History UsefulNotes / PrehistoricLifePrimitiveOrnithischians

* Heterodontosaurians were originally thought ornithopods, then ancient relatives of ceratopsians and pachycephalosaurs; today they are generally 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: English ''Echinodon'' lived alongside ''Iguanodon'' and ''Hypsilophodon''! Half the length of ''Heterodontosaurus tucki'' and with small tusks only in the upper jaws, ''Echinodon'' ("hedgehog tooth") 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 (it was also briefly believed a ''Scutellosaurus'' relative in the nineties). Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian group. For example, ''Fruitadens'' ("Fruita's tooth" from the geological formation that preserved it) lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to the "younger" ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Microraptor]]''), ''Fruitadens'' is currently the smallest known North American dinosaur; it and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered, only equalled by some marginocephalians (ceratopsians & pachycephalosaurs) like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Microceratus]]'' and ''[[UsefulNotes/PrehistoricLifePachycephalosaurs Wannanosaurus]]'', and some "hypsilophodont" ornithopods.

* Also South-African and Early-Jurassic, ''Abrictosaurus'' and ''Lanasaurus'' (the latter often synonimized with ''Lycorhinus'' below) were found about in the same time of ''Heterodontosaurus''; the former's name, "awake lizard", is actually ironical, because it was hypothized that ''Abrictosaurus'' underwent "hibernations" (just like what has been proposed for ''Lesothosaurus'', but again, this is not demonstrated). Curiously for a heterodontosaur, ''Abrictosaurus'' was believed totally tusk-less (it actually had four tiny "tusks", but much smaller than the ones of ''Heterodontosaurus''), and because of this was once believed a possible female ''Heterodontosaurus'' -- this originated from a confrontation with the modern musk-deers, whose males only bear long tusks visible when the mouth is closed. ''Geranosaurus'' ("crane lizard") and ''Lycorhinus'' ("wolf nose") were both found in South Africa at the start of the XX century, and were originally not classified as heterodontosaurs because ''Heterodontosaurus'' was not known yet: ''Lycorhinus'', with its typically heterodontosaurian mammal-like dentition, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/StockDinosaursNonDinosaurs Cynognathus]]''.

* One significative thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well (often put in the "fabrosaurid" assemblage): ''Technosaurus'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian"; other two examples are ''Revueltosaurus'' (actually related with the pseodosuchians named [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles aetosaurs]]) and chinese ''Dianchungosaurus'' (the latter was believed a heterodontosaur and was also informally called "Tianchungosaurus"). The evocative name ''Technosaurus'' comes from the Texas Tech University; interestingly, a true basal ornithischian, the European ''[[http://en.wikipedia.org/wiki/Emausaurus 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. Other three animals are usually considered closer to ''Scelidosaurus'' than to ''Scutellosaurus'': Portuguese ''Lusitanosaurus'' ("lizard from Portugal") and Chinese ''Bienosaurus'' and ''Tatisaurus''.

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Neornithischians. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Neornithischians include almost all the other ornithischians. Apart from some basal form, all neornithischians ("new ornithischians") belonged to the group named Cerapods. The latter were furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Recently the belonging of ''Hypsilophodon'' in the Ornithopod group has been called into question: ''Hypsilophodon'' seems a basal Neornithischian, and not still a proper Cerapod. While the heterodontosaurians probably were even more archaic, having evolved before the split between Thyreophorans and Neornithischians.

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Neornithischians. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Neornithischians include almost all the other ornithischians. Apart from some basal form, all neornithischians ("new ornithischians") belonged to the group named Cerapods. The latter were furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Rcently the belonging of ''Hypsilophodon'' in the Ornithopod group has been called into question: ''Hypsilophodon'' seems a basal Neornithischian, and not still a proper Cerapod. While the heterodontosaurians probably were even more archaic, having evolved before the split Thyreophorans/Neornithischians.

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Neornithischians. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Neornithischians include almost all the other ornithischians. Apart from some basal form, all neornithischians ("new ornithischians") belonged to the group named Cerapods. The latter were furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Heterodontosaurians were once believed Ornithopods, or at least Cerapods, but are of uncertain placement in the ornithischian evolutive tree. Recently even the belonging of ''Hypsilophodon'' in the Ornithopod and even in the Cerapod group has been called into question: it seems a basal Neornithischian, while heterodontosaurus probably were even more basal and outside the group.

'''The Ornithischian Roots:''' the [[http://en.wikipedia.org/wiki/Neornithischia Neornithischians]]

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Neornithischians. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Neornithischians include almost all the other ornithischians. Apart from some basal form, all neornithischians ("new ornithischians") belonged to the group named Cerapods. The latter were furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Heterodontosaurians were once believed Ornithopods, or at least Cerapods, but are of uncertain placement in the ornithischian evolutive tree. Recently even the belonging of ''Hypsilophodon'' in the Ornithopod and even in the Cerapod group has been called into question.

'''The Ornithischian Roots'''

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Cerapods. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scelidosaurus'', ''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Cerapods include almost all the other ornithischians, furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Heterodontosaurians were once believed Ornithopods, or at least Cerapods, but are of uncertain placement in the ornithischian evolutive tree. Recently even the belonging of ''Hypsilophodon'' in the Ornithopod and even in the Cerapod group has been called into question.

[[/folder]]

* Heterodontosaurians were originally thought ornithopods, then ancient relatives of ceratopsians and pachycephalosaurs; today they are generally 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: English ''Echinodon'' lived alongside ''Iguanodon'' and ''Hypsilophodon''! Half the length of ''Heterodontosaurus tucki'' and with small tusks only in the upper jaws, ''Echinodon'' ("hedgehog tooth") 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 (it was also briefly believed a ''Scutellosaurus'' relative in the nineties). Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian group. For example, ''Fruitadens'' ("Fruita's tooth" from the geological formation that preserved it) lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to the "younger" ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Microraptor]]''), ''Fruitadens'' is currently the smallest known North American dinosaur; it and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered, only equalled by some marginocephalians (ceratopsians & pachycephalosaurs) like ''[[UsefulNotes/PrehistoricLifeCeratopsidPredecessors Microceratus]]'' and ''[[UsefulNotes/PrehistoricLifePachycephalosaurs Wannanosaurus]]'', and some "hypsilophodont" ornithopods.

Here we've listed those basal ornithischians which do not belong to any of the main groups of bird-hipped dinosaurs. ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Scelidosaurus]]'',[[note]]According to recent cladistic researches it could be a very primitive ankylosaurian.[[/note]] ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Heterodontosaurus]]'' (its skull is portrayed in the image), ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Lesothosaurus]]'', and (less-frequent) ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Scutellosaurus]]'' are the most common in dino-books; in older works you'll frequently also read the name "''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Fabrosaurus]]''".

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Cerapods. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). Cerapods include almost all the other ornithischians, furthermorely divided in Ornithopods (duckbills, ''Iguanodon'', ''Camptosaurus'' etc.) and Marginocephalians (ceratopsians+pachycephalosaurs). Indeed, Cerapods is just a {{Portmanteau}} made of “Cera(topsian)” and “(Ornitho)pod”. Heterodontosaurians were once believed Ornithopods, or at least Cerapods, but are of uncertain placement in the ornithischian evolutive tree. Recently even the belonging of ''Hypsilophodon'' in the Ornithopod and even in the Cerapod group has been called into question.

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Cerapods. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). 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”. Heterodontosaurians were once believed Ornithopods, or at least Cerapods, but are of uncertain placement in the ornithischian evolutive tree.

* Found in the last decades of the XX century, the Argentinian ''Pisanosaurus mertii'' lived in the Middle Triassic (well before ''Coelophysis'' and ''Plateosaurus'') and shared its habitat with the alleged “first theropods" ''Herrerasaurus'' & ''Eoraptor'' and many [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles non-dinosaur reptiles]] such as rhynchosaurs, "thecodonts", and mammal-ancestors (all these were much more common at the time than dinosaurs, never forget this). The pisanosaur was believed the most ancient ornithischian known to science, but sadly, is known only from one incomplete fossil, and now is considered only a dinosaur-like archosaur. It was arguably similar to ''Lesothosaurus'' in shape and size, and with no armor like the latter.

* One significative thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well (often put in the "fabrosaurid" assemblage): ''Technosaurus'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian"; other two examples are ''Revueltosaurus'' (actually related with the pseodosuchians named [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles aetosaurs]]) and chinese ''Dianchungosaurus'' (the latter was believed a heterodontosaur and was also called "Tianchungosaurus"). The evocative name ''Technosaurus'' comes from the Texas Tech University; interestingly, a true basal ornithischian, the European ''[[http://en.wikipedia.org/wiki/Emausaurus 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. Other three animals are usually considered closer to ''Scelidosaurus'' than to ''Scutellosaurus'': Portuguese ''Lusitanosaurus'' ("lizard from Portugal") and Chinese ''Bienosaurus'' and ''Tatisaurus''.

* Like the basal saurischians, basal ornithischians as a whole are mostly known only since the 1960s -- not counting ''Scelidosaurus'', which has been known since the XIX century but has recently re-classified as an extremely basal ankylosaurian -- and still aren’t well-understood. So, every recent discover could be ''very'' significative. ''Eocursor'' and ''Tianyulong'' in particular, have fairly gained much consideration in scientific field because of their objective importance. Found in 2007, ''Eocursor parvus'' (“small dawn-runner”) was discovered in South Africa like ''Heterodontosaurus'' and ''Lesothosaurus'', and its name recalls that of the famous ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Eoraptor]]'' (“dawn robber”). Its relevance is due to the fact that it was initially believed the ''only'' Triassic ornithischian known so far from a complete skeleton (while the remain of the even earlier ''Pisanosaurus'' is only partial, and probably not dinosaurian); today ''Eocursor'' is usually considered Early Jurassic like ''Lesothosaurus'', but its completeness gives equally to us precious information about the deepest ornithischian roots, and also could better explain the relationship between bird-hipped dinosaurs and the saurischians. Found even more recently, in year 2014, ''[[http://en.wikipedia.org/wiki/Kulindadromeus Kulindadromeus]]'' ("Kulinda's runner") from Russia was also a very basal Jurassic ornithischian, with tracks of proto-feathers left.

* According to the most accepted classification, ornithischians are divided in two main lineages: Thyreophorans and Cerapods. The former are Stegosaurs+Ankylosaurs+some basal forms (''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). 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”.

* Also South-African and Early-Jurassic, ''Abrictosaurus'' and ''Lanasaurus'' (the latter often synonimized with ''Lycorhinus'' below) were found about in the same time of ''Heterodontosaurus''; the former's name, "awake lizard", is actually ironical, because it was hypothized that ''Abrictosaurus'' underwent "hibernations" (just like what has been proposed for ''Lesothosaurus'', but again, this is not demonstrated). Curiously for a heterodontosaur, ''Abrictosaurus'' was believed totally tusk-less (it actually had four tiny "tusks", but much smaller than the ones of ''Heterodontosaurus''), and because of this was once believed a possible female ''Heterodontosaurus'' (this originated from a confrontation with the modern musk-deers, whose males only bear long tusks visible when the mouth is closed). ''Geranosaurus'' ("crane lizard") and ''Lycorhinus'' ("wolf nose") were both found in South Africa at the start of the XX century, and were originally not classified as heterodontosaurs because ''Heterodontosaurus'' was not known yet: ''Lycorhinus'', with its typically heterodontosaurian mammal-like dentition, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/StockDinosaursNonDinosaurs Cynognathus]]''.

* Also South-African and Early-Jurassic, ''Abrictosaurus'' and ''Lanasaurus'' (the latter often synonimized with ''Lycorhinus'' below) were found about in the same time of ''Heterodontosaurus''; the former's name, "awake lizard", is actually ironical, because it was hypothized that ''Abrictosaurus'' underwent "hibernations" (just like what has been proposed for ''Lesothosaurus'', but again, this is not demonstrated). Curiously for a heterodontosaur, ''Abrictosaurus'' was totally tusk-less, and because of this was once believed a possible female ''Heterodontosaurus'' (this originated from a confrontation with the modern musk-deers, whose males only bear tusks). ''Geranosaurus'' ("crane lizard") and ''Lycorhinus'' ("wolf nose") were both found in South Africa at the start of the XX century, and were originally not classified as heterodontosaurs because ''Heterodontosaurus'' was not known yet: ''Lycorhinus'', with its typically heterodontosaurian mammal-like dentition, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/StockDinosaursNonDinosaurs Cynognathus]]''.

* One significative thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well (often put in the "fabrosaurid" assemblage): ''Technosaurus'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian"; other two examples are ''Revueltosaurus'' and chinese ''Dianchungosaurus'' (the latter was believed a heterodontosaur). The evocative name ''Technosaurus'' comes from the Texas Tech University; interestingly, a true basal ornithischian, the European ''[[http://en.wikipedia.org/wiki/Emausaurus 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. Other three animals are usually considered closer to ''Scelidosaurus'' than to ''Scutellosaurus'': Portuguese ''Lusitanosaurus'' ("lizard from Portugal") and Chinese ''Bienosaurus'' and ''Tatisaurus''.

* Like the basal saurischians, basal ornithischians as a whole are mostly known only since the 1960s -- not counting ''Scelidosaurus'', which has been known since the XIX century but has recently re-classified as an extremely basal ankylosaurian -- and still aren’t well-understood. So, every recent discover could be ''very'' significative. ''Eocursor'' and ''Tianyulong'' in particular, have fairly gained much consideration in scientific field because of their objective importance. Found in 2007, ''Eocursor parvus'' (“small dawn-runner”) was discovered in South Africa like ''Heterodontosaurus'' and ''Lesothosaurus'', and its name recalls that of the famous ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Eoraptor]]'' (“dawn robber”). Its relevance is due to the fact that it was initially believed the ''only'' Triassic ornithischian known so far from a complete skeleton (while the remain of the even earlier ''Pisanosaurus'' is only partial, and probably not dinosaurian); today ''Eocursor'' is usually considered Early Jurassic like ''Lesothosaurus'', but its completeness gives equally to us precious information about the deepest ornithischian roots, and also could better explain the relationship between bird-hipped dinosaurs and the saurischians. Found even more recently, in year 2014, ''[[http://en.wikipedia.org/wiki/Kulindadromeus Kulindadromeus]]'' ("Kulinda's runner") from Russia was also a very basal ornithopod like ''Eocursor'', with tracks of proto-feathers left.

* Found in the last decades of the XX century, the Argentinian ''Pisanosaurus mertii'' lived in the Middle Triassic (well before ''Coelophysis'' and ''Plateosaurus'') and shared its habitat with the alleged “first theropods" ''Herrerasaurus'' & ''Eoraptor'' and many [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles non-dinosaur reptiles]] such as rhynchosaurs, "thecodonts", and mammal-ancestors (all these were much more common at the time than dinosaurs, never forget this). The pisanosaur still remains the most ancient ornithischian known to science, but sadly, is known only from one incomplete fossil. It was arguably similar to ''Lesothosaurus'' in shape and size, and with no armor like the latter.

* One significative thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well (often put in the "fabrosaurid" assemblage): ''Technosaurus'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian"; other two examples are ''Revueltosaurus'' and chinese ''Dianchungosaurus'' (the latter was believed a heterodontosaur). The evocative name ''Technosaurus'' comes from the Texas Tech University; interestingly, another basal ornithischian, the European ''[[http://en.wikipedia.org/wiki/Emausaurus 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. Other three animals are usually considered closer to ''Scelidosaurus'' than to ''Scutellosaurus'': Portuguese ''Lusitanosaurus'' ("lizard from Portugal") and Chinese ''Bienosaurus'' and ''Tatisaurus''.

* Like the basal saurischians, basal ornithischians as a whole are mostly known only since the 1960s -- not counting ''Scelidosaurus'', which has been known since the XIX century but has recently re-classified as an extremely basal ankylosaurian -- and still aren’t well-understood. So, every recent discover could be ''very'' significative. ''Eocursor'' and ''Tianyulong'' in particular, have fairly gained much consideration in scientific field because of their objective importance. Found in 2007, ''Eocursor parvus'' (“small dawn-runner”) was discovered in South Africa like ''Heterodontosaurus'' and ''Lesothosaurus'', and its name recalls that of the famous ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs 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 remain of the even earlier ''Pisanosaurus'' 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. Found even more recently, in year 2014, ''[[http://en.wikipedia.org/wiki/Kulindadromeus Kulindadromeus]]'' ("Kulinda's runner") from Russia was also a very basal ornithopod like ''Eocursor'', with tracks of proto-feathers left.

* ''Tianyulong [[Creator/{{Confucius}} confuciusi]]'' is a heterodontosaurid, believed closer to ''Fruitadens'' than to ''Heterodontosaurus''. From the Late Jurassic, it was first found in 2009 in the same Liaoning site from which the Jurassic near-bird ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods Anchiornis]]'' was discovered. Another specimen was discovered in 2012 in the same formation. ''Tianyulong'' had four tusks like ''Heterodontosaurus'' but was slightly smaller. Like ''Anchiornis'', it 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'' found in 2001). See [[UsefulNotes/{{Dinosaurs}} the useful notes about dinosaurs in general]] to understand the revolutionary implications of this discovery.

* ''Tianyulong [[Creator/{{Confucius}} confuciusi]]'' is a heterodontosaurid believed more similar to ''Fruitadens'' or ''Echinodon'' than to ''Heterodontosaurus'' or ''Abrictosaurus''. From the Late Jurassic, it was found in 2009 in the same Liaoning site from which the Jurassic near-bird ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods 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'' found in 2001). See [[UsefulNotes/{{Dinosaurs}} the useful notes about dinosaurs in general]] to understand the revolutionary implications of this discovery.

* Heterodontosaurians were originally thought ornithopods, then ancient relatives of ceratopsians and pachycephalosaurs; today they are generally 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: English ''Echinodon'' lived alongside ''Iguanodon'' and ''Hypsilophodon''! Half the length of ''Heterodontosaurus tucki'' and with small tusks only in the upper jaws, ''Echinodon'' ("hedgehog tooth") 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 (it was also briefly believed a ''Scutellosaurus'' relative in the nineties). Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian group. For example, ''Fruitadens'' ("Fruita's tooth" from the geological formation that preserved it) lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to the "younger" ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Microraptor]]''), ''Fruitadens'' is currently the smallest known North American dinosaur; it and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered, only equalled by some marginocephalians (ceratopsians & pachycephalosaurs) like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Microceratus]]'' and ''[[UsefulNotes/PrehistoricLifePachycephalosaurs Wannanosaurus]]'', and some "hypsilophodont" ornithopods.

* ''Tianyulong [[Creator/{{Confucius}} confuciusi]]'' is a heterodontosaurid from the Late Jurassic found in 2009 in the same Liaoning site from which the Jurassic near-bird ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods 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'' found in 2001). See [[UsefulNotes/{{Dinosaurs}} the useful notes about dinosaurs in general]] to understand the revolutionary implications of this discovery.

* Heterodontosaurians were originally thought ornithopods, then ancient relatives of ceratopsians and pachycephalosaurs; today they are generally 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: English ''Echinodon'' lived alongside ''Iguanodon'' and ''Hypsilophodon''! Half the length of ''Heterodontosaurus tucki'' and with small tusks only in the upper jaws, ''Echinodon'' ("hedgehog tooth") 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 (it was also briefly believed a ''Scutellosaurus'' relative in the nineties). ''Geranosaurus'' ("crane lizard") and ''Lycorhinus'' ("wolf nose") were both found in South Africa at the start of the XX century, and also were originally not classified as heterodontosaurs because ''Heterodontosaurus'' was not known yet: ''Lycorhinus'', with its typically heterodontosaurian mammal-like dentition, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/StockDinosaursNonDinosaurs Cynognathus]]''.

* Also South-African and Early-Jurassic, ''Abrictosaurus'' and ''Lanasaurus'' (the latter often synonimized with ''Lycorhinus'') were found about in the same time of ''Heterodontosaurus''; the former's name, "awake lizard", is actually ironical, because it was hypothized that ''Abrictosaurus'' underwent "hibernations" (just like what has been proposed for ''Lesothosaurus'', but again, this is not demonstrated). Curiously for a heterodontosaur, ''Abrictosaurus'' was totally tusk-less, and because of this was once believed a possible female ''Heterodontosaurus'' (this originated from a confrontation with the modern musk-deers, whose males only bear tusks). Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian group. For example, ''Fruitadens'' ("Fruita's tooth" from the geological formation that preserved it) lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to the "younger" ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Microraptor]]''), ''Fruitadens'' is currently the smallest known North American dinosaur; it and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered, only equalled by some marginocephalians (ceratopsians & pachycephalosaurs) like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Microceratus]]'' and ''[[UsefulNotes/PrehistoricLifePachycephalosaurs Wannanosaurus]]'', and some "hypsilophodont" ornithopods.

* Like the basal saurischians, basal ornithischians as a whole are mostly known only since the 1960s -- not counting ''Scelidosaurus'', which has been known since the XIX century but has recently re-classified as an extremely basal ankylosaurian -- and still aren’t well-understood. So, every recent discover could be ''very'' significative. ''Eocursor'' and ''Tianyulong'' in particular, have fairly gained much consideration in scientific field because of their objective importance. Found in 2007, ''Eocursor parvus'' (“small dawn-runner”) was discovered in South Africa like ''Heterodontosaurus'' and ''Lesothosaurus'', and its name recalls that of the famous ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs 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 remain of the even earlier ''Pisanosaurus'' 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 Stegosaurs+Ankylosaurs+some basal forms (''Scutellosaurus'', ''Emausaurus'', and maybe ''Lesothosaurus''). 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”.

* Found even more recently, in year 2014, ''[[http://en.wikipedia.org/wiki/Kulindadromeus Kulindadromeus]]'' ("Kulinda's runner") from Russia was also a very basal ornithopod like ''Eocursor'', with tracks of proto-feathers left. About ''Tianyulong [[Creator/{{Confucius}} confuciusi]]'': this is a heterodontosaurid from the Late Jurassic found in 2009 in the same Liaoning site from which the Jurassic near-bird ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods 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'' found in 2001). See [[UsefulNotes/{{Dinosaurs}} the useful notes about dinosaurs in general]] to understand the revolutionary implications of this discovery.

'''The Tuskless: ''[[http://en.wikipedia.org/wiki/Abrictosaurus Abrictosaurus]]''

* Heterodontosaurians were originally thought ornithopods, then ancient relatives of ceratopsians and pachycephalosaurs; today they are generally 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: English ''Echinodon'' lived alongside ''Iguanodon'' and ''Hypsilophodon''! Half the length of ''Heterodontosaurus tucki'' and with small tusks only in the upper jaws, ''Echinodon'' ("hedgehog tooth") 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 (it was also briefly believed a ''Scutellosaurus'' relative in the nineties). ''Geranosaurus'' ("crane lizard") and ''Lycorhinus'' ("wolf nose") were both found in South Africa at the start of the XX century, and also were originally not classified as heterodontosaurs because ''Heterodontosaurus'' was not known yet: ''Lycorhinus'', with its typically heterodontosaurian mammal-like dentition, was initially believed a non-dinosaurian therapsid like ''[[UsefulNotes/StockDinosaursNonDinosaurs Cynognathus]]''. Also South-African and Early-Jurassic, ''[[http://en.wikipedia.org/wiki/Abrictosaurus Abrictosaurus]]'' and ''Lanasaurus'' (the latter often synonimized with ''Lycorhinus'') were found about in the same time of ''Heterodontosaurus''; the former's name, "awake lizard", is actually ironical, because it was hypothized that ''Abrictosaurus'' underwent "hibernations" (just like what has been proposed for ''Lesothosaurus'', but again, this is not demonstrated). Curiously for a heterodontosaur, ''Abrictosaurus'' was totally tusk-less, and because of this was once believed a possible female ''Heterodontosaurus'' (this originated from a confrontation with the modern musk-deers, whose males only bear tusks). Some important dinosaur discoveries that have been made since the 2009 regard the heterodontosaurian group. For example, ''Fruitadens'' ("Fruita's tooth" from the geological formation that preserved it) lived in the Late Jurassic North America alongside the famous jurassic StockDinosaurs; in opposite to the "younger" ''Echinodon'', ''Fruitadens'' has tusks only in its lower jaw. With only two feet of length (the same size of a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Microraptor]]''), ''Fruitadens'' is currently the smallest known North American dinosaur; it and ''Echinodon'' are among the smallest bird-hipped dinosaurs ever discovered, only equalled by some marginocephalians (ceratopsians & pachycephalosaurs) like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Microceratus]]'' and ''[[UsefulNotes/PrehistoricLifePachycephalosaurs Wannanosaurus]]'', and some "hypsilophodont" ornithopods.

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/heterodontosaurus_skull_in_okklusion_and_moderate_gape_4.jpg]][[caption-width-right:350:A Herbivore with Fangs?]]

* Found in the last decades of the XX century, the Argentinian ''Pisanosaurus mertii'' lived in the Middle Triassic (well before ''Coelophysis'' and ''Plateosaurus'') and shared its habitat with the alleged “first theropods" ''Herrerasaurus'' & ''Eoraptor'' and many [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles non-dinosaur reptiles]] such as rhynchosaurs, "thecodonts", and mammal-ancestors (all these were much more common at the time than dinosaurs, never forget this). The pisanosaur still remains the most ancient ornithischian known to science, but sadly, is known only from one incomplete fossil. It was arguably similar to ''Lesothosaurus'' in shape and size, and with no armor like the latter. One significative thing is that some Triassic non-dinosaurian archosaurs were once considered basal ornithischians as well (often put in the "fabrosaurid" assemblage): ''[[http://en.wikipedia.org/wiki/Technosaurus Technosaurus]]'' from Texas is one example, sometimes mentioned as "the most ancient North American ornithischian"; other two examples are ''Revueltosaurus'' and chinese ''Dianchungosaurus'' (the latter was believed a heterodontosaur). The evocative name ''Technosaurus'' comes from the Texas Tech University; interestingly, another basal ornithischian, the European ''[[http://en.wikipedia.org/wiki/Emausaurus 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. Other three animals are usually considered closer to ''Scelidosaurus'' than to ''Scutellosaurus'': Portuguese ''Lusitanosaurus'' ("lizard from Portugal") and Chinese ''Bienosaurus'' and ''Tatisaurus''.

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/heterodontosaurus_skull_in_okklusion_and_moderate_gape_4.jpg[[caption-width-right:350:A Herbivore with Fangs?]]]]

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/heterodontosaurus_skull_in_okklusion_and_moderate_gape_4.jpg]]

Here we've listed those basal ornithischians which do not belong to any of the main groups of bird-hipped dinosaurs. ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Scelidosaurus]]'',[[note]]According to recent cladistic researches it could be a very primitive ankylosaurian.[[/note]] ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Heterodontosaurus]]'', ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Lesothosaurus]]'', and (less-frequent) ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Scutellosaurus]]'' are the most common in dino-books; in older works you'll frequently also read the name "''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Fabrosaurus]]''".

[[folder: Heterodontosaurs]]

[[/folder]]

[[folder: Other Basal Ornithischians]]

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