''Cargninia'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of basal

lepidosauromorph Lepidosauromorpha (in PhyloCode known as ''Pan-Lepidosauria'') is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). The only living sub-group is the Lepidosauria, which contains ...

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 ...

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 type and only known species is ''Cargninia enigmatica''. It is known from 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 ...

UFRGS PV 1027 T, a partial left

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

(lower jaw bone) found in what is now

Faxinal do Soturno Faxinal do Soturno is a municipality in the state of Rio Grande do Sul, Brazil. See also *List of municipalities in Rio Grande do Sul This is a list of the municipalities in the state of Rio Grande do Sul (RS), located in the South Region of Br ...

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 ...

, southern

, in the geopark Paleorrota. This locality is from the middle section of the

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 ...

-age

Caturrita Formation The Caturrita Formation is a geological formation, rock formation found in Rio Grande do Sul, Brazil. Its sediments were deposited in the Paraná Basin. The formation is from the Upper Triassic and forms part of the Santa Maria Supersequence in th ...

. ''Cargninia'' was named by José Fernando Bonaparte, César Leandro Schultz, Marina Bento Soares and Agustín G. Martinelli in

2010 File:2010 Events Collage New.png, From top left, clockwise: The 2010 Chile earthquake was one of the strongest recorded in history; The Eruption of Eyjafjallajökull in Iceland disrupts air travel in Europe; A scene from the opening ceremony of ...

. The generic name honors Daniel Cargnin, a Brazilian priest and fossil collector, and 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 ...

means “enigmatic”, in reference to its uncertain phylogenetic placement. The preserved dentary has small, peg-like teeth, with the underlying jaw bone about four times deeper than the height of each tooth crown. The jaw was originally collected with eleven preserved teeth and two or three more spaces for broken teeth. However, during preparation the front half of the fossil was destroyed, leaving only the rear part of the jaw with five preserved teeth and one or two empty spaces. Up to 20 teeth may have been present in a complete lower jaw. The teeth are positioned apicolingually (slightly inwards of the upper edge of the jaw bone). The penultimate tooth in the back of the jaw has a higher attachment point and its base is cemented to the jaw bone. The jaw as a whole can be characterized as having pleuro

acrodont Acrodonty (from Greek ''akros'' 'highest' + ''dont'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be rela ...

tooth implantation. ''Cargninia'' was originally described as a

lepidosaur The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 species ...

(

crown-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

lepidosauromorph), possibly related to the gliding kuehneosaurids. A 2020 redescription later considered it a valid, albeit fragmentary, lepidosauromorph with uncertain relations to other members of the group. Its pleuroacrodont dentition is similar to ''

Gephyrosaurus ''Gephyrosaurus'' is a genus of early rhynchocephalian first described and named in 1980 by Susan E. Evans. They are distantly related to the extant ''Sphenodon'' (tuatara of New Zealand) with which they shared a number of skeletal features incl ...

'' (a basal

rhynchocephalian Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse gro ...

) and ''

Gueragama ''Gueragama'' is an extinct genus of iguanian lizard from the Late Cretaceous of Brazil. It belongs to a group of iguanians called Acrodonta, whose living members include chameleons and agamids and are currently restricted to the Old World. ' ...

'' (a basal acrodontan

squamate Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, ...

), which are each early members of major lepidosaur lineages with acrodont dentition. In the absence of more data, ''Cargninia'''s condition is considered to be a case of

homoplasy Homoplasy, in biology and phylogenetics, is the term used to describe a Phenotypic trait, feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from Homology (biology), homology, w ...

(

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

). Several additional pleuroacrodont jaw fragments are known from Faxinal do Soturno, though a lack of overlap prevents an unambiguous referral to ''Cargninia''.

References

Prehistoric reptile genera Triassic lepidosauromorphs Late Triassic reptiles of South America Triassic Brazil Fossils of Brazil Fossil taxa described in 2010 Taxa named by José Bonaparte {{triassic-reptile-stub