extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
holocephalan
Holocephali (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fi ...
s from the
Carboniferous
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...
. Likely one of the earliest and most basalcaseodontoids, it can be characterized by its broad, ridge-ornamented crushing teeth made of various types of
dentin
Dentin ( ) (American English) or dentine ( or ) (British English) () is a calcified tissue (biology), tissue of the body and, along with tooth enamel, enamel, cementum, and pulp (tooth), pulp, is one of the four major components of teeth. It i ...
e. The type species, ''C. agassizianus'', was originally described in 1844 based on a small number of teeth from the
Namurian
The Namurian is a stage in the regional stratigraphy of northwest Europe, with an age between roughly 331 and 319 Ma (million years ago). It is a subdivision of the Carboniferous system or period, as well as the regional Silesian series. The Na ...
of
Belgium
Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...
.
Additional fossils have been referred to the genus. These include Belgian specimens referred by Lohest (1884), fossils from
Missouri
Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...
referred by Zangerl (1981), and symphyseal tooth-whorls from
Nebraska
Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...
and
Kansas
Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
referred by Eastman (1902). The tooth whorls were given their own species, ''C. variabilis''. They shared some similarity to a massive "''
Agassizodus
''Agassizodus'' is an extinct genus of eugeneodont holocephalian from the Carboniferous. It belongs to the family Helicoprionidae, which is sometimes called Agassizodontidae. Like other members of its family, it possessed a symphyseal tooth who ...
''" jaw apparatus found in Osage, Kansas and described by St. John & Worthen (1875). This has led some authors to the conclusion that ''Agassizodus'' and ''Campodus'' were synonyms. However, others note that clearly identifiable ''Campodus'' teeth have not been found in the same areas from which ''Agassizodus'' was originally described. Ginter (2018) concluded that Eastman's "''C. variabilis''" and St. John & Worthen (1875)'s "''Agassizodus''" belonged to neither ''Campodus'' nor ''Agassizodus'', and instead represented a new unnamed genus. Ginter additionally referred a specimen from
Derbyshire
Derbyshire ( ) is a ceremonial county in the East Midlands of England. It borders Greater Manchester, West Yorkshire, and South Yorkshire to the north, Nottinghamshire to the east, Leicestershire to the south-east, Staffordshire to the south a ...
,
England
England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...