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

taxon In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...

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

, and of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Amphiaspididae Amphiaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula The Taymyr Peninsula ( ) is a peninsula in the Far North of Russia, ...

.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 The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

-aged marine strata of the

Taimyr Peninsula The Taymyr Peninsula ( ) is a peninsula in the Far North of Russia, in the Siberian Federal District, that forms the northernmost part of the mainland of Eurasia. Administratively it is part of the Krasnoyarsk Krai Federal subject of Russia. Ge ...

, Early

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

. ''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 the Ancient Greek word (), meaning "the depths". ...

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

that lived on top of, or buried just below the surface of the substrate of

hypersaline A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing those of ocean water (3.5%, i.e. ). Specific microbial species can thrive i ...

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