Its pineal foramen was large, and anteriorly placed, with its anterior edge bordered by the frontal bones. Unlike most of its relatives, its ectopterygoid is not known and may not be present, as in Protenodontosaurus. The P. alpinum species had decidedly elongated, posterior, tooth-bearing plates for crushing the shellfish that formed its diet.
Its pineal foramen was spacious, and anteriorly situated, with its anterior edge bordered by the frontal bones. Unlike most of its relatives, its ectopterygoid is not recognized and may be absent, as in Protenodontosaurus. The P. alpinum species had notably extended, posterior, tooth-bearing plates for crushing the shellfish that formed its diet.