''Amphiaspis argo'' is the type species of the cyathaspidid

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

Amphiaspidida Amphiaspidida is a taxon of extinct cyathaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. Some authorities treat it as a suborder of Cyathaspidiformes,Lundgre ...

, and of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Amphiaspididae.Novitskaya, Larisse. Les amphiaspides (Heterostraci) du Devonien de la Siberie. Éditions du Centre national de la recherche scientifique, 1971. Its fossils are restricted to early Emsian-aged marine strata of the Taimyr Peninsula, Early

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

. ''A. argo'', as with all other amphiaspidids, is thought to have been a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

that lived on top of, or buried just below the surface of the substrate of hypersaline lagoon-bottoms.

Anatomy

So far, ''A. argos'' is known from at least one, incomplete cephalothoracic armor that is shaped vaguely like a pillow and is, from anterior to posterior, 24 centimeters long. The armor has a pattern of lateral sensory line canals. There is a prominent dorsal spine on the dorsoposterior end of the cephalothoracic armor. The animal had small, possibly degenerate eyes that were flanked laterally by a small, crescent-shaped preorbital opening at the anterior end of the armor. The small eyes, in turn, laterally flank a small, slit-shaped mouth at the center of the anterior-most end of the cephalothorax.

References

Cyathaspidiformes genera Amphiaspidida Devonian jawless fish Early Devonian fish Heterostraci genera Fauna of Siberia Fossils of Russia Early Devonian first appearances Devonian extinctions {{Devonian-jawless-fish-stub