Rhizodus Temporal range: Visean–Serpukhovian PreꞒ Ꞓ O S D C P T J K Pg N
Fossil tooth of Rhizodus hibberti
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Sarcopterygii
Clade:	Tetrapodomorpha
Class:	†Rhizodontida
Order:	†Rhizodontiformes
Family:	†Rhizodontidae
Genus:	†Rhizodus Owen, 1840
Species
R. hibberti Owen, 1840 (Type) R. serpukhovensis Smirnova, 2022

Rhizodus (root tooth) is an extinct genus of basal, finned tetrapodomorphs (the group of sarcopterygians that contains modern tetrapods and their extinct relatives). It belonged to Rhizodontida, one of the earliest-diverging tetrapodomorph clades. Two valid species have been described, both of which lived during the Early Carboniferous epoch. The type species R. hibberti is known from the Viséan stage of the United Kingdom, whereas the species R. serpukhovensis is from the Serpukhovian of Russia. Some fossils referred to the genus Rhizodus have also been found in North America.^[1][2]

Description

The most notable characteristics of Rhizodus, compared to other giant rhizodonts such as Barameda, were the two 22-centimetre (8.7 in) fangs located near the front of its jaws,^[3] 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 measuring 5.14–5.63 metres (16.9–18.5 ft) long^[4] and weighing 1–1.5 metric tons (1.1–1.7 short tons).^[5] 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.^[6]

Fossil skin imprints show that Rhizodus had large, plate-like scales, similar to those found on modern day arapaima.^[7]

Diet

The diet of Rhizodus' included medium-sized fish and tetrapods. It has been proposed that Rhizodus lunged at terrestrial, shorebound prey, just like a modern-day crocodile.^[7]