''Peirosaurus'' 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 n ...

of peirosaurid

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...

known from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

period (late

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

stage) of

Minas Gerais Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literall ...

, southern

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 ...

. It contains a single species, ''Peirosaurus torminni''. It is the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nomina ...

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Peirosauridae Peirosauridae is a Gondwanan family of mesoeucrocodylians that lived during the Cretaceous period. It was a clade of terrestrial crocodyliforms that evolved a rather dog-like form, and were terrestrial carnivores. It was phylogenetically define ...

Discovery

''Peirosaurus'' 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 seve ...

DGM 433-R, fragmentary

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, t ...

(left

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 ...

bearing five

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, te ...

, isolated maxillary and dentary teeth and left

palpebral bone The palpebral bone is a small dermal bone found in the region of the orbit (anatomy), eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. It is also known as the adlacrimal or supraorbital, although the latter te ...

) and 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 s ...

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

including

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

, left pubis and

ischium The ischium () form ...

, some presacral and a single caudal vertebrae, ribs, haemal arches and dermal plates. It was collected by Llewellyn Ivor Price in 1947-1949 at the Price Quarry 3, Peirópolis Site near

Uberaba Uberaba () is a city in the state of Minas Gerais, southeast Brazil. It is located in the Brazilian Highlands at above sea level on the Uberaba River, and away from the state capital, Belo Horizonte. The city status was granted in 1856, and ...

, in the

Serra de Galga Member Serra (Latin for "saw") may refer to: People * Serra (footballer) (born 1961), Portuguese footballer * Serra (surname) * Serra (given name) Cities, towns, municipalities Brazil * Serra, Espírito Santo, a city in the Greater Vitória area *Amp ...

of the

Marília Formation The Marília Formation is a geological formation in Minas Gerais state of southeastern Brazil. Its strata date back to the Maastrichtian, and are part of the Bauru Group. The fossil-bearing Serra da Galga and Ponte Alta members were originally th ...

(

Bauru Group The Bauru Group is a geological group of the Bauru Sub-basin, Paraná Basin in Minas Gerais, São Paulo, General Salgado, Itapecuru-Mirim, Mato Grosso, Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils t ...

), dating to the late

stage of the

, about 68-66

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

. A partial skull and several postcranial elements such as

vertebrae 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 characteristi ...

and dermal plates from the

Bajo de la Carpa Formation The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that crops out in northern Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the oldest of two formations belonging to the Río Colorado Subgro ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

and another partial skull and several unprepared postcranial elements from the

Anacleto Formation The Anacleto Formation is a geologic formation with outcrops in the Argentine Patagonian provinces of Mendoza, Río Negro, and Neuquén. It is the youngest formation within the Neuquén Group and belongs to the Río Colorado Subgroup. Formerl ...

, Argentina, were assigned to ''Peirosaurus'' by Gasparini, Chiappe and Fernandez (1991) and Praderio, Martinelli and Candeiro (2008), respectively. However, more recently Agustín G. Martinelli, Joseph J.W. Sertich, Alberto C. Garrido and Ángel M. Praderio concluded that the traits which used to unite the holotype (from Brazil) and the referred material from Argentina are shared with other peirosaurids and some other

mesoeucrocodylia Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day. Diagnosis It was long known that M ...

ns. They reassigned the Argentinian specimens to a new genus, '' Gasparinisuchus'', and although overlapping materials between the genera are limited to the premaxilla and the

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...

, ''Gasparinisuchus'' can be differentiate from ''Peirosaurus'' on the basis of its broad, rounded rostrum, anteroposteriorly short premaxilla, reduced perinareal fossa, and short premaxillary interdental spaces. Hence, ''Peirosaurus'' is known only from its holotype.

Description

''Peirosaurus'' has a ziphodont dentition that is somewhat heterodont, with conical

ry teeth and serrated

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. The ...

ry and posterior

mandibular 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 ...

teeth. The rostrum is laterally compressed with a grove between the maxilla and premaxilla to accommodate for an enlarged mandibular tooth. A maxillary wedge-like anterior process is also present. The external nares face slightly forward and anteriorly protrude. The dorsal osteoderms are thin and sculptured with low longitudinal keels while the abdominal ones are smaller and lack keels. ''Peirosaurus'' shares a number of features with the closely related genus '' Uberabasuchus'', found from a nearby locality in Uberaba. These include a similar tooth size pattern and the large maxillary anterior process. These genera were differentiated from each other as the rostrum of ''Uberabasuchus'' is more compressed than that of ''Peirosaurus'', which is relatively broad. However, the rostrum wasn't preserved in the holotype of ''Peirosaurus''. The removal of MOZ 1750 PV (which preserved the rostrum) from the genus ''Peirosaurus'' suggests a possible synonymy between ''Peirosaurus'' and ''Uberabasuchus''. Though many of the features of the premaxilla and dentition of Peirosaurus are widespread among peirosaurids and many mesoeucrocodylians, several are shared exclusively with ''Uberabasuchus''. Among these features some are not observed in other peirosaurids. These include the relatively long anteroposterior facial length of the

, the elongate and strongly anteromedially directed dorsomedial process of the premaxilla, and the sharply defined and elevated margin of the perinarial fossa. There are differences between the two taxa such as differences in the relative thickness of dorsal osteoderms and the absence of a denticulate mesial carina on the first premaxillary tooth in ''Peirosaurus'', but not in ''Uberabasuchus''. However, these characters are considered to be minor and their taxonomic value may be individually variable. As postcranial materials of both ''Peirosaurus'' and ''Uberabasuchus'' are known but are not yet formally described, they are tentatively considered to be valid taxa.

References

{{Taxonbar, from=Q7160960 Late Cretaceous crocodylomorphs of South America Marília Formation Bajo de la Carpa Formation Prehistoric pseudosuchian genera