''Stenoscelida'' (meaning "narrow hind leg") is a genus of proterochampsid

archosauriforms Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthi ...

from the

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 ...

Santa Maria Supersequence ( Paraná Basin) of

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 st ...

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, ''S. aurantiacus'', known from a right hind limb.

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen, CAPPA/UFSM 0293, was found at the '' Exaeretodon'' sub-Assemblage Zone (''

Hyperodapedon ''Hyperodapedon'' is a genus of rhynchosaurs (beaked, archosaur-like reptiles) from the Triassic, Late Triassic period (Carnian stage). Fossils of the genus have been found in Africa, Asia, Europe and North and South America. Its first discovery ...

'' Assemblage Zone) of the Santa Maria Supersequence (lower Candelaria Sequence) in the Paraná Basin. This locality is dated to the late Carnian/early

Norian The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic defi ...

ages of the upper

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

period, around 228 million years old. It consists of a complete, articulated right hind limb. In 2022, ''Stenoscelida aurantiacus'' was described as a new genus and species of proterochampsid archosauriforms by Rodrigo T. Müller, Mauricio S. Garcia, and André O. Fonseca based on these remains. The generic name, "''Stenoscelida ''", is derived from the Greek words " στενός", meaning "narrow", and " σκέλος" meaning "hind leg", in reference to the morphology of the holotype remains. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''aurantiacus''", means "orange" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, in reference to the color of the sediments of the type locality.

Description

Pseudochampsa life restoration white background

Based on the known fossil remains, ''Stenoscelida'' would have been smaller than the related ''

Pseudochampsa ''Pseudochampsa'' is an extinct genus of proterochampsid archosauriform known from the Late Triassic (Carnian) Cancha de Bochas Member of the Ischigualasto Formation of San Juan Province, Ischigualasto-Villa Unión Basin in northwestern Arge ...

'' and ''

Proterochampsa ''Proterochampsa'' is a genus of proterochampsid archosauromorph from the Late Triassic (Carnian) Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina and the Alemoa Member of ...

'' from

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Classification

In their phylogenetic analyses, Müller, Garcia & Fonseca (2022) recovered ''Stenoscelida'' as a member of the Proterochampsidae

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

within Proterochampsia, as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to ''

Tropidosuchus ''Tropidosuchus'' is an extinct genus of carnivorous archosauriforms from the Middle Triassic period (Anisian to Ladinian stage). It is a proterochampsid which lived in what is now Argentina. It is known from the holotype PVL 4601, which consist ...

'', ''

Cerritosaurus ''Cerritosaurus'' is a genus of proterochampsid archosauromorph from the Late Triassic. It has been found in the Santa Maria Formation, in the Geopark of Paleorrota, Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Bra ...

'', ''

Gualosuchus ''Gualosuchus'' is an extinct genus of proterochampsian archosauriform from the Middle Triassic Chañares Formation of Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the ...

'', and ''

'' spp. The cladogram below displays the results of their phylogenetic analyses.

References

{{Taxonbar, from=Q115164850 Late Triassic reptiles of South America Fossil taxa described in 2022 Proterochampsians Triassic Brazil Fossils of Brazil Santa Maria Formation