centrodorsal

from The Century Dictionary.

• Central and dorsal or aboral: applied to the central ossicle of the stem of crinoids, as members of the genus Comatula.
• noun In crinoids, a centrodorsal ossicle which unites the skeleton of the stalk with the body.
• noun In paleont., a pentagonal plate found in many non-pedunculate crinoids (for example, Uintacrinus) at the base of the cup and probably representing an atrophied stalk.