3. The rarity in the deposits of animals of larger body size than Captorhinus, the exceptions being a few limb fragments and skull fragments of labyrinthodont or pelycosaurian nature.
"Two New Pelycosaurs from the Lower Permian of Oklahoma"
Richard C. Fox
labyrinthodont Foot-prints in Coal-measures.
"The Student's Elements of Geology"
Sir Charles Lyell
Remains of labyrinthodont reptiles have also been met with in the same slate near Durham.
"The Student's Elements of Geology"
Sir Charles Lyell