Morphology,morphogenesis, and molecular phylogeny of a new marine urostylid ciliate (Ciliophora,Stichotrichia) from the South China Sea,and a brief overview of the convergent evolution of the midventral pattern within the Spirotrichea

The morphology, infraciliature, morphogenetic events, and small subunit ribosomal RNA (SSU rRNA) gene‐based phylogeny of a stichotrich ciliate, Bergeriella ovata gen. et sp. nov. , found in coastal waters off Daya Bay, Guangdong, South China, were investigated. The new taxon has an atypical midventral pattern, and is characterized by several rather unusual morphological features: frontal cirri forming an irregular tricorona; one nonmigratory row located right of the midventral rows, which is morphogenetically derived from the posteriormost fronto‐ventral‐transverse (FVT) streak; conspicuously enlarged postoral ventral cirri, whereas the left ventral cirri are delicate and arranged in oblique rows. Based on both the morphological and morphogenetical data, a new family, Bergeriellidae fam. nov. , is proposed. In the SSU rRNA phylogenetic trees, B. ovata gen. et sp. nov. groups with the classic urostylids (urostylids s.s.) with high nodal support. Our phylogenetic analyses have revealed at least seven separate clades for midventral pattern‐bearing taxa (e.g. Pattersoniella, Neokeronopsis, Rigidothrix, urostylids s.s., Uroleptidae, Holostichidae + Psammomitridae, and Pseudoamphisiellidae), suggesting that the order Urostylida Jankowski, 1979 sensu Lynn, 2008 is a polyphyletic assemblage, and that the convergent evolution of the urostylid midventral pattern might have occurred more times among the spirotrichs than has previously been recognized. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 697–710.