''Rhizodus'' (root tooth) is an extinct genus of basal, finned

tetrapodomorph The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advance ...

s (the group of

sarcopterygian Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includ ...

s that contains modern

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...

s and their extinct relatives). It belonged to

Rhizodontida Rhizodontida is an extinct group of predatory tetrapodomorphs known from many areas of the world from the Givetian through to the Pennsylvanian - the earliest known species is about 377 million years ago (Mya), the latest around 310 Mya. Rhizodo ...

, one of the earliest-diverging tetrapodomorph clades. Two valid species have been described, both of which lived during the

Early Carboniferous Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * ...

epoch. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''R. hibberti'' is known from the

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follow ...

stage of the United Kingdom, whereas the species ''R. serpukhovensis'' is from the

Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed b ...

of Russia. Some fossils referred to the genus ''Rhizodus'' have also been found in North America.

Description

The most notable characteristics of ''Rhizodus'', compared to other giant rhizodonts such as '' Barameda'', were the two fangs located near the front of its jaws, followed by other teeth scaling downwards in size. ''Rhizodus'' was a giant apex predator that resided in freshwater lakes, river systems and large swamps, with ''R. hibberti'' reaching in length. It fed on small to medium-sized amphibians, using its teeth to kill prey and rip it into digestible sizes, rather than swallowing prey whole like other, smaller-toothed

sarcopterygians Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includin ...

. Fossil skin imprints show that ''Rhizodus'' had large, plate-like scales, similar to those found on modern day

arapaima The arapaima, pirarucu, or paiche is any large species of bonytongue in the genus ''Arapaima'' native to the Amazon and Essequibo basins of South America. ''Arapaima'' is the type genus of the subfamily Arapaiminae within the family Osteoglossi ...

Diet

The diet of ''Rhizodus included medium-sized fish and tetrapods. It has been proposed that ''Rhizodus'' may have lunged at terrestrial, shorebound prey, just like a modern-day crocodile.

References

Rhizodonts Prehistoric lobe-finned fish genera Viséan genera Serpukhovian life Carboniferous United Kingdom Carboniferous North America Fossils of Great Britain Fossils of Russia Fossil taxa described in 1840 Taxa named by Richard Owen {{paleo-lobefinned-fish-stub