Definition of ambulacrum in US English:



  • (in a starfish or other echinoderm) each of the radially arranged bands, together with their underlying structures, through which the double rows of tube feet protrude.

    • ‘Food particles were transported along the radial ducts, which penetrate through the marginals, to ambulacra on the underside of the disc, and eventually to the central mouth.’
    • ‘Four different groups of blastoids with moderately wide ambulacra evolved from groups with narrow ambulacra.’
    • ‘Although there are ridges on the radial plates that underlie the most distal points of the ambulacra, they did not support recumbent ambulacra as shown by growth lines crossing these ridges.’
    • ‘It is contained by four rows of plates with the plates smaller along the dorsal side, probably indicating an ambulacrum.’
    • ‘Furthermore, the placement of the ambulacra relative to the radials appears to be incorrect.’


Early 19th century: Latin, ‘avenue’, from ambulare ‘to walk’.