The arthropod trace fossil Cruziana and associated ichnotaxa from the Lower Permian Abo Formation, Soccorro County, New Mexico

A trace fossil assemblage consisting of Cruziana problematica, Diplichnites gouldi, Diplichnites isp., Monomorphichnus isp., Palaeophycus tubularis, Rusophycus carbonarius, Striatichnium cf. S. natalis and compound traces of C. problematica × R. carbonarius is reported from the Lower Permian Abo Formation of the Joyita Hills in Socorro County, New Mexico. The assemblage is an example of the Scoyenia ichnofacies and indicates deposition under a continental regime during the last phase of Abo sedimentation in central New Mexico. It is atypical of Abo trace fossil assemblages in that it is dominated by striated bilobate traces whereas other assemblages from the Abo Formation are dominated by tetrapod and arthropod trackways. This reflects the production of this assemblage within a small ephemeral water body on a floodplain whereas other Abo assemblages formed during fleeting preservation windows on exposed surfaces after sheetfloods on the floodplain. The majority of trace fossils are attributed to notostracan branchiopod crustaceans, which are adapted to inhabit ephemeral water bodies.