clades  

The classification of Acoela down to the “family level” was recently revised based on a phylogenetic study (U. Jondelius, A. Wallberg, M. Hooge, and O. I. Raikova, “How the Worm Got its Pharynx: Phylogeny, Classification and Bayesian assessment of Character Evolution in Acoela,” Systematic Biology, 2011.doi:10.1093/sysbio/syr073 )

Here is an overview of the current, i.e. new, acoel classification with diagnostic features of higher taxa in brackets and some comments regarding synonymizations. The suprafamilial clade names (without author and year) are informal, i.e. not part of a linnean classification.

• Acoela (digestive parenchyma, biflagellate spermatozoa)
  • Diopisthoporidae Westblad, 1940
  • Bitesticulata (Paired or follicular testes, ventral gonopore. The most inclusive clade that contains Paratomella rubra and Symsagittifera roscoffensis but not Diopisthoporus longitubus)
    • Paratomellidae Dörjes, 1966
    • Bursalia (Copulatory bursa often present. The most inclusive clade that contains Oligofilomorpha interstitiophilum and Childia groenlandica but not Paratomella rubra)
      • Prosopharyngida (Muscular pharynx in anterior part of body. The most inclusive clade that contains Hofstenia miamia and Oligofilomorpha interstitiophilum but not Haploposthia rubra)
        • Hallangidae Westblad, 1946
        • Hofsteniidae Papi, 1957
        • Solenofilomorphidae Dörjes, 1968
      • Crucimusculata (Ventral crossover muscle fibres). The most inclusive clade that contains Actinoposthia beklemischevi and Childia groenlandica but not Haploposthia rubra)
        • Dakuidae Hooge 2003
        • Isodiametridae Hooge & Tyler 2005
        • Otocelididae Westblad, 1948
        • Proporidae Graff, 1882
        • Aberrantospermata       (Spermatozoa with 9+0 or 9+1 axonemes. The most inclusive clade that contains Neochildia fusca and Childia                   groenlandica but not Actinoposthia beklemischevi)
          • Convolutidae Graff, 1905  This family now includes species formerly classified in Anaperidae and Sagittiferidae, which have both been synonymized with Convolutidae
          • Mecynostomidae Dörjes, 1968 This family now includes the species formerly classified in Childiidae as that taxon was synonymized with Mecynostomidae

1. • Acoela Incertae cedis, no phylogenetic hypothesis available
     • Actinoposthiidae (poorly sampled in the phylogenetic study, indications that this may be a polyphyletic assemblage)
     • Anthroposthiidae (single species)
     • Antigonariidae (single species)
     • Nadinidae (single species)
     • Tauridiidae (single species)