DISTRIBUTION
Chitinozoa appeared during the Cambrian, diversified rapidly in the Ordivician and Silurian, and became extinct toward the end of the Devonian Period. They lived 510-360 million years ago.
| PERIOD | DATES (Ma) |
| Devonian | 360-408 |
| Silurian | 408-438 |
| Ordovician | 438-505 |
| Cambrian | 505-570 |