The Swordtails or Moluccan lobsters ( Merostomata , Xiphosuridae , Xiphuridae ) are very eccentric creatures, remnants of an extinct animal world, not closely related to any of the existing groups to be included. In important respects they deviate from the Shellfish, to which most zoologists add them, albeit with some reservations. They draw closer to the Arachnids and more specifically to the Scorpions. Unified with the latter order, they should probably form a separate class.
Great Sea Spider
They are attached to a flexible muscular stem and have a flat, three-sided shell. A large number of genera are distinguished according to the number and the greater or lesser development of the limestone plates. Among the most common are Lepas and Otion . About half of all Lepadid species attach themselves to objects moving in water, to the keel of ships, to pieces of wreckage, etc., or to animals that often change places. Anelasma squalicolaeg lives parasitically on Northern Sharks, into whose skin it has penetrated with its stem; With Lepas anserifera and a few other species, the ships are not infrequently overgrown on their return from almost all southern and tropical seas.
[As translated online ]