Paranthodon (/pəˈrænθədɒn/ pə-RAN-thə-don[5]) is a genus of stegosaurian dinosaur that lived in what is now South Africa during the Early Cretaceous, between 139 and 131 million years ago.

After remaining untouched for years in the British Museum of Natural History, the partial skull was identified by South African paleontologist Robert Broom as belonging to a different genus; he named the specimen Palaeoscincus africanus.

In identifying the remains as those of Palaeoscincus, Broom initially classified Paranthodon as an ankylosaurian, a statement backed by the research of Coombs in the 1970s.

In 1845, amateur geologists William Guybon Atherstone and Andrew Geddes Bain discovered several fossils near Dassieklip, Cape Province, in the Bushman's River Valley.

[7][1] In 1929, Franz Nopcsa, unaware of Broom's previous publication, provided a second novel name as D. M. S. Watson believed that the jaw should be differentiated from Anthodon.

[7][10] The holotype of Paranthodon, BMNH 47338, was found in a layer of the Kirkwood Formation that has been dated between the Berriasian and early Valanginian ages.

One additional specimen was assigned to it based on the dentition, BMNH (now NHMUK) R4992, including only isolated teeth sharing the same morphology as those from the holotype.

[4] The Mugher Mudstone of Ethiopia was screened in the 1990s by the University of California Museum of Paleontology, and in it were discovered multiple dinosaur teeth, pertaining to many groups of taxa.

Stegosaurus was the only stegosaurid known from adequate cranial material to compare with Paranthodon during the 1981 review of the taxon, and even though their resemblance is great, tooth morphology is very distinguishing among the stegosaurians.

This is similar to in Miragaia, Huayangosaurus, the ankylosaur Silvisaurus, and Heterodontosaurus, but unlike in Chungkingosaurus, Stegosaurus, Edmontonia and Lesothosaurus.

Also, like Huayangosaurus, but unlike Kentrosaurus and Stegosaurus, Paranthodon possesses a prominent buccal margination (a ridge beside the tooth row).

Initially, when Broom assigned the name Palaeoscincus africanus to the Paranthodon fossils, he classified them as an ankylosaurian.

Coombs (1978) did not follow Nopcsa's classification, keeping Paranthodon as an ankylosaurian, like Broom, although he only classified it as Ankylosauria incertae sedis.

[19] A subsequent review by Galton and Coombs in 1981 instead confirmed Nopcsa's interpretation, redescribing Paranthodon as a stegosaurid from the Lower Cretaceous.

[11] Not all of these features were considered valid in a 2008 review of Stegosauria, with the only autapomorphy found being the possession of a partial second bony palate on the maxilla.

A 2010 analysis including nearly all species of stegosaurians found that Paranthodon was outside Stegosauridae, and in a polytomy with Tuojiangosaurus, Huayangosaurus, Chungkingosaurus, Jiangjunosaurus, and Gigantspinosaurus.

All taxa were remained included, and Paranthodon grouped with Tuojiangosaurus, Huayangosaurus and Chunkingosaurus as the most basal true stegosaurians.

[21] Lesothosaurus diagnosticus Laquintasaura venezuelae Scutellosaurus lawleri Emausaurus ernsti Scelidosaurus harrisonii Alcovasaurus longispinus Sauropelta edwardsi Gastonia burgei Euoplocephalus tutus Huayangosaurus taibaii Chungkingosaurus jiangbeiensis Tuojiangosaurus multispinus Paranthodon africanus Jiangjunosaurus junggarensis Gigantspinosaurus sichuanensis Kentrosaurus aethiopicus Dacentrurus armatus Loricatosaurus priscus Hesperosaurus mjosi Miragaia longicollum Stegosaurus stenops Stegosaurus homheni Other analyses have found Paranthodon closely related to Tuojiangosaurus, Loricatosaurus, and Kentrosaurus within Stegosaurinae.

[20] The Kirkwood Formation is in South Africa, and many fossils of different species and genera have been discovered in it, with Paranthodon being the first uncovered.

A large amount of the material of the Kirkwood formation only includes isolated teeth or partial and fragmentary pieces of bone.

Dinosaurs of the formation include a basal tetanuran, the primitive ornithomimosaurian Nqwebasaurus, the sauropod Algoasaurus, a potential titanosaurian, many ornithischians, a genus of ornithopod Iyuku, and a "hypsilophodontid" (the family Hypsilophodontidae is no longer considered to be a natural grouping[26]).

[23][27] Multiple additional sauropod taxa have been discovered, including a basal eusauropod, a brachiosaurid, a dicraeosaurid and a derived diplodocid.