The Santa Maria Formation is a

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

rock formation A rock formation is an isolated, scenic, or spectacular surface rock (geology), rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock. The term ''rock Geological formation, formation ...

found in

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. It is primarily

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

in age (

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

), and is notable for its

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s, "

rauisuchia "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians ...

pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

ns, and early

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s and other dinosauromorphs, including the

herrerasaur Herrerasauridae is a family of carnivorous dinosaurs, possibly basal to either theropods or even all of saurischians, or even their own branching from Dracohors, separate from Dinosauria altogether. They are among the oldest known dinosaurs, ...

id ''

Staurikosaurus ''Staurikosaurus'' (Pronounced /ˌstɔɹ̠ikoʊˈsɔɹ̠ʌs/, '' STOR-ree-koh-SOR-ruhs''; "Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colber ...

'', the basal

sauropodomorphs Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...

Buriolestes ''Buriolestes'' is a genus of early sauropodomorph dinosaurs from the Late Triassic Santa Maria Formation of the Paraná Basin in southern Brazil. It contains a single species, ''B. schultzi'', named in 2016. The type specimen was found alongsid ...

'' and ''

Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...

,'' and the

lagerpetid Lagerpetidae (; originally Lagerpetonidae) is a family of basal avemetatarsalians (early-diverging members of the reptile lineage leading to birds and other dinosaurs). Though traditionally considered the earliest-diverging dinosauromorphs (ar ...

Ixalerpeton ''Ixalerpeton'' (meaning "leaping reptile") is a genus of lagerpetid avemetatarsalian containing one species, ''I. polesinensis''. It lived in the Late Triassic of Brazil alongside the sauropodomorph dinosaur '' Buriolestes''. Discovery and ...

''. 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 In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is call ...

, separated from each other by short

unconformities An unconformity is a buried erosion surface, erosional or non-depositional surface separating two Rock (geology), rock masses or Stratum, strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer ...

. 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 The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

-age Caturrita Formation. The fourth and youngest sequence (the Mata sequence) is equivalent to the

Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...

-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 ''Dinodontosaurus'' (meaning "terrible-toothed lizard") is a genus of dicynodont therapsid. It was medium to large dicynodont of the Triassic (with skull up to long) and had a beak corneum. It lived in the Middle Triassic but disappeared in the ...

Assemblage Zone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties ...

. 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 ''Hyperodapedon'' (from , 'above' and , 'pavement') is an extinct genus of rhynchosaur reptiles which lived during Triassic, Late Triassic period. Like other rhynchosaurs, it was an heavily built Archosauromorpha, archosauromorph, distantly rel ...

'' Acme Zone (most of the zone, where the

rhynchosaur Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs ...

''Hyperodapedon'' is widely reported) and ''

Exaeretodon ''Exaeretodon'' is an Extinction, extinct genus of fairly large, low-slung traversodontid cynodonts from the southern parts of Pangea. Four species are Knowledge, known, hailing from various geologic formation, formations. ''E. argentinus'' is fr ...

'' Zone (restricted to about three known and sampled localities, where rhynchsaurs 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 The Ischigualasto Formation is a Late Triassic geological formation in the Ischigualasto-Villa Unión Basin of southwestern La Rioja Province, Argentina, La Rioja Province and northeastern San Juan Province, Argentina, San Juan Province in northw ...

and younger than Los

Chañares Formation The Chañares Formation is a Carnian-age geologic formation of the Ischigualasto-Villa Unión Basin, located in La Rioja Province, Argentina. It is characterized by drab-colored fine-grained volcaniclastic claystones, siltstones, and sandstones ...

. 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).

Vertebrate paleofauna

Temnospondyls

Fish

Synapsids

Dicynodonts

Cynognathians

Probainognathians

Reptiles

Pseudosuchians

Avemetatarsalians

Other reptiles

Formations

See also

References