''Cargninia'' is an extinct

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 n ...

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

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 contain ...

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 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. * Ty ...

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 seve ...

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 teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

(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, 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 ...

-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 the ...

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

César Leandro Schultz Cesar, César or Cèsar may refer to: Arts, entertainment, and media * ''César'' (film), a 1936 film directed by Marcel Pagnol * ''César'' (play), a play by Marcel Pagnolt * César Award, a French film award Places * Cesar, Portugal * Ce ...

Marina Bento Soares A marina (from Spanish , Portuguese and Italian : ''marina'', "coast" or "shore") is a dock or basin with moorings and supplies for yachts and small boats. A marina differs from a port in that a marina does not handle large passenger ship ...

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 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 amphisbaenia, amphisbaenians. Squamata contains over 9, ...

(

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'' (a basal rhynchocephalian) and '' Gueragama'' (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, it ...

), 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 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