Three-dimensional morphology and palaeobiology of the trace fossil Dactyloidites jordii nov. isp. from the Carboniferous of England

Abstract

The diverse ichnological assemblage from the outcrops near Howick (Northumberland, United Kingdom) is exceptionally well-preserved. Among these Carboniferous ichnotaxa is a new ichnospecies of Dactyloidites. Specimens were collected and processed using high-resolution serial grinding and photography to produce an accurate and precise three-dimensional model of these new burrows in full colour. The model produced in association with petrographic thin sections and field observations is used as the basis for comparison between Dactyloidites jordii nov. isp. and other ichnospecies of Dactyloidites. The current taxonomic status of the ichnogenus is examined and reviewed. D. jordii nov. isp. is a broadly bisymmetrical, stellate to palmate burrow composed of numerous long, narrow rays that exhibit three orders of branching arranged into tiered galleries radiating from a central shaft. The trace maker is suggested to be a vermiform organism with an adaptive burrowing strategy that facilitates alteration of its burrow construction to accommodate suboptimal sediment conditions. The adaptive nature of trace-making organisms and the inherent anisotropy of many burrowed media highlight the need for ichnologists to provide a type series rather than a single holotype, in order to capture the inherent range of common burrow morphologies.