Siberiaspidoidei

Siberaspidoidei is a taxon of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, siberaspids 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.

Siberiaspidoidei Temporal range: Early Devonian
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Pteraspidomorphi
Subclass:	Heterostraci
Order:	Cyathaspidiformes
(unranked):	Amphiaspidida
Superfamily:	Siberiaspidoidei
Families
Siberiaspididae Tuxeraspididae
Synonyms
Amphiaspidiformes

Taxonomy

Siberaspidoidei contains two families, Siberaspididae, and Tuxeraspididae.

Siberaspididae

This family contains two monotypic genera, Siberaspis, 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.[1]

References

1. Новицкая ЛИ (1986), "Древнейшие бесчелюстные СССР: Гетеростраки: Циaтacпиды, Aмфиacпиды, Птepacпиды." Труды ПИН 219: 159c. [Novitskaya, LI (1986), The most ancient agnathans of the USSR: Heterostraci: Cyathaspidae, Amphiaspidae, Pteraspidae. Trudy Paleontol. Inst. Nauk 219: 159 pp.]