| Annelids and Arthropods | Asheaia |
| Invertebrates and Vertebrates | Pikaia |
So called
"MISSING LINKS"
between:
| Fish and Amphibians | Eusthenopteron, Acanthostega, Ichthyostega |
| Amphibians and Reptiles | Seymouria |
| Reptiles and Birds | Archaeopteryx |
| Reptiles and Mammals | Diarthrognathus |
| Ferns and Conifers | Archaeopteris |
| Ferns and Flowering Plants | Medullosa |
| Annelids and Arthropods | Asheaia |
| Invertebrates and Vertebrates | Pikaia |