The taxonomic treatment of trace fossils needs a uniform approach, independent of the ethologic groups concerned. To this aim, trace fossils are rigorously defined with regard to biological taxa and physical sedimentary structures. Potential ichnotaxobases are evaluated, with morphology resulting as the most important criterion. For trace fossils related to bioerosion and herbivory, substrate plays a key role, as well as composition for coprolites. Size, producer, age, facies and preservation are rejected as ichnotaxobases. Separate names for undertracks and other poorly preserved material should gradually be replaced by ichnotaxa based on well‐preserved specimens. Recent traces may be identified using established trace fossil taxa but new names can only be based on fossil material, even if the distinction between recent and fossil may frequently remain arbitrary. It is stressed that ichnotaxa must not be incorporated into biological taxa in systematics. Composite trace fossil structures (complex structures made by the combined activity of two or more species) have no ichnotaxonomic standing but compound traces (complex structures made by one individual tracemaker) may be named separately under certain provisions. The following emendations are proposed to the International Code of Zoological Nomenclature: The term ‘work of an animal’ should be deleted from the code, and ichnotaxa should be based solely on trace fossils as defined herein.

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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.

ABSTRACT-We document evidence of endophytic oviposition on fossil compression/impression leaves from the early Eocene Laguna del Hunco and middle Eocene Río Pichileufú floras of Patagonia, Argentina. Based on distinctive morphologies and damage patterns of elongate, ovoid, lens-, or teardrop-shaped scars in the leaves, we assign this insect damage to the ichnogenus Paleoovoidus, consisting of an existing ichnospecies, P. rectus, and two new ichnospecies, P. arcuatum and P. bifurcatus. In P. rectus, the scars are characteristically arranged in linear rows along the midvein; in P. bifurcatus, scars are distributed in double rows along the midvein and parallel to secondary veins; and in P. arcuatum, scars are deployed in rectilinear and arcuate rows. In some cases, the narrow, angulate end of individual scars bear a darkened region encompassing a circular hole or similar feature indicating ovipositor tissue penetration. A comparison to the structure and surface pattern of modern ovipositional damage on dicotyledonous leaves suggests considerable similarity to certain zygopteran Odonata. Specifically, members of the Lestidae probably produced P. rectus and P. bifurcatus, whereas species of Coenagrionidae were responsible for P. arcuatum. Both Patagonian localities represent an elevated diversity of potential fern, gymnosperm, and especially angiosperm hosts, the targets of all observed oviposition. However, we did not detect targeting of particular plant families. Our results indicate behavioral stasis for the three ovipositional patterns for at least 50 million years. Nevertheless, synonymy of these oviposition patterns with midMesozoic ichnospecies indicates older origins for these distinctive modes of oviposition.

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Higher termites of the subfamily Macrotermitinae (fungus-growing termites) are known to build fungus gardens where a symbiotic fungus (Termitomyces sp.) is cultivated. The fungus grows on a substrate called fungus comb, a structure built with the termites' own faeces. Here we present the first fossil fungus combs ever found in the world. They were extracted from 7-million-year-old continental sandstone (Chad basin). Fossilized fungus combs have an ovoid morphology with a more or less flattened concave base and a characteristic general alveolar aspect. Under lens, they display a typical millimetre-scale pelletal structure. The latter, as well as the general shape and alveolar aspect, are similar to the morphology of fungus combs from extant fungus-growing termites.

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