Offshore marine actinopterygian assemblages from the Maastrichtian–Paleogene of the Pindos Unit in Eurytania, Greece

Abstract

The fossil record of marine ray-finned fishes (Actinopterygii) from the time interval surrounding the Cretaceous–Paleogene (K–Pg) extinction is scarce at a global scale, hampering our understanding of the impact, patterns and processes of extinction and recovery in the marine realm, and its role in the evolution of modern marine ichthyofaunas. Recent fieldwork in the K–Pg interval of the Pindos Unit in Eurytania, continental Greece, shed new light on forgotten fossil assemblages and allowed for the collection of a diverse, but fragmentary sample of actinopterygians from both late Maastrichtian and Paleocene rocks. Late Maastrichtian assemblages are dominated by Aulopiformes (†Ichthyotringidae, †Enchodontidae), while †Dercetidae (also Aulopiformes), elopomorphs and additional, unidentified teleosts form minor components. Paleocene fossils include a clupeid, a stomiiform and some unidentified teleost remains. This study expands the poor record of body fossils from this critical time interval, especially for smaller sized taxa, while providing a rare, paleogeographically constrained, qualitative glimpse of open-water Tethyan ecosystems from both before and after the extinction event. Faunal similarities between the Maastrichtian of Eurytania and older Late Cretaceous faunas reveal a higher taxonomic continuum in offshore actinopterygian faunas and ecosystems spanning the entire Late Cretaceous of the Tethys. At the same time, the scarcity of Paleocene findings offers tentative clues for a depauperate state of Tethyan ichthyofaunas in the aftermath of the K–Pg Extinction.

The Fossil Record of Ray-Finned Fishes (Actinopterygii) in Greece

“…thesis has shed light on the late Miocene freshwaterbrackish clupeids of Aidonochori, Serres Basin, Northern Greece (Kevrekidis 2016). Finally, a new study dealing with the Maastrichtian-Paleogene actinopterygian assemblages from Eurytania has been made available while this work was in press (Argyriou and Davesne 2021).…”

“…Numerous hard-tissue synapomorphies support teleost monophyly, including: (i) orbital region of skull narrower than postorbital; (ii) presence of one suborbital bone between the posterodorsal margin of the infraorbital Placement of fossil taxa is as follows: †Pycnodontidae are established as non-teleosteomorphs; †Leptolepididae and †Ichthyodectoidei ( †Ichthyodectiformes) sensu Arratia 2017; †Dercetidae and †Enchodontidae as closely related to modern Aulopifomes sensu Davis and Fielitz 2010, although an agnostic placement of fossil taxa relative to extant ones is preferred here. Results from Argyriou and Davesne (2021) were not incorporated in the figures, or the text, as this work became available after the preparation of this chapter series and the opercular apparatus; (iii) presence of two supramaxillae; (iv) lower jaw articulation located ventral to the posterior margin of the orbit; (v) articular fused with angular and retroarticular; (vi) notch on ascending margin of dentary; (vii) coronoid process formed by angular and dentary; (viii) lateral ridge on dentary separating dental and splenial portions of lower jaw; (ix) long epineural processes; (x) presence of 20-26 principal rays; (xi) presence of an enlarged dorsal scute preceding caudal fin (sensu Arratia 2017).…”

“…The marine actinopterygian record of Greece begins with some poorly preserved †leptolepids from the Toarcian of the Ionian Unit, Leukada Island (Kottek 1964). Other published Mesozoic occurrences are restricted to the Cenomanian of Lindos, Rhodos Island (Melentis 1967a, b), and the terminal Maastrichtian of Pindos Unit, in Eurytania (Koch and Nikolaus 1969;Argyriou and Davesne 2021) and Gavdos Island (Cavin et al 2012). Unpublished teleost remains are also present in Late Cretaceous exposures of Pindos Unit in Northern and central Peloponnese (T.A.…”

“…The Cenozoic record of Greece is very rich, but is largely skewed toward the late Miocene and Pliocene. The oldest reported Cenozoic occurrences come from flysch deposits of the Pindos Unit in Eurytania and are dated as Paleocene-early Eocene (Koch and Nikolaus 1969;Argyriou and Davesne 2021). Rich Tortonian marine assemblages can be found in the vicinity of Ierapetra and possibly Heraklion, Crete (Symeonidis 1969;Gaudant et al 1997a;Gaudant 2004), and Gavdos Island (Gaudant et al 2005), while a fish-bearing, bituminous horizon in Keri, Zakynthos has been identified, but not yet studied (Dermitzakis 1979;T.A.…”

“…The presumably rich Toarcian bonebeds of Ionian Unit exposures in Lefkada have been totally neglected since their first discovery (Kottek 1964), despite their potential informativeness on early teleost diversification. Moreover, understudied fish assemblages from the late Cretaceous-Paleogene of Pindos Unit can shed light on the evolution and biogeography of Tethyan faunas (Koch and Nikolaus 1969;Cavin et al 2012;Argyriou and Davesne 2021; pers. obs.…”