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Ancient desert deposits preserve a copious ichnofossil record, particularly Permian-age deposits where the record of tetrapod footprints is present and abundant in almost all desert settings. We propose to analyze, from a taphonomic perspective, Permian footprints preserved in eolian deposits from Argentina with a detailed sedimentological study of the trackway-bearing levels, in order to find evidence of processes that may have enhanced their preservation. We defined four taphonomic modes based on preservation quality, and the morphological and extra-morphological features of the footprints. Mode 1 includes footprints with detailed impressions of the palm, digits and claws. Mode 2 includes tracks with palm and digit impressions associated with small bulbous-shape marginal rims. Mode 3 includes tracks characterized by large, bulbous, marginal rims and randomly preserved palm impressions. Mode 4 includes footprints with shallow digit and palm impressions associated with sand-crescent marginal rims. The Los Reyunos footprints suggest preservation in: (1) dry sand, evidenced by sediment slipping down-slope structures and (2) subsurface damp sand, evidenced by digit impressions and claw drag traces. Also, we found vertical water content variations along the dune foresets, evidenced by a varying amount of sediment slipping down-slope in the same trackway. Moreover, differences in the time of entombment are suggested by the morphology of rims (bulbous-shape or sand-crescent). The stratigraphic genetic framework resulting from the Los Reyunos taphonomic analysis supports changes in the interstitial subsurface water and rapid entombment of the tracking surface due to a high rate of sediment supply as the main factor for footprint preservation.
An Early Triassic continental ichnofossil assemblage dominated by ∼ 4 cm diameter burrow casts was discovered in the transitional zone of the Katberg and Burgersdorp formations in the SE main Karoo Basin (Eastern Cape, South Africa). Analyses of the burrow architecture and associated sedimentary facies aim to identify the possible trace makers, their behavior, and the local depositional conditions in the Olenekian (Early Triassic) in this part of Gondwana. The burrows were excavated into a floodplain where alternating periods of flooding, drying, and pedogenesis occurred, a set of conditions often mentioned for the Lower and Middle Triassic continental deposits in southern Gondwana. However, the burrow architecture and superficial morphology are distinct from previously reported older and younger burrows in this part of Pangea. These burrows are simple vertical shafts that are occasionally J-shaped with a circular to slightly elliptical cross-section (average aspect ratio 1.2), ∼ 4 cm in diameter, 9–76 cm in length (average ∼ 26 cm) and have subvertical axes with average vertical inclinations of approximately 30°. The passively filled burrow casts lack surficial morphology, lining, or branching and have semi-rounded and unenlarged burrow terminations. Potential burrow-makers, ranging from crayfish to lungfish and tetrapods, have been considered, but a definitive producer for these probably dwelling, preying and/or sheltering structures remains elusive. Finally, the results reinforce that burrowing into semi-arid floodplains was a favored behavior among certain organisms in southern Gondwana in the aftermath of the largest biological crisis in the Earth's history. The study also highlights stratigraphic changes in the style of burrow architecture.