Non-arthropod burrows from the Middle and Late Cambrian of the Holy Cross Mountains, Poland

During the Middle and Late Cambrian in the area of the present-day Holy Cross Mountains all the traces of infaunal activity were produced by animals burrowing parallel to and immediately below the sediment surface, deeper infaunal burrowers being missing. Deeper penetration was probably not possible due to anoxic conditions within the sediment. This was not the case in the Early Cambrian, where numerous deep vertical burrows with spreite structures are known in the area. Diversity of the Middle and Late Cambrian trace fossil assemblages of the Holy Cross Mts is low, with only six ichnogenera of non-arthropod traces in the Middle Cambrian and eight ichnogenera in the Late Cambrian, compared with 24 ichnogenera in the Early Cambrian. The most unusual is a large hemispherical burrow, possibly of actinian origin, for which the name Bergaueria elliptica isp. n. is proposed. Treptichnus rectangularis isp. n. represents horizontal burrows with stiff walls, being systems of short units connected with one another. Some units contain faecal pellets produced by the host animal.