Tetrapod Ichnotaxonomy: Preservation, practice, and meaning

Ichnotaxonomy is the naming and classification of trace fossils based on their morphological features, which incorporate tracemaker anatomy, behaviour, and substrate. Unlike traditional taxonomy, it is a parataxonomic system whereby ichnotaxa are named independently of the animal that produced them. Tetrapod ichnotaxonomy was established by Edward Hitchcock, who applied Linnaean binomial nomenclature to the naming of dinosaur tracks. Today, ichnotaxonomy follows rules established by the International Code of Zoological Nomenclature.

Historically, tetrapod ichnotaxonomy has struggled with inconsistent descriptive standards, nomenclatural issues, a legacy of producer-focused naming, and a reliance on qualitative methods. Efforts have been made to standardise tetrapod ichnotaxonomy, especially since the vertebrate ichnology “renaissance”, and several scholars have provided guidelines to streamline the practice and for its greater utility in palaeobiological and palaeoecological studies. Nonetheless, subjective interpretation is common, and the incorporation of quantitative methods is not consistent. A conceptual divide concerns preservation bias and the definition of “preservation” in tetrapod ichnology. Preservation can relate to anatomical fidelity (morphological preservation) and thus be diagnostic for ichnotaxonomy, while an alternative view defines preservation in terms of post-formation modification. This perspective treats formation variation from foot–sediment interaction and behaviour as distinct from taphonomic loss. These approaches differ on when taphonomy begins.

The need to separate formational from post-formational variation to combat ichnotaxonomic inflation is illustrated by several case studies in the literature, including ongoing reassessments of historically oversplit ichnotaxa and morphometric analyses of conservative track morphologies. By defining and assessing preservation, applying standardised methods, and considering ichnotaxonomic decisions within morphological, sedimentological, and behavioural contexts, tetrapod ichnology can be holistic, ensuring that what we name aligns with what we can know.