|Timoshkin OA (1997)
Taxonomic revision of the relict turbellarian group Prolecithophora Protomonotresidae from Lake Baikal (Plathelminthes): Description of Porfirievia n. gen., six new species of the genus and notes on the phylogeny of the Baicalarctiinae. In: Wada E...
New Scope on Boreal Ecosystems in East Siberia,151-179
Abstract / Notes
The descriptions of Porfirievia, a new genus of Baikal endemic Prolecithophora and six new species of the genus are given. The species of the new genus differ from the representatives of two previously described genera of Baikal prolecithophorans, Friedmaniella and Baicalarctia, by the following main characteristics: a) pharynx constructed as a pharynx plicatus with poorly developed muscles, b) extremelly numerous epidermal rhabdoids, c) the lateral branches of the vitellaria extending from the rostral to the caudal end of the body, d) small body size of sexually mature worms, etc. A close morphological similarity of the three genera is briefly demonstrated; this provides evidence about: 1) the monophyletic and autochthonous origin of the subfamily Baicalarctiinae in the lake; 2) the repeated and independent occurrence of a separate mouth tube (pharynx pocket) and genital pore within Prolecithophora Separata, which makes this feature invalid for phylogenetic analysis of the group; 3) the non-monophyletic origin of the Prolecithophora Separata. The phylogeny of the Baicalarctiinae based on comparative-morphological and molecular-biological analyses is discussed. Porfirievia is considered the most primitive genus of Baikal endemic prolecithophorans, close to their ancestral form; on the other hand, Baicalarctia should be considered as the youngest and most specialized genus among them. It is shown that food specialization drastically changed the general morphological organization and structure of the digestive system in the Baicalarctiinae, and thus played one of the most important roles in the evolution of this species flock in Baikal.
Return to taxon listing
|Home page -- (Main hierarchy)|