Recent advances in ichnology of crawling stalked crinoids

Stalked crinoids have generally been overlooked when considering trace fossil makers - largely because they were long considered fully sessile. However, observations both in the field and in laboratory experiments revealed that some members of the order Isocrinida use their arms to actively move along the bottom, dragging the stalk behind. This activity leaves distinct traces on the sediment surface. Here, we re-examined time-lapse movies made in 2017 and
crawling traces produced by stalked crinoids (the isocrinine Metacrinus rotundus) in previously published neoichnological experiments using new 3D digitization techniques (laser scanning and photogrammetry) in order to provide a more detailed 3D morphology of these traces. These data reveal some previously unnoticed crawling behavior and features of the traces of M. rotundus. We also demonstrate that crinoid-bearing beds are sometimes associated with ichnofossils that can be potentially interpreted as crinoid crawling traces. These data sources may provide more direct evidence of active locomotion in fossil crinoids.