The first virtual cranial endocast of a lungfish (sarcopterygii: dipnoi)

PLoS One. 2014 Nov 26;9(11):e113898. doi: 10.1371/journal.pone.0113898. eCollection 2014.

Abstract

Lungfish, or dipnoans, have a history spanning over 400 million years and are the closest living sister taxon to the tetrapods. Most Devonian lungfish had heavily ossified endoskeletons, whereas most Mesozoic and Cenozoic lungfish had largely cartilaginous endoskeletons and are usually known only from isolated tooth plates or disarticulated bone fragments. There is thus a substantial temporal and evolutionary gap in our understanding of lungfish endoskeletal morphology, between the diverse and highly variable Devonian forms on the one hand and the three extant genera on the other. Here we present a virtual cranial endocast of Rhinodipterus kimberleyensis, from the Late Devonian Gogo Formation of Australia, one of the most derived fossil dipnoans with a well-ossified braincase. This endocast, generated from a Computed Microtomography (µCT) scan of the skull, is the first virtual endocast of any lungfish published, and only the third fossil dipnoan endocast to be illustrated in its entirety. Key features include long olfactory canals, a telencephalic cavity with a moderate degree of ventral expansion, large suparaotic cavities, and moderately enlarged utricular recesses. It has numerous similarities to the endocasts of Chirodipterus wildungensis and Griphognathus whitei, and to a lesser degree to 'Chirodipterus' australis and Dipnorhynchus sussmilchi. Among extant lungfish, it consistently resembles Neoceratodus more closely than Lepidosiren and Protopterus. Several trends in the evolution of the brains and labyrinth regions in dipnoans, such as the expansions of the utricular recess and telencephalic regions over time, are identified and discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Australia
  • Biological Evolution
  • Brain / anatomy & histology
  • Fishes / anatomy & histology*
  • Fossils / anatomy & histology*
  • Skull / anatomy & histology

Grant support

This work was funded by a Wallenberg Scholarship from the Knut and Alice Wallenberg foundation, awarded to PEA. https://www.wallenberg.com/kaw/en/foundation/knut-and-alice-wallenberg-foundation. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.