Taxonomy

Morphology

Neocrinus decorus, like most echinoderms, is composed of numerous calcite plates which are arranged into different organs.

N. decorus is divided into 3 sections:

  1. The stem:
    • raises the calyx and arms above the sediment and is composed of a stack of numerous 5-sided star-shaped plates. 
    • bears flexible, finger-like appendages called cirri that are used to reattach itself to the substrate after moving.
  2. The calyx (body or theca):
    • is formed of 2 bands of 5 plates that form a cup-shaped body, from which the bases of the arms arise. 
    • is covered on top by numerous small polygonal plates. The mouth and anus are found on this surface.
    Neocrinus decorus calyx with mouth, food groove and anus

    Neocrinus decorus calyx with mouth, food groove and anus.

  3. Arms:
    • 5 originate in the calyx but these frequently divide, similar to tree branches, so that there may be up to 40 arms in total
    • are formed of stacks of U-shaped calcite plates
    • bear numerous projections called pinnae (like those of a fern frond). It is on these pinnae that tube feet, covered in mucus, extend into the water and catch plankton. 
    • are moveable
    • are usually arranged in a parabolic fan to collect food
    • can be used for crawling (dragging the stem behind it).
  • Diagnostic description of Neocrinus decorus

    Learn the diagnostic description of this crinoid species.

  • Evolution

    Fossil remains of this species suggest it has undergone very little change over the last 20 million years. Find out what is known about the evolution of Neocrinus decorus and its relatives in the wider crinoid family.