Neoichnology of mygalomorph spiders: Improving the recognition of spider burrows in the geological record

摘要: Abstract The female Mygalomorphae spiders are sedentary and long-lived organisms that spend most of their lives inside burrows. Neoichnological studies provide relevant information can help the recognition these structures in paleosols. Body fossils known since Carboniferous burrowing is a primitive behavior spiders. However, trace attributable to ground-dwelling still poorly documented geological record. In this work, we examine burrows Rachias intermedius Soares, 1944 (Araneae: Mygalomorphae: Nemesiidae) its natural environment discuss characteristics be used as ichnotaxobases for fossil spider Three major architectures, straight shaft with terminal ovoid chamber, J-shaped winding Y-shaped teardrop-shaped described compared morphologically similar ichnogenera, like Capayanichnus, Loloichnus, Macanopsis, Psilonichnus. Differences burrow shape architecture linked spider's sex ontogenetic stage. Pedipalps, chelicerae, fangs soil excavation, forming variety wall ornaments represented by delicate sub-horizontal parallel ridges, irregular knobby micro-relief surface attached wall, rounded pits, millimeter-scale vertical striations along length. A thick inorganic clay lining covers inner feature has not been yet. These allow distinguishing from produced other soil-dwelling arthropods. They should paleosols, mainly had before. data discussed herein improve knowledge about mechanism play main role preserving burrows' features