Diagnosis: Circular to subcircular holes bored into a bone substrate. Holes may penetrate fully though the substrate or terminate within the bone. Penetrative holes may have straight or convex vertical margins. Non-penetrative pits terminate within the substrate as a shallow, bowl-shaped pit or as a deeper shaft with a rounded, blunt, or pointed terminus.

Remarks: The observed diameter of Karethraichnus ranges from 0.5 to 8.0 mm with 1 to 5 mm being typical. Karethraichnus bears morphological and size similarities to the ichnogenera Sedilichnus (Müller, 1977), Oichnus (Bromley, 1981), Tremichnus (Brett, 1985), and Fossichnus (Nielsen et al., 2001), which occurs in marine and freshwater invertebrates. Karethraichnus differs in the plasticity of its overall morphology and the nature of the substrate in which the trace occurs.