''Bonacynodon'' 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 ...

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s that lived in what is now southern Brazil during the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

period (

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

–

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 227.3 ...

ages). The genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

, containing only the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

''Bonacynodon schultzi''. ''B. schultzi'' is known from two specimens, consisting of two partial skulls and some badly preserved parts of the

postcranium The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...

. Both specimens were recovered from the

Pinheiros-Chiniquá Sequence 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 ...

, part of the

Santa Maria Supersequence The Santa Maria Formation is a sedimentary geological formation, 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 ear ...

of the

Paraná Basin The Paraná Basin (, ) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande do Sul states. The remainder area is distribu ...

. This sequence preserves a faunal association known as the ''Dinodontosaurus'' Assemblage Zone, which contains numerous other species of cynodonts,

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

s and

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s. ''Bonacynodon'' was a small, likely

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...

cynodont, whose length has been estimated at around . It can be distinguished from other cynodonts by its large,

serrated Serration is a saw-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied pr ...

(saw-like)

canine teeth In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, eye teeth, vampire teeth, or fangs, are the relatively long, pointed teeth. In the context of the upper jaw, they are also known as '' fangs''. They can appear more fl ...

. Together with the genus ''

Probainognathus ''Probainognathus'' meaning “progressive jaw” is an extinct genus of cynodonts that lived around 235 to 221.5 million years ago, during the Late Triassic in what is now Argentina. Together with the genus ''Bonacynodon'' from Brazil, ''Probain ...

'' of Argentina, it made up the family

Probainognathidae Probainognathidae is an extinct Family (biology), family of insectivorous cynodonts which lived in what is now South America during the Middle Triassic, Middle to Late Triassic. The family was established by Alfred Romer in 1973 and includes two ...

, one of the earliest-diverging lineages of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Probainognathia Probainognathia is one of the two major subgroups of the clade Eucynodontia, the other being Cynognathia. The earliest forms were carnivorous and insectivorous, though some groups eventually also evolved herbivorous diets. The earliest and most b ...

. It was a fairly close relative of

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s, the only group of cynodonts alive today.

Discovery and naming

''Bonacynodon schultzi'' is known from two specimens, 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 ...

MCT-1716-R and the referred specimen (

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...

) MCT-1717-R. They were both discovered in the 1940s by the Brazilian palaeontologist

Llewellyn Ivor Price Llewellyn Ivor Price (October 9, 1905 – June 9, 1980) was one of the first Brazilian paleontologists. His work contributed not only to the development of Brazilian but also to global paleontology. He collected ''Staurikosaurus'' in 1936, th ...

in two separate rocky outcrops (''sangas'') in the Pinheiros region, around south of the town of Candelária, Rio Grande do Sul. The rocks belong to the

of the

, which has been dated to the

to early

ages. The holotype was found in an outcrop known as the ''Sanga do Janguta'', and was preserved together with a specimen of the

Dinodontosaurus ''Dinodontosaurus'' (meaning "terrible-toothed lizard") is a genus of dicynodont therapsid. It was medium to large dicynodont of the Triassic (with skull up to long) and had a beak corneum. It lived in the Middle Triassic but disappeared in the ...

''. It consists primarily of a partial skull, including parts of the

skull roof The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...

, lower jaw, upper and lower dentition,

basicranium The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria. Structure Structures found at the base of the skull are for ...

and

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

. The skull roof was heavily damaged during preparation. The holotype also includes some very fragmentary

postcranial The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...

elements, which have not been described in detail. The referred specimen was found in a different outcrop, the ''Sanga do Forno''. Like the holotype, it preserves parts of the cranium, lower jaw and upper and lower dentition. Its shape has been heavily distorted during fossilisation, but it preserves some parts of the skull that are missing in the holotype. Based on the lack of wear facets on the teeth, it has been suggested that both specimens represent

subadult A juvenile is an individual organism (especially an animal) that has not yet reached its adult form, sexual maturity or size. Juveniles can look very different from the adult form, particularly in colour, and may not fill the same niche as t ...

individuals. The specimens were first given a proper description in 2016, when they were given a new generic and specific name by Agustín G. Martinelli and colleagues. The first part of the generic name ''Bonacynodon'' is derived from the surname of

José Bonaparte José Fernando Bonaparte (14 June 1928–18 February 2020) was an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists. He has been described by paleontologist ...

, an Argentine palaeontologist who specialised in the Mesozoic vertebrates of South America. The second part, ''cynodon'', is partly derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

word (), meaning "dog", and is a reference to it being a

. The specific epithet ''schultzi'' honours Cesar L. Schultz, a Brazilian palaeontologist and professor at the

Federal University of Rio Grande do Sul The Federal University of Rio Grande do Sul (, UFRGS) is a Brazilian Public university, public National university, federal research university based in Porto Alegre, Rio Grande do Sul. UFRGS is among the largest and highest-rated universities ...

Description

''Bonacynodon'' was a small cynodont, with an estimated total length of around .

Skull

The skull of ''Bonacynodon'' was about long. The temporal region (area behind the

eye sockets In anatomy, the orbit is the cavity or socket/hole of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is ...

) was wide, and somewhat longer than the snout. The

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...

(a narrow ridge running across the top of the skull) was relatively low. The

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves med ...

(roof of the mouth) consisted of two parts, a larger section formed by the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

e (upper jaw bones), and a smaller one formed by the

palatine bone In anatomy, the palatine bones (; derived from the Latin ''palatum'') are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxilla, they comprise the hard palate. Stru ...

s. As in the closely related ''

'', the palate ended in front of the last postcanine; this is somewhat shorter than what is seen in the more basal (early-diverging) chiniquodontids and the more derived (late-diverging)

prozostrodont Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade contai ...

s. The upper jaw consisted of two bones, the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

in the front, and the maxilla in the back. Above the canines and front

postcanine Cheek teeth or postcanines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles). Mammals have multicuspidate molars (three in placentals, four in marsupials, in each jaw quadrant) and p ...

s were multiple small holes called

infraorbital foramina In human anatomy, the infraorbital foramen is one of two small holes in the skull's upper jawbone (maxillary bone), located below the eye socket and to the left and right of the nose. Both holes are used for blood vessels and nerves. In anatomica ...

; at least three foramina are seen in the holotype, while the referred specimen preserves two or three. Based on other basal

probainognathia Probainognathia is one of the two major subgroups of the clade Eucynodontia, the other being Cynognathia. The earliest forms were carnivorous and insectivorous, though some groups eventually also evolved herbivorous diets. The earliest and most b ...

ns, ''Bonacynodon'' likely had additional foramina which have not been preserved in the fossils. The tooth-bearing part of the upper jaw had a

sigmoid Sigmoid means resembling the lower-case Greek letter sigma (uppercase Σ, lowercase σ, lowercase in word-final position ς) or the Latin letter S. Specific uses include: * Sigmoid function, a mathematical function * Sigmoid colon, part of the l ...

(S-shaped) curve, sloping downwards near the postcanines before curving upwards again near the orbit. The lower jaw consisted primarily of a single bone, the

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 ...

. The dentary body was somewhat tall, and the

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

(the connection between the two halves of the dentary) was apparently unfused. The front part of the dentary bore at least three

mental foramina The mental foramen is one of two foramina (openings) located on the anterior surface of the mandible. It is part of the mandibular canal. It transmits the terminal branches of the inferior alveolar nerve and the mental vessels. Structure The ...

on each side. The back part possessed a long and backwards-pointing projection known as the coronoid process. A large basin called the masseteric fossa stretched from near the last postcanine to the tip of the coronoid process. Like in other probainognathians, the postdentary bones (a set of bones at the back of the lower jaw) were highly reduced compared to the condition in more basal cynodonts, forming a small, rod-like structure.

Dentition

''Bonacynodon'' possessed three types of teeth:

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

, canines and postcanines. It appears to have had four pairs of incisors in its upper jaw; these were slender, with a round cross section. The first three incisors were roughly equal in size, while the fourth one was slightly smaller. The incisors were widely spaced, with a particularly large gap (

diastema A diastema (: diastemata, from Greek , 'space') is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to ...

) between the third and fourth ones. There was a similarly large gap between the last incisor and the canine. The upper canines were large, and flattened from side to side. The canines had strongly

(saw-like) back edges, which is an

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a Synapomorphy, derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or Outgroup (cladistics), outgroup taxa, not ...

(unique derived feature) of the taxon. The lower incisors are not known from either specimen. Of the lower canines, only a partial left

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

from the holotype is known. The shape and size of this root was however similar to that of the upper canines. Behind each upper canine were six postcanine teeth, which were widely spaced and did not contact each other. The crowns were compressed from side to side, and possessed multiple straight, unserrated cusps (pointed projections of the teeth) which were arranged in a line. The first three upper postcanines bore three cusps, with the one in the middle (cusp A) being the largest, and the ones in front and back (cusps B and C respectively) being smaller. The fourth and fifth upper postcanines additionally possessed a small fourth cusp (cusp D) behind cusp C, and there may also have been a fifth (accessory) cusp. The sixth upper postcanine was apparently less developed than the fourth and fifth ones, and it bore at least three cusps. The lower postcanines are incompletely known, but they appear to have been similar to the upper ones. The

cingula ''Cingula'' is a genus of minute sea snails, marine gastropod mollusks or micromollusks in the family Rissoidae. Species Species within the genus ''Cingula'' include: * '' Cingula aequa'' (E. A. Smith, 1890) * '' Cingula agapeta'' (E. A. Smith ...

were poorly developed and bore no cusps. Unlike in the prozostrodonts, there was no abrupt change in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

between the front and back postcanines, and the roots were not constricted.

Classification

When describing ''Bonacynodon'', Martinelli and colleagues performed a

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

to find out its relationships to other cynodonts. It was recovered as the sister taxon of ''Probainognathus'', a similar probainognathian from the

Chañares Formation The Chañares Formation is a Carnian-age geologic formation of the Ischigualasto-Villa Unión Basin, located in La Rioja Province, Argentina. It is characterized by drab-colored fine-grained volcaniclastic claystones, siltstones, and sandstones ...

of Argentina. Together with ''Probainognathus'', ''Bonacynodon'' was placed in the family

. The probainognathids were found to be closely related to Prozostrodontia, a

(group formed by all descendants of a common ancestor) which includes

s, the only

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

(living) cynodonts, as well as several other groups. Subsequent analyses have upheld the sister relationship of ''Bonacynodon'' and ''Probainognathus''. Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

following the analysis of Martinelli ''et al.'' (2016):

Palaeobiology

Early-diverging probainognathians like the

ecteniniid Ecteniniidae is an extinct family (biology), family of probainognathian cynodonts from the Triassic of South America. They are notable for their large size, as well as for being among the first synapsids with specializations towards cursoriality. ...

s and ''

Chiniquodon ''Chiniquodon'' is an extinct genus of carnivorous cynodonts, which lived during the Late Triassic (Carnian) in South America (Argentina and Brazil) and Africa (Namibia and Madagascar). ''Chiniquodon'' was closely related to the genus ''Aleodon'' ...

'' had postcanine teeth with strongly recurved (and in the case of the ecteniniids, even serrated) cusps, which would have been well-suited for a

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

diet. The straight, unserrated postcanine cusps of probainognathids like ''Bonacynodon'' were more similar to those of basal prozostrodonts; this is thought to be an adaptation towards

insectivory A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...

. As the holotype was preserved together with the remains of a dicynodont, Schwanke & Kellner (2009) hypothesised that the animal might have been an opportunistic

scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...

. However, in 2016 Martinelli and colleagues suggested that it could instead have eaten insect

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e and other

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s that fed on the

decomposing Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essen ...

dicynodont.

Palaeoenvironment

''Bonacynodon'' belongs to the ''Dinodontosaurus'' Assemblage Zone, the lowermost of the four

biostratigraphic unit Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

s of the Santa Maria Supersequence of the

. The ''Dinodontosaurus'' AZ corresponds to the Pinheiros-Chiniquá Sequence, one of the three stratigraphic sequences of the Supersequence. Together with the overlying Santa Cruz Sequence (containing the ''Santacruzodon'' AZ) and the lower part of the Candelária Sequence (containing the ''Hyperodapedon'' AZ), it comprises the traditional

Santa Maria Formation 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 othe ...

. The Pinheiros-Chiniquá and Santa Cruz Sequences appear to have been deposited during a dry period, in which the landscape was dominated by

loess A loess (, ; from ) is a clastic rock, clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposition (geology), deposits. A loess ...

ic plains. Cynodonts make up a large portion of the fauna of the ''Dinodontosaurus'' Assemblage Zone. In addition to ''Bonacynodon'', these include the probainognathians ''

Aleodon ''Aleodon'' is an extinct genus of cynodonts that lived from the Middle to Late Triassic. Relatively few analyses have been conducted to identify the phylogenetic placement of ''Aleodon'', although some have placed it as a sister taxon to '' Chin ...

'', ''

Candelariodon ''Candelariodon'' is an extinct genus of carnivorous probainognathian cynodonts from the Middle to Late Triassic Santa Maria Formation of the Paraná Basin in Rio Grande do Sul state, Brazil. ''Candelariodon'' is known from a partial mandible h ...

'', ''Chiniquodon'' and ''

Protheriodon ''Protheriodon'' is an extinct genus of probainognathian cynodonts which existed in the Santa Maria Formation of the Paraná Basin in southeastern Brazil during the middle Triassic period. It contains the species ''Protheriodon estudianti''. It ...

'', and 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 North America. Traversodon ...

s '' Luangwa'', '' Massetognathus'', ''

Protuberum ''Protuberum'' is an extinct genus of traversodontid cynodonts known from a single species ''Protuberum cabralense'',The specific name ''cabralense'' is "necessarily emended from the original ''P. cabralensis'' because ''Protuberum'' is a neuter ...

'', ''

Scalenodon ''Scalenodon'' is an extinct genus of traversodontid cynodonts from the Middle Triassic of Africa and possibly Russia. The type species ''S. angustifrons'' was named in 1946 and several other species were named in the following years. Most of th ...

'' and ''

Traversodon ''Traversodon'' is an extinct genus of cynodonts. It was a relative of the ancestor to modern mammals. ''Traversodon'' lived in what is now South America. Species ''Traversodon stahleckeri'' was first found by Friedrich von Huene in 1936 in the ...

''. Other vertebrates from this Assemblage Zone include the dicynodonts ''Dinodontosaurus'' and ''

Stahleckeria ''Stahleckeria'' is an extinct genus of Middle Triassic (Ladinian) dicynodonts.''Stahle ...

'', the

parareptile Parareptilia ("near-reptiles") is an extinct group of Basal (phylogenetics), basal Sauropsida, sauropsids ("Reptile, reptiles"), traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds ...

'' Candelaria'', the

rhynchosaur Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs ...

Brasinorhynchus ''Brasinorhynchus'' is an extinct genus of derived stenaulorhynchine known from the late Middle Triassic (Ladinian stage) Santa Maria Formation of Rio Grande do Sul, Brazil.archosauriform Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common anc ...

Barberenasuchus ''Barberenasuchus'' is an extinct genus of an archosauriform. Fossils (poorly preserved skull and axis vertebra) have been found from the Santa Maria Formation of southern Brazil of Late Triassic age. Its phylogenetic position within Archosauri ...

'', several species of

pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

ns (the group that contains modern-day

crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...

ns and their extinct relatives), and the aphanosaur (primitive stem-bird) ''

Spondylosoma ''Spondylosoma'' (meaning "vertebra body") is a genus of avemetatarsalian archosaur belonging to the clade Aphanosauria from the late Ladinian-age Middle Triassic Lower Santa Maria Formation in Paleorrota Geopark, Brazil. History Friedrich v ...

''.

References

{{Taxonbar, from=Q37577828 Probainognathia Ladinian genera Carnian genera Middle Triassic synapsids of South America Late Triassic synapsids of South America Triassic Brazil Fossils of Brazil Santa Maria Formation Fossil taxa described in 2016