Behaviors mapped by new geographies: Ichnonetwork analysis of the Val Dolce Formation (lower Permian; Italy-Austria)

The following ichnotaxa are documented from the Val Dolce Formation: Archaeonassa isp., Curvolithus simplex, Cylindrichnus isp., Helminthoidichnites tenuis, Nereites missouriensis, Planolites isp., Phymatoderma isp., Pramollichnus pastae, Psammichnites plummeri, Taenidium isp., and Zoophycos isp. Network analysis indicates that the Val Dolce ichnological system is structured, with ichnotaxa organized in environment-driven ichnoassociations: Cylindrichnus-Planolites (proximal delta front), Phymatoderma-Zoophycos (prodelta with dysoxic porewaters), Cylindrichnus-Helminthoidichnites-Curvolithus-Zoophycos (distal delta front–proximal prodelta), and Helminthoidichnites-Taenidium-Curvolithus-Nereites-Zoophycos (prodelta). Furthermore, the delta front–prodelta gradient is accompanied by increasing bioturbation intensity and diversity, reflecting the decreasing intensity of major environmental stressors (hydrodynamics, freshwater input, turbidity). Centrality measures of network analysis allow the topological position of traces to be discerned within the studied system, detecting the paleoenvironmental resolution of individual ichnotaxa.

As intersections of sets can be described by networks, the studied ichnoassociations can be considered as occupying intersecting behavioral niches. In analogy with the concept of a Hutchinsonian niche, an ichnotaxon’s niche exists in a multidimensional abstract space defined by environmental parameters, which are expressed as spatial variables in the paleolandscape. Consequently, ichnoassociations are not just association patterns, but represent spatial, environmental, and topological entities. This approach allows the reconstitution of spatial relationships between the geographical ranges of ichnotaxa and ichnoassociations, providing information on the physical arrangement of different subenvironments, that is, the structure of the paleoenvironment.