PalZ https://doi.org/10.1007/s12542-017-0387-z REVIEW ARTICLE A synoptic review of the Eocene (Ypresian) cartilaginous fshes (Chondrichthyes: Holocephali, Elasmobranchii) of the Bolca Konservat‑Lagerstätte, Italy Giuseppe Marramà1 · Giorgio Carnevale2 · Andrea Engelbrecht1 · Kerin M. Claeson3 · Roberto Zorzin4 · Mariagabriella Fornasiero5 · Jürgen Kriwet1 Received: 17 March 2017 / Accepted: 2 September 2017 © The Author(s) 2017. This article is an open access publication 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 fshes from these Eocene sites remains elusive and largely inadequate. The celebrated Eocene Bolca Lagerstätte has yielded several exquisitely preserved articulated remains of chondrichthyan fshes in which delicate structures and soft tissues are preserved, as well as isolated teeth. The cartilaginous fsh 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 occur- rence of holocephalans represented by an isolated fn-spine of the chimeroid Ischyodus in the Bolca assemblage is reported here for the frst time and represents the frst record of chimeroids in the Eocene of Italy and also southern Europe. The Bolca chondrichthyan assemblage is remarkably diferent from those of other contemporaneous Boreal or Tethyan deposits, suggest- ing that its taxonomic composition is largely infuenced by the palaeoenvironmental context. However, this synoptic review also highlights the importance of detailed revisions of all chondrichthyan remains from the Bolca Konservat-Lagerstätten. Keywords Neoselachii · Holocephali · Ypresian · Diversity · Konservat-Lagerstätte · Tethys Kurzfassung Obwohl Knochenfsche in der berühmten eozänen (Ypresium) Bolca-Konservatlagerstätte in NE-Italien äußerst divers sind und in den vergangenen Jahren Gegenstand zahlreicher Studien waren, ist der derzeitige Kenntnisstand über die Systematik, Taxonomie und Phylogenie der Knorpelfsche aus dieser Lagerstätte überraschend gering und ungenau. In dieser Studie geben wir einen Über- blick über die Knorpelfsche der Bolca-Konservatlagerstätte und diskutieren ihre Verbreitung und ihre Taxonomie. Aus den beiden Fundstellen Pesciara und Monte Postale stammen einige sehr gut erhaltene Exemplare, bei denen auch sehr feine Strukturen und Weichgewebe fossilisiert sind, sowie isolierte Zähne. Die Knorpelfschfauna von Bolca umfasst mindestens 17 Arten, die zu zehn Familien und sechs Ordnungen gehören wie Haie (Carcharhiniformes, Lamniformes), Rochen (Torpediniformes, Myliobatiformes, Rajiformes) und Chimären. Chimären sind erstmals für Bolca durch einen isolierten Flossenstachel von Ischyodus belegt, was gleichzeitig der erste Nachweis für Chimären im Eozän von Italien und Süd-Europa ist. Die Knorpelfschassoziation von Bolca unterscheidet sich in ihrer taxonomischen Zusammensetzung aufällig von anderen tethyalen und auch borealen Faunen. Dies lässt vermuten, dass die taxonomische Zusammensetzung im Wesentlichen durch Umweltbedingungen bestimmt ist. Der hier präsentierte synoptische Überblick der Bolca-Knorpelfsche zeigt aber auch deutlich, dass detaillierte Revisionen aller Knorpelf- ischreste der Bolca-Konservatlagerstätte für ein besseres Verständnis dieser wichtigen eozänen Fundstelle dringend nötig sind. Schlüsselwörter Neoselachii · Holocephali · Ypresium · Diversität · Konservat-Lagerstätte · Tethys Handling editor: Adriana López-Arbarello. Extended author information available on the last page of the article Vol.:(0123456789)1 3 G. Marramà et al. Introduction also very strongly biased towards taxa with larger teeth, whereas small teeth are not consistently processed in most The Paleogene (ca. 66–23 Ma) represents a critical interval deposits as results of taphonomic or collecting biases. in the development of the current global climatic patterns. The celebrated Eocene (Ypresian, ca. 50 Ma; Papazzoni With a short-lived thermal maximum that occurred at the et al. 2014a) Bolca Konservat-Lagerstätte from northeastern Paleocene–Eocene boundary (PETM), in turn followed by Italy is one of the few fossiliferous sites in which fossils of extensive greenhouse conditions during the Early Eocene chondrichthyan fshes are exquisitely preserved. In addition to Climatic Optimum, a considerable global warming resulted, isolated teeth, fossils include complete and fully articulated which lasted until the end of the middle Eocene (ca. 37 Ma). skeletal remains, in which delicate mineralised cartilaginous The PETM subsequently was followed by a late Eocene (ca. structures and soft tissues are easily preserved and recogniz- 49–34 Ma) transition from greenhouse to icehouse condi- able. Several recent studies extensively contributed knowledge tions (Zachos et al. 2008). The fnal cooling phase, which of the outstanding palaeobiodiversity of this deposit, with took place at the Eocene–Oligocene boundary (ca. 33.7 Ma), more than 230 described species-level taxa (see Carnevale was characterised by declining atmospheric CO2 content, et al. 2014), belonging to a variety of teleost lineages (e.g., long-term deep-sea cooling and establishment of large Ant- anguilliforms, atheriniforms, aulopiformes, beryciforms, clu- arctic ice sheets, resulting in one of the most dramatic cli- peiforms, lophiiforms, pleuronectiforms, tetraodontiforms and matic shifts in the Cenozoic (see Zachos et al. 2001; Pagani several other percomorph lineages; Blot 1969; Tyler and San- et al. 2005; Lear et al. 2008). These climatic changes, which tini 2002; Bannikov 2004, 2006, 2008; Carnevale and Pietsch persisted into the early Oligocene, resulted in major biotic 2009, 2010, 2011, 2012; Marramà and Carnevale 2015a, b, turnovers in marine and terrestrial faunas and foras (Pro- 2016, 2017a, b; Pfaf et al. 2016; Carnevale et al. 2017). How- thero et al. 2003; Pearson et al. 2008). ever, the diversity of certain groups as well as many aspects of Although the general patterns of abiotic disruptions dur- their evolutionary palaeoecology have been totally neglected ing the Paleogene have been documented extensively (see or underestimated. In particular, most of the selachians and Culver and Rawson 2000) and the fossil record documents batoids from Bolca have not been studied using modern meth- profound changes in both marine and terrestrial ecosystems odological approaches. Consequently, a revisionary study of across the PETM (e.g., Gingerich 2006), little is known the Eocene sharks, skates and rays from the Bolca Lagerstätte about the impact of the global changes on overall biodiver- is warranted. The goal of this paper is therefore to provide an sity, particularly on organisms occupying the higher trophic overview of the chondrichthyan assemblage in the Eocene levels in marine ecosystems. In particular, the evolutionary Bolca Konservat-Lagerstätte, in order to properly defne the and diversity dynamics of cartilaginous fshes (Chondrich- diversity of sharks, skates and rays from this celebrated locality thyes) during the Paleogene Climatic Optimum has received and their palaeoecological role and biogeographic afnities. little attention, mostly due to the fact that there are few Pale- ogene faunas that are not from marginal environments (there Institutional abbreviations: CNHM, Croatian Natural are many in the North Sea Basin) or very poorly dated (e.g., History Museum, Zagreb; MC, Carnegie Museum, Pitts- Morocco). The taxonomy, systematics and evolutionary his- burgh; MCSNV, Museo Civico di Storia Naturale, Verona; tory of the Paleogene chondrichthyans in general are prob- MGP-PD, Museo di Geologia e Paleontologia, Università lematic because of the lack of comprehensive non-dental degli Studi di Padova; MNHN, Muséum National d’Histoire morphological studies. Studying fossil chondrichthyan fshes Naturelle, Paris; MSNM, Museo Civico di Storia Naturale, is hindered by the nature of their fossil record, which gener- Milano; NHMUK, Natural History Museum, London; ally is rather rich, although heavily biased towards isolated NHMW, Naturhistorisches Museum, Vienna. teeth (see Cappetta 2012). This is due to their predominantly cartilaginous skeleton that has only little chance to fossilize, so that their taxonomy is mostly based on dental characters. Historical notes Few Paleogene localities, including the marine Bolca Lager- stätte (Italy) and Grube Unterfeld deposit (Germany), and Since the sixteenth century, the locality of Bolca and its the non-marine Green River Formation (Wyoming), yielded fossils have yielded materials that stimulated philosophi- fully or partially complete articulated skeletal remains of cal and scientifc discussions. The existence of exquisitely cartilaginous fshes (see e.g., Jaekel 1894; de Carvalho et al. preserved “petrifed” fshes in the limestones of Bolca was 2004; Hovestadt et al. 2010), which are crucial in order to reported for the frst time by the famous botanist and physi- properly understand their evolutionary trajectories and mor- cian Pietro Andrea Mattioli in the third edition of the transla- phological patterns during this part of the Cenozoic