The posterior cranial portion of the earliest known Tetrapodomorph Tungsenia paradoxa and the early evolution of tetrapodomorph endocrania

摘要: Abstract Here the posterior cranial portion of the tetrapodomorph Tungsenia from the Lower Devonian (Pragian, ~409 million years ago) of Yunnan, southwest China, is reported for the first time. The pattern of posterior skull roof and the morphology of the otoccipital region of the neurocranium are described in detail, providing precious insight into the combination of cranial characters of the earliest known tetrapodomorph to date. The posterior cranium of Tungseniadisplays a mosaic of features previously linked either to basal dipnomorphs such as Youngolepis(e.g., the well-developed subjugular ridge, the strong adotic process, and the poorly developed fossa bridgei) or to typical tetrapodomorphs (e.g., the lateral dorsal aortae commenced from the median dorsal aorta postcranially). The independent ventral arcual plate is also found in the advanced tetrapodomorph Eusthenopteron. The new endocranial material of Tungsenia further fills in the morphological gap between Tetrapodomorpha (tetrapod lineage) and Dipnomorpha (lungfish lineage) and unveils the sequence of character acquisition during the initial diversification of the tetrapod lineage. The new phylogenetic analysis strongly supports the basalmost position of Tungsenia amongst the tetrapod lineage.