Genus: Porosteognathus VJUSHKOV, 1955
Etymology: Greek, poros, “passage, opening,” Greek, osteon, “bone” and Greek, gnathos,” jaw + us: Porous-boned jaw.

Species: efremovi VJUSHKOV, 1955
Etymology: In honor of Ivan E. Efremov.

Holotype: PIN 157/19

Locality: Isheevo Locality, Kamennyi Ravine, left bank of Ulema River, tributary of Sviaga River, 7 km from Isheevo-Nikiforovo Village, Apastovskii (Apostov) District, Tartstan (Tartar), SSSR, European Russia.

Horizon: Urzhumian Stage, Urzhumian Horizon (Dinocephalian Complex).

Biostratigraphy: Isheevo Faunal Assemblage, Isheevo Faunal Subassemblage, Zone II.

Age: Lower Tatarian Substage, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material: Parietal bones.

Referred material:

PIN 157/20:

PIN 157/21:

PIN 157/22:

PIN 157/23:

PIN 157/497:

PIN 157/488:

PIN 157/489: