Ordovician jawless fish

Arandaspis is an extinct genus of jawless fish that lived in Australia during the early Ordovician period around 480 to 470 million years ago. It contains two species, A. prionotolepis and A. sp.

Sacabambaspis is an extinct genus of armored jawless fish which lived in the Ordovician period. Sacabambaspis inhabited shallow waters on the continental margins of the southern supercontinent Gondwana. The most complete specimens have been found in Bolivia, while armor fragments are also known from Argentina, Australia, and Oman. Sacabambaspis vaguely resembles a slender tadpole, with an oversized armor-plated head, flat body, and no discernible fins outside of its narrow tail. The eyes are closely spaced and positioned at the very front of the head, akin to car headlamps. It was about long i

Astraspis ('star shield') is an extinct, monotypic genus of primitive jawless fish from the Ordovician of Central North America including the Harding Sandstone of Colorado and Bighorn Mountains of Wyoming. It is also known from Bolivia. It is related to other Ordovician fishes, such as the South American Sacabambaspis, and the Australian Arandaspis.

thumb|left|Sacabambaspis, the best known arandaspid, from the Ordovician of Bolivia. Shows the characteristic, frontally positioned eyes, like car head lamps Arandaspida is a taxon of very early, jawless prehistoric fish which lived during the Ordovician period. Arandaspids represent some of the oldest known vertebrates. The group represents a subclass within the class Pteraspidomorphi, and contains only one order, the Arandaspidiformes. The oldest known genus of this group is Sacabambaspis found in South America.

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 placed among the Pteraspidomorphi because of the large dorsal and ventral shield of their head armor. They are represented by a single genus, Astraspis, including possibly two species, A. desiderata and A. splendens 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