abnormal tail morphology abnormal morphology of tail post-anal tail morphology phenotype tail morphology variant WBPhenotype:0000073 tail morphology abnormal C_elegans_phenotype_ontology Animals exhibit variations in the form, structure or composition of any portion of the most posterior region of the body compared to control. The anterior bound of the tail is not well defined though it might range from the position of the post-deirids to the opening of the anus (Wormatlas). body region morphology variant organism segment morphology variant abnormal tail morphology