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Ornithischia
 
 
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Ornithischia or Predentata is an extinct order
Order (biology)

In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
 of beaked, herbivorous
Herbivore

Herbivory is a form of predation in which an organism, known as an herbivore, heterotrophs principally autotrophs such as plants, algae and photosynthesizing bacteria....
 dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
s. The name ornithischia is derived from the Greek
Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
 ornitheos (?????e???) meaning 'of a bird' and ischion (?s????) meaning 'hip joint'. They are known as the 'bird-hipped' dinosaurs because of their bird-like hip structure, even though bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s actually descended from the 'lizard-hipped' dinosaurs (the saurischia
Saurischia

Saurischia is one of the two Order s, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure....
ns).






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Ornithischia or Predentata is an extinct order
Order (biology)

In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
 of beaked, herbivorous
Herbivore

Herbivory is a form of predation in which an organism, known as an herbivore, heterotrophs principally autotrophs such as plants, algae and photosynthesizing bacteria....
 dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
s. The name ornithischia is derived from the Greek
Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
 ornitheos (?????e???) meaning 'of a bird' and ischion (?s????) meaning 'hip joint'. They are known as the 'bird-hipped' dinosaurs because of their bird-like hip structure, even though bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s actually descended from the 'lizard-hipped' dinosaurs (the saurischia
Saurischia

Saurischia is one of the two Order s, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure....
ns). Being herbivores that sometimes lived in herds, they were more numerous than the saurischians. They were prey animals for the theropods and were smaller than the sauropods.

Characteristics

Ornithischia
The Dinosauria superorder was divided into the two orders Ornithischia and Saurischia by Harry Seeley
Harry Seeley

Harry Govier Seeley was a UK paleontologist who determined that dinosaurs fell into two great groups, the Saurischians and the Ornithischians, based on the nature of their pelvis....
 in 1887. This division, which has generally been accepted, is based on the evolution of the pelvis
Pelvis

The pelvis or pelvic girdle is the irregular bone structure located at the base of the spine . In the adult human, it is formed by the sacrum and the coccyx, the caudal part of the axial skeleton, and a pair of hip bones, part of the appendicular skeleton or human leg....
 into a more bird-like structure (although birds did not descend from these dinosaurs), details in the vertebrae and armor
Armour (zoology)

Armour in animals is external or superficial protection against attack by predators, formed as part of the body , usually through the hardening of body tissues, outgrowths or secretions....
 and the possession of a 'predentary
Predentary

The predentary is an 'extra' bone in the front of the Jaw, which extended the dentary . It is found in the fossilised remains of ornithischian dinosaurs, which were herbivore....
' bone. The predentary is an extra bone in the front of the lower jaw
Jaw

The jaw is either of the two opposable structures forming, or near the entrance to the mouth.The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals....
, which extends the dentary
Jaw

The jaw is either of the two opposable structures forming, or near the entrance to the mouth.The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals....
 (the main lower jaw bone). The predentary coincides with the premaxilla
Jaw

The jaw is either of the two opposable structures forming, or near the entrance to the mouth.The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of most animals....
 in the upper jaw. Together they form a beak-like apparatus used to clip off plant material.

The ornithischian pubis bone points downward and toward the tail (backwards), parallel with the ischium, with a forward-pointing process to support the abdomen. This makes a four-pronged pelvic structure. In contrast to this, the saurischian pubis points downward and towards the head (forwards), as in ancestral lizard types. Ornithischians also had smaller holes in front of their eye sockets (antorbital fenestrae) than saurischians, and a wider, more stable pelvis. A bird-like pubis arrangement, parallel to the vertebral column
Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
, independently evolved three times in dinosaur evolution
Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
, namely in the ornithischians, the therizinosauroids and in bird-like dromaeosaurids.

Classification


Taxonomy

Linnaean
Linnaean

"Linnaean" can refer to:*Carolus Linnaeus*Linnaean taxonomy*Linnaean enterprise*alternate spelling Linnean...
 ranks after Benton (2004),

  • Order Ornithischia
    • Family Pisanosauridae
      Pisanosaurus

      Pisanosaurus is a genus of primitive ornithischian dinosaur from the Late Triassic of what is now South America. It was a bipedalism herbivore described by Argentine paleontologist Rodolfo Casamiquela in 1967....
    • Family Fabrosauridae
      Fabrosauridae

      The Fabrosauridae was originally proposed by Galton , as a group of basal ornithischian dinosaurs from the Late Triassic and Jurassic. However, recent studies indicate the Fabrosaurs are not a natural grouping of dinosaurs, consisting of unrelated genera....
    • Suborder Thyreophora
      Thyreophora

      The Thyreophora were a subgroup of the ornithischian dinosaurs. They were Armour herbivorous dinosaurs, living from the early Jurassic until the end of the Cretaceous....
       - (armored dinosaurs)
      • Family Scelidosauridae
        Scelidosaurus

        Scelidosaurus is a genus of quadrupedal, lightly plated, Herbivore dinosaur about 4 metres long . It lived during the Early Jurassic Period , during the Hettangian to Sinemurian faunal stage around 208 to 194 mya ....
      • Infraorder Stegosauria
        Stegosauria

        Known colloquially as stegosaurs, the Stegosauria are a group of Herbivore dinosaurs of the Jurassic and Early Cretaceous Period , being found mostly in the Northern Hemisphere, predominantly in what is now North America and China....
      • Infraorder Ankylosauria
        Ankylosauria

        Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with Armour in the form of bony osteoderms....
    • Suborder Cerapoda
      Cerapoda

      Cerapoda is a clade or suborder of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. They are divided either into two or three groups....
      • Family Heterodontosauridae
        Heterodontosauridae

        Heterodontosauridae is a family of early ornithischian dinosaurs that have often been considered Basal ornithopods, although recent studies suggest they may have been more closely related to marginocephalians....
      • Infraorder Ornithopoda
        • Family Hypsilophodontidae*
          Paraphyly

          In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor Common descent but does not contain all the descendants of that ancestor....
        • Family Hadrosauridae - (duck-billed dinosaurs)
      • Infraorder Pachycephalosauria
        Pachycephalosauria

        Pachycephalosauria is a clade of ornithischian dinosaurs. Well-known genera include Pachycephalosaurus, Stegoceras, Stygimoloch, and Dracorex....
      • Infraorder Ceratopsia
        Ceratopsia

        Ceratopsia or Ceratopia is a group of herbivore, beaked dinosaurs which thrived in what are now North America and Asia, during the Cretaceous Period , although ancestral forms lived earlier, in the Jurassic....
         - (horned dinosaurs)


Phylogeny

The ornithischians are divided in the two clades: the first are the Thyreophora
Thyreophora

The Thyreophora were a subgroup of the ornithischian dinosaurs. They were Armour herbivorous dinosaurs, living from the early Jurassic until the end of the Cretaceous....
 and the second the Cerapoda
Cerapoda

Cerapoda is a clade or suborder of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. They are divided either into two or three groups....
. The Thyreophora include the Stegosauria
Stegosauria

Known colloquially as stegosaurs, the Stegosauria are a group of Herbivore dinosaurs of the Jurassic and Early Cretaceous Period , being found mostly in the Northern Hemisphere, predominantly in what is now North America and China....
 (like the armored Stegosaurus
Stegosaurus

Stegosaurus is a genus of Stegosauria Thyreophora dinosaur from the Late Jurassic Period in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well....
) and the Ankylosauria
Ankylosauria

Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with Armour in the form of bony osteoderms....
 (like Ankylosaurus
Ankylosaurus

Ankylosaurus is a genus of ankylosaurid dinosaur, containing one species, A. magniventris. Fossils of Ankylosaurus are found in geologic formations dating to the very end of the Cretaceous Period in western North America....
). The Cerapoda include the Marginocephalia
Marginocephalia

Marginocephalia is a clade of ornithischian dinosaurs that includes the thick-skulled pachycephalosauria, and horned ceratopsians. They were all herbivores, walking on two or four legs, and are characterized by a bony ridge or frill the back of the skull....
 (Ceratopsia
Ceratopsia

Ceratopsia or Ceratopia is a group of herbivore, beaked dinosaurs which thrived in what are now North America and Asia, during the Cretaceous Period , although ancestral forms lived earlier, in the Jurassic....
 like the frilled ceratopsidae
Ceratopsidae

Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous of Western North America and are characterized by beaks, rows of shearing teeth in the back of the jaw, and elaborate horns and frills....
 and Pachycephalosauria
Pachycephalosauria

Pachycephalosauria is a clade of ornithischian dinosaurs. Well-known genera include Pachycephalosaurus, Stegoceras, Stygimoloch, and Dracorex....
) and the Ornithopoda (among which duck-bills (hadrosaurs) such as Edmontosaurus
Edmontosaurus

Edmontosaurus is a genus of hadrosaurid dinosaur. Its fossils have been found in rocks of western North America that date to the late Campanian and Maastrichtian Stage of the Cretaceous Geologic time scale#Terminology, between 73 and 65.5 million years ago....
). The Cerapoda are a relatively recent grouping (Sereno, 1986), and may conceivably be identical to (synonymous with) the older group, Ornithopoda: most of these divisions are not true by definition.

Ornithischia |-?Pisanosaurus
Pisanosaurus

Pisanosaurus is a genus of primitive ornithischian dinosaur from the Late Triassic of what is now South America. It was a bipedalism herbivore described by Argentine paleontologist Rodolfo Casamiquela in 1967....
 `--+-?Fabrosauridae
Fabrosauridae

The Fabrosauridae was originally proposed by Galton , as a group of basal ornithischian dinosaurs from the Late Triassic and Jurassic. However, recent studies indicate the Fabrosaurs are not a natural grouping of dinosaurs, consisting of unrelated genera....
 `--Genasauria
Genasauria

Genasauria is an extinct cladogram of beaked, herbivore dinosaurs which were prey for carnivorous theropods. The group was first named by paleontology Paul Sereno in 1986, and is typically split into Thyreophora, a group of armored dinosaurs; and Cerapoda, which included the Ceratopsia and Hadrosauridae dinosaurs....
 |--Thyreophora
Thyreophora

The Thyreophora were a subgroup of the ornithischian dinosaurs. They were Armour herbivorous dinosaurs, living from the early Jurassic until the end of the Cretaceous....
 | |--Scutellosaurus
Scutellosaurus

Scutellosaurus is a genus of herbivore dinosaur that lived in North America around 200 to 196 million years ago, in the Early Jurassic times....
 | `--Thyreophoroidea | |--Emausaurus
Emausaurus

Emausaurus is a genus of thyreophoran or armored dinosaur from the Early Jurassic. Its fossils have been found in Germany. It is known from a skull and partial postcranial remains, although only the skull is known well....
 | `--Eurypoda ||--Stegosauria
Stegosauria

Known colloquially as stegosaurs, the Stegosauria are a group of Herbivore dinosaurs of the Jurassic and Early Cretaceous Period , being found mostly in the Northern Hemisphere, predominantly in what is now North America and China....
 |`--Ankylosauromorpha | |--Scelidosaurus
Scelidosaurus

Scelidosaurus is a genus of quadrupedal, lightly plated, Herbivore dinosaur about 4 metres long . It lived during the Early Jurassic Period , during the Hettangian to Sinemurian faunal stage around 208 to 194 mya ....
 | `--Ankylosauria
Ankylosauria

Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with Armour in the form of bony osteoderms....
 `--Cerapoda
Cerapoda

Cerapoda is a clade or suborder of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. They are divided either into two or three groups....
 |--Stormbergia
Stormbergia

Stormbergia is a genus of early ornithischian dinosaur known from the upper Elliot Formation of South Africa and Lesotho, named by Richard Butler in 2005....
 |--Agilisaurus
Agilisaurus

Agilisaurus is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin agilis meaning 'agile' and the Ancient Greek sauros meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs....
 |--Hexinlusaurus
Hexinlusaurus

Hexinlusaurus is a genus of basal ornithischian dinosaur from the Middle Jurassic of China. The holotype , consists of an almost complete, articulated skull and some postcranial material, collected from a terrestrial sandstone within the Lower Shaximiao Formation at the famous dinosaur-bearing quarries at Dashanpu....
 |--Heterodontosauridae
Heterodontosauridae

Heterodontosauridae is a family of early ornithischian dinosaurs that have often been considered Basal ornithopods, although recent studies suggest they may have been more closely related to marginocephalians....
 `--+--Ornithopoda `--Marginocephalia
Marginocephalia

Marginocephalia is a clade of ornithischian dinosaurs that includes the thick-skulled pachycephalosauria, and horned ceratopsians. They were all herbivores, walking on two or four legs, and are characterized by a bony ridge or frill the back of the skull....
 |--Pachycephalosauria
Pachycephalosauria

Pachycephalosauria is a clade of ornithischian dinosaurs. Well-known genera include Pachycephalosaurus, Stegoceras, Stygimoloch, and Dracorex....
 `--Ceratopsia
Ceratopsia

Ceratopsia or Ceratopia is a group of herbivore, beaked dinosaurs which thrived in what are now North America and Asia, during the Cretaceous Period , although ancestral forms lived earlier, in the Jurassic....


(basal Cerapoda after Butler, 2005)

External links

  • , from Palæos. (cladogram, characteristics)