Here we've listed the Heterodontosaurians and other basal ornithischians which do not belong to any of the main groups of bird-hipped dinosaurs. ''Heterodontosaurus'', ''Lesothosaurus'', and (less-frequently) ''Scutellosaurus'' are the most common in dino-books; in older works, however, you'll more frequently read the name "''Fabrosaurus''".


'''Boar-Bird:''' ''[[ Heterodontosaurus]]''

Among basal Ornithischian dinosaurs, there were curious things. ''Heterodontosaurus'', for example, might be renamed the [[MixAndMatchCritter boar-bird]].

Living in Early Jurassic South Africa 190 million years ago, ''Heterodontosaurus'' superficially resembled the ornithopod ''Hypsilophodon'' with its slender, bipedal body, but was even smaller (1.20 m/4 ft long), more robust and with longer forelimbs. Discovered only in the sixties, its name means “lizard with different teeth”, and with reason: no other dinosaur had such a diversified dentition, with ''three'' kinds of teeth surprisingly similar to those found in mammals. The most noticeable are two pairs of canine-like “tusks” visible when the mouth closed, giving it a vaguely boar-like look; behind, molar-like teeth to grind up tough vegetation; in front of them, small peg-like teeth only on the tip of its upper jaw.

With this dentition, ''Heterodontosaurus'' was probably a mostly herbivorous omnivore, eating insects other than vegetation, while the tusks could have been used for display and/or competiton. Some scientists suspect only males did have the large canines, but there is no evidence. Other close relatives, like ''[[ Abrictosaurus]]'', are devoid of tusks: their skull could either pertain to females, or, more probably, to totally tusk-less species.

''Heterodontosaurus'' is the prototype of its own ornithischian family, Heterodontosaurids. Once thought ornithopods or ancient relatives of ceratopsians and pachycephalosaurs, now they are regarded as very basal ornithischians. Despite their primitiveness, heterodontosaurs not only flourished in the Early Jurassic, but also managed to survive until the Late Jurassic and even the Early Cretaceous, with species such as the poorly-known ''[[ Echinodon]]'' from England. Even smaller than ''Heterodontosaurus'' and with small tusks only in the upper jaws, ''Echinodon'' is known to science since the middle XIX century, but its classification as a heterodontosaurian has been confirmed only after the discovery of the namesake of the group.

The same thing happened to ''Geranosaurus'' and ''Lycorhinus'', both found in South Africa at the start of the XX century, and both showing prominent tusks (the latter, because of this, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Cynognathus]]''). Also South-African and Early-Jurassic, ''Abrictosaurus'' was found about in the same period of ''Heterodontosaurus''; its name, "awake lizard", is actually ironical, because it was hypothized that this animal underwent long "hibernations" to survive the harsh desertical conditions -- the same hyp was made about another contemporary basal ornithischian, ''Lesothosaurus'' (see below).

Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian Group. For example, ''[[ Fruitadens]]'' lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of ''Microraptor''), ''Fruitadens'' and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered -- if the smallest. But the most extraordinary recent discovery about the "boar-birds" is another: see at the bottom of the page.


'''Size doesn't matter (just for once):''' ''[[ Lesothosaurus]]'' & ''[[ Fabrosaurus]]''

When talking about Ornithischians, we can find the same issues of Saurischians: in the Triassic/Early Jurassic they were all so-similar each other, it’s hard task to classify them accurately. Nonetheless, they are extremely important animals for scientists, no matter their often tiny size. Other than the heterodontosaurians, we have several other examples.

''Lesothosaurus'', ''Scutellosaurus'' and ''Pisanosaurus'' have traditionally been the most relevant. ''Lesothosaurus'' in particular was once considered the forerunner of all bird-hipped dinos, and thought not to belong to any great ornithischian group; [[ScienceMarchesOn recent research]] suggest it could be a very basal Thyreophoran, thus ancestor of Stegosaurs and Ankylosaurs. From Early Jurassic Southern Africa like ''Heterodontosaurus'', its name derives from [[ExactlyWhatItSaysOnTheTin the Kingdom of Lesotho]] (a small South African enclave) where its remains were dug out in 1978. Merely 3 ft long, the bulk of a ''Compsognathus'', ''Lesothosaurus'' seems not to have any specialization in its anatomy. Its mouth had simple teeth and small cheeks, its forelimbs short and five-digited, its hindlimbs apt for running. It was said that ''Lesothosaurus'' resembles a lizard more than any other dinosaur.

Fragmentary remains from the same location that have been named ''Fabrosaurus'' may be synonymous with ''Lesothosaurus''; since they were named before ''Lesothosaurus'', ''Fabrosaurus'' would be the valid name for this dinosaur. Other possible ''Lesothosaurus'' remains have been classified in 2005 in another genus, ''Stormbergia''. In old textbooks, the "fabrosaur" was often shown as the prototypical basal ornithischian; since the 1980s, ''Lesothosaurus'' took over this role; now the recently-discovered ''Eocursor'' (see below) is going to become the new archetypical ur-ornithischian. Once, the "fabrosaurid" family was recognized by scientists as a catch-all grouping for all undetermined basal ornithischians, but modern cladistic science do not accept artificial assemblages like this, and "fabrosaurid" has disappeared in literature.


'''Armor or not-armor?:''' ''[[ Scutellosaurus]]'' & ''[[ Pisanosaurus]]''

''Scutellosaurus'' has traditionally been the most primitive thyreophoran. Discovered only in the 1980s, was also a small bipedal animal with a similar look, but slighty bigger, longer-tailed, more robustly-built than the lesothosaur, and with a light armor made by small bony plates placed in rows upon its torso, similar to that of the bigger ''Scelidosaurus''. Like the scelidosaur, ''Scutellosaurus'' lived in Early Jurassic, but was found in Arizona, where the popular double-crested ''[[StockDinosaurs Dilophosaurus]]'' lived (and could have been that dinosaur's prey).

Also found in the last decades of the XX century, the Argentinian ''Pisanosaurus'' lived with the alleged “first theropods" ''Eoraptor'' and ''Herrerasaurus'', and still remains the most ancient ornithischian known to science. Sadly, is known only from one incomplete fossil, but was arguably similar to ''Lesothosaurus'' in shape and size and with no armor like the latter. One curious thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well: ''[[ Technosaurus]]'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian". Its evocative name comes from the Texas Tech University; interestingly, another basal ornithischian, the European ''[[ Emausaurus]]'' (known only from a skull) also derives its name from an university, the German EMAU. It is usually believed in the middle between ''Scutellosaurus'' and ''Scelidosaurus'', but some think it's a very primitive stegosaurian.

'''Two great little discoveries:''' ''[[ Eocursor]]'' & ''[[ Tianyulong]]''

Like the basal saurischians, basal ornithischians as a whole are known only since the 1960s, and still aren’t well-understood. So, every recent discover could be ''very'' significative. ''Eocursor'' and ''Tianyulong'' in particular, are fairly gaining more and more consideration in scientific field because of their objective importance.

Found in 2007, ''Eocursor'' (“dawn runner”) was discovered in South Africa like ''Heterodontosaurus'' and ''Lesothosaurus'', and its name is cleary inspired from that of ''Eoraptor'' (“dawn robber”). Its relevance is due to the fact that it’s the ''only'' Triassic ornithischian known so far from a complete skeleton (while the ''Pisanosaurus'' one is only partial); this gives us precious information about the deepest ornithischian roots, and also could better explain the relationship between bird-hipped dinosaurs and the saurischians.

According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Cerapods. The former are, as is known, Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus''). Cerapods include almost all the other ornithischians, furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Hypsilophodon'' etc) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera[topsian]” and “[Ornitho]pod”.

About ''Tianyulong'' ([[RhetoricalQuestionBlunder guess which country it comes from]]?): this is a heterodontosaurid from the Late Jurassic found in 2009 in the same Liaoning site from which the Jurassic troodont ''Anchiornis'' was discovered, ''Tianyulong'', like the latter, has preserved some sort of proto-feathers around its body. The thing is, this is the ''first time'' that unequivocally feather-like structures have been found in a non-theropod dinosaur (not counting the quills of ''Psittacosaurus'' of course) see [[UsefulNotes/{{Dinosaurs}} the useful notes about dinosaurs in general]] to understand the revolutionary implications of this discovery.