Prionosuchus

The fragmentary remains of this animal have been found in the Pedra de Fogo Formation in the Parnaíba Basin of northeastern Brazil, in the states of Piauí and Maranhão, and it was described by L.I. Price in 1948. The incomplete skull of the holotype specimen has been estimated to be long. 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. ==Classification==

Prionosuchus has been classified as an archegosaurid by Carroll. The genus is monotypic with P. plummeri being the only species described. The archegosaurs were a group of temnospondyls that occupied the ecological niche of crocodiles and alligators 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 phytosaurs in the Triassic 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 de Fogo Formation was reevaluated to be of Middle-to-Late Permian age. 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 de Fogo Formation in which fossils of this animal have been found. The strata composed of siltstones, shales and limestones were deposited in lagoonal and fluvial environments. Other animals discovered in the same formation include other amphibians (Procuhy, Timonya, and a rhinesuchid), captorhinids (Captorhinikos and two other, unnamed taxa), parareptile (Karutia) and fish including chondrichthyans (Rubencanthus, Sphenacanthus, Bythiacanthus, Taquaralodus, Itapyrodus, Anisopleurodontis), palaeoniscids (Brazilichthys), and lungfish. == References ==