Meiobenthic trace fossils comprising a miniature ichnofabric from Late Permian carbonates of the Oman Mountains

An ichnofabric composed of meiobenthic trace fossils is described from Late Permian shelf carbonates of the Arabian Platform from the Oman Mountains (Saiq Formation, Akhdar Group). It mainly consists of an 8–10 cm deep boxwork with an undulating burrow outline, with an average burrow diameter of about 0.5 mm. The pinch-and-swell-like features lead to bulbous enlargements and alternating blade-like contractions and are diagnostic for Virgaichnus undulatus igen. et isp. nov. In the upper tier of the ichnofabric, V. undulatus is associated with miniature spreiten-like lobes, which originate from a vertical shaft. These circular, elliptical or elongated lobes in the centimetre-range consist of irregularly arranged probes less than 1 mm in diameter and are assigned to Hydrancylus isp. The assessment of burrowing mechanism, burrow complexity, burrow size and geological age indicates worm-like organisms as potential trace makers for V. undulatus. The undulating shape of the burrow segments is in agreement with a peristaltic movement of a non-segmented, highly deformable vermiform body as known from nemerteans. The presented case demonstrates that morphology in combination with size is invaluable for the interpretation of the trace maker and consequently strengthens the importance of meiobenthic trace fossils for palaeoenvironmental and facies analysis.