Peirosaurus
Encyclopedia
Peirosaurus is an extinct genus
of peirosaurid crocodylomorph. It is the type genus
of the family
Peirosauridae
. Fossil
s of the type species
P. tormini, first described in 1955, have been found from the Marília Formation
in Uberaba
, Brazil
and date back to the late Maastrichtian
stage of the Late Cretaceous
. The genus is known from a partial skull and several postcranial elements such as vertebrae and dermal plates
. Material of the genus is also known from the Bajo de la Carpa Formation
in Argentina
.
Peirosaurus has a ziphodont dentition that is somewhat heterodont, with conical premaxilla
ry teeth and serrated maxilla
ry and posterior mandibular
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 the same locality in Uberaba. These include a similar tooth size pattern and the large maxillary anterior process. However, the rostrum of Uberabasuchus is more compressed than that of Peirosaurus, which is relatively broad.
The occurrence of Peirosaurus in both Argentina and Brazil provides evidence for the interchange of crocodylomorphs that is thought to have occurred as a result of the connection of the drainage systems of southern Argentina and central South America throughout the Late Cretaceous in the Bauru Basin.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of peirosaurid crocodylomorph. It is the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Peirosauridae
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 defined in 2004 as the most recent common ancestor of...
. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
P. tormini, first described in 1955, have been found from the Marília Formation
Marilia Formation
The Marília Formation is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Crurotarsans:-Ornithodirans:...
in Uberaba
Uberaba
Uberaba is a city and municipality in the west of the state of Minas Gerais in Brazil. Its population is 296.000 with an area of 4529.7 km², giving a density of 60.71 people per km². It is located on a plateau at an elevation of 785 meters and is in the Uberaba River floodplain...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and date back to the late Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
. The genus is known from a partial skull and several postcranial elements such as vertebrae and dermal plates
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
. Material of the genus is also known from the Bajo de la Carpa Formation
Bajo de la Carpa Formation
The Bajo de la Carpa Formation is a geologic formation that outcrops in Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the first of two formations belonging to the Río Colorado Subgroup within the Neuquén Group...
in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
Peirosaurus has a ziphodont dentition that is somewhat heterodont, with conical premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry teeth and serrated maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
ry and posterior mandibular
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
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
Uberabasuchus
Uberabasuchus is an extinct genus of crocodylomorph from the Late Cretaceous of Brazil.-Sources:* - original description of genus...
, found from the same locality in Uberaba. These include a similar tooth size pattern and the large maxillary anterior process. However, the rostrum of Uberabasuchus is more compressed than that of Peirosaurus, which is relatively broad.
The occurrence of Peirosaurus in both Argentina and Brazil provides evidence for the interchange of crocodylomorphs that is thought to have occurred as a result of the connection of the drainage systems of southern Argentina and central South America throughout the Late Cretaceous in the Bauru Basin.
External links
- Peirosaurus in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...