Criteria for recognition and taphonomy of coprolites from the Serra da Galga Member, Marília Formation (Upper Cretaceous), Minas Gerais, Brazil

Abstract

The Cretaceous sedimentary rocks from Uberaba, Minas Gerais, have provided a rich vertebrate fauna unearthed from rocks of the Serra da Galga Member, Marília Formation, Bauru Group, of Maastrichtian age. Together with these fossils, a large number of coprolites have also been found from two main localities, here called the Peirópolis and Serra da Galga sites. During field trips carried out in the last few years, 340 samples have been collected, prepared, and analyzed in laboratory. By using parameters such as weight, density, mineralogical composition, and content, we identified 199 coprolites and 141 inorganic nodules (pseudocoprolites). The coprolites have been divided into four morphotypes, which suggest their producers varied in feeding strategies and size. The taphonomic study, based on morphological characters such as wear, presence of pebbles or pebble marks, and desiccation cracks, suggests they underwent temporal and spatial-mixing, and that the material from the Peirópolis Site were transported essentially by alluvial processes (alluvial fans), whereas the material from the Serra da Galga Site were reworked mainly by fluvial streams. The same taphonomic processes may well have affected other fossils from these sites, which are highly abundant in the rocks of this area. Because of that, this taphonomic aspect becomes an important parameter to be taken into account in future studies on the biota of the region.