''Agassizodus'' is an extinct genus of eugeneodont holocephalian 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 ...

. It belongs to the family

Helicoprionidae Helicoprionidae (sometimes referred to as Agassizodontidae) is an extinct family of holocephali, holocephalans within the order (biology), order Eugeneodontida. Members of the Helicoprionidae possessed a "whorl" of Crown (tooth), tooth crowns con ...

, which is sometimes called Agassizodontidae. Like other members of its family, it possessed a symphyseal tooth whorl, which was likely present at the tip of the lower jaw and associated with lateral crushing toothplates. The type species, ''A. variabilis'', was originally named ''Lophodus variabilis'' until the name "Lophodus" was determined to be preoccupied. Listracanthus hystrix

''A. variabilis'' was originally based on tooth fragments from the Pennsylvanian of

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

, but the authors who named the genus (St. John and Worthen, 1875) also referred a massive jaw from

Osage County, Kansas Osage County is a county located in the U.S. state of Kansas. Its county seat is Lyndon, and its most populous city is Osage City. As of the 2020 census, the county population was 15,766. The county was originally organized in 1855 as We ...

. The Osage jaw shared some similarities to tooth-whorls from the area, which were later described by Eastman (1902). Eastman concluded that the tooth whorls and jaw belonged to '' Campodus'', so he renamed ''Agassizodus variabilis'' to ''Campodus variabilis''. Other authors disagree, arguing that the Eastman specimens and the Osage jaw represent neither ''Agassizodus'' or ''Campodus'', but rather an entirely new genus.

References

Agassizodontidae Monotypic prehistoric cartilaginous fish genera {{paleo-holocephalan-stub