Holocephali From The Irati Formation (Parana Basin), Brazil: Origin, Paleogographical And Paleoenvironmental Considerations

The Permian (Cisuralian) Irati Formation, from the Brazilian southeastern Parana Basin bears, at some levels, Chondrichthyes, besides other vertebrates. Outcrops of this unit are frequent at the state of Sao Paulo eastern belt. Two members of the Irati are recognized at this state, Assistencia, the upper, and Taquaral. A sandy facies, mostly at the base of the Taquaral, is noteworthy by the richness of the Chondrichthyes, mainly Holocephali. The Petalodontiformes are the Chondrichthyes most abundant, so far referred to Itapyrodus punctatus. Recent studies of several specimens revealed that some morphotypes must belong to different species of the genus Itapyrodus. Others are akin to this genus, justifying a proposition of an endemic family Itapyrodidae. The presence of this endemic family is an argument, among others, for a proposed isolation of two Brazilan Basins northeast Parnaiba and southeast Parana, during the time of deposition of the Irati, inasmuch as Itapyrodidae are present in both basins.