''Cargninia'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of basal lepidosauromorph 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 a ...

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 ...

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

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

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

UFRGS PV 1027 T, a partial left

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

(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 ...

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 ...

, southern

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

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 Caturrita Formation is a 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 the upper section of th ...

. ''Cargninia'' was named by José Fernando Bonaparte,

César Leandro Schultz Cesar or César may refer to: Arts and entertainment * ''César'' (film), a 1936 French romantic drama * ''César'' (play), a play by Marcel Pagnolt Places * Cesar, Portugal * Cesar Department, Colombia * Cesar River, in Colombia * Cesar R ...

, Marina Bento Soares and Agustín G. Martinelli in

2010 The year saw a multitude of natural and environmental disasters such as the 2010 Haiti earthquake, the Deepwater Horizon oil spill, and the 2010 Chile earthquake. The 2009 swine flu pandemic, swine flu pandemic which began the previous year ...

. 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' + ''odont-'' '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 r ...

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

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 an extinct genus of lepidosaurian reptile known from the Late Triassic to Early Jurassic of the United Kingdom. It is generally considered to be one of the most primitive members of the clade Rhynchocephalia. Description ''Ge ...

'' (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 speciose g ...

) and '' Gueragama'' (a basal acrodontan

squamate Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest Order (biology), order of reptiles; most members of which are commonly known as Lizard, lizards, with the group also including Snake, snakes. With over 11,991 species, it i ...

), 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 feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize ...

(

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 comm ...

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

References

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