The interrelationships of Devonian lungfishes (Sarcopterygii: Dipnoi) as inferred from neurocranial evidence and new data from the genus Soederberghia Lehman, 1959

Authors


*Committee on Evolutionary Biology, University of Chicago, 1025 E. 57th St., Chicago, IL 60637, USA. E-mail: mattf@uchicago.edu

Abstract

New data are presented on the neurocranial complex (endocranium plus intimately associated bones of the palate) of the Late Devonian (Famennian) ‘rhynchodipterid’ lungfish Soederberghia groenlandica from the Aina Dal Formation (Celsius Bjerg Group) of East Greenland. Only the otic and occipital regions of the braincase are ossified in Soederberghia. The neurocranium of this genus shares a series of derived features with ‘Griphognathuswhitei, including a cranial centrum, fenestrate lateral cristae, and gutters on the ventral surface of the parasphenoid interpreted as accommodating the lateral dorsal aortae. The interrelationships of early lungfishes have been the subject of considerable disagreement. New data from Soederberghia are coupled with a data set focused on the character-rich neurocranial complex in order to examine the systematic utility of this underexploited morphological system. Different methods of phylogenetic inference (maximum parsimony, Bayesian) return broadly consistent results. The Early to Middle Devonian forms Dipnorhynchus, Stomiahykus and Uranolophus are placed among the most basal of lungfishes. ‘Holodontids’ plus ‘rhynchodipterids’ (comprising Griphognathus and Soederberghia) occupy an apical position, and are separated from the earliest lungfishes by a paraphyletic assemblage of taxa generally identified as ‘chirodipterids’ and ‘dipterids.’ This finds broad agreement with the results of previous cladistic studies focused on non-neurocranial data sets, but diverges from functional-adaptive scenarios that posit three lineages of early lungfishes based on aspects of the dentition. As currently defined, both ‘chirodipterids’ and the genus Chirodipterus are heterogeneous assemblages; this analysis fails to find support for the monophyly of either. While this study indicates that Griphognathus is probably paraphyletic, it nevertheless supports a close relationship between the nominal species of this genus and Soederberghia. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 151, 115–171.

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