Cruziana semiplicata from the Furongian (Late Cambrian) of Severnaya Zemlya Archipelago, Arctic Russia, with a review of the spatial and temporal distribution of this ichnospecies

The Furongian (Late Cambrian) Kurchavinskaya Formation of October Revolution Island, Severnaya Zemlya Archipelago, Arctic Russia, contains two distinctive morphotypes of the trace fossil Cruziana, both of which we assign to Cruziana semiplicata. A wider form shows characteristics typical of this ichnospecies with inner and outer lobes and marginal ridges. A narrow form has only an inner lobe with siculate, often interfering scratch-marks, and rare, narrow marginal ridges. This narrow form, which shows characters in common with Cruziana tortworthi, probably represents burrowing in a strongly head-down orientation. The record from October Revolution Island provides additional evidence that the palaeogeographical distribution of Cruziana semiplicata is not restricted to Gondwana, but also extend to parts of Baltica and North Kara. Cruziana semiplicata is known from the Furongian and Tremadocian of Gondwana, whereas on Baltica it is known only from the Furongian.