A quantitative approach to determine the taxonomic identity and ontogeny of the pycnodontiform fish (Neopterygii, Actinopterygii) from the Eocene of Bolca Lagerstätte, Italy.

BACKGROUND

The pycnodontiform fish is one of the representatives of the highly diverse actinopterygian fish fauna from the early Eocene Bolca Lagerstätte, representing one of the youngest and thus last occurrences of this extinct neopterygian clade. This genus has historically been used as a wastebasket taxon in regards to poorly known pycnodontiform fossils. Authors have argued over the specific status of the Bolca Lagerstätte in terms of how many species are contained within the genus with some arguing for multiple species and others suggesting lumping all Bolca specimens together into one species.

METHODS

Here, we use a quantitative approach performing biometric and geometric morphometric analyses on 52 specimens of in order to determine if the morphological variability within the sample might be related to inter- or intraspecific variation.

RESULTS

The analyses revealed that the variations of body shape, morphometric and meristic characters cannot be used to distinguish different morphotypes. On the contrary, our results show a remarkable link between shape and size, related to ontogeny.

DISCUSSION

Differences in body shape of small (juvenile) and large (adult) individuals is probably related to different microhabitats occupation on the Bolca reef with juveniles sheltering within crevices on the reef and adults being more powerful swimmers that swim above the coral. Taxonomically, we suggest that the Bolca should be referred to strictly as as this was the name given to the holotype. Additionally, an overview of species assigned to is given.