page_title: Glossary of dinosaur anatomy
section_title: D
hierarchical_section_title: Glossary of dinosaur anatomy / D
caption_attribution_description: The mandible (lower jaw) of an Edmontosaurus at the Museum of the Rockies in Bozeman, Montana, seen from the inner side (i.e. from the tongue side). It is not clear where this specimen was collected. Edmontosaurs belong to the so-called duck-billed dinosaurs (hadrosaurs), and were exceptionally numerous in Latest Cretaceous times throughout upper North America. As herbivores, they ripped leaves and plants using their bills, and then, unlike reptiles usually do, chewed the leaves and stems extensively. This caused wear to their teeth, which ground down quickly. The teeth were not only lying next to each other but were also stacked one above the other within the jawbone to form vertical tooth rows. So there were quite a lot of teeth in one jaw and all the densely packed teeth together are referred to as ‘tooth battery’. In the jaw that is shown above, many unworn, keeled, diamond-shaped surfaces of the stacked teeth are visible. Furthermore, the teeth erupted in a way that there was more than one tooth functional in each vertical row: The teeth rotated during their lifetime around the long axis of the jaw so that a new tooth first reached the mouth cavity on the inner side of the jaw, yet before the older tooth or teeth, sitting closer to the cheek, were entirely worn down. The tooth wear acting on the surfaces of about one hundred functional teeth formed an inclined chewing surface on each tooth battery. In the image above the chewing or wear surface is not visible because in the mandible it faces toward the cheek, not toward the tongue (but see this image for comparison). Only the inner edge of the chewing surface, running along the top of the inner surface of the tooth battery, with the keels forming conspicious spikes, is discernible.
context_page_description: This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.
context_section_description: dental battery 
  
  A dental battery is a type of dentition in some herbivorous dinosaurs where individual teeth are packed tightly together to form a continuous grinding surface. In the hadrosaurid Edmontosaurus, the dental battery of each half of the upper and lower jaws contains more than 60 rows of teeth, with each row comprising up to three functional teeth stacked upon each other and up to five replacement teeth beneath this stack that would erupt from the jaws once the functional teeth were worn down and shed. The most sophisticated dentition type in dinosaurs, it evolved independently in hadrosaurids, ceratopsians, and some sauropods, and differs in form and function in these separate clades.
  dentary 
  
  The dentary is the main bone of the mandible. It is the only mandible bone that bears teeth, and is located anterior to all other jaw bones except in ornithischians, where the tip of the lower jaw is formed by the predentary. At their anterior ends, the dentaries of the left and right jaw are connected together, forming the mandibular symphysis.
  dentition 
  
  Dentition is a collective term for all teeth present within the jaws of an individual dinosaur. The dentition can be homodont, when only a single type of teeth is present, or heterodont in the case of different types. Teeth are continuously replaced during life. Teeth that are erupted and currently in use are termed the functional teeth. For each tooth position, there are typically one or two unerupted replacement teeth at any time, which successively migrate into the tooth socket and replace the functional tooth once the latter fell out. Some herbivorous species may show up to six replacement teeth per tooth position. Tooth turnover started with the resorption of the root of the functional tooth. Teeth ejected after replacement lack their root, and are called shed teeth.
  deltopectoral crest 
  
  The deltopectoral crest is a forward directed bony flange on the upper part of the humerus. An especially long and prominent deltopectoral crest is a dinosaurian synapomorphy, i.e., a feature differentiating the group from other groups. In dinosaurs, the crest measures 30–40% of the length of the humerus. It provided insertion surfaces for muscles of the shoulder and chest (the deltoid and pectoralis muscles, respectively), which, when contracted, drew the arm towards the body.
  digits
  
  The digits, or fingers and toes, form the distal part of the autopodium, following after the metacarpus of the hand and the metatarsus of the foot. They are identified with Roman numerals from I–V, with I denoting the innermost and V the outermost digit. The individual digits have of one or more phalanges (finger and toe bones).
  dolichoiliac 
  
  Dolichoiliac refers to one of two principal hip bone configurations in early saurischian dinosaurs. The dolichoiliac type is characterised by large front and back extensions of the ilium as well as elongated and narrow pubes and ischia. In contrast, the brachyiliac type is characterised by short ilium extensions and more robust pubes and ischia. The brachyiliac type is typical for basal sauropodomorph dinosaurs of the Triassic, while the dolichoiliac type is characteristic of theropods. Both terms were introduced by Edwin Colbert in 1964.
  dorsals 
  
  The dorsals, also termed dorsal vertebrae or back vertebrae, are the vertebrae of the back region between the cervicals of the neck and the sacrals of the hip. The Nomina Anatomica Avium (NAA) terminology instead uses the term thoracic vertebrae. In mammals, the term thoracic vertebrae refers only to the rib-bearing vertebrae of the chest, while the vertebrae of the lower back, which lack ribs, are referred to as lumbar vertebrae. This subdivision of the dorsal vertebral column is not applicable in dinosaurs, and the NAA term "thoracic vertebrae" refers to the dorsal vertebral column as a whole. Most dinosaurs had around 15 dorsals. In comparison with the cervicals, the dorsals are shorter, their neural spines longer, and their transverse processes more robust and directed outwards.
caption: Lower jaw of Edmontosaurus showing the dental battery
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