Radial Domichnia–Fodinichnia ichnofossil from the Lower Cretaceousof San Andrés (Santander, Colombia)

Abstract

Introduction. Burrow and tunnel systems preserved in sandy and muddy marine substrates are commonly associated with the behavioral activities of polychaete worms and other benthic invertebrates, providing relevant ethological information in sedimentary records. Objectives. This study aims to i) describe the morphological and ethological characteristics of a radial ichnofossil, ii) evaluate its possible correspondence with previously established radial ichnogenera, and iii) propose paleoecological interpretations of the trace-making organism and its depositional environment. Materials and Methods. A detached sandstone block from the Aguardiente Formation (Albian–Cenomanian, Lower Cretaceous) was examined along the banks of the Hisgaura River, San Andrés municipality (Santander, Colombia). The trace architecture was documented through high-resolution photography, digital image processing, and artificial intelligence–assisted three-dimensional reconstruction to enhance visualization of its morphology and internal organization. UPGMA–Jaccard similarity and parsimony analyses were applied to assess relationships with other radial and rosette ichnogenera. Results. The specimen is preserved in full relief and consists of a central ellipsoidal chamber from which slightly sinuous tubular galleries radiate, locally arranged in superposed tiers. Similarity analysis groups the structure with Arenituba, Guanshanichnus, and Hartsellea. Parsimony analysis recovered a single most- parsimonious tree (length = 32 steps; CI = 0.34; RI = 0.7) in which the specimen forms part of a clade characterized primarily by branched galleries and shallow-marine occurrence. Conclusions. The structure records ethological evidence of a benthic organism  inhabiting sandy shallow-marine environments. Diagnostic differences preclude confident assignment to any previously established radial ichnogenus.