Pissarrachampsa
Encyclopedia
Pissarrachampsa is an extinct genus
of baurusuchid
mesoeucrocodylia
n from the Late Cretaceous
of Brazil
. It is based on a nearly complete skull and a referred partial skull and lower jaw from the ?Campanian
- ?Maastrichtian
-age Vale do Rio do Peixe Formation of the Bauru Group
, found in the vicinity of Gurinhatã
, Brazil.
skull with the tip of the snout eroded away. The end of the snout and the bottom of the palate are also represented by a second fossil. Like other baurusuchids, it has a deep skull that narrow in front of the eyes and wider at the back, giving it a roughly triangular shape when viewed from above. The snout is not as narrow as other related baurusuchids, however. At around 70% the length of the entire skull, the snout is also short in comparison to those of other crocodyliforms. Like other baurusuchids, Pissarrachampsa has an enlarged caniniform tooth in the upper jaw. Including the enlarged caniniform, there are four teeth implanted in the maxilla
, less than other baurusuchids. A groove extends behind the last of the maxillary teeth. While other baurusuchids have more teeth implanted this groove, Pissarrachampsa likely lost these teeth, giving it a reduced dentition. A deep notch between the maxillae and premaxilla
e provides room for an enlarged fourth dentary tooth in the lower jaw when the mouth is closed. Another large dentary tooth fits into a hole at the back of the upper jaw. Except for the fourth dentary tooth, no teeth in the lower jaw are visible when the mouth is closed.
The nostrils are positioned at the tip of the snout and face forward. They are found in a depressed region called the circumnarial fossa. Thick palpebral
bones overly the eyes. The supratemporal fenestrae, two large holes on the skull roof
, are almost the same size as the eye sockets and are roughly triangular in shape. The thick anterior and medial rims of the supratemporal fenestrae are a diagnostic feature of Pissarrachampsa. At the back of the skull are four quadrate
fenestrae, small depressions that Pissarrachampsa shares with other notosuchians. In Pissarrachampsa, these fenestrae are visible when the skull is viewed from the side, but in other baurusuchids, they are hidden within a deep notch in the back of the skull. The pterygoid wings extend down from the bottom of the skull as two large triangular pieces of bone. A deep depression on each wing serves as another diagnostic characteristic of the genus. Another unique feature can be found underneath the back of the skull; four holes called Eustachian foramina provide an opening for the Eustachian tube
s, and in Pissarrachampsa the outer or lateral pair are larger than the inner or medial pair.
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 baurusuchid
Baurusuchidae
Baurusuchidae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It is a group of terrestrial hypercarnivorous crocodilians from South America and possibly Pakistan. Baurusuchidae has been defined as a clade containing the most recent common ancestor of Baurusuchus...
mesoeucrocodylia
Mesoeucrocodylia
Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
n from 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...
of 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...
. It is based on a nearly complete skull and a referred partial skull and lower jaw from the ?Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
- ?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...
-age Vale do Rio do Peixe Formation of the Bauru Group
Bauru Group
The Bauru Group 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. The Bauru Group was divided by Fernandes and Coimbra in four formations,namely Adamantina, Uberaba Araçatuba and...
, found in the vicinity of Gurinhatã
Gurinhatã
Gurinhatã is a municipality in the west of the Brazilian state of Minas Gerais. As of 2007 the population was 6,194 in a total area of 1,844 km². It became a municipality in 1962.-Location:...
, Brazil.
Description
Pissarrachampsa is known from a nearly complete holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
skull with the tip of the snout eroded away. The end of the snout and the bottom of the palate are also represented by a second fossil. Like other baurusuchids, it has a deep skull that narrow in front of the eyes and wider at the back, giving it a roughly triangular shape when viewed from above. The snout is not as narrow as other related baurusuchids, however. At around 70% the length of the entire skull, the snout is also short in comparison to those of other crocodyliforms. Like other baurusuchids, Pissarrachampsa has an enlarged caniniform tooth in the upper jaw. Including the enlarged caniniform, there are four teeth implanted in the 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...
, less than other baurusuchids. A groove extends behind the last of the maxillary teeth. While other baurusuchids have more teeth implanted this groove, Pissarrachampsa likely lost these teeth, giving it a reduced dentition. A deep notch between the maxillae and 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....
e provides room for an enlarged fourth dentary tooth in the lower jaw when the mouth is closed. Another large dentary tooth fits into a hole at the back of the upper jaw. Except for the fourth dentary tooth, no teeth in the lower jaw are visible when the mouth is closed.
The nostrils are positioned at the tip of the snout and face forward. They are found in a depressed region called the circumnarial fossa. Thick palpebral
Palpebral (bone)
The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. In ornithischians, it can form a prong that projects from the front upper corner of the orbit...
bones overly the eyes. The supratemporal fenestrae, two large holes on the skull roof
Skull roof
The skull roof , or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land living vertebrates. The bones are derived from dermal bone, hence the alternative name dermatocranium...
, are almost the same size as the eye sockets and are roughly triangular in shape. The thick anterior and medial rims of the supratemporal fenestrae are a diagnostic feature of Pissarrachampsa. At the back of the skull are four quadrate
Quadrate bone
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint .- Evolutionary variation :In snakes, the quadrate bone has become elongated...
fenestrae, small depressions that Pissarrachampsa shares with other notosuchians. In Pissarrachampsa, these fenestrae are visible when the skull is viewed from the side, but in other baurusuchids, they are hidden within a deep notch in the back of the skull. The pterygoid wings extend down from the bottom of the skull as two large triangular pieces of bone. A deep depression on each wing serves as another diagnostic characteristic of the genus. Another unique feature can be found underneath the back of the skull; four holes called Eustachian foramina provide an opening for the Eustachian tube
Eustachian tube
The Eustachian tube is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 35 mm long. It is named after the sixteenth-century anatomist Bartolomeo Eustachi...
s, and in Pissarrachampsa the outer or lateral pair are larger than the inner or medial pair.