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]

Temporal range: ViseanSerpukhovian
Rhizodus hibberti.JPG
Fossil tooth of Rhizodus hibberti
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Order: Rhizodontida
Family: Rhizodontidae
Genus: Rhizodus
Owen, 1840
  • R. hibberti Owen, 1840 (Type)
  • R. serpukhovensis Smirnova, 2022


Restoration of R. hibberti

The most notable characteristics of Rhizodus, compared to other giant rhizodonts such as Barameda, were the two 22 centimetres (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 reaching 7 metres (23 ft) in length.[4] 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.[5]

Fossil skin imprints show that Rhizodus had large, plate-like scales, similar to those found on modern day arapaima.[6]


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.[6]


  1. ^ Smirnova, A. Y. (2022). "A new species of rhizodontiform sarcopterygian fish (Sarcopterygii: Rhizodontiformes) from the Lower Carboniferous of the Moscow Region". Paleontological Journal. 56 (4): 431–440. doi:10.1134/S0031030122040128.
  2. ^ Jeffery, J. E. (2012). "Cranial morphology of the Carboniferous rhizodontid Screbinodus ornatus (Osteichthyes: Sarcopterygii)". Journal of Systematic Palaeontology. 10 (3): 475–519. doi:10.1080/14772019.2011.595961. S2CID 84810001.
  3. ^ "Rhizodus hibberti". www.europeana.eu. Archived from the original on 2014-11-29.
  4. ^ Jeffery, J.E. (2003). "Mandibles of rhizodontids: anatomy, function andevolution within the tetrapod stem-group". Transactions of the Royal Society of Edinburgh: Earth Sciences. 93 (3): 255–276. doi:10.1017/S0263593300000432. S2CID 129517553.
  5. ^ http://www.twmuseums.org.uk/geofinder/search/item.php?record=NEWHM:2004.H206 at the Wayback Machine (archived 2014-11-29)
  6. ^ a b "3.4 Rhizodus". www.ucl.ac.uk. Retrieved 29 April 2019.