Axelrodichthys araripensis Maisey, 1986 revisited

Abstract

Axelrodichtys is a genus of fossil coelacanth of the family Mawsoniidae with a wide spatial and temporal range, spanning from the Aptian/Albian of Brazil to the Campanian of France. In light of new discoveries in recent years a renewed interest in Axelrodichthys has emerged. Here we offer new insights on the type species – A. araripensis – based on a complete new description of all its morphological characters and a comparative study of several other Mawsoniidae. A relatively large sample composed of 113 specimens of A. araripensis and associated Mawsoniidae species was observed. Among the newly observed features are the broad aspect of premaxillae supporting the anterior opening of the rostral organ; a unique pattern of skull roof ornamentation; the basioccipital; a passage of nerves in the prootic; the passage for the superior ophthalmic nerve; the anocleithrum; and ossified zygal plates. Observation of two juvenile specimens in different growth stages allowed for the inference of negative allometric growth in the epicaudal lobe. Morphological comparisons pointed out that M. lavocati is more closely associated with the Axelrodichthys than with Mawsonia, therefore we included it in the Axelrodichthys genus as A. lavocati.

Keywords:

• Axelrodichthys araripensis
• Axelrodichthys lavocati
• coelacanths
• anatomical review
• gondwanian mawsoniids

Acknowledgments

The present study would not be possible without the cooperation of several individuals and their respective institutions to which we are profoundly grateful. Dr John G. Maisey and Dr Alana Gishlick from the American Museum of Natural History; Dr William F. Simpson from the Field Museum; Dr Martha Richther, Dr Peter L. Forey and Dr Emma Bernard from the Natural History Museum of London; Dr Gaël Clément and Philippe Loubry from the Muséum National d’Histoire Naturelle; Dr Yoshitaka Abe Aquamarine Fukushima; Dr Teruya Uyeno and Dr Chisako Sakata from the National Museum of Nature and Science; Dr Ismar de Souza Carvalho from Museu Nacional in Rio de Janeiro; Dr Fernando Perini from Universidade Federal de Minas Gerais (UFMG); Dr Florias Mees and Dr Jonathan Brecko from The Royal Museum of Central Africa. We thank Universidade do Estado do Rio de Janeiro (UERJ) for the logistical support during the development of this research, in special Dr Camila Cupello and the team of the laboratory of Palaeoichthyology of UERJ.

Graphical Abstract by Jackeline Carnier Leão Guedes.

The images of the fossils of the Natural History Museum United Kingdom are copyrighted. Copyright: The Trustees of the Natural History Museum, London.

We appreciate the comments and suggestions made by Dr Lionel Cavin (Natural History Museum of Geneva, Switzerland) and anonymous referee for their crucial suggestions.

Dedicated to the memory of Léo Galvão Fragoso, Sr.