These are animals which at some stage in their life-cycle having had a notochord or spinal column, gill-slits, and post-anal tail. It includes humans and other vertebrates.  There are 14 classes, often in three subphyla:

1. Subphylum Cephalochordata¹ — Lancelets
   1. Class Leptocardii — Lancelets
2. Subphylum Tunicata¹ — Tunicates
   1. Class Appendicularia — Pelagic Tunicates
   2. Class Ascidiacea — Sea Squirts
   3. Class Thaliacea — Thaliaceans
3. Subphylum Vertebrata¹ — Vertebrates
   1. Class Actinopterygii — Ray-finned Fishes
   2. Class Amphibia — Amphibians
   3. Class Aves — Birds
   4. Class Cephalaspidomorphi² — Lampreys
   5. Class Elasmobranchii — Elasmobranchs
   6. Class Holocephali — Chimaeras
   7. Class Mammalia — Mammals
   8. Class Myxini² — Hagfishes
   9. Class Reptilia — Reptiles
   10. Class Sarcopterygii — Lobe-finned Fishes

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¹ NBN Atlas and iNaturalist subdivide Chordata into the three subphyla shown, CoL and BOLD do not.
² iNaturalist include these in a superclass Agnatha —Jawless Fishes