[4] Metaspriggina is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates, albeit this has been questioned because it seems to possess most of the characteristics attributed to craniates.

[1] In Metaspriggina the myomeral configuration has an additional ventral chevron, and a clear dorsal bend which defines a W-shaped arrangement that is directly comparable to fish.

In this explanation, Pikaia is not a close relative of Craniates at all, nor of cephalochordates, but something even more primitive, and the defining feature of the craniate-cephalochordate group is their gill bars.

[7] Considering that conodonts, the teeth elements of a type of extinct fish belonging to the Agnatha, are already found in Cambrian stage 2 (521-529 MA BP), some 20 million years before the Burgess shale, this latter explanation does not stand.

Phylogenetic analysis suggests that Metaspriggiidae are "stem-vertebrates" along with Haikouella and the Myllokunmingiids leading to the crown vertebrates, who divided themselves into two main directions: jawless fishes like conodonts leading to the Cyclostomi, and jawless fishes like the Cephalaspidomorph who developed armors and jaws to become the gnathostomes.