A review of the glacial environment arthropod trace fossils Umfolozia and Warvichnium with the description of new ichnotaxa

Trace fossils are important records of the presence and behaviour of animals in the past, especially in deposits where few body fossils are preserved. They tend to provide the main palaeobiological record for past glacial environments and are thus very important for understanding the ecology of these palaeoenvironments. Two ichnogenera are common from past glacial environments: Umfolozia and Warvichnium. Both Umfolozia and Warvichnium are attributed to arthropods, and the former occurs across the Late Palaeozoic Ice Age (LPIA) and the latter occurs during both the LPIA and the Quaternary glacial event. Here, we review the stratigraphic record, ichnotaxonomy, palaeoecology, palaeoenvironments, and likely tracemakers of these two ichnogenera. In addition to assessing morphological ichnotaxobases, we use multivariate morphometric analysis and inferential statistical tests to support our ichnotaxonomic revisions. The diagnosis of Umfolozia is revised, with the description of a new ichnospecies, Umfolozia terere isp. nov., and the emendation of the previously named Umfolozia riojana (formerly Umfolozia longula) nom. rev. emend. We revised Warvichnium, maintaining the original Warvichnium ulbrichi, and allocating two morphologies to the ichnogenus Irichnus: Irichnus saltatorius and I. paripinnatus isp. nov.  These trace fossils record several behaviours, and have implications for palaeoenvironmental interpretations and the evolution of invertebrate ecosystems. Using Umfolozia and Warvichnium as case studies, we demonstrate the application of morphometric analysis in ichnotaxonomy and highlight this as a tool that may be applied to other trace-fossil groups.

Methods
The data was collected from previous publications and new material collected samples that are housed in the Coleção Arqueológica e Paleontológica (CAP) at the Federal University of São Carlos (UFSCar – Sorocaba campus, São Paulo, Brazil) at the Laboratório de Paleobiologia e Astrobiologia (LPA) under codes CAP/1D- and CAP/1H-. We processed the data using Zeiss ZEN 3.5 Lite (Blue Edition) software and later in RStudio.

The archives are uploaded as follows:

Appendix S1. A Dataset of the 173 specimens analysed.

Appendix S2. Specimen photos (Figs. S1–S12):

            Fig. S1. Umfolozia terere (CAP/1D-165).

Fig. S2. Umfolozia terere (CAP/1D-28).

Fig. S3. Umfolozia terere and ?Irichnus saltatorius (CAP/1D-162).

Fig. S4. Irichnus saltatorius (CAP/1D-134).

Fig. S5. Irichnus saltatorius (CAP/1D-144).

Fig. S6. Irichnus saltatorius (CAP/1D-145).

Fig. S7. Irichnus saltatorius (CAP/1D-168).

Fig. S8. Irichnus saltatorius (CAP/1D-398).

Fig. S9. Irichnus paripinnatus and Umfolozia terere (CAP/1D-29).

Fig. S10. Irichnus paripinnatus and Umfolozia terere (CAP/1D-51).

Fig. S11. Warvichnium ulbrichi (FG 290/6).

Fig. S12. Irichnus saltatorius (FG 290/26).

Appendix S3. List of occurrences (Tables S1–S6):

            Table S1. Umfolozia sinuosa Savage, 1971.

            Table S2. Umfolozia riojana (Aceñolaza, 1978) nom. rev. emend.

            Table S3. Umfolozia terere isp. nov.

            Table S4. Warvichnium ulbrichi Walter, 1985.

            Table S5. Irichnus saltatorius Skompski, 1991.

            Table S6. Irichnus paripinnatus isp. nov.

Appendix S4. Results of the Kruskal-Wallis and Wilcoxon-Mann-Whitney tests (Tables S7–S8):

            Table S7. Umfolozia

            Table S8. Warvichnium+Irichnus

Appendix S5. R Script.

Appendix S6. Deep sea isopods (video).

Appendix S7. Dive 01: Giant isopod (video).

Appendix S8. Dive 11: Winner, winner, fish head dinner (video).