Fustiglyphus annulatusfrom the Ordovician of Ontario, Canada, with a systematic review of the ichnogeneraFustiglyphusVialov 1971 andRhabdoglyphusVassoievich 1951

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Abstract
The ichnogenera Rhabdoglyphus Vassoievich 1951 and Fustiglyphus Vialov 1971, both a source of taxonomic confusion and inconsistent usage, are re‐examined. Many specimens of Fustiglyphus have been incorrectly described as Rhabdoglyphus, both prior and subsequent to the formulation of the former by Vialov in 1971. Updated synonymies for both ichnogenera and their ichno‐species indicate that two ichnospecies of Rhabdoglyphus can be distinguished, namely R. grossheimi Vassoievich 1951 and R. spinosus Ksiazkiewicz 1977, while F. annulatus Vialov 1971 is the only acknowledged ichnospecies of Fustiglyphus. The significant feature distinguishing the two ichnogenera is regarded as the presence of invaginated segments on Rhabdoglyphus as opposed to well‐defined rings or knots with no invagination on Fustiglyphus. Although Spongolithus annulatus Fritsch 1908 is technically the senior synonym of Fustiglyphus annulatus, it is recommended that the latter name continue to be used in the interests of maintaining nomenclatural stability. Previously unreported specimens of Fustiglyphus annulatus from the Ordovician of Ontario are described and illustrated; one of these suggests that the swellings in Fustiglyphus possibly represent brood chambers of the producing‐organism(s). We also suggest that Fustiglyphus "retreated”; from onshore to deep‐water offshore environments at the end of the Paleozoic.