First record of non-mineralized cephalopod jaws and arm hooks from the latest Cretaceous of Eurytania, Greece

Dirk Fuchs,Christian Klug,Donald Davesne,Thodoris Argyriou

doi:10.1186/s13358-020-00210-y

Abstract

Due to the lower fossilization potential of chitin, non-mineralized cephalopod jaws and arm hooks are much more rarely preserved as fossils than the calcitic lower jaws of ammonites or the calcitized jaw apparatuses of nautilids. Here, we report such non-mineralized fossil jaws and arm hooks from pelagic marly limestones of continental Greece. Two of the specimens lie on the same slab and are assigned to the Ammonitina; they represent upper jaws of the aptychus type, which is corroborated by finds of aptychi. Additionally, one intermediate type and one anaptychus type are documented here. The morphology of all ammonite jaws suggest a desmoceratoid affinity. The other jaws are identified as coleoid jaws. They share the overall U-shape and proportions of the outer and inner lamellae with Jurassic lower jaws of Trachyteuthis (Teudopseina). We also document the first belemnoid arm hooks from the Tethyan Maastrichtian. The fossils described here document the presence of a typical Mesozoic cephalopod assemblage until the end of the Cretaceous in the eastern Tethys.

Highlights

Fossil cephalopods are mainly known from preserved mineralized parts such as aragonitic phragmocones, calcitic jaws, and calcitic rostra
We described nine cephalopod jaws and two arm hooks from the latest Maastrichtian of continental Greece
One aptychus (?Lissaptychus), one anaptychus and one of the intermediate type as well as two of the formerly chitinous upper jaws can be assigned to monomorph ammonites

Summary

Introduction

Fossil cephalopods are mainly known from preserved mineralized parts such as aragonitic phragmocones (e.g., nautilids: Tajika et al 2020; ammonoids: Hoffmann et al 2019, coleoids: Klug et al 2016a, b, 2019; Iba et al 2012; Wani et al 2018; Hoffmann and Stevens 2020), calcitic jaws (e.g., nautilids: Saunders et al 1978; Klug 2001; ammonites: Lehmann 1972; Morton & Nixon 1987; Engeser and Keupp 2002; Keupp and Mitta 2015; Tanabe et al 2015), and calcitic rostra (e.g., belemnites; Hoffmann et al 2016, 2019; Hoffmann and Stevens 2020; Iba et al 2012, 2014). As far as coleoid jaws (or beaks or mandibles) and ammonoid upper jaws are concerned, these occur sometimes in black shales and platy limestones of conservation deposits (KonservatLagerstätten) Such preservation was documented from, e.g., the Devonian Hangenberg Black Shale in Morocco (Klug et al 2016a, b), Carboniferous deposits of Bear Gulch in the USA (Landman et al 2010; Klug et al 2019; Mapes et al 2019), the Jurassic Posidonia Slate, the platy. We describe cephalopod jaws from thin-bedded marly limestones of late Maastrichtian age of the Pindos Unit, Eurytania, continental Greece These sediments yielded rich fossil fish assemblages (Koch and Nikolaus 1969; Argyriou and Davesne in review). We describe cephalopod arm hooks from the Tethyan Realm of Maastrichtian age for the first time

Results

Discussion

Conclusion