''Pravusuchus'' 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 leptosuchomorph parasuchid phytosaur known 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 ...

(

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 ...

stage) of

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

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

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 ...

, its phylogenetic position as well as a trait shared with mystriosuchins, justified the erection of a new

taxon In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...

for the material.

Discovery and naming

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

and 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 ...

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

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

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

Greek Greek may refer to: 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 of all kno ...

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

Sobek Sobek (), also known as Suchus (), was an ancient Egyptian deities, ancient Egyptian deity with a complex and elastic history and nature. He is associated with the Nile crocodile and is often represented as a crocodile-headed humanoid, if not a ...

. 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 (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 ...

AMNH FR 30646, mostly complete but partially disarticulated

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

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

mandible 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 i ...

, and possible partial postcrania. 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

-aged Sonsela Member, Chinle Formation from Navajo County,

. 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 also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

rim of its external naris (i.e.

nostril A nostril (or naris , : 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 turbinates ...

) is formed by the " septomaxilla", and not by the

nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

. The element in phytosaur skulls anterior to the external nares, located between the nasal,

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 ...

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 mammals h ...

, 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 (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 ...

s and

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

s. The antorbital fossa 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 () is the portion of bone containing the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The alveolar process is covered by gums within the mouth, terminating roughly along the line of the mandib ...

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 ancestra ...

, 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 The fus ...

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 Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...

Phylogeny

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

phylogenetic 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 dat ...

analysis of

Phytosauria Phytosaurs (Φυτόσαυροι in greek language, Greek, meaning 'plant lizard') are an extinct group of large, mostly semiaquatic Late Triassic archosauriform or Basal (phylogenetics), basal archosaurian reptiles. Phytosaurs belong to the ord ...

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 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 ...

containing species of ''Mystriosuchus'' and ''Pseudopalatus'' (now ''

Machaeroprosopus ''Machaeroprosopus'' (from , 'large knife' and , 'bordering on') 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 ''M ...

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

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

References

{{Taxonbar, from=Q7238894 Phytosauria 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