Virgaichnus Knaust, 2010
Knaust, 2010a
Diagnosis: complex, three-dimensional, irregular burrow system with horizontal and inclined elements, ‘Y’-shaped and/or ‘T’-shaped branching and smooth-walled and passively filled burrows.
Discussion: Virgaichnus resembles ichnospecies of Thalassinoides, especially Thalassinoides paradoxicus. However, it differs from Thalassinoides by a much more irregular branching and the dominance of bifurcation instead of anastomosing (cf. Kennedy, 1967; Häntzschel, 1975; Ekdale, 1992; Ekdale and Bromley, 2003; Seilacher, 2007). The type ichnospecies Virgaichnus undulatus differs from Thalassinoides ichnospecies by having the diagnostic undulating burrow outline between the junctions, which lead to pinch-and-swell-like features with highly varying burrow diameter. In addition, the size of V. undulatus known so far is several orders below the size of hitherto described Thalassinoides ichnospecies.