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Late Triassic invertebrate and plant trace fossils are described from the Pebbly Arkose Formation of the Upper Karoo Group (Gwembe Sub-basin, Mid-Zambezi Basin), Zimbabwe. These ichnofossils appear in pedogenically modified siltstone and silty mudstone floodplain deposits and overbank fluvial channels. The ichnofossil-bearing sites show variability in their pedogenic features, maturity and preservation. Invertebrate ichnofossils are primarily recorded as horizontal, vertical and inclined burrows, sometimes branched, lined or unlined and may have an active meniscate infill. The common forms documented are Taenidium, Beaconites, Palaeophycus, Skolithos, and Planolites ispp. with some rare and more unusual morphologies (i.e., ‘Y'-shaped burrow type). Ichnofossil-bearing sites show a low-diversity but high-density of traces commonly dominated by Taenidium and Planolites ispp. The greatest diversity of invertebrate ichnofossils are within interbedded overbank sandstones in weakly pedogenically modified overbank sites. Rhizohalos and rhizoliths are common and often include carbonate infilled roots. Given the abundance and dimensions of fossilized wood and the rhizohalos and rhizoliths, the Pebbly Arkose Formation supported both large and small stature plants. Overall, the studied Pebbly Arkose Formation overbank areas are typically well-drained, calcic palaeosols subject to variable discharge, subaerial exposure, and supporting a diversity of plant and invertebrates tracemakers that lived in a semi-arid to sub-humid environment.
The morphological variability of Ciconia boyciana (oriental white stork) tracks is documented in an actualistic ichnological experiment using wet potter's clay. Measurements were obtained from 54 tracks left by two individuals comprising area, length, width, depth, volume, and rotation for each track. The trackmakers were also filmed while walking. An anatomical feature unique to C. boyciana is that, unlike other wading birds, it does not leave metatarsophalangeal pad impressions. This feature can be used to distinguish C. boyciana tracks from those left by other birds of similar body weight and habitat. Track width varied by up to 30%, with wider tracks showing more splayed digits occurring in trackways with shorter stride length and larger trackway width. Conversely, narrow trackways with a large stride length were composed of tracks with a smaller digit divarication. Coefficient analysis of track geometry revealed that the widths and depths of tracks vary inversely to maintain a consistent volume. Sorting the C. boyciana tracks into morphological types (14 types for avians with four digits) demonstrates the result that most tracks are deeper between digits III and IV than between digits II and III. Combining track data with video footage shows that C. boyciana moves its hips from side to side while walking. Noting that the tracks within any given trackway are outwardly rotated, we interpret this track morphology as resulting from laterally directed pressure exerted primarily through digit IV.
Microstructural and biomolecular preservation is reported in fossils as old as the Triassic. Such preservation suggests unusual taphonomic conditions. We collected fragments of fossil whale bone from silty, tuffaceous, and diatomaceous rocks of the middle-upper Miocene portion of the Pisco Formation. The whale fossils within the region are generally well-preserved and mostly articulated, including some specimens with in situ baleen. Due to the depositional setting associated with the preservation of these fossils, they could be expected to be favorable candidates for the preservation of cellular microstructures and/or original biomolecules. To test this hypothesis, fossil whale bone fragments were subjected to microscopic analysis and EDTA-mediated demineralization to release extractable materials. Microscopy of partially demineralized fossil bones revealed quartz-permineralized osteocyte-like and vessel-like structures. Protein assay (micro-Bicinchoninic Acid Assay) of the supernatants obtained from demineralized fossils yielded 12 to 19.5 µg of protein per gram of bone. MALDI-TOF analysis of the extracted protein demonstrated the presence of approximately 5 kD molecules in one fossil sample, consistent with the presence of highly fragmented polypeptides. An LC-MS/MS analysis of the fragmentation pattern of the tryptic digest of extracted protein was performed. However, attempted protein identification was unsuccessful. Nevertheless, this study first documents the microstructural preservation with some silicification of the fossil whale bones of the Pisco Formation, and then quantifies extractable protein from these bones. It adds to the growing body of reports of microstructural and organic preservation in fossils.