Crinoids with unusual morphology

PUBLICATION — Gorzelak, P., M. A. Salamon, & W. I. Ausich. 2025. Part T, Revised, Volume 1, Paleoecology and functional morphology of unusual crinoids: stretching the limits of the crinoid Bauplan. Treatise Online 192:1–36, 20 fig. https://doi.org/10.17161/to.vi.24794

Figure: Devonian Ammonicrinus with a planispirally coiled stem and a retracted crown (Rekonstruction M. Łukowiak).

In the prestigious series Treatise on Invertebrate Paleontology, a chapter was released that synthesizes data on the functional morphology and paleoecology of crinoids with unusual morphologies. It illustrates how, over more than 485 million years, they repeatedly deviated from their original body plan: from benthic forms to pelagic species. Some forms lost their arms, others transformed their holdfasts into bulbs, or developed extremely long stems. These examples highlight the remarkable morphological plasticity of crinoids and their ability to occupy diverse ecological niches.