''Erythrovenator'' () is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of basal

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

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

s from the Late Triassic of Rio Grande so Sul,

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. The genus contains a single species, ''Erythrovenator jacuiensis''.

Discovery

The holotype and only known specimen of ''Erythrovenator'', CAPPA/UFSM 0157, is an isolated proximal portion of the left femur. This fossil was found in red mudstone of the Niemeyer Site, near Agudo in Rio Grande Sul. The site is tentatively considered to be early Norian (or possible late

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 m ...

) in age and belongs the Candelária Sequence of the

Santa Maria Supersequence 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 ...

. No other dinosauromorphs are known from this site, which is dominated by the

traversodontid Traversodontidae is an extinct family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and eastern North America. Tra ...

cynodont '' Siriusgnathus''. The site probably corresponds to the ''Riograndia'' Assemblage Zone based on the presence of ''Siriusgnathus''. The generic name, ''Erythrovenator'', is derived from the Greek word ερυθρός (''erythrós''), meaning "red" (in reference to the color of the holotype), and the Latin word vēnātor, meaning "hunter." The specific name, ''jacuiensis'', references a nearby river, the Jacuí River.

Description

Although only partially preserved, the femur has an estimated total length of about 190 millimeters (7.5 inches). The femoral head has a strongly concave lower edge, a rounded inner edge, and a distinct anterolateral tuber, all characteristics of dinosaur femora. It also had small anteromedial and posteromedial tubers, with the former structure quite different from the folded anteromedial tuber of other theropods. The rear surface of the femoral head has a thin vertical ridge in its medial portion and a raised scar in its lateral portion, similar to '' Buriolestes''. There is no evidence for a dorsolateral trochanter, unlike all other known Triassic dinosaurs. On the other hand, the anterior trochanter is a prominent pyramidal structure offset from the shaft by a cleft. This is most similar to neotheropods among early dinosaurs, and is also observed in some silesaurids. Although there is no distinct trochanteric shelf, the anterior trochanter does have a plate-like medial extension.

Classification

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

placed ''Erythrovenator'' as the most basal theropod, supported by the structure of the anterior trochanter. This would make it one of the oldest verifiable theropods known and one of the few known from the Triassic of Brazil. Other potentially older theropods include ''

Eodromaeus ''Eodromaeus'' (meaning "dawn runner") is an extinct genus of probable basal theropod dinosaurs from the Late Triassic of Argentina. Like many other of the earliest-known dinosaurs, it hails from the Carnian-age (~230 Ma) Ischigualasto Form ...

'' (from Argentina), potentially ''

Nhandumirim ''Nhandumirim'' (meaning "small rhea" in the Tupi language) is a genus of basal sauropodomorph dinosaur from the Carnian age of Late Triassic Brazil. It is currently considered a saturnaliid sauropodomorph. The type and only species, ''Nhandu ...

'' (also from Brazil), and herrerasaurids, but these taxa are not universally considered theropods. ''Nhandumirim'' is now considered to be a basal

sauropodomorph 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 lon ...

. '' Lepidus'' and ''

Camposaurus ''Camposaurus'' ( ) is a coelophysid dinosaur genus from the Norian stage of the Late Triassic period of North America. The pertinent fossil remains date back to the early to middle Norian stage, and is widely regarded as the oldest known neot ...

,'' a pair of coelophysids from the

United States of America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...

, are the only other agreed-upon theropods which may have a similar age to ''Erythrovenator''.

References

{{Taxonbar, from=Q102381502 Prehistoric theropods Late Triassic dinosaurs of South America Fossils of Brazil Triassic Brazil Fossil taxa described in 2021 Paraná Basin