Macrocephalosaurus

Macrocephalosaurus Temporal range: Late Triassic (Carnian), ~231–227  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Order:	† Rhynchosauria
Family:	† Rhynchosauridae
Subfamily:	† Hyperodapedontinae
Genus:	† Macrocephalosaurus Tupi Caldas, 1933
Type species
†Macrocephalosaurus mariensis Tupi Caldas 1933
Species
† M. mariensis Tupi Caldas, 1933 (type)

Macrocephalosaurus is a genus of rhynchosaurs (beaked, archosaur-like reptiles) from the Late Triassic period (Carnian stage) of southern Brazil. It contains a single species, Macrocephalosaurus mariensis. Although usually synonymized with Hyperodapedon (as the species Hyperodapedon mariensis), some cladistic analyses have called this synonymy into question. ^[1]

Classification

The type species of Macrocephalosaurus, M. mariensis, was described in 1933 by Jaci Antonio Louzada Tupi Caldas on the basis of MCN 1867, a complete specimen from the upper member of the Santa Maria Formation in Rio Grande Do Sul State, southern Brazil. The skeleton was transferred to another museum in the mid-1950s, and as of 1998 only the skull and front part of the torso have been recovered; the rest of the skeleton is presumed lost. Langer (1996, 1998) regarded Macrocephalosaurus mariensis as a probable junior synonym of Hyperodapedon huxleyi, synonymizing Macrocephalosaurus with Hyperodapedon. ^{[2] [3]}

Nevertheless, Langer and Schultz (2000) listed M. mariensis as a valid species within Hyperodapedon, as H. mariensis. ^[4] Mukherjee and Ray (2014) followed this interpretation. ^[5] In their cladistic analysis of the newly described taxon Beesiiwo , Fitch et al. (2023) recovered Macrocephalosaurus as more closely related to Supradapedon and Teyumbaita rather than Hyperodapedon gordoni (the type species of Hyperodapedon) or Oryctorhynchus . As a result, they recommended the revalidation of Macrocephalosaurus. ^[1]

The following cladogram is based on the phylogenetic analysis of Hyperodapedontinae by Mukherjee & Ray (2014): ^[5]

Hyperodapedontinae	Isalorhynchus genovefae Teyumbaita sulcognathus Hyperodapedon H. huenei H. mariensis (Macrocephalosaurus) H. sanjuanensis H. sp from Wolfville ( Oryctorhynchus ) H. sp from India H. huxleyi ( Paradapedon ) H. gordoni H. sp from Wyoming ( Beesiiwo ) H. sp from Zimbabwe H. tikiensis Supradapedon stockleyi

   Valid species that were first assigned to Scaphonyx .

The following cladogram is based on the phylogenetic analysis by Fitch et al. (2023): ^[1]

	Isalorhynchus genovefae Hyperodapedontinae Beesiiwo cooowuse Oryctorhynchus bairdi Hyperodapedon gordoni "Zimbabwe Form" Paradapedon huxleyi "Scaphonyx" sanjuanensis Macrocephalosaurus mariensis "Hyperodapedon" tikiensis Supradapedon stockleyi "Hyperodapedon" huenei Teyumbaita sulcognathus

References

1. Fitch, Adam; Haas, Merle; C'Hair, Wayne; Ridgley, Eugene; Ridgley, Ben; Oldman, Devin; Reynolds, Crystal; Lovelace, David (10 April 2023). "A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna". Diversity. 15 (4): 544. doi: 10.3390/d15040544 . hdl: 10919/114487 .
2. Langer, M.C. 1996. [Rincossaurossul-brasileiros histórico e filogenia. Dissertação de Maestrado, Instituto de Geociências, Universidad Federal do Rio Grande do Sul, Porto Alegre, 361 p. Unpublished.].
3. Langer, M.C. 1998. Gilmoreteiidae new family and Gilmoreteius new genus (Squamata, Scincomorpha): replacement names for Macrocephalosauridae Sulimski, 1975 and Macrocephalosaurus Gilmore, 1943. Comunicações do Museu de Ciências e Tecnologia da PUCRS, Série Zoologia Porto Alegre 11: 13–18.
4. Langer, Max C.; Schultz, Cesar L. (2000). "A New Species Of The Late Triassic Rhynchosaur Hyperodapedon From The Santa Maria Formation Of South Brazil" (PDF). Palaeontology. 43 (4): 633–652. Bibcode:2000Palgy..43..633L. doi:10.1111/1475-4983.00143. ISSN   0031-0239. S2CID   83566087.
5. Mukherjee, Debarati; Ray, Sanghamitra (2014). Benson, Roger (ed.). "A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper Triassic of India: implications for rhynchosaur phylogeny". Palaeontology. 57 (6): 1241–1276. Bibcode:2014Palgy..57.1241M. doi:10.1111/pala.12113. ISSN   0031-0239.