Evolution & Systematics
Evolutionary origins
The evolutionary origin of turbellarians is still under debate. Two schools of thought surround their origin. One theory states that turbellarians and cnidarians have a common ancestor, which place them in a basal position.
The second theory suggests they evolved from a coelomate ancestor by paedomorphosis or reduction (Ruppert et al., 2004).
Systematic Relationships
Molecular and phylogenetic studies have confirmed that the Pseudocerotidae family is a monophyletic group. Taxonomically, the separation of Pseudoceros and Pseudobiceros based on the number of male reproductive systems has been confirmed.
A molecular study based on the Pseudocerotidae family (P. bedfordi belongs to this family) were examined using nucleotide sequences from the 28S rDNA gene, results indicated that Pseudoceros form a monophyleticclade and Pseudobiceros is a paraphyletic group ( Goggins et al., 1996).
Molecular data also support species separations based on colour patterns (Litvaitis & Newman, 2001).
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