The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, "rauisuchian" pseudosuchians, and early dinosaurs and other dinosauromorphs, including the herrerasaurid Staurikosaurus, the basal sauropodomorphs Buriolestes and Saturnalia, and the lagerpetid Ixalerpeton. The formation is named after the city of Santa Maria in the central region of Rio Grande do Sul, where outcrops were first studied.
The Santa Maria Formation makes up the majority of the Santa Maria Supersequence, which extends through the entire Late Triassic. The Santa Maria Supersequence is divided into four geological sequences, separated from each other by short unconformities. The first two of these sequences (Pinheiros-Chiniquá and Santa Cruz sequences) lie entirely within the Santa Maria Formation, while the third (the Candelária sequence) is shared with the overlying Norian-age Caturrita Formation. The fourth and youngest sequence (the Mata sequence) is equivalent to the Rhaetian-age Mata Sandstone.
The oldest sequence in the formation is the Pinheiros-Chiniquá Sequence (latest Ladinian-earliest Carnian, ~237 Ma), which is biostratigraphically equivalent to the Dinodontosaurus Assemblage Zone. It is followed by the shorter Santa Cruz Sequence (early Carnian-middle Carnian, ~236 Ma), biostratigraphically equivalent to the Santacruzodon Assemblage Zone.
The final sequence, which is only partially present within the formation, is the Candelária Sequence (middle Carnian-latest Carnian, ~233-228 Ma). The lower portion of this sequence, coinciding with the upper part of the Santa Maria Formation, is equivalent to the Hyperodapedon Assemblage Zone.The Hyperodapedon Assemblage Zone is itself subdivided into Hyperodapedon Acme Zone (most of the zone, where the rhynchosaur Hyperodapedon is widely reported) and Exaeretodon Zone (restricted to about three known and sampled localities, where rhynchosaurs are almost completely absent, but the traversodontid cynodont Exaeretodon is widely reported). These subdivisions are also known as Lower and Upper Hyperodapedon Assemblage Zone, respectively.
U-Pb radiometric dating of Cerro da Alemoa (the type locality of Saturnalia tupiniquim) in the Upper portion of the Santa Maria Formation found an estimated age of 233.23±0.73 million years ago, putting that locality 1.5 million years older than the Ischigualasto Formation and younger than Los Chañares Formation. The Santa Maria and Ischigualasto formations are approximately equal as having the earliest dinosaur localities.
Vertebrate paleofauna Most of the information below was included on a revision of the Triassic faunal successions of the Paraná Basin, southern Brazil by Schultz et al. (2020).
Temnospondyls Temnospondyls of the Santa Maria Formation Genus Species Location Stratigraphic position Material Notes ImagesCompsoceropsD. P. Sengupta. 1995. Chigutisaurid temnospondyls from the Late Triassic of India and a review of the Family Chigutisauridae. Palaeontology 38(2):313-339C. sp.Dias-da-Silva, Sérgio, et al. 2011. The presence of Compsocerops (Brachyopoidea: Chigutisauridae) (Late Triassic) in southern Brazil with comments on chigutisaurid palaeobiogeography. Palaeontology 55(1):163-172Restinga SêcaUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneA partial skullA chigutisaurid temnospondyl
Fish Fish of the Santa Maria Formation Genus Species Location Stratigraphic position Material Notes ImagesPtychoceratodusP. cf. phillipsiUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneA ptychoceratodontid lungfish
Synapsids
Dicynodonts Dicynodonts of the Santa Maria Formation Genus Species Location Stratigraphic position Material Notes ImagesDinodontosaurusD. pedroanumSão Pedro do Sul, Candelária, Dona Francisca, Bom Retiro, Vale Verde, Novo Cabrais, Bom Retiro do Sul, Dilermando de AguiarLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial and postcranial remainsA kannemeyeriiform dicynodontStahleckeriaS. potensDona Francisca, CandeláriaLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial and postcranial remainsA stahleckeriid dicyndont
Cynognathians Cynognathians of the Santa Maria Formation Genus Species Location Stratigraphic position Material Notes Images Exaeretodon E. majorSão Pedro do Sul Lower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone Cranial and postcranial remains A traversodontid cynodontE. riograndensisAgudo, Santa Maria Upper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Exaeretodon ZoneCranial and postcranial remainsA traversodontid cynodontGomphodontosuchusG. brasiliensisSanta MariaUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneCranial remainsA traversodontid cynodontLuangwaL. sudamericanaVera Cruz, CandeláriaLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial remainsA traversodontid cynodontMassetognathusM. ochagavieBom Retiro, Vale Verde, Dona FranciscaLower and Middle Santa Maria Formation, Alemoa Member, Santa Cruz nad Pinheiros-Chiniquá Sequences, Santacruzodon Assemblage Zone and Dinodontosaurus Assemblage ZoneCranial and postcranial remains A traversodontid cynodontMenadonM. besairieiSanta CruzMiddle Santa Maria Formation, Alemoa Member, Santa Cruz Sequence, Santacruzodon Assemblage ZoneCranial remainsA traversodontid cynodont Protuberum P. cabralensis Paraíso do Sul, Novo Cabrais Lower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone Partial articulated skeleton including skull, vertebrae and ribs A traversodontid cynodont Santacruzodon S. hopsoni Santa Cruz Middle Santa Maria Formation, Alemoa Member, Santa Cruz Sequence, Santacruzodon Assemblage Zone Cranial remains A traversodontid cynodontSantagnathusS. mariensisHyperodapedon Assemblage ZoneNumerous cranial and postcranial remainsA traversodontid cynodontScalenodonS. ribeiroaeAgudoLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial remainsA traversodontid cynodontTraversodonT. stahleckeriSão Pedro do SulLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial remainsA traversodontid cynodont
Probainognathians Probainognathians of the Santa Maria Formation Genus Species Location Stratigraphic position Material Notes ImagesAlemoatheriumMartinelli, A.G.; Eltink, E.; Da-Rosa, Á.A.S.; Langer, Max C. (2017). "A new cynodont from the Santa Maria formation, south Brazil, improves Late Triassic probainognathian diversity". Papers in Palaeontology. 3 (3): 401–423. doi:10.1002/spp2.1081A. huebneriSanta MariaUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneA partial dentaryA prozostrodontian cynodontAleodonA. cromptoniVale Verde, Candelária, Bom Retiro do Sul, Novo CabraisLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial and postcranial remainsA chiniquodontid cynodontBonacynodonB. schultziCandeláriaLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial remainsA probainognathid cynodont Candelariodon C. barberenai Candelária Lower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone A partial mandible having some complete teeth A basal probainognathian cynodont CharruodonAbdala, F.; Ribeiro, A. M. (2000). "A new therioherpetid cynodont from the Santa Maria Formation (middle Late Triassic), southern Brazil" (PDF). Geodiversitas. 22 (4): 589–596. Archived from the original (PDF) on 2011-06-12. Retrieved 2010-04-05.C. tetracuspidatusCandeláriaUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneA partial dentaryA basal probainognathian cynodont ChiniquodonVon Huene. Die Fossilien Reptilien des südamerikanischen Gondwanalandes an der Zeitenwende (Denwa-Molteno-Unterkeuper = Ober-Karnisch). Ergebnisse der Sauriergrabungen in Südbrasilien 1928/29. (The fossil reptiles of South American Gondwana during the temporal transition) (Denwa-Molteno-Upper Triassic = Upper Carnian). Results of the excavations in South Brazil 1928/29, part II.) 1936. Pages 93–159. C. theotonicus São Pedro do Sul Lower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage Zone Several cranial remains A chiniquodontid cynodontC. sp.Santa CruzMiddle Santa Maria Formation, Alemoa Member, Santa Cruz Sequence, Santacruzodon Assemblage ZoneCranial and postcranial remainsA chiniquodontid cynodontProtheriodonP. estudiantiDona FranciscaLower Santa Maria Formation, Alemoa Member, Pinheiros-Chiniquá Sequence, Dinodontosaurus Assemblage ZoneCranial remainsA basal probainognathian cynodontProzostrodonP. brasiliensisSanta Maria, São João do PolêsineUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneCranial remainsA prozostrodontian cynodontSantacruzgnathusS. abdalaiSanta CruzMiddle Santa Maria Formation, Alemoa Member, Santa Cruz Sequence, Santacruzodon Assemblage ZoneCranial remainsA prozostrodontian cynodontTherioherpetonOliveira, É. V. (2006). "Reevaluation of Therioherpeton cargnini Bonaparte & Barberena, 1975 (Probainognathia, Therioherpetidae) from the Upper Triassic of Brazil" (PDF). Geodiversitas. 28 (3): 447–465.T. cargniniSanta MariaUpper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Hyperodapedon Acme ZoneCranial remainsA prozostrodontian cynodont Trucidocynodon T. riograndensis Agudo Upper Santa Maria Formation, Alemoa Member, Candelária Sequence, Hyperodapedon Assemblage Zone, Exaeretodon ZoneCranial and postcranial elements of an almost complete skeleton and an additional large skull An ecteniniid cynodont
Reptiles
Pseudosuchians