Exercise 3
Now you're getting the hang of this! Once again,
use the data below to order organisms and shared apomorphies in the following
table into their correct position on the cladogram.
| Homalozoa (Outgroup) |
Echinoid | Asteroid | Crinoid | Holothuroid | Opthiuriod | |
| Water vascular system | Yes | Yes | Yes | Yes | Yes | Yes |
| Number of ambulacral grooves | 3 | 5 | 5 | 5 | 5 | 5 |
| Madreporite | Aboral | Aboral | Aboral | None | Internal | Oral |
| Suckers | Not on podia | On podia | On podia | Absent | On podia | On podia |
| Closed ambulacral grooves | No | Yes | Yes | No | Yes | Yes |
| Aboral surface reduced | No | Yes | No | No | Yes | Yes |
| Ambulacral grooves extended from oral to aboral | No | Yes | No | No | Yes | No |
| Endoskeleton | Highly flexible | Not flexible | Flexible | Highly flexible | Highly reduced | Highly flexible |