Figure 3 : Schematic diagram depicting a time-lapse series of a polyp burrowing into a soft-bottom substrate and exhibiting soft-part behaviours characteristic of Deltocyathoides orientalis.

From: Burrowing hard corals occurring on the sea floor since 80 million years ago

Figure 3

(A) initial placement of a coral on a sand substrate. (B) expansion of tentacles. (CF) gradual expansion of the polyp’s aboral base results in the upward and outward lateral shedding of adjacent sediments. (C,E) the polyp’s aboral base assumes the shape of a horn so as to dig itself into the substrate and shed adjacent sediments laterally. (D,F) seawater stored in the interior of the soft parts moves to the aboral side of the polyp through canal over the skeleton powered by contraction of the polyp. (G) the corallum is buried with its tentacles extended above the substrate.