†Caruso, a new genus of anglerfishes from the Eocene of Monte Bolca, Italy, with a comparative osteology and phylogeny of the family Lophiidae (Teleostei: Lophiiformes)

†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 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.