Stegosaurs have always been one of the dinosaur groups with very few species described (the same cannot be said of their relatives the ankylosaurs). This explains the shortness of this page despite the fame of the stegosaurs.
Note that all the examples below are found outside North America; indeed, only one kind of stegosaur is known definitively to come from this landmass, the ever-popular Stegosaurus. Another North American genus was described in the 2000s, the round-plated Hesperosaurus ("western lizard"), but it could be another Stegosaurus species. A third genus, "Diracodon", was named during the Bone Wars, but now is regarded as an invalid synonym of Stegosaurus.
Among non-Stegosaurus stegosaurs, you will see Tuojiangosaurus and Kentrosaurus more often than others, but you could also see Dacentrurus, Huayangosaurus, Wuerhosaurus, Lexovisaurus, Gigantspinosaurus, Miragaia, and others, as well as getting the occasional mention of "Dravidosaurus".
Bigger than Stegosaurus?: Dacentrurus
- Dacentrurus armatus was first described in the mid 1800s by Richard Owen with the now-invalid name "Omosaurus", before Stegosaurus itself was discovered in the USA: it was indeed the very first stegosaur discovered by science, but was put in the Stegosauria only after the description in North America of the genus Stegosaurus. Unfortunately, the dacentrurus is known from incomplete remains, so its appearance and even its size are uncertain. Illustrations usually show it with a kentrosaur-like armor (with or without shoulder-spikes). Some however suspect Dacentrurus was a very large animal, maybe even bigger than Stegosaurus itself, which is usually considered the largest stegosaur; but we need more fossils to prove it true.
- Three similar-looking stegosaurs are known from Middle Jurassic Europe. Both Dacentrurus ("tail full of points") described above, and Lexovisaurus (named from an ancient Celtic people) are found in several European countries: England, France, and Portugal. Lexovisaurus durobrivensis was named in the 20th century. Sadly, Lexovisaurus too is known from scanty remains. Illustrations usually show it with the same kentrosaur-like look of Dacentrurus, even though the lexovisaur sometimes appears with a more tuojiangosaur-like look. Recently, many alleged "Lexovisaurus" remains have been reclassified in another genus, Loricatosaurus ("armored lizard"), almost-identical to the former. But in 2009, a brand new stegosaur was excavated in Portugal: the quite simple-named but very peculiar Miragaia. Late Jurassic like Stegosaurus, Kentrosaurus & Tuojiangosaurus, it was medium-sized for a stegosaur, and with its small but abundant plates and unusually long neck, it looks a bit like Dinny from Alley Oop. Its full scientifical name is Miragaia longicollis, the latter term meaning "long necked" indeed. Miragaia suddenly increased the diversity of the small taxonomic group of the stegosaurs: before its discover all stegos were believed to have had the same short-necked shape of Stegosaurus. Miragaia has already appeared in one TV documentary, and its unusual look could even make it interesting for pop-cultural producers, either.
- The People's Republic of China has given us about half the steggies around the world. Chialingosaurus was the first discovered, in 1940s: Late Jurassic, it was similar to Kentrosaurus and more slender than other stegosaurs. The others have been found since the 1970s: other than Tuojiangosaurus there are the Middle Jurassic Huayangosaurus; the small Chungkingosaurus (Late Jurassic); Jiangjunosaurus, which was found in the western region of Xinjiang; Monkonosaurus, found in Tibet; the Middle Cretaceous Wuerhosaurus; and Yingshanosaurus, with flattened shoulder-spikes. A find from the 1990s has received a more obvious name: Gigantspinosaurus (it was not a cross between a ''Giganotosaurus'' and a ''Spinosaurus''!) Kentrosaurus-sized, thus small for stegosaur standards, it had small plates oddily only on its back (not on its tail) and an uncospicuous thagomizer: both features vividly contrast with its truly gigantic spines on its shoulders: thick, curved, and each as long as the whole trunk! Like Miragaia above, Gigantspinosaurus has notably increased the variety of the stegosaur world thanks to its look, and its colossal shoulder-spikes could even make it interesting for the broader pop-culture.
- Huayangosaurus is particolarly notable among stegosaurians in general, because is the most primitive stegosaur known from good fossil material. note It was small, 4 m long, and preserved several ancestral traits in its skeleton, such as a big head, small frontal teeth on its upper jaw, and long forelimbs. The frontal upper teeth is a typical primitive trait among ornithischians, which were lost in more evolved stegosaurs. The huayangosaur's armor, however, was already fully stegosaurian, rather similar to Tuojiangosaurus with a true thagomizer, and also with shoulder spikes like Kentrosaurus. Because of their primitiveness, Huayangosaurus and few others, like Chungkingosaurus and the little-known Craterosaurus and Regnosaurus, both from Early Cretaceous England, make a family on their own, Huayangosaurids, while most other stegosaurs make together the more evolved Stegosaurids. At the other extremity, Wuerhosaurus was one of the latest-surviving stegosaurs, and the most known among the Cretaceous stegosaurs in spite of being scantier than several Jurassic relatives. Almost as large as a Stegosaurus, it had the same alternate plates and four-spiked tail, but has traditionally been depicted with wery low, rectangular plates instead of pentagonal. According to recent research its plates could have been taller and more Stegosaurus-like than formerly thought. We don't know if it had shoulder spikes or not, but flat bony skin-scutes are known from fossils.
Under The Sea: Dravidosaurus
- Definitive stegosaurs appeared in the Middle Jurassic: ex. Huayangosaurus, Dacentrurus, Lexovisaurus. They reached their heyday in the Late Jurassic with genera such as Stegosaurus, Tuojiangosaurus, Kentrosaurus, Chialingosaurus, Gigantspinosaurus, Miragaia, and several others. However, they began to decline in Early Cretaceous, perhaps due to competition from the more armored ankylosaurs, yet there were still a few holdouts such as Wuerhosaurus and the african Paranthodon. However, there was a stegosaur which, uniquely, survived until the Late Cretaceous: Dravidosaurus. Discovered in 1979, it's one of the few dinosaurs (and the only stegosaur) found in Indian subcontinent note , a huge separate landmass in the Late Mesozoic. Dravidosaurus, whose name could be translated to "lizard of Southern India", somehow managed to arrive there, and flourished thanks to the absence of competition which other relatives faced in the mainland. Its status as "the last stegosaur" gave it several mentions in books and even some documentaries, which usually showed it like an undersized "Stegosaurus" (it was believed one of the smallest stegosaurs ever). However, all this was shown to be false. In 1996, a re-examination of its extremely fragmentary remains has revealed our Last Stegosaur to be 1. not a stegosaur, 2. not a dinosaur, and 3. not even a land-dweller. It was a marine reptile, more precisely a plesiosaur.