Deciphering Cainocara enigma from the Late Devonian Gogo Formation, Australia

The Late Devonian Gogo Formation, Western Australia, preserves a diverse collection of Frasnian vertebrates, including the most diverse assemblage of lungfishes (Sarcopterygii, Dipnoi) from any geological period or locality. One enigmatic Gogo fossil known from a single specimen was originally dubbed Cainocara enigma Campbell and Barwick, 2011, interpreted as having osteichthyan affinity but otherwise considered not to belong to “any known described major systematic order”. Original interpretation of the specimen was hampered by its poor state of preservation, but thanks to increasing application of computed tomography, we can now use a more comprehensive comparative dataset, elucidating both internal and external anatomy, to study and visualise fossils more thoroughly than previously possible. Herein we show that the original orientation of the specimen was wrong, identify a kite-shaped parasphenoid and pterygoid bones that meet in their midline. We also reconstruct a partial digital cranial endocast, including portions of the inner ears, for comparison with other known endocasts from Gogo taxa, including the first cranial endocast of a holodontid lungfish ( Holodipterus gogoensis Miles, 1977). We now recognise Cainocara enigma, as a lungfish (order Dipnoi) based on anatomy revealed via CT, but concede that this enigmatic specimen most likely remains a nomen nudum and nomen dubium.