Siberiaspidoidei is a
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 ...
of extinct
amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of
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 ...
near the
Taimyr Peninsula. In life, siberiaspids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of
hypersaline lagoons. As with all amphiaspids, siberiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single,
muff-like unit, so that the forebody of the living animal would have looked like a flattened potpie or a hot waterbottle with a pair of small, or degenerated eyes sometimes flanked by preorbital openings, a pair of branchial openings for exhaling, and a simple, slit-like, or tube-like mouth.
Taxonomy
Siberiaspidoidei contains two families,
Siberiaspididae, and
Tuxeraspididae.
Siberiaspididae
This family contains two monotypic genera, ''
Siberiaspis'', and ''
Argyriaspis''.
Tuxeraspididae
This family contains three monotypic genera, ''
Tuxeraspis'', ''
Litotaspis'', and ''
Dotaspis''. ''Tuxeraspis'' and ''Litoaspis'' are known primarily from fragments and portions of the head-region, while ''Dotaspis'' is known from a mostly intact headshield. These fragments, together with the anatomy of ''Dotaspis'' suggest the animals had large, flattened, circular cephalothoracic armor.
[Новицкая ЛИ (1986), "Древнейшие бесчелюстные СССР: Гетеростраки: Циaтacпиды, Aмфиacпиды, Птepacпиды." Труды ПИН 219: 159c. ovitskaya, LI (1986), The most ancient agnathans of the USSR: Heterostraci: Cyathaspidae, Amphiaspidae, Pteraspidae. Trudy Paleontol. Inst. Nauk 219: 159 pp./ref>
]
References
Amphiaspidida
Devonian jawless fish
Prehistoric animal superfamilies
Vertebrate superfamilies
Early Devonian fish
Fauna of Siberia
Fossils of Russia
Early Devonian first appearances
Devonian extinctions
{{Devonian-jawless-fish-stub