Platyoposaurus stuckenbergi - archegosauroid from Middle Permian of Russia. This exemplar is about 1 m long (based on full skeleton from PIN museum).
Are pycnodontids th fishes in the background? or simply random ones?
I thought it was named after the Platypus
For a moment, I thought it was a small pliosaur.
It's an archegosaur, older name - "Platyops", close relative of Prionosuchus. By the way, according some Russian sources, this animals can be over 2,5 m long! It's smaller than Prionosuchus, but big temnospondyl. Platyoposaurs lived in rivers and so named "very shallow seas" (VSS)on East European placket in Permian.