''Cyathaspis'' is the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...

of the

heterostracan Heterostraci (Ancient Greek, ἕτερος+ὄστρακον "those itha different shell" i is pl. of -us is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci exi ...

order

Cyathaspidiformes Cyathaspidiformes is an extinct order of heterostracan vertebrates known from extensive fossil remains primarily from Silurian to Early Devonian strata of Europe, and North America, and from Early Devonian marine strata of Siberia. Anatomy ...

. Fossils are found in late

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

strata in the Cunningham Creek Formation, New Brunswick, Canada and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, especially in the

Downton Castle Sandstone The Downton Castle Sandstone is a geologic formation in England. It preserves fossils dating back to the Silurian period. As its name would suggest the formation predominantly consists of sandstone with minor siltstone and mudstone. The oldest kn ...

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...

and

Gotland Gotland (, ; ''Gutland'' in Gutnish), also historically spelled Gottland or Gothland (), is Sweden's largest island. It is also a province, county, municipality, and diocese. The province includes the islands of Fårö and Gotska Sandön to the ...

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

. The living animal would have looked superficially like a

tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found i ...

, albeit covered in bony plates composed of the tissue aspidine, which is unique to heterostracan armor. ''Cyathaspis ludensis'' is the earliest British vertebrate fossil. It was found in rocks at

Leintwardine Leintwardine ( ) is a small to mid-size village and civil parish in north Herefordshire, England, close to the border with Shropshire. History Roman A popular misconception is that the Romans called the village ''Branogenium''. Branogenium in f ...

in Herefordshire, a noted fossil locality.

References

Cyathaspidida Cyathaspidiformes genera Wenlock first appearances Ludlow life Silurian extinctions Silurian jawless fish Silurian fish of Europe Fossils of Sweden Silurian England Silurian fish of North America Paleozoic life of New Brunswick Paleozoic life of Nunavut {{silurian-animal-stub