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''Prionosuchus'' 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 ...
of large
temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...
. 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 appropriat ...
''P. plummeri'', is recognized from the
Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * 01'' (Richard Müller album), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawan ...
(some time between 299 and 272 million years ago). Its
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s have been found in what is now northeastern
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 ...
.


Description

The fragmentary remains of this animal have been found in the Pedra do Fogo Formation in the
Parnaíba Basin The Parnaíba Basin (Portuguese: ''Bacia do Parnaíba'') is a large cratonic sedimentary basin located in the North and Northeast portion of Brazil. About 50% of its areal distribution occurs in the state of Maranhão, and the other 50% occurrin ...
of Northeastern Brazil, in the states of
Piauí Piaui (, ) is one of the states of Brazil, located in the country's Northeast Region. The state has 1.6% of the Brazilian population and produces 0.7% of the Brazilian GDP. Piaui has the shortest coastline of any coastal Brazilian state at 66& ...
and
Maranhão Maranhão () is a state in Brazil. Located in the country's Northeast Region, it has a population of about 7 million and an area of . Clockwise from north, it borders on the Atlantic Ocean for 2,243 km and the states of Piauí, Tocantins a ...
, and it was described by L.I. Price in 1948. The incomplete skull of 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 ...
specimen has been estimated to be long.Cox, C.B., and Hutchinson, P. (1991). "Fishes and amphibians from the
Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...
Pedra de Fogo Formation of Northern Brazil" ''Palaeontology'', 34(3): 561–573.
Several more fragmentary specimens have been found. One very fragmentary but very large specimen (BMNH R12005) appears to have come from an individual nearly three times the size of most other specimens, and may have had a skull that measured up to long. Based on related species and comparisons with living gharials, the total body length of this specimen has been estimated at more than 5.5 meters (18 ft). With an elongated and tapered snout, numerous sharp teeth, long body, short legs, and a tail adapted for swimming, its general appearance was very similar to a modern
gharial The gharial (''Gavialis gangeticus''), also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are long, and males . Adult males have a distinct ...
or gar, and it probably had a similar lifestyle as an ambush aquatic predator feeding on fish and other aquatic animals. A study on the closely related '' Archegosaurus'' shows that it had a heat balance, gas exchange, osmoregulation, and digestion more similar to that of
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...
than modern aquatic amphibians; the same probably applied to ''Prionosuchus'' as well.


Classification

''Prionosuchus'' has been classified as an archegosaurian by Carroll. 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 "unispe ...
with ''P. plummeri'' being the only species described. The archegosaurs were a group of
temnospondyli Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...
that occupied the ecological niche of crocodiles and
alligator An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additional ...
s during the Permian, and of which the European genus '' Archegosaurus'' is typical. The group became extinct at the end of the Permian and the niche was subsequently filled by other, new temnospondyls, later joined by reptiles such as the
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 ...
s in the
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
period. Cox and Hutchinson re-evaluated ''Prionosuchus'' in 1991 and synonymized it with the genus '' Platyoposaurus'' from Russia. On the basis of this study, the Pedra do Fogo Formation was reevaluated to be of Middle to Late Permian age. However, studies based on plants and pollens indicate that this formation is actually early Permian in age, making ''Prionosuchus'' not contemporary with ''Platyoposaurus''. More recent research rejects the later Permian date.


Paleoecology

''Prionosuchus'' lived in a humid and tropical environment as indicated by the petrified forest of the Pedra do Fogo formation in which fossils of this animal have been found. The strata composed of
siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...
s,
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
s and
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...
s were deposited in
lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons ...
al and fluvial environments.Schobbenhaus, C., Campos, D. A., Derze, G. R., and Asmus, H. E., 1984, Geologia do Brasil: Brasõlia, D.N.P.M., Brasília, 501 pp. Other animals discovered in the same rocks include fish (primitive
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...
s, palaeoniscids, and
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
) and amphibians.


References

{{Taxonbar, from=Q2341275 Prehistoric amphibian genera Cisuralian temnospondyls Permian temnospondyls of South America Permian Brazil Fossils of Brazil Fossil taxa described in 1948