The naked truth? New insights on the Early Jurassic (Sinemurian) genus Pholidolepis (Osteno Lagerstätte, Como, Italy)

The stem-teleost fish genus Pholidolepis (Nybelin, 1966) was originally referred to the Pholidophoridae based on peculiar features of the skull and caudal-fin structure (Patterson, 1968); however, it also exhibits several traits that are in many ways reminiscent of more derived lineages, such as the Leptolepidae. The original material from Lyme Regis (Southern England) is not fully adequate to interpret its phylogenetic relationships, hindering a complete description of the skull anatomy, axial skeleton, and fins. In a recent revision of the Triassic pholidophorid fishes (Arratia, 2013), Pholidolepis is excluded from this group, leaving its phylogenetic position unresolved. Articulated skeletal remains that can be referred to this genus have been reported from the Sinemurian Osteno Lagerstätte (Como, Italy) since the early 1990s (Duffin & Patterson, 1993). A detailed morpho-anatomical analysis of this material allows for a better definition of Pholidolepis. The phylogenetic analysis confirms its intermediate status between stem-teleosts akin to pholidophoriforms and more advanced forms. Furthermore, the Osteno specimens differ from the Lyme Regis ones, suggesting their separate status at the species level—most notably, the Osteno material exhibits a completely naked body, while the Lyme Regis specimens are covered by cycloid scales.