Tetrapod Tracks Taphonomy in Eolian Facies From the Permian of Argentina

Abstract

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 integrative physical, mineralogical and ichnological approach to characterize underfilled lake‐basins

“…Taphonomic tetrapod‐track modes are evaluated according to physical and morphological (fidelity of the trackmaker's pedal anatomy) traits within footprints in order to identify the source of such variation (see Gatesy & Falkingham, ). Thus, the presence or absence of different morphological and extra‐morphological features such as palm‐sole pads, digit impressions, claw marks and marginal rims, among others, are documented (Mancuso et al ., ). These taphonomic modes include the Preservation Scale recently defined by Marchetti et al .…”

Tetrapod tracks in Permo–Triassic eolian beds of southern Brazil (Paraná Basin)

“…Lateral compression structures in sand tend to have a large size and are not common in strata deposited by grain saltation ( Loope, 1986 ; McKee, Douglass & Rittenhouse, 1971 ). According to Mancuso et al (2016) , the biogenic origin of the structures in cross section from the Areniscas Altígradas Member of the Yacimiento Los Reyunos Formation in Argentina were justified by their frequency in size and regular shape, features also observed in the Brazilian materials. Additionally, the size of the cross-section structures described here (SLIA-5; UFRGS-PV-0602-P) is in accordance with the C. bucklandi tracks from the same strata (i.e., SLIA-2).…”

“…However, despite the terrestrial tetrapod faunal turnover and extinctions that marked the Guadalupian–Lopingian transition ( Day et al, 2015a ; Lucas, 2017 ) and the end-Permian biotic crisis ( Benton & Twitchett, 2003 ; Retallack, Smith & Ward, 2003 ; Lucas, 2009 ), the Permian eolian tetrapod track record is dominated by Chelichnus tracks, which are morphologically constant during the entire Permian ( McKeever & Haubold, 1996 ). This dominance is partially explained by the role of the preservation of tetrapod tracks in eolian sands, which add new non-morphological, substrate-controlled features to the original autopodium impression, referred to as extramorphological characters ( Peabody, 1948 ; Haubold et al, 1995 ; Mancuso et al, 2016 ). Also, species that lived in arid ergs often present similar adaptations to walk on desert eolian substrates (such as short and broad digits, wider than long soles and palms, and the lack of a tail dragging on the ground).…”

Ichnology and sedimentology of aeolian and shallow‐marine interactions in the Permian Unayzah Group of central Saudi Arabia: Towards a mechanism for infaunal colonization of coastal dune fields and erg margins

“…The main tracemakers are inferred to be wasps, beetles, flies, ants, crickets, termites, arachnids, molluscs, dinosaurs, toads and rodents (Ahlbrandt et al., ; Loope, , ). Preservation of these structures is favoured by increased moisture, sediment cohesiveness, rapid burial or organic reinforcement, such as secretion of binding organic mucus (Hasiotis, , ; Kraus & Hasiotis, ; Mancuso et al., ). Therein, the record of animal–sediment interactions is dominated by tracks and trails recording surface locomotion structures with subordinate presence of invertebrate trace fossils and subsurface invertebrate activity (Hasiotis, ; Ekdale et al., ; Ekdale & Bromley, ).…”

“…Organisms inhabiting the dune and interdune environment, such as insects and hemipterans, have been well‐documented and constitute in most cases diagnostic criteria to identify these subenvironments (e.g. McKee, , , ; Stokes, ; Hanley et al., ; Picard, ; Ekdale & Picard, ; Hasiotis & Bown, ; Hasiotis & Dubiel, ; Hasiotis, ; Mancuso et al., ). More recently, Krapovickas et al .…”