Ichnotaxonomy and ichnostratigraphy of chambered trace fossils in palaeosols attributed to coleopterans, ants and termites

Most recorded trace fossils in palaeosols are burrows and chambers attributed to bees, ants, termites and coleopterans. Ichnogenera attributed to bees are grouped in the ichnofamily Celliformidae, whereas those attributed to ants, termites and coleopterans are included herein in the new ichnofamilies Pallichnidae, Krausichnidae and Coprinisphaeridae respectively. Shape, type of wall, fillings and associated burrows of chambers are the main morphological ichnotaxobases used for this classification; they are weighed with regard to the behaviour and architecture of the supposed trace-makers. Coprinisphaeridae are spherical, pear-shaped or ovoid structures, having active or passive fillings and constructed walls. The ichnogenera included are: Fontanai, Coprinisphaera, Eatonichnus, Monesichnus, Teisseirei and Rebuffoichnus, attributed to coleopterans. The similar Pallichnidae show lined or structureless walls, and include Pallichnus, Fictovichnus and Scaphichnium, also attributed to coleopterans. The Krausichnidae constitutes trace fossils composed of chambers of different shapes interconnected by burrow systems of inconsistent diameter or isolated chambers associated with burrow systems of different diameters. The Krausichnidae include Attaichnus, Parowanichnus, Krausichnus, Archeoentomichnus, Tacuruichnus, Vondrichnus, Fleaglellius, Termitichnus and Syntermesichnus, attributed to ants and termites. The stratigraphic ranges of insect ichnotaxa in palaeosols are reviewed and compared with the body fossil record of potential tracemakers, revealing that in most cases insect trace and body fossils show similar ranges. As stated by earlier authors, the Cretaceous was a critical period during which the oldest body fossils of dung-beetles, bees, termites and ants are recorded, whereas the trace fossils of these groups are recorded from this period or shortly after, during Cenozoic times.