An Ediacaran trace-like body fossil of a Palaeopascichnus specimen from Oman under 3D micro-tomography

Abstract

Palaeopascichnus is an Ediacaran organism, whose phylogenetic affiliation and functional anatomy are both shrouded in mystery. Different studies and assessments have interpreted this fossil as macrophytes or foraminifera-like protists. Currently ongoing discussions concerns the possible phylogenetic relation between Palaeopascichnus and modern xenophyophores; benthic organisms that built agglutinated tests. We present micro-XRD, SEM-EDS and three-dimensional microtomographic data on a possible Palaeopascichnus specimen from the Ediacaran Fara Formation, in Wadi Bani Awf, Jabal Akhdar, Oman. The unique preservation of this specimen as a full positive epirelief of drusy calcite growths represents a new taphotype for this organism, enabling a more accurate observation of chamber structure and better morphological characterization. The data gathered concerning both chamber´s dimensions and morphology does not point towards an affiliation with any known Paleopascichnus species, except for much smaller P. jiumenensis. Therefore, it is possible that this specimen represents a new, previously unknown species.