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Powichthys spitsbergensis sp. nov., a new member of the Dipnomorpha (Sarcopterygii, lobe-finned fishes) from the Lower Devonian of Spitsbergen, with remarks on basal dipnomorph anatomy

2004; Wiley; Linguagem: Inglês

10.18261/9781405169868-2004-07

2637-6032

Gaël Clément, Philippe Janvier,

Fish biology, ecology, and behavior

The Powichthyidae (Dipnomorpha, Sarcopterygii) were hitherto known from a single species, Powichthys thorsteinssoni, from the Lochkovian-Pragian of Arctic Canada. New material from the Early Devonian of Spitsbergen is referred here to a new species Powichthys spitsbergensis sp. nov., and provides additional data on the skull, dermal palate, palatoquadrate, post-orbital, and scales of the Powichthyidae. In particular, it reveals new morphological features, such as an internal process of the lacrimal, a strong anteroventral process of the scales, and the presence of large, upperoral dental plates, which cover the palate and suggest a crushing palatal bite, as in lungfishes. The structure of the skull agrees with Jessen's description of Powichthys thorsteinssoni, except that the junction between the supra-orbital and infra-orbital sensory-line canals is lacking in the Spitsbergen species. The exceptional preservation of the dermal elements of the palate shows that the presumed choana is in fact absent in the Powichthyidae, as in the Porolepiformes. The shape of the nasal capsule and the size and arrangement of the adjoining nerve canals are similar to those of the Porolepiformes, but contrary to Jessen's assumption, the palatoquadrate seems to be significantly different.