extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
holocephalan
Holocephali ("complete heads"), sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primit ...
s from the
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
. Likely one of the earliest and most basalcaseodontoids, it can be characterized by its broad, ridge-ornamented crushing teeth made of various types of
dentine
Dentin () (American English) or dentine ( or ) (British English) ( la, substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by ena ...
. 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 326 and 313 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is ...
of
Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
.
Additional fossils have been referred to the genus. These include Belgian specimens referred by Lohest (1884), fossils from
Missouri
Missouri 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 is bordered by eight states (tied for the most with Tennessee ...
referred by Zangerl (1981), and symphyseal tooth-whorls from
Nebraska
Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...
and
Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
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 holocephalan 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 wh ...
''" 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, England. It includes much of the Peak District National Park, the southern end of the Pennine range of hills and part of the National Forest. It borders Greater Manchester to the nor ...
,
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...