Defining and refining principles in ichnotaxonomy: Markus Bertling (1959–2022)

In the peaceful days before Christmas 2021, fate struck hard on fellow ichnologist Markus Bertling (Figure 1), when he learned of a devastating diagnosis that gave him very little chance to turn the tide. On February 13, 2022, Markus passed away, leaving behind a painful void in his family and the ichnologic community alike. Starting off in 1985 with research on Upper Jurassic coral reef palaeoecology and sedimentology in northern Germany, Markus received his doctoral degree in 1990 and quickly picked upon an interest in the trace fossils he found in Jurassic reef settings and established his f irst new ichnogenus, Arachnostega Bertling, 1992. In the following years, it was the bioerosion trace fossils and the lessons to learn from the bioerosion at Mesozoic coral reef settings that caught his particular interest (e.g., Bertling, 1995, 1997a, 1999a, 1999b, 1999c, 2002; Perry & Bertling, 2000). Since 1998, Markus was curator for palaeontology at the Institute of Palaeontology of the Westphalian Wilhelm’s University in Münster, Germany, and in 2007 he became one of the heads of the University’s Geomuseum. For the past decade, Markus was heavily involved in the complete refurnishing and modernization of the museum and had less valency to follow his scientific passion in ichnology and ichnotaxonomy. Nevertheless, he sustained his interest in this field of science and was involved, for instance, in various case studies on bioerosion traces in osteic and xylic substrates (e.g., Feng et al., 2019; Höpner & Bertling, 2017; Mikuláš et al., 2020) and contributed with this expertise to an extensive review and annotated list of all the known bioerosion ichnotaxa (Wisshak et al., 2019). Aside from Arachnostega gastrochaenae, Markus co-authored the erection of at least three ichnospecies, three ichnogenera and fourteen ichnofamilies (Höpner & Bertling, 2017; Wisshak et al., 2019). Markus was best known to the ichnologic research community as a leading authority when it came to both the nomenclature of trace fossils and ichnotaxonomic principles. His effort helped to implement the rules established in the International Code of Zoological Nomenclature and to advocate their application in all kinds of ichnotaxonomic work. This, in turn, enabled the ichnotaxonomist to apply ichnotaxobases more consistently, to focus on the erection of ichnotaxa by a valid procedure and avoiding the erection of too many monotypic taxa. Whenever there was a problem to solve on how to apply the Code, the trickier the better, it became a reflex for many ichnologists to send an e-mail to Markus, asking for his advice. His in-depth knowledge of the Code put him into the position to lead or contribute to several comments on the draft proposal to emend the Code with respect to trace fossils (Bertling et al., 2003, 2004; Genise et al., 2004). From 2017 onward, Markus himself served as a commissioner on the Internat ional Commission for Zoologica l Nomenclature, striving to foster the status of ichnotaxonomy in zoological nomenclature and contributing to the ongoing revision of the Code. His involvement with the ICZN was much appreciated by the broader taxonomic community and to honour his work, the vertebrate genus Bertlinggekko was named after him. Markus’ engagement in improving the Code testifies to his great talent and profound interest in sound (methodo)logical thinking and theories of scientific cognition – an invaluable trait he brought into the admittedly chaotic situation that was ichnotaxonomy in the 1990s. Markus became central to the ichnotaxonomic community in 1998 when spearheading