1. Allis AP (1922) The cranial anatomy of Polypterus, with special reference to Polypterus bichir. J Anat 56: 189–294.
2. Beaumont E (1977) Cranial morphology of the Loxommatidae (Amphibia: Labyrinthodontia). Phil Trans R Soc LondB 280:29–101.
3. Beer GR de (1937) The development of the vertebrate skull. Oxford University Press.
4. Bendix-Almgreen SE, Clack JA, Olsen H (1988) Upper Devonian and Upper Permian vertebrates collected in 1987 around Keyser Franz Joseph Fjord, central East Greenland. Rapp Grønlands Geol Unders 140:95–102.
5. Bolt JR, Lombard RE (1985) Evolution of the amphibian tympanic ear and the origin of frogs. Biol J Linn Soc 24:83–99.