A synoptic review of the Eocene (Ypresian) cartilaginous fishes (Chondrichthyes: Holocephali, Elasmobranchii) of the Bolca Konservat-Lagerstätte, Italy

Abstract

Here, we review and discuss the records and taxonomy of the Ypresian (Eocene) chondrichthyans from the famous Bolca Konservat-Lagerstätte in northeastern Italy. Despite the outstanding diversity and the numerous studies focusing on the actinopterygian faunas from Pesciara and Monte Postale, the current knowledge about the systematics, taxonomy and phylogenetic relationships of the cartilaginous fishes from these Eocene sites remains elusive and largely inadequate. The celebrated Eocene Bolca Lagerstätte has yielded several exquisitely preserved articulated remains of chondrichthyan fishes in which delicate structures and soft tissues are preserved, as well as isolated teeth. The cartilaginous fish assemblage of Bolca comprises at least 17 species-level taxa belonging to 10 families in 6 orders, including selachians (Carcharhiniformes, Lamniformes), batoids (Torpediniformes, Myliobatiformes, Rajiformes) and holocephalans (Chimaeriformes). The occurrence of holocephalans represented by an isolated fin-spine of the chimeroid Ischyodus in the Bolca assemblage is reported here for the first time and represents the first record of chimeroids in the Eocene of Italy and also southern Europe. The Bolca chondrichthyan assemblage is remarkably different from those of other contemporaneous Boreal or Tethyan deposits, suggesting that its taxonomic composition is largely influenced by the palaeoenvironmental context. However, this synoptic review also highlights the importance of detailed revisions of all chondrichthyan remains from the Bolca Konservat-Lagerstätten.

Reappraisal of the Eocene whiptail stingrays (Myliobatiformes, Dasyatidae) of the Bolca Lagerstätte, Italy

“…Like the latter, in particular, the Bolca fauna is characterized by the presence of small odontaspidids, small carcharhinids, and juvenile triakids, all generalist feeders preying on small nectobenthic preys and zooplanktivorous coastal bony fishes. Among batoids, the Fayum area and the Bolca Lagerstätte share the presence of thornbacks (Platyrhinidae) and, as detected in the present study, neotrygonines, which are absent in other deposits (Marramà et al, ; Underwood et al, ).…”

“…The Bolca chondrichthyan assemblage is remarkably different from those of other contemporaneous Boreal (London Clay, Paris basin, Lede Sand Formation, Fürstenau Formation, Lillebælt Clay) or Tethyan (SW France and Northern Morocco) deposits, suggesting that its taxonomic composition is largely influenced by the different palaeoenvironmental setting (Marramà et al, ). Conversely, the Bolca palaeoenvironmental and palaeoecological characters appear to be more consistent with the tropical shallow settings reported from south‐western Morocco and, even more, with those of the Fayum area in Egypt (Marramà et al, ). Like the latter, in particular, the Bolca fauna is characterized by the presence of small odontaspidids, small carcharhinids, and juvenile triakids, all generalist feeders preying on small nectobenthic preys and zooplanktivorous coastal bony fishes.…”

“…Although the fossil record of stingrays is well represented and dates back to the Early Cretaceous, it is heavily biased towards isolated teeth, dermal denticles and caudal spines (Cappetta, ; Underwood, Mitchell, & Veltcamp, ). Nearly complete and articulated fossil stingrays have been only recovered from Palaeogene marine sediments of the Bolca Lagerstätte in Italy (Marramà, Carnevale, Engelbrecht, et al, ) and Grube Unterfeld in Germany (Hovestadt, Hovestadt‐Euler, & Micklich, ), from Eocene freshwater deposits of the Green River Formation, USA (Carvalho et al, ), and from Miocene marine deposits of Indonesia (Marramà et al, ). The celebrated Eocene (Ypresian, ca.…”

“…However, Bolca is also one of the few fossiliferous sites in which fossils of chondrichthyan fishes are exquisitely preserved and represented by nearly complete and articulated skeletons. Recent studies have provided a new perspective about the chondrichthyan palaeobiodiversity of this deposit, which includes possibly more than a dozen of species‐level taxa belonging to a variety of holocephalan, selachian and batoid lineages, including chimaeriformes, carcharhiniformes, lamniformes, torpediniformes, rhinopristiforms and myliobatiformes (Fanti, Minelli, Larocca Conte, & Miyashita, ; Marramà et al, ; Marramà, Carnevale, & Kriwet, ; Marramà, Claeson, Carnevale, & Kriwet, ; Marramà, Engelbrecht, Carnevale, & Kriwet, ). However, since the comprehensive account of cartilaginous fishes from Bolca written by Jaekel (), no modern systematic studies have been carried out on the Bolca stingrays.…”

An Eocene paraclupeid fish (Teleostei, Ellimmichthyiformes) from Bolca, Italy: the youngest marine record of double‐armoured herrings

“…, ; Marramà & Carnevale ; Marramà et al . ) have been described from this locality so far, double‐armoured herrings have not previously been reported. On the other hand, clupeomorph fishes are by far the most common group of fishes in this deposit, represented by four taxa belonging to the order Clupeiformes: the sardine Bolcaichthys catopygopterus , the round herring Trollichthys bolcensis , the possible shad Eoalosa janvieri , and the anchovy Eoengraulis fasoloi (Marramà & Carnevale 2015 a – b , 2016, 2018).…”