Van Steenkiste, N. W. L.; Leander, B. S. (2018). Molecular phylogeny of trigonostomine turbellarians (Platyhelminthes: Rhabdocoela: Trigonostomidae), including four new species from the Northeast Pacific Ocean. Zoological Journal of the Linnean Society. 182(2): 237-257.
Molecular phylogeny of trigonostomine turbellarians (Platyhelminthes: Rhabdocoela: Trigonostomidae), including four new species from the Northeast Pacific Ocean
Zoological Journal of the Linnean Society
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Rhabdocoels comprise a species-rich group of microturbellarians in marine habitats around the globe. Knowledge of their species diversity in the Northeast Pacific Ocean is limited to a few studies. Here we present nine species within Trigonostominae and one species within Brinkmanniellinae associated with intertidal algae, sandy beaches and mudflats from the coast of British Columbia and Washington. Four species, Trigonostomum tillicum sp. nov., Ceratopera cascadiensis sp. nov., Ceratopera complicata sp. nov. and Ptychopera unicornis sp. nov., are new to science and are established based on molecular data and distinctive traits associated with the stylet and bursal appendage. Furthermore, we report on the occurrence of Trigonostomum tori, Ceratopera axi, Ceratopera pilifera, Ceratopera pacifica comb. nov., Ptychopera japonica and Tvaerminnea karlingi and provide new data on their morphology. A molecular phylogenetic analysis of Trigonostominae and other Thalassotyphloplanida using 18S rRNA and partial 28S rRNA sequences from 42 species demonstrates the phylogenetic positions of the four new species in addition to other inter- and intrageneric relationships within Trigonostominae (e.g. Messoplana is embedded within Ceratopera). This molecular phylogenetic context enables us to reassess homology statements about stylet morphology and the organization of the afferent system within Trigonostominae.