| Protaspididae Temporal range: Early Devonian
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| Fossil of Cosmaspis transversa in the Field Museum of Natural History, Chicago | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Infraphylum: | Agnatha |
| Class: | †Pteraspidomorphi |
| Subclass: | †Heterostraci |
| Order: | †Pteraspidiformes |
| Suborder: | †Pteraspidoidei |
| Family: | †Protaspididae |
| Genera | |
Protaspididae is an extinct family of pteraspidid heterostracan agnathans. Fossils of the various genera are found in early Devonian-aged marine strata. Protaspidids were once thought to represent a transitional form between the Pteraspididae and the Psammosteida, bearing the broad head shield shape of the latter, due to a more benthic (bottom-dwelling) existence, but recent phylogenical comparisons demonstrate that the protaspidids are actually highly derived pteraspidids,[1] and that the anchipteraspidids, the most primitive of pteraspidids, are the sister-group of the psammosteids.
- ^ Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403.