Morphology, relationships and palaeobiology of the Eocene barracudina †Holosteus esocinus (Aulopiformes, Paralepididae) from Monte Bolca, Italy

The shallow water barracudina †Holosteus esocinus Agassiz, 1835, from the Eocene of Monte Bolca, Italy, is redescribed in detail. This paralepidid taxon exhibits a unique combination of features, including the following: articular-quadrate joint located below the posterior margin of the orbit; eight branchiostegal rays; small recurved teeth on premaxilla; large, thin and pointed teeth on palate and lower jaw without corrugate pattern or serrate margin; about 19-22 anal-fin rays; about 10-12 pelvic-fin rays; five or six autogenous hypurals; proximal ends of the epaxial caudal-fin rays that extensively overlap the associated hypurals; bony fulcral scales just in front of the dorsal and ventral caudal-fin lobes; and body completely naked, with a broad, uniform, mid-dorsal brown-pigmented band along the back. †Holosteus esocinus shares a number of features with the Oligocene †Pavlovichthys mariae, and together they constitute the extinct subfamily Holosteinae, which is redefined herein. A phylogenetic analysis of aulopiform genera using 140 morphological traits supports the monophyletic status of the holosteines as crown group Paralepididae. The peculiar morphology of holosteines resembles in many aspects the body plan of certain modern and extinct ambush predators, suggesting that the morphological adaptations of these Palaeogene fishes can be related, at least in part, to a predatory strategy experimented with by paralepidid fishes uniquely in the context of the massive adaptive radiation of teleost fishes in the aftermath of the end-Cretaceous extinction.