Palaeobiology of tanaidaceans (Crustacea: Peracarida) from Cretaceous ambers: extending the scarce fossil record of a diverse peracarid group.

Abstract

Diverse assemblages of tanaidacean peracarid crustaceans from western Tethyan continental deposits suggest that the group was relatively common in or around ancient resin-producing forests. Here we report the results of an examination of 13 tanaidacean specimens from three Cretaceous (Albian to Turonian) French amber deposits. Two new species of the fossil family Alavatanaidae are placed in the previously described Early Cretaceous genus Eurotanais: Eurotanais pyrenaensissp. nov. from Cenomanian Pyrenean amber (Fourtou, Aude) and Eurotanais seilacherisp. nov. from Turonian Vendean amber (La Garnache, Vendée). The remaining specimens are placed in three newly erected genera and species (but family incertae sedis): Arcantitanais turpisgen. et sp. nov. from Albian-Cenomanian Charentese amber (Archingeay, Charente-Maritime), and Tytthotanais tenvisgen. et sp. nov. and Armadillopsis raragen. et sp. nov. from Pyrenean amber. These are the first formally described fossils that might be related to the paratanaoidean families Nototanaidae and Paratanaidae, sharing with these some putatively derived features and providing possible evidence for the antiquity and morphological stability of these families and the suborder Tanaidomorpha. The distinctive features and character combinations of these fossil taxa are discussed in connection with possible relationships to the living lineages of tanaidaceans. Propagation phase-contrast X-ray synchrotron microtomography was used to obtain high-quality 3D images for some fossils. A discussion is provided on the putative palaeobiology of tanaidaceans and the French resiniferous forest ecosystem. The discovery of these new tanaidaceans extends the palaeogeographical distribution and stratigraphical range of the family Alavatanaidae and sheds new light on the palaeoecology and diversity of tanaidaceans in pre-angiospermous woodlands.