Astraspida, or astraspids, are a small group of extinct armored jawless vertebrates, which lived in the Late Ordovician (about 450 million years ago) in North America.
They are represented by a single genus, Astraspis, including possibly two species, A. desiderata and A. splendens[2] but their remains are fairly abundant in Ordovician sandstones of the USA (Colorado, Arizona, Oklahoma, Wyoming) and Canada (Quebec).
The head armor of Astraspis is rather massive, with a series of ten gill openings lining the margin of the dorsal shield, and laterally placed eyes.
[3] Astraspids are characterized by a dermal ornamentation of large, mushroom shaped tubercles of fine-tubuled dentine ("astraspidine"), covered with a thick, glassy cap of enameloid.
Their dorsal and ventral shield is made up by numerous polygonal platelets of aspidine, ornamented with large dentine tubercles capped with a thick enameloid layer.