Pioneer colonization, evidenced by Rhizocorallium in the Middle Triassic of Poland

A large collection of the trace fossil Rhizocorallium from Middle Triassic Polish part Germanic Basin (Peri-Tethys) is analysed and their ichnotaxonomical classification presented. Special attention given to deep form with a vertical retrusive spreite, filled faecal pellets, detailed documentation this structure, based on isolated specimens serial sections. This analysis also reveals ∩-shaped deep, protrusive structures. former interpretation as rapidly formed fugichnion not followed here; instead, an complex fodinichnion proposed. Scavengers relation crinoid meadows, well predators, are indicated potential tracemakers some . Although common throughout Triassic, unusual forms domination substrates by in general mostly occur transgressive system lowermost Muschelkalk, regressive, marginal facies lower Keuper. Such distribution interpreted representing opportunistic, pioneer burrow assemblages that developed during long-term benthic recovery after P-T crisis, or unfavourable conditions generally. Moreover, dynamic mixed clastic-carbonate sedimentation varying salinity promoted smooth transitions Diplocraterion Similar successions dominant trace-fossil assemblages, comparable sizes, many sections around world demonstrate record slow continued through Triassic. The illustrated evolution Poland documents last two stages benthos boundary. similar situation observed and, cases, great abundance seems be indication burrowing dynamic, environments.