 "Pikaia", discovered much earlier but from the Mid Cambrian Burgess Shale, is also regarded as a primitive chordate.On the other hand, fossils of early chordates are very rare, as non-vertebrate chordates have no bone tissue or teeth, and fossils of no Post-Cambrian non-vertebrate chordates are known aside from the Permian-aged "Paleobranchiostoma", trace fossils of the Ordovician colonial tunicate "Catellocaula", and various Jurassic-aged and Tertiary-aged spicules tentatively attributed to ascidians.Below is a phylogenetic tree showing consensus relationships among deuterostome taxa.