FIGURE 1. The deuterostomes, and possible places for vetulicolians in the evolutionary scheme of events.

Shu and colleagues¹ regard vetulicolians as 'basal' deuterostomes — phylogenetically outside all extant deuterostomes. But they also suggest that the fossils have an endostyle, a structure generally seen as characteristic of a more exclusive deuterostome group, the chordates, and implying that the vetulicolians have a more 'crownward' position in the tree of life. As interpreted by Shu and colleagues, the fossils lack a notochord and so cannot be regarded as chordates. But vetulicolians could be their immediate sister taxon.