Pennatulacea
General description:
Pennatulids or seapens are colonial cnidarians which have an stiff internal calcite rod - the rachis. They have two types of polyps: large feeding polyps (autozooids) armed with eight tentacles and smaller openings (syphonozooids) which regulate and maintain water currents within the body of the sea-pen. Zooids can be arranged individually over the body or as linear groups on 'leaves'.
Pennatulids stand erect anchored in the sediment by a long base section of the rachis buried in the sediment. Sea-pens are suspension feeders, the zooids capture plankton with their tentacles.
Phylogeny:
Class Anthozoa
Subclass Octocorallia
Order Pennatulacea
Distribution:
Found in Tung Nang Dam, PhangNha Province.
Habitat:
They have been found in seagrass beds and off-shore sediments.