Two almost‐forgotten Trypanites ichnospecies names for the most common Palaeozoic macroboring

Trypanites is the most common macroboring with a global occurrence throughout the Phanerozoic and is the eponym of the Trypanites ichnofacies. It has great value for the recognition of discontinuity and hiatal surfaces on top of carbonate hardgrounds. Four ichnospecies of this ichnogenus are currently regarded as valid, while a characteristic fifth form from the early Palaeozoic is frequently reported in open nomenclature. The latter commonly occurs in lithic hardgrounds and skeletal hard substrates (such as stromatoporoids, bryozoans and corals) in Ordovician and Silurian carbonates of the Baltic region. A review of the old literature found that this ichnospecies has previously been introduced twice, as Trypanites sozialis Eisenack from a Silurian erratic boulder found on the Sambia Peninsula near Kaliningrad (now Russia), and as T. keilaensis Orviku from the Ordovician of Estonia. Both ichnospecies became forgotten names for unknown reasons. A morphometric analysis of the type material and topotype specimens indicates gradational transitions between both ichnospecies, rendering T. sozialis as the senior synonym of T. keilaensis. A lectotype from the type series of both ichnospecies is defined and additional material from Ordovician and Silurian carbonates of Estonia and Russia is described and illustrated to show the morphological and morphometric variation of this important bioerosion trace fossil. To enable interspecies comparison, a lectotype of the type ichnospecies of Trypanites, T. weisei Mägdefrau, is selected. Trypanites sozialis is a common boring in Cambrian to Devonian hardgrounds and occurs on the palaeocontinents of Baltica, Laurentia and Gondwana.