae|

* Xuanhanosaurus?
* Yangchuanosaurus
* Yuanmouraptor

Metriacanthosaurinae|

* Alpkarakush
* Metriacanthosaurus
* Shidaisaurus
* Siamotyrannus
* Sinraptor

Allosauria

| Allosauridae|

* Allosaurus
* Antrodemus?
* Epanterias?
* Saurophaganax?

|

Carcharodontosauria|

* Datanglong
* Lusovenator
* Siamraptor
* Siats?
* Veterupristisaurus

Neovenatoridae|

* Chilantaisaurus?
* Gualicho?
* Neovenator
* Siats?
* Megaraptora?

Carcharodontosauridae|

* Acrocanthosaurus
* Altispinax?
* Concavenator
* Eocarcharia?
* Kelmayisaurus
* Lajasvenator
* Sauroniops
* Shaochilong
* Tameryraptor
* Ulughbegsaurus
* Veterupristisaurus

Carcharodontosaurinae|

* Carcharodontosaurus

Giganotosaurini|

* Giganotosaurus
* Mapusaurus
* Meraxes
* Taurovenator
* Tyrannotitan

| Megaraptora?|

* Aoniraptor
* Bahariasaurus?
* Fukuiraptor
* Phuwiangvenator
* Rapator
* Siats?
* Chilantaisaurus?

Megaraptoridae|

* Aerosteon
* Australovenator
* Maip
* Megaraptor
* Murusraptor
* Orkoraptor
* Tratayenia

Coelurosauria|

*     * see below↓

Coelurosauria

Coelurosauria

* Aratasaurus
* Asiamericana
* Bicentenaria
* Chilantaisaurus?
* Gualicho?
* Richardoestesia
* Sciurumimus?
* Vayuraptor
* Xinjiangovenator
* Zuolong

Tyrannoraptora

Tyrannosauroidea

* Chingkankousaurus
* Labocania?

Coeluridae?|

* Coelurus
* Tanycolagreus?

Proceratosauridae|

* Guanlong
* Kileskus
* Proceratosaurus
* Sinotyrannus
* Yutyrannus

Pantyrannosauria

* Alectrosaurus
* Aviatyrannis
* Bagaraatan?
* Dilong
* Eotyrannus
* Jinbeisaurus
* Juratyrant
* Khankhuuluu
* Moros
* Santanaraptor
* Stokesosaurus
* Suskityrannus
* Timimus?
* Timurlengia
* Xiongguanlong
* Megaraptora?

Eutyrannosauria

* Appalachiosaurus
* Bistahieversor?
* Dryptosaurus

Tyrannosauridae

| Albertosaurinae|

* Albertosaurus
* Gorgosaurus

|

Tyrannosaurinae|

* Asiatyrannus
* Nanuqsaurus

Alioramini|

* Alioramus
* Qianzhousaurus

Daspletosaurini|

* Daspletosaurus
* Thanatotheristes

Teratophoneini|

* Bistahieversor?
* Dynamoterror
* Labocania?
* Lythronax
* Teratophoneus

Tyrannosaurini|

* Tarbosaurus
* Tyrannosaurus
* Zhuchengtyrannus

| Maniraptoromorpha|

*     * see below↓

|

| Dubious coelurosaurs|

* Iliosuchus
* Kakuru
* Phaedrolosaurus
* Shanyangosaurus

|

Maniraptoromorpha

Maniraptoromorpha

* Coelurus?
* Juravenator
* Ornitholestes

Neocoelurosauria

* Aniksosaurus

Compsognathidae|

* Aniksosaurus?
* Aristosuchus
* Beipiaognathus?
* Compsognathus
* Huaxiagnathus?
* Mirischia?
* Scipionyx?
* Sinocalliopteryx?
* Sinosauropteryx?
* Xunmenglong

Sinosauropterygidae?|

* Huadanosaurus
* Huaxiagnathus
* Mirischia
* Sinocalliopteryx
* Sinosauropteryx

* Compsognathidae?

Ornithomimosauria|

* Arkansaurus
* Aviatyrannis?
* Calamosaurus?
* Hexing
* Kinnareemimus
* Nedcolbertia
* Nqwebasaurus
* Thecocoelurus?
* Valdoraptor

Macrocheiriformes|

* Harpymimus
* Pelecanimimus
* Shenzhousaurus

Deinocheiridae|

* Beishanlong
* Deinocheirus
* Garudimimus
* Harpymimus?
* Paraxenisaurus?
* Tyrannomimus

Ornithomimidae|

* Aepyornithomimus
* Anserimimus
* Archaeornithomimus
* "Coelosaurus"
* Dromiceiomimus
* Dzharacursor
* Gallimimus
* Mexidracon
* Ornithomimus
* Qiupalong
* Rativates
* Sinornithomimus
* Struthiomimus
* Tototlmimus

Maniraptora|

*     * see Maniraptora
* includes birds

Portal:

* Dinosaurs

Taxon identifiers

Meraxes gigas|

* Wikidata: Q112966897
* Paleobiology Database: 462128
* ZooBank: 84B1D98B-2E5F-4000-866C-19625DB6C428

Meraxes|

* Wikidata: Q112969374
* GBIF: 12379807
* Paleobiology Database: 462127

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