Crawling crinoid trace
Out-takes from:
"Stalked Crinoid Locomotion and Its Ecological and Evolutionary Implications"
Tomasz K. Baumiller and Charles G. Messing

Knowing what crawling crinoid traces look like increases
the odds of specimens being found and images shared with others

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fig4  fig5

Figure 4. Still frames showing the drag mark left by the stalk of the isocrinid Neocrinus decorus just after it had crawled across the substrate (single arrow). Movement was from left to right, and the distal end of the stalk can be seen in the lower right corner. Scale 100 mm

Figure 5.: Traces left by a crawling comatulid, Davidaster rubiginosa, on mud covering the bottom of an aquarium (Discovery Bay Marine Lab, Jamaica). A few of the arms can be seen in the lower left corner. Scale: 20 mm.

The arms and stalk of crawling crinoids interact with the substrate, and this activity ought to produce traces. Previously, Messing et al. (1988) recognized what they considered to be two types of traces left by a crawling isocrinid: “a drag mark over 1m long…” left by the stalk (p. 481); and “short radiating scratch marks” on the substrate around the crown and on the sediment surface behind an isocrinid made by the arms involved in crawling. Unfortunately, no photos of either trace are available. Our observations provide further proof for at least one such trace: in the video footage, grains of sediment are displaced as the stalk is pulled behind the crawling N. decorus producing a drag mark (Figure 4). While the low angle at which the video footage was shot makes it difficult to recognize any of the fine traces that would be produced by the power strokes of the arms, experiments with comatulids crawling on fine-grained substrate reveal the types of traces that such behavior is likely to produce (Figure 5).

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Credits (images and text)
Stalked Crinoid Locomotion and Its Ecological and Evolutionary Implications
Tomasz K. Baumiller and Charles G. Messing