Paleoenvironmental significance of saproxylic invertebrate coprolites preserved in Agathoxylon fossil wood from the Araripe Basin, Brazil

Abstract

Fossil woods hosting communities of colonizing organisms provide valuable paleoecological information, offering insights into plant–arthropod interactions, feeding strategies, and trophic organization in ancient ecosystems. Here we report the first record of coprolite-bearing fossil woods of the coniferous morphogenus Agathoxylon (with affinity to Agathoxylon santanensis Santos et al., 2021) from the Aptian–Albian Romualdo Formation, Araripe Basin, northeastern Brazil. The silicified wood preserves decay features and evidence of saproxylic activity, including coprolites attributed to wood-boring coleopterans, oribatid mites, and termites. Thin section analysis reveal decay features associated with fungal activity, indicating that colonization occurred only post-mortem. The occurrence of coleopteran, oribatid mite, and termite coprolites may represent a successive colonization by wood-feeding arthropods, driven by changing substrate conditions during wood decay. Although this interpretation is plausible the synchronicity of colonization remains uncertain. The presence of Microcarpolithes hexagonalis (Vangerow, 1954), a type of coprolite related commonly to drywood termites (Kalotermitidae or Mastotermitidae), indicates a later stage of decay, when the wood was already thoroughly dried, and their presence suggests prolonged low-moisture conditions within the substrate, in an arid to semi-arid environment. Although the global record of termite coprolites remains sparse, the specimens from the Araripe Basin provide robust evidence for the presence of dry-wood termites during the Aptian-Albian, in agreement with an increasing number of records from South America. Additionally, our findings, evidenced by borings containing coprolites of termites and oribatid mites, support the hypothesis that cohabitation in termite nests was already established during the Cretaceous.