| Trinucleidae Temporal range:
| |
|---|---|
| |
| Cryptolithoides ulrichi, 12 mm (0.47 in) | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Order: | †Asaphida |
| Superfamily: | †Trinucleioidea |
| Family: | †Trinucleidae Hawle & Corda, 1847 |
| Subfamilies | |
| |
Trinucleidae is a family of small to average size asaphid trilobites that first occurred at the start of the Ordovician and became extinct at the end of that period. It contains approximately 227 species divided over 51 genera in 5 subfamilies.[1] The most conspicuous character is the wide perforated fringe of the head.
- ^ D.A.T. Harper; T. Servais, eds. (2014). Early Palaeozoic Biogeography and Palaeogeography. Memoirs of the Geological Society of London. Vol. 38. Geological Society of London. p. 490. ISBN 978-1862393738.