A new Pliensbachian elasmobranch (Vertebrata, Chondrichthyes) assemblage from Europe, and its contribution to the understanding of late Early Jurassic elasmobranch diversity and distributional patterns

Abstract

Here we describe a new, previously unrecognized elasmobranch microfossil assemblage consisting of isolated dental material from late Pliensbachian marginal marine, near-shore deposits of Grimmen in north-eastern Germany. The faunal composition indicates close affinities to other European pre-Toarcian elasmobranch-bearing localities, as it is predominantly composed of Hybodontiformes (Hybodus reticulatus?, H. hauffianus?, Lissodus sp.), Synechodontiformes (Palidiplospinax enniskilleni, P. occultidens, Paraorthacodus sp., Sphenodus sp.), and Hexanchiformes (Notidanoides sp.), as well as teeth attributable of the enigmatic Early Jurassic galeomorph shark Agaleus dorsetensis. In addition, the here reported elasmobranch tooth assemblage includes the oldest undisputable fossil records of Orectolobiformes and Batomorphii, each being represented by a single complete tooth only. The orectolobiform specimen is reminiscent of hemiscyllids but left in open nomenclature due to its very generalized morphology preventing any taxonomic identification. The batomorph tooth, conversely, is characterized by a unique combination of morphological features, which allows the introduction of new genus and species, Antiquaobatis grimmenensis gen. et sp. nov. The fossil assemblage presented here contributes to our current knowledge of late Early Jurassic chondrichthyan diversity and distributional patterns, providing some support for the hypothesis that most modern neoselachian lineages were initially linked to marginal marine, near-shore environments, before moving into open marine, offshore habitats by the Toarcian.