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30-410: During the mastication process, the food is positioned by the cheek and tongue between the teeth for grinding. The muscles of mastication move the jaws to bring the teeth into intermittent contact, repeatedly occluding and opening. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food. After chewing, the food (now called

60-467: A bolus ) is swallowed. It enters the esophagus and via peristalsis continues on to the stomach, where the next step of digestion occurs. Increasing the number of chews per bite increases relevant gut hormones. Studies suggest that chewing may decrease self-reported hunger and food intake. Chewing gum has been around for many centuries; there is evidence that northern Europeans chewed birch bark tar 9,000 years ago. Chewing, needing specialized teeth,

90-435: A swab or " Q-Tip ". The procedure of collecting a sample in that way is typically called a "cheek swab"). The cheeks are covered externally by hairy skin, and internally by stratified squamous epithelium . This is mostly smooth, but may have caudally directed papillae (e.g., in ruminants ). The mucosa is supplied with secretions from the buccal glands, which are arranged in superior and inferior groups. In carnivores,

120-403: A machine called a masticator (also called a forestry mulching machine ) to "chew" through brush and timber in order to clear firelines in advance of a wildfire. Cheek The cheeks ( Latin : buccae ) constitute the area of the face below the eyes and between the nose and the left or right ear . Buccal means relating to the cheek. In humans , the region is innervated by

150-416: A year earlier ) as one of his three families of dinosaurs (alongside Megalosauridae and Scelidosauridae ), including within it the genera Iguanodon , Hypsilophodon , and Hadrosaurus , in addition to Cetiosaurus and tentatively Stenopelix . The term Ornithopoda was erected by Othniel Charles Marsh in 1881 as part of his then still ongoing investigation of the classification of Dinosauria. It

180-507: Is a clade of ornithischian dinosaurs , called ornithopods ( / ˈ ɔːr n ə θ ə ˌ p ɒ d z , ɔːr ˈ n ɪ θ -/ ). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous . The most primitive members of the group were bipedal and relatively small-sized, while advanced members of the subgroup Iguanodontia became quadrupedal and developed large body size. Their major evolutionary advantage

210-517: Is a hypothesized central nervous system function by which the complex patterns governing mastication are created and controlled. It is thought that feedback from proprioceptive nerves in teeth and the temporomandibular joints govern the creation of neural pathways, which in turn determine duration and force of individual muscle activation (and in some cases muscle fiber groups as in the masseter and temporalis). This motor program continuously adapts to changes in food type or occlusion. This adaptation

240-559: Is a learned skill that may sometimes require relearning to adapt to loss of teeth or to dental appliances such as dentures . It is thought that conscious mediation is important in the limitation of parafunctional habits as most commonly, the motor program can be excessively engaged during periods of sleep and times of stress. It is also theorized that excessive input to the motor program from myofascial pain or occlusal imbalance can contribute to parafunctional habits . Chewing stimulates saliva production and increases sensory perception of

270-506: Is known as a soft diet . Such a diet may lead to inadequate nutrition due to a reduction in fruit and vegetable intake. Chewing also stimulates the hippocampus and is necessary to maintain its normal function. Chewing stimulates hippocampal neurogenesis in both humans and mice. Chewing is largely an adaptation for mammalian herbivory . Carnivores generally chew very little or swallow their food whole or in chunks. This act of gulping food (or medicine pills) without chewing has inspired

300-455: Is masticated in the mouth of the parent into a bolus and then transferred to the infant for consumption (some other animals also premasticate). Cattle and some other animals, called ruminants , chew food more than once to extract more nutrients. After the first round of chewing, this food is called cud . Chewing is primarily an unconscious ( semi-autonomic ) act, but can be mediated by higher conscious input. The motor program for mastication

330-445: Is mostly a mammalian adaptation that appeared in early Synapsids , though some later herbivorous dinosaurs, since extinct, had developed chewing too. Nowadays, only mammals chew in the strict sense of the word, though some fishes have a somewhat similar behavior. Neither birds, nor amphibians or any living reptiles chew. Premastication is sometimes performed by human parents for infants who are unable to do so for themselves. The food

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360-494: Is often listed as an infraorder within a suborder Ornithopoda, though Benton (2004) lists Ornithopoda as an infraorder and does not rank Iguanodontia. Traditionally, iguanodontians were grouped into the superfamily Iguanodontoidea and family Iguanodontidae . However, phylogenetic studies show that the traditional "iguanodontids" are a paraphyletic grade leading up to the hadrosaurs (duck-billed dinosaurs). Groups like Iguanodontoidea are sometimes still used as unranked clades in

390-512: Is usually given the rank of Suborder, within the order Ornithischia. While ranked taxonomy has largely fallen out of favour among dinosaur paleontologists, some researchers have continued to employ such a classification, though sources have differed on what its rank should be. Benton (2004) placed it as an infraorder within the suborder Cerapoda (originally named as an unranked clade ), while others, such as Ibiricu et al. 2010, have retained it at its traditional ranking of suborder. Iguanodontia

420-412: The Cretaceous period; this advanced, cow-like dentition allowed the creatures to obtain more nutrients from the tough plant life. This may have given them the advantage needed to compete with the formidable sauropods , who depended on their massive gastrointestinal tracts to digest food without grinding it. The process of chewing has, by analogy, been applied to machinery. The U.S. Forest Service uses

450-507: The Greek ornithos , ornis ("bird") and pous , podos ("feet"); this is in reference to members’ characteristic birdlike feet. They were also characterized as lacking in body armour, not developing a horny beak , having an elongated pubis (that eventually extended past the ilium ), and having a missing hole in the lower jaw (a Mandibular fenestra ). A variety of ornithopods, and related ornithischians , had thin cartilaginous plates along

480-823: The Hypsilophodontidae is problematic. The group previously consisted of all non- iguanodontian bipedal ornithischians, but a phylogenetic reappraisal has shown such species to be paraphyletic . As such, the hypsilophodont family is currently represented only by Hypsilophodon . Later ornithopods became larger, but never rivalled the incredible size of the long-necked, long-tailed sauropods that they partially supplanted. The very largest, such as Shantungosaurus , were as heavy as medium-sized sauropods (up to 23 metric tons /25 short tons ), but never grew much beyond 15 metres (50 feet). Historically, most indeterminate ornithischian bipeds were lumped in as ornithopods. Most have since been reclassified. Ornithopoda

510-405: The buccal nerve . The area between the inside of the cheek and the teeth and gums is called the vestibule or buccal pouch or buccal cavity and forms part of the mouth . In other animals, the cheeks may also be referred to as " jowls ". Cheeks are fleshy in humans, the skin being suspended by the chin and the jaws , and forming the lateral wall of the human mouth, visibly touching

540-412: The cheekbone below the eye. The inside of the cheek is lined with a mucous membrane ( buccal mucosa, part of the oral mucosa ). During mastication (chewing), the cheeks and tongue between them serve to keep the food between the teeth. The cheek is the most common location from which a DNA sample can be taken. (Some saliva is collected from inside the mouth, e.g. using a cotton-tipped rod called

570-506: The theropods , to help them balance as they ran on their hind legs. Later ornithopods became more adapted to grazing on all fours; their spines curved, and came to resemble the spines of modern ground-feeders, such as the bison . As they became more adapted to eating while bent over, they became facultative quadrupeds; still running on two legs, and comfortable reaching up into trees, but spending most of their time walking or grazing on all fours. The taxonomy of dinosaurs previously ascribed to

600-592: The English idiom "wolfing it down". Other animals such as cows chew their food for long periods to allow for proper digestion in a process known as rumination. Rumination in cows has been shown by researchers to intensify during the night. They concluded that cows chewed more intently in the night time compared to the morning. Ornithopods , a group of dinosaurs including the Hadrosaurids ("duck-bills"), developed teeth analogous to mammalian molars and incisors during

630-631: The European Hypsilophodon and three American taxa he named himself, Camptonotus , Laosaurus , and Nanosaurus . Camptonotus was in 1885 renamed to Camptosaurus , as the original name was pre-occupied by a cricket ; the associated family followed suit, becoming Camptosauridae. In Iguanodontidae, only found in Europe, he included Iguanodon and Vectisaurus . In Hadrosauridae, he included Hadrosaurus , Cionodon , and tentatively Agathaumas . Ornithopoda means "bird feet", from

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660-501: The food being eaten, controlling when the food is swallowed. Evidence from one study suggests that chewing almonds 25-40 times kept people fuller while also allowing them to get more nutrients out of the almonds. The researchers also suggest that this is likely to be the case in other foods. A 2015 systemic review found evidence that chewing can decrease self-reported hunger and therefore food intake. Eating food which does not require chewing, by choice or for medical reasons as tooth loss ,

690-415: The outside of the ribs; in some cases, these plates mineralized and were fossilized. The function of these intercostal plates is unknown. They have been found with Hypsilophodon , Nanosaurus , Parksosaurus , Talenkauen , Thescelosaurus , and Macrogryphosaurus to date. The early ornithopods were only about 1 metre (3 feet) long, but probably very fast. They had a stiff tail, like

720-537: The paraphyletic nature of Hypsilophodontidae . A 2017 study which named and described Burianosaurus noted that the type species Iguanodon bernissartensis must be part of the definition, and that the 2005 definition would, in their analysis, include a far larger group than intended (including Marginocephalia ). They proposed an entirely new, node-based definition: the last common ancestor of Iguanodon bernissartensis , Dryosaurus altus , Rhabdodon priscus , and Tenontosaurus tilletti . In 2021, Iguanodontia

750-470: The scientific literature, though many traditional "iguanodontids" are now included in the more inclusive group Hadrosauroidea . Iguanodontia was originally phylogenetically defined, by Paul Sereno , in 1998, as the most inclusive group containing Parasaurolophus walkeri but not Hypsilophodon foxii . Later, in 2005, he amended the definition to include Thescelosaurus neglectus as a secondary external specifier, alongside Hypsilophodon , accounting for

780-539: The superior buccal gland is large and discrete: the zygomatic gland. During mastication , the cheeks and tongue between them serve to keep the food between the teeth. Some animals such as squirrels and hamsters use the buccal pouch to carry food or other items. In some vertebrates , markings on the cheek area, particularly immediately beneath the eye, often serve as important distinguishing features between species or individuals . Ornithopoda Ornithopoda ( / ˌ ɔːr n ə ˈ θ ɒ p ə d ə / )

810-501: Was considered one of the four definite orders of dinosaurs, the others being Theropoda , Sauropoda , and Stegosauria ( Hallopoda was considered a possible fifth). He subdivided the order into three families: Camptonotidae , Iguanodontidae , and Hadrosauridae ; the former was a new name, whereas the latter two were carried over from the nomenclatures of Huxley and Edward Drinker Cope respectively. Within Camptonotidae he included

840-585: Was given a formal definition under the PhyloCode : "The smallest clade containing Dryosaurus altus , Iguanodon bernissartensis , Rhabdodon priscus , and Tenontosaurus tilletti , provided that it does not include Hypsilophodon foxii ." Under this revised definition, Iguanodontia is limited to its traditionally included species, and if it were found to include hypsilophodonts, which were not traditionally considered iguanodontians, it would become an invalid grouping. The slightly less inclusive clade Dryomorpha

870-608: Was named by Paul Sereno in 1986 and given a formal definition in the PhyloCode as "the smallest clade containing Dryosaurus altus and Iguanodon bernissartensis ". This group includes basal members such as Hesperonyx , members of the family Dryosauridae , and the derived clade Ankylopollexia . In 2021, Ornithopoda was given a formal definition under the PhyloCode : "The largest clade containing Iguanodon bernissartensis but not Pachycephalosaurus wyomingensis and Triceratops horridus ." The cladogram below follows

900-599: Was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow . They reached their apex of diversity and ecological dominance in the hadrosaurids (colloquially known as 'duck-bills'), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non- avian dinosaurs . Members are known worldwide. In 1870, Thomas Henry Huxley listed Iguanodontidae (coined by Cope

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