Diversity, palaeoecology and palaeoenvironmental significance of the Eocene chondrichthyan assemblages of the Bolca Lagerstätte, Italy

Abstract

Over the last few years, the morphology, taxonomy and systematics of the cartilaginous fish taxa of the two main sites of the Bolca Lagerstätte, Italy, (Pesciara and Monte Postale sites) have been extensively discussed in a series of papers, resulting in a complete revision of this neglected component of the Eocene Tethyan ichthyofauna. Here, we provide a comprehensive overview of the diversity, palaeoecology and palaeoenvironmental significance of the two chondrichthyan assemblages of the Pesciara and Monte Postale sites. The assemblages include 14 shark species (Lamniformes and Carcharhiniformes) and batoids (Torpediniformes, Rhinopristiformes, Myliobatiformes, Platyrhinidae and Zanobatidae), as well as a single putative chimaeriform. The Pesciara and Monte Postale sites are characterized by eight chondrichthyan taxa each, but the taxonomic compositions are distinctly different reflecting the dissimilarities in the overall composition of both fish assemblages. Palaeoecological interpretations and habitat preferences of the two chondrichthyan assemblages are consistent with previously hypothesized palaeoenvironmental settings based on sedimentological, palaeontological and geochemical evidence. The chondrichthyan assemblages of the two sites appear to be constituted by ecologically vicariant taxa, with both characterized by a predominance of benthic species with durophagous/cancritrophic feeding modes. Taxonomic composition, habitat preferences and palaeobathymetric analyses support the hypothesis that both assemblages occupied tropical marine shallow waters (likely up to 50 m deep) of the inner portion of the Lessini Shelf. The taxonomic composition of both sites is considerably different from that of any other contemporaneous Tethyan and Boreal chondrichthyan assemblages.

A Rupelian Coral Reef Fish Assemblage From the Venetian Southern Alps (Berici Hills, Ne Italy)

“…Moreover, the occurrence of the apogonine †Arconiapogon deangelii gen. et sp. n. of the tribe †Eoapogonini is consistent with this palaeoenvironmental scenario, as the other three fossil taxa belonging to this clade, †Apogoniscus, †Bolcapogon and †Eoapogon (Bannikov 2005), are solely known from the celebrated Ypresian Bolca Lagerstätten, whose sediments accumulated in tropical shallow waters associated with coral reefs (e.g., Carnevale et al 2014;Marramà et al 2016Marramà et al , 2021aFriedman & Carnevale 2018).…”

“…This is mostly because most of the Palaeogene marine deposits from the Tethyan realm are usually not associated with coral reefs. The only exception to this pattern are the Bolca Lagerstätten, which include a series of Ypresian sites yielding fossil remains of bony and cartilaginous fishes that lived in heterogeneous palaeobiotopes undoubtedly associated with coral reefs (e.g., Carnevale et al 2014;Friedman & Carnevale 2018;Marramà et al 2016Marramà et al , 2021a, which are crucial to properly understand the origin and evolution of fishes on coral reefs.…”

Skin patterning and internal anatomy in a fossil moonfish from the Eocene Bolca Lagerstätte illuminate the ecology of ancient reef fish communities

“…2014; Marramà et al . 2021); M . rhombea is an iconic taxon for the Bolca ichthyofauna and is represented by abundant material (the exact number of specimens is not available).…”

The evolutionary origin of the durophagous pelagic stingray ecomorph

“…Taphonomic features and palaeoecological analyses confirm that the sediments were deposited in a shallow intraplatform basin (up to 50 m depth) in which benthic anoxic conditions and the development of a biofilm acted as promoters of the high‐quality preservation of the fossils (Marramà et al . 2016a , 2021 ).…”