After Parker, 1982 and Kerr, 2000 [“The Tree of Life Project”]

<==o HOLOTHUROIDEA (merimakkarat)
   |?- Gephyrothuriidae [has been treated as Molpadiid (Parker, 1982)]
   |?- Eupyrgidae [has been treated as Molpadiid (Parker, 1982)]
   |--o Apodida [paraphyletic Apodacea]
   |  |-- Synaptidae
   |  |-- Chiridotidae
   |  `-- Myriotrochidae
   `--+--o Elasipodida (deep-sea sea cucumbers) [paraphyletic Aspidochirotacea]
      |  |-- Deimatidae
      |  |-- Laetmogonidae
      |  |-- Elpidiidae
      |  |-- Psychropotidae
      |  `-- Pelagthuriidae
      `--+--o Aspidochirotida (beche-de-mer, trepang, etc.) [paraphyletic Aspidochirotacea]
         |  |-- Holothuriidae
         |  |-- Stichopodidae
         |  `-- Synallactidae
         `--+--o Molpadiida (rat-tailed sea cucumbers) [paraphyletic Apodacea]
            |  |-- Molpadiidae
            |  `-- Caudinidae
            `--o Dendrochirotacea
               |--o Dentrochirotida (suspension-feeding sea cucumbers)
               |  |-- Placothuriidae
               |  |-- Paracucumidae
               |  |-- Psolidae
               |  |-- Heterothyonidae
               |  |-- Phyllophoridae
               |  |-- Sclerodactylidae
               |  `-- Cucumariidae
               `--o Dactylochirotida (plated sea cucumbers, in partim)
                  |-- Ypsilothuriidae
                  |-- Vaneyellidae
                  `-- Rhopalodinidae

Reference(s):