Chirotherium trackways and feeding traces on seismic-influenced carbonate intertidals of the Middle Triassic of Central Europe: global food chain reactions onto horseshoe crab reproduction mud flat beaches of the Germanic Basin

• Autores: Cajus G. Diedrich
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 31, Nº. 2, 2016, págs. 187-211
• Idioma: inglés
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• Resumen

  • Newly excavated Middle Triassic reptile Chirotherium, Rhynchosauroides and horseshoe crab Kouphichnium imprints from the uppermost Pelsonian megatracksite Bernburg, Germany (Central Europe) represent different behavioural trackways. The Chirotherium/Rhynchosauroides/Kouphichnium track assemblage of the lower intertidal carbonate flats is dominated by well-known horseshoe crab tracks of various subaquatic benthic movements which were all left on mud-cracked biolaminites in reproduction coastal zones. Most abundant reptile Rhynchosauroides trackways (50 % of reptile tracks) are oriented more beach-parallel (to Rhenish Massif Island) as a result of food searching along the intertidal seismic-influenced coast (16 slickensided biolaminate layers within 2 m biolaminates due to Alpine fold belt and Germanic intracratonic Basin tectonics), most probably for feeding on high abundant horseshoe crab eggs resulting from mating events in the lower intertidal. Large basal archosaur predators (?Ticinosuchus) produced large Chirotherium trackways (25 % of reptile tracks) which are represented in the new material with exceptional unusual trackways (slipping and side steps), but in directions to and from the beach to the Rhenish Massif main land, indicating predation on small reptiles. Finally, medium-sized Chirotherium trackways of subadult animals are present (25 % of reptile tracks). One trackway has a unique “feeding place” area, indicating the unexpected either predation, playing or feeding of a basal archosaur on a horseshoe crab. The horseshoe crab migrations from the North Tethys onto the extended mating intertidal mud flat beaches of the Germanic Basin, and recently known even into Chinese lagoons migrating limulid populations of different horseshoe crab species must have caused a global and seasonal food chain reaction, whereas Macrocnemus reptiles (Rhynchosauroides trackmaker) might have fed only on Millions of their eggs.