Actuopalaeontological trackway experiments withIguana on intertidal flat carbonates of the Arabian Gulf — a comparison to fossilRhynchosauroides tracks of Triassic carbonate tidal flat megatracksites in the European Germanic Basin

Abstract

In the recent carbonate tidal flats of the lower to upper intertidal zone of the Khor Al Qirqishan Bay western of Abu Dhabi at the southern Arabian Gulf actuopaleontological trackway experiments with the lizardIguana were made. The different moving activities such as basking, slow walk or running over dry to wet biolaminate surfaces and swimming or walking activities through ponds and tide channels have left a variety of quadruped track preservations.Iguana has produced trackways on nearly dry microbial mats of the upper intertidal only with claw marks. On slightly wet substrates detailed imprints of the subdigital lamellae were produced, while in wet mud a medium impressed imprint type without subdigital structures was typical. On very wet mud scratch marks were left by the long claws combined with medium impressed imprints. In about 25 cm deep intertidal channels or pondsIguana began to swim and touched the ground. In less deep water the lacertid left swimming and subaquatic walk scratch marks. In slow move the tail produced a more or less straight deep impression and the pes was printed behind the manus. By running activities the pelvic girdle was uplifted, the tail did not touch the ground and the pes was printed besides the manus. Astonishing is the identical track preservation of the fossil European Triassic trackways on biolaminates. The experiment results are very similar to the fossil record with the very abundant Lower to Middle Triassic track genusRhynchosauroides in the southern margin of the Germanic Basin with its ancient carbonate tidal flat megatracksites. With the study of the recent lower or upper intertidal environments in the Arabian Gulf fossil footprints can be positioned in the palaeoenvironments of the old tidal flats, tidal ponds or channels. Also the biolaminate consistence of the fossil Middle Triassic carbonate tidal flats and moving activity zones of the most possible trackmakerMacrocnemus, a fossil Middle Triassic prolacertilian of Europe, can be reconstructed. These old reptiles must have lived primary in the carbonate tidal flats, especially searching for food in the lower intertidal, where they left the highest density of their trackways in the entire surrounding Germanic Basin coastline about 240 Mio. years ago under the same subtropical arid conditions as in the recent Ana logon, the southern Arabian Gulf.