''Protome'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of 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 ...

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 ...

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 ...

, represented by a single

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, ''Protome batalaria''. It is known from a single

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 several ...

incomplete, 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, the ...

and left

lower jaw 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 ...

called PEFO 34034 from the Upper Lot's Wife beds, Sonsela Member of the

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In Ne ...

Petrified Forest National Park Petrified Forest National Park is an American national park in Navajo County, Arizona, Navajo and Apache County, Arizona, Apache counties in northeastern Arizona. Named for its large deposits of petrified wood, the park covers about , encompassin ...

. The skull was discovered in 2004 by Michelle Stocker and Bill Parker and was described by them as a specimen of '' Smilosuchus adamanensis'' (then a species of ''

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 ...

''). It was placed in the new genus ''Protome'' in 2012. The genus name ''Protome'' is the

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 ...

word for an animal's face. The specific name ''batalaria'' is the

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 ...

word for battleship, which is a reference to Battleship NW, the locality within Petrified Forest where the skull was found.

Description

''Protome'' has a long, narrow, tubular-shaped snout. It has a partial rostral crest at the back of the snout, a feature which it shares with phytosaurs like '' Smilosuchus adamanensis'', '' Pravusuchus'', and ''

'', but which is not as prominent as it is in other ''Smilosuchus'' species and some ''

Pseudopalatus ''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 ba ...

'' species. It lacks 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 mammal has b ...

ry crest along the midline of the snout that is present in '' Leptosuchus studeri'' and ''

Mystriosuchus westphali ''Mystriosuchus'' (meaning "spoon-crocodile")
Retrieved on May 25th, 2008. is an

''. Many characteristics that associate ''Protome'' with other phytosaurs can be found in its

squamosal bone 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 ...

, which makes up the cheek region and extends behind the main portion of the skull. ''Protome'' was named on the basis of several unique characteristics, or

autapomorphies 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 t ...

. The first autapomorphy is the flat shape of the basitubera, an area at the base of the skull in front of its attachment point with the neck. Another is that bony projections called exoccipital prongs at the back of the skull make up the top margin of the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...

, the hole through which the spinal cord enters the skull. A third autapomorphy is a small depression or fossa surrounding the front tip of a hole in the lower jaw called the

mandibular fenestra The skull is a bone protective Cranial cavity, 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 ...

. These features were used to distinguish PEFO 34034 as a new genus and species, distinct from ''Leptosuchus adamanensis''. ''Protome'' and ''Leptosuchus'' are similar in that both have broad squamosals and holes called

supratemporal fenestrae 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, the ...

that are located on top of the skull. When it was described in 2004, PEFO 34034 was thought to represent a small ''Leptosuchus'' individual, possibly a juvenile. The lack of a premaxillary crest has been used as evidence for it being a juvenile, although the absence of a crest has also been interpreted as a distinct characteristic of some species, and more recently as a possible characteristic of

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. Most juvenile phytosaurs are identified on the basis of incomplete fusion of different parts of each

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

, but ''Protome'' is not known from any postcranial remains.

Phylogeny

When ''Protome'' was named in 2012, a

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 was conducted to determine its evolutionary relationships. The analysis placed PEFO 34034 outside the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s containing species of ''Leptosuchus'' and ''Smilosuchus'', the two most likely genera to which the specimen could be referred. PEFO 34034's placement outside these groups justified the erection of a new genus and species. ''Protome'' was found to be a

phytosaurid 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 equivale ...

just outside the clade

Leptosuchomorpha 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 ...

. As was the case in previous studies, species of ''Leptosuchus'' formed a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

grouping, meaning that they did not represent one coherent genus. Many isolated phytosaur skull fragments from Petrified Forest have been assigned to ''Leptosuchus'' because they had broad squamosals, but the presence of this type of squamosal in the distinct taxon ''Protome'' suggests that not all of these fragments can be assigned with confidence to ''Leptosuchus''. 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 d ...

showing the phylogenetic relationships of ''Protome'' from Stocker (2012):

References

{{Taxonbar, from=Q3280960 Phytosaurs Prehistoric reptile genera Late Triassic reptiles of North America Triassic Arizona Paleontology in Arizona Chinle fauna Fossil taxa described in 2012