In Depth
Because Phreatophasma is known only from a single femur (upper leg bone), there is great uncertainty about what kind of animal Phreatophasma actually was, with suggestions ranging from it being a pelycosaur to parareptile. Most researchers consider Phreatophasma to be a nomen dubium.
Further Reading
– A re-examination of the enigmatic Russian tetrapod Phreatophasma aenigmaticum and its evolutionary implications. – Fossil Record. 20: 87–93. – N. Brocklehurst & J. Frobisch – 2017.