†Caruso, a new genus of anglerfishes from the Eocene of Monte Bolca, Italy, with a comparative osteology and phylogeny of the teleost family Lophiidae

Abstract

†Caruso, a new genus of lophiid anglerfishes, erected to contain †Lophius brachysomus Agassiz from the Eocene of Monte Bolca, Italy, is described and compared osteologically with all known representatives of the family, both extinct and extant. Together with †Sharfia, known from a single specimen also from Monte Bolca, †Caruso is the oldest member of the teleost family Lophiidae known to date, based on articulated skeletal remains. It possesses several autapomorphic features as well as a unique combination of character states that clearly separate it from all other known lophiiform fishes. Evidence is provided to show that †Sharfia is the sister group of all other known lophiid taxa, that †Caruso is most closely related phylogenetically to the extant genus Sladenia, and that these two genera together form the sister group of all remaining members of the family. †Caruso brachysomus is the third valid extinct taxon of the Lophiidae known from articulated skeletal remains. Candidate developmental mechanisms that may have contributed to the origin of the lophiiform body plan are also suggested. The hypertrophic development of the jaws, suspensorium, hyoid apparatus and branchial arches typical of lophiiforms may be correlated, possibly under the influence of discrete sets of genes. The synapomorphic elongation of the pectoral-fin radials might be related to a heterochronic shift of the onset of the expression of the gene sonic hedgehog. Finally, the highly modified spinous dorsal fin may have arisen by submodularization and co-option of the first dorsal-fin module, whereas its forward shift over the neurocranium may represent an anterior shift of the stripes of competency for dorsal-fin formation along the dorsal midline.

Keywords:

• Teleostei
• Lophiiformes
• Lophiidae
• comparative osteology
• phylogenetic analysis
• Eocene
• Monte Bolca

Acknowledgements

We wish to thank Walter Landini (Università di Pisa) for suggestions and a critical review of an early draft of the text. Presubmission reviews of the manuscript were also provided by James W. Orr and Duane E. Stevenson (NOAA Fisheries, Seattle). We are particularly obliged to Gaël Clement and Monette Veran (Muséum National d’Histoire Naturelle, Paris) and Roberto Zorzin and Anna Vaccari (Museo Civico di Storia Naturale di Verona) for access to fossil material under their care and for hospitality during our visits to Paris and Verona in April and February 2010 respectively. Loans of additional fossil material were kindly provided by Zerina Johanson (Natural History Museum, London) and Alexandre F. Bannikov (Borysiak Paleontological Institute, Russian Academy of Sciences, Moscow). Thanks are also due to the following individuals for providing access to comparative extant material, and permission to clear and stain specimens for osteological study: Katherine P. Maslenikov (University of Washington, Seattle), Karsten Hartel (Museum of Comparative Zoology, Harvard University), John H. Caruso (Tulane University, New Orleans), Dianne J. Bray (Museum Victoria, Melbourne), and Jeffrey Johnson (Queensland Museum, Brisbane). Many thanks go to Anna Vaccari (Museo Civico di Storia Naturale di Verona) and Philippe Loubry (Muséum National d’Histoire Naturelle, Paris) for photographs. This work was supported in part by US National Science Foundation Grant DEB–0314637, T. W. Pietsch, principal investigator. A visit to Paris by the senior author was supported by a European Union SYNTHESYS grant.