''Ctenaspis'' (''Ctenaspis kaieri'') is an
extinct genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of
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 exis ...
cyathaspid agnatha
Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present ( cyclostomes) and extinct (conodonts and ostracoderms) species. Among recent animals, cyclos ...
ns from the 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, w ...
of
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
,
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
and
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...
416.0 to 412.3 million years ago. Species of ''Ctenaspis'' are typically 10 to 18 cm long with the max length being 40 cm long. The genus contains only one known species, namely ''Ctenaspis kaieri''.
''C. kaieri'' has no adorbital opening and only two
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
and
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
plates . The dorsal plate is fused with
branchials and the plates notably thin. C. kiaeri has its branchial openings located at the posterior edge of armour. The dorsal shield is flat.
Sources
* ''Vertebrate Fossils and the Evolution of Scientific Concepts'' by W. Sargeant
* ''BioLib.cz''
External links
''Ctenaspis''at Palaeos.com
Cyathaspidida
Devonian fish of North America
Fossils of Canada
Early Devonian fish
Devonian jawless fish
Cyathaspidiformes genera
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