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The postcranial skeleton of the Middle Devonian lungfish Dipterus valenciennesi

Published online by Cambridge University Press:  03 November 2011

Per Erik Ahlberg
Affiliation:
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD
Nigel H. Trewin
Affiliation:
Department of Geology and Petroleum Geology, Meston Building, King's College, University of Aberdeen, Aberdeen AB9 2UE

Abstract

The axial skeleton and fin supports of the Middle Devonian lungfish Dipterus are described from a range of specimens from the Orcadian Basin of Scotland. The axial skeleton of the trunk region consists of intercentra, relatively short ribs, and neural arches bearing two rows of supraneural spines; posteriorly, the intercentra are replaced by haemal arches. The notochord seems to have been essentially unconstricted. There may have been two pairs of cranial ribs. In general terms the vertebral column resembles that of Neoceratodus but is more fully ossified. The only known paired fin support of Dipterus is an archipterygial structure resembling those of Neoceratodus, with at least seven mesomeres and jointed pre- and postaxial radials. The pectoral fin is rotated as in modern lungfishes. The median fin supports all consist of basal plates supporting radials. In the posterior dorsal fin support the posterior radials form a branched structure. The heterocercal tail is supported by segmental radials. A new body reconstruction is presented.

The characters possessed by Dipterus offer support for a lungfish–porolepiform sistergroup relationship. All known lungfishes fit into a single cumulative series of postcranial morphologies. The evidence for a paedomorphic trend in lungfish phylogeny is interesting but inconclusive.

Information

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1994

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