''Pravusuchus'' 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 nom ...

leptosuchomorph Leptosuchomorpha is a clade of phytosaurs. It is a node-based taxon defined as the last common ancestor of '' Leptosuchus studeri'' and '' Pseudopalatus pristinus'' and all of its descendants. Phylogeny Below is a cladogram A cladogram (fr ...

parasuchid

phytosaur Phytosaurs (Φυτόσαυροι in greek) are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. Phytosauria and Phytosauridae are often considered to be equivalent g ...

known from the

Late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

( Norian stage) of

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, United States. It contains a single species, ''Pravusuchus hortus'', which is known from three specimens. These specimens were previously referred to ''

Smilosuchus ''Smilosuchus'' (meaning "chisel crocodile") is an extinct genus of leptosuchomorph parasuchid from the Late Triassic of North America. History The type species was first described in 1995 as a replacement generic name for ''Leptosuchus g ...

'' or to ''

Leptosuchus ''Leptosuchus'' is an extinct genus of leptosuchomorph phytosaur with a complex taxonomical history. Fossils have been found from the Dockum Group and lower Chinle Formation outcropping in Texas, New Mexico, and Arizona, USA, and date back to th ...

'', but ''Pravusuchuss

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a 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 taxa, not even those most closely related to ...

, its phylogenetic position as well as a trait shared with

mystriosuchin Mystriosuchini, historically known as Pseudopalatinae, is an extinct tribe (formerly subfamily) of derived phytosaurs in the clade Leptosuchomorpha. As with all other phytosaurs, mystriosuchins lived during Late Triassic. The name is derived from ...

s, justified the erection of a new

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

for the material.

Discovery and naming

''Pravusuchus'' was first described and named by Michelle R. Stocker in 2010 and the

type species In 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 species that contains the biological type specime ...

is ''Pravusuchus hortus''. The generic name is derived from

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 ...

, ''pravus'', "evil" or "wicked", and

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

, ''souchus'', for the Egyptian crocodile-headed god

Sobek Sobek (also called Sebek or Sobki, cop, Ⲥⲟⲩⲕ, Souk) was an ancient Egyptian deity with a complex and elastic history and nature. He is associated with the Nile crocodile or the West African crocodile and is represented either in its f ...

. The specific name, ''hortus'', is the

word for park or grounds. The name refers to Devil's Playground, the locality in Petrified Forest National Park from which all specimens of this taxon were collected. ''Pravusuchus'' 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 sever ...

AMNH FR 30646, mostly complete but partially disarticulated

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

, and from the referred specimens PEFO 31218, a partial skull, and PEFO 34239, partial skull, partial

mandible 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 ...

, and possible partial

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

. Although the holotype is slightly crushed dorsoventrally, it is not as flattened as PEFO 31218. All specimens referable to ''Pravusuchus'' were collected from the Sonsela Sandstone Bed (later referred to as Jasper / Rainbow Forest Bed) of the Norian-aged Sonsela Member, Chinle Formation from

Navajo County Navajo County is in the northern part of the U.S. state of Arizona. As of the 2020 census, its population was 106,717. The county seat is Holbrook. Navajo County comprises the Show Low, Arizona Micropolitan Statistical Area. Navajo County c ...

. PEFO 31218 and PEFO 34239 were found in the same stratigraphic horizon just west of Colbert's 1946 locality where AMNH FR 30646 was collected, and only 2–3 m higher stratigraphically than the holotype. Other phytosaur specimens from the Sonsela Member occur in other beds, stratigraphically lower (e.g. '' Protome batalaria'', '' Smilosuchus adamanensis'' and '' S. lithodendrorum'') or higher (e.g. '' Machaeroprosopus jablonskiae'' and '' M. pristinus'') then the white Rainbow Forest sandstone.

Description

Stocker (2010) diagnosed ''Pravusuchus hortus'' by a single unambiguous

(unique trait) and additionally by a unique combination of characters. Unlike all other phytosaurs, the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

rim of its external naris (i.e.

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

) is formed by the " septomaxilla", and not by the nasal bone. The element in phytosaur skulls anterior to the external nares, located between the nasal,

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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. T ...

and

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 mammal has ...

, has traditionally been referred to as the septomaxilla, however it probably is not homologous to the septomaxillae of

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 ...

s and

synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...

s. The

antorbital fossa An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds ...

is absent in ''Pravusuchus'', as in ''Pseudopalatus'', ''Smilosuchus gregorii'' and ''S. adamanensis'', however, unlike ''Pseudopalatus'' its interpremaxillary fossa (a depression on the premaxilla) is broad and rounded. In ''Pravusuchus'',

alveolar ridge The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity. The synonymous t ...

s visible in lateral view (from the sides), unlike the condition in ''S. gregorii'' and ''Pseudopalatus''. Its rostrum is partially crested, as in ''Leptosuchus crosbiensis'', ''L. studeri'' and ''S. adamanensis'', but it lacks a premaxillary crest, as also seen in ''Protome'', ''Smilosuchus'' and ''L. crosbiensis''. ''Pravusuchus'' shares with ''Pseudopalatus'', ''L. crosbiensis'' and ''L. studeri'' the presence of a long posterior process of the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

, unlike the condition seen in ''S. gregorii'' and ''S. adamanensis''. However, in contrast to the condition in ''Pseudopalatus'', it is also greatly dorsoventrally expanded and rounded posteriorly as in ''Rutiodon'', ''Protome'', ''Leptosuchus'', ''Smilosuchus'' and ''"Phytosaurus" doughtyi''. As in ''"Machaeroprosopus" zunii'', ''Protome'', ''Smilosuchus'' and ''Pseudopalatus'', ''Pravusuchus'' has basitubera, in front of the attachment point between the skull and the neck, that are connected and form a sharp ridge along their anterior border. Its supratemporal fenestrae (upper temporal openings) partially depressed as in ''Rutiodon'', ''Leptosuchus'' and ''S. gregorii'', in contrast to the condition in ''Pseudopalatus'', and are mostly visible in

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

view as in ''Smilosuchus''. In contrast to all other phytosaurs, ''Pravusuchus'' shares the presence of a subsidiary opisthotic process of the squamosal with Mystriosuchini, a possible

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

Phylogeny

To test the evolutionary relationships of ''Pravusuchus'', Stocker (2010) performed the most inclusive

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of

Phytosauria Phytosaurs (Φυτόσαυροι in greek) are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. Phytosauria and Phytosauridae are often considered to be equivalent g ...

up to that time. ''Pravusuchus'' was coded in the analysis using solely its holotype, as both referred specimen had identical codings for applicable characters. The analysis placed ''Pravusuchus'' outside the clade containing species of ''Mystriosuchus'' and ''Pseudopalatus'' (now ''

Machaeroprosopus ''Machaeroprosopus'' is an extinct genus of mystriosuchin leptosuchomorph phytosaur from the Late Triassic of the southwestern United States. ''M. validus'', once thought to be the type species of ''Machaeroprosopus'', was named in 1916 on the b ...

''), suggesting that it is 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 ...

of Mystriosuchini. However, to confirm its exclusion from Mystriosuchini, '' Nicrosaurus kapffi'' must be included in the analysis, as Mystriosuchini is a

node-based taxon Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a '' type'', which ...

and ''Nicrosaurus'' usually occupies the most basal position in it. Furthermore, ''Pravusuchus'' was found to occupy a more derived position then ''

'' and even ''

''. This justified the erection of a new genus and species for ''Pravusuchus'', as its holotype was previously referred to these genera. Below is a

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

showing the phylogenetic relationships of ''Pravusuchus'' from Stocker (2010) which was also recovered in Stocker (2012):

References

{{Taxonbar, from=Q7238894 Phytosaurs Prehistoric reptile genera Norian genera Late Triassic reptiles of North America Triassic Arizona Paleontology in Arizona Fossil taxa described in 2010 Taxa named by Michelle R. Stocker