- Some parasites leave marks or traces ( leaf mines and certain anomalies seen in invertebrate endoskeletal remains.
- This feature can now be distinguished as digits instead of the endoskeletal radials seen in earlier tetrapods.
- The evolution of endoskeletal plates with stereom structure and of external ciliary grooves for feeding were early echinoderm developments.
- Chondrichthyes are distinguished based on a two unique autapomorphous character sets : the development of tesserae endoskeletal mineralisation and internal fertilisation with copulation.
- As in other arthropods, a true endoskeleton is absent, but the body does have an endoskeletal structure made up of cartilaginous plates that support the book gills.