Figure 1: Phylogenetic analyses of 170 nuclear proteins and 13 mitochondrial proteins support a monophyletic chordate clade and an independent deuterostome phylum of Xenoturbellida. We note that ...

A study on the development of priapulids or ‘penis’ worms throws doubt on a feature that has been thought for more than 100 years to define the largest branch of the animal tree of life. Members of ...