Plant-eating sauropod dinosaurs (Apatosaurus, Diplodocus, Brachiosaurus, Supersaurus and many more) were equipped with peg-like or spoon-shaped teeth they used for stripping leaves off of plants. These teeth were not used for chewing, however, because of their shape. The plant material that these dinosaurs ate was swallowed and digested in their guts, maybe in fermentation chambers where the materials would break down, often with the help of gastroliths, or stones that the dinosaur swallowed to help break up the leaves and twigs in its gut.
Meat-eating theropods (Tyrannosaurus rex, Carcharodontosaurus, Allosaurus, Gigantosaurus, Spinosaurus and many more) had sharp, pointed teeth they used to tear flesh and sometimes even crush bones. Recently, a Tyrannosaurus rex coprolite (fossilized feces) was discovered containing bits of crushed bone, which tells scientists that the dinosaur did in fact crush its food with his powerful teeth and strong jaws.
Plant-eating Ornithischians, as well as some prosauropods had varying teeth but many had horny beaks and many leaf-like cheek teeth for nipping and chewing through tough foliage.
Stegosaurids (Kentrosaurus and Stegosaurus as well as others) had leaf-shaped teeth that were built for slicing at weeds that grew close to the ground.
Hadrosaurs (Edmontosaurus, Maiasaura, Lambeosaurus, Parasaurolophus and many more) were duck-billed dinosaurs and had around 960 self-sharpening cheek teeth; the most teeth of all of the dinosaurs.
Iguanodontids (Iguanodon, Probactrosaurus, and Ouranosaurus among others) had teeth that look similiar to today’s iguanas. They were rounded outward, notched on top and curved, indicating that perhaps today’s iguanas originated as iguanodontids.
Heterodontosaurus was a small dinosaur that had three different types of teeth in addition to a beak. It had sharp upper teeth which it used with its beak to bite and cheek teeth for grinding its food and two pairs of long canine-type teeth that fit into sockets when Heterodontosaurus closed its mouth.
Ceratopsians (Triceratops, Monoclonius and Styracosaurus belonged to this group) had toothless beaks they used to gather food and lots of flat cheek teeth they used to grind and chew tough plant material.
Ankylosaurs (such as Euoplocephalus, Sauropelta and Ankylosaurus) were unable to chew their food so they may have had large fermentation chambers where they were able to digest the tough plant fibers. Ankylosaurs had teeth shaped like a hand with the fingers together. Ornithomimids (like Ansermimus, Gallimimus, Ornithomimus and Struthiomimus) did not have teeth, but they had beaks with which they ate plants and insects and small animals.
Here are 5 interesting facts about dinosaur teeth:
1. Tyrannosaurus Rex had a mouth full of serrated teeth, but not all of the dinosaur’s teeth served the same function, according to a 2012 study in the Canadian Journal of Earth Sciences. T-rex’s front teeth gripped and pulled; its side teeth tore flesh and its back teeth diced chunks of meat and forced food into the throat. (More info: www.livescience.com/23868-tyrannosaurus-rex-facts.html)
3. All dinosaurs could regrow teeth. Scientists believe plant-eating dinosaurs grew new teeth more frequently to keep their chompers from getting too worn down on all that vegetation. Diplodocus replaced their teeth fairly frequently — growing one new tooth every 35 days — while the Camarasaurus took nearly 62 days to form a new tooth. (More info: www.livescience.com/38249-dinosaurs-teeth-replacement.html)
5. Apatosaurus had teeth but couldn’t chew. According to the American Museum of Natural History, the Apatosaurus had “stripper teeth” that removed leaves from branches. Then, this plant-eater, believed to have weighed 19.8 tons, just swallowed plants whole. They swallowed stones (gastroliths) to help grind vegetation in their enormous stomachs. (More info: www.livescience.com/25093-apatosaurus.html)
The Saurischian Dinosaurs, like all other tetrapods, had pelves (hips) composed of three elements: the ilium, ischium, and pubis. What distinguishes Saurischians (among other major characteristics; including a grasping hand, asymmetrical fingers, and a long, mobile neck) is the pubis that points downward and forward at an angle to the ischium. The saurischians form two major groups. The Sauropoda were large herbivores such as Apatosaurus and Diplodocus. The Theropoda were bipedal carnivores (meat eaters), ranging from the chicken-sized Compsognathus and the fearsome Deinonychus and Velociraptor to the crested Dilophosaurus and the gigantic Tyrannosaurus. The oldest known dinosaurs, from the middle Triassic of South America, were saurischians. Living birds had common ancestors on the theropod lineage. Oddly, birds are derived from the "lizard-hipped" dinosaurs and not from the "bird-hipped" Ornithischian dinosaurs. The "bird-hipped" condition of a pubis pointing toward the back of the animal occured twice independently, once in the Ornithischians and once in the lineage leading to birds, an example of convergent evolution. Thus "Ornithischia," taken literally, is a misnomer, since the Ornithischians have Ornithischian-like pelves, not bird-like. Only birds (and their immediate ancestors) have bird-like pelves.
Herrerasaurids are among the oldest known dinosaurs, appearing in the fossil record 231.4 million years ago (Late Triassic). These dinosaurs became extinct by the end of the Triassic period. Herrerasaurids were small-sized, not more than 4 metres (13 ft) long, and carnivorous. The best known representatives of this group are from South America (Brazil, Argentina), where they were first discovered in the 1960s. A nearly complete skeleton of Herrerasaurus ischigulastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete herrerasaurids have been found in North America, and they may have inhabited other continents as well. Herrerasaurid anatomy is unusual and specialized, and they are not considered to be ancestral to any later dinosaur group. They only superficially resemble theropods and often present a mixture of very primitive and derived traits. The acetabulum is only partly open, and there are only two sacral vertebrae, the lowest number among dinosaurs. The pubic bone has a derived structure, being rotated somewhat posteriorly and folded to create a superficially tetanuran-like terminal expansion, especially prominent in H. ischigulastensis. The hand is primitive in having five metacarpals and the third finger longer than the second, but clearly theropod in having only three long fingers, with curved claws. Herrerasaurids also have a hinged mandible, which is also found in theropods. [(c) Wikipedia] There is also evidence of proto-feathers [see illustration below]
Velociraptor is one of the dinosaurs that without question had feathers. Evidence for this comes from the quill knobs on the fossil material, particularly the forearms. These are where feathers were anchored in place, and without feathers there would be no quill knobs (although on the other hand, lack of quill knobs does not mean lack of feathers). The feathers on Velociraptor would have provided insulation allowing it to maintain a high metabolism, a vital requirement for a very agile and active hunter. Also Velociraptor lived in a fairly arid landscape and the feathers would have provided extra protection against the cold nights that are often associated with arid environments. A further idea is that the feathers may have also served a display purpose.
Discovered in China in 2012, this “beautiful feathered tyrant” weighed 1.5 tons and was a fearsome THEROPOD predator like its relative Tyrannusaurus rex.
The mix of feathers and scales on Kulindadromeus--an early, plant-eating ORNITHISCHIAN DINOSAUR--shows that both epidermal structures could coexist, just as in modern birds--chickens for example have scaly legs, and vultures and turkeys have scaly patches over their necks and heads. Developmental experiments in modern chickens suggest that bird scales are aborted feathers, an idea that explains why birds have scaly legs. Perhaps the molecular mechanisms needed for this switch might have existed already in Kulindadromeus.
Tianyulong confuciusi is a feathered ORNITHISCHIANDINOSAUR that belongs to the same branch of the family tree as Stegosaurus and Triceratops. What makes the discovery important is that it supports the idea that both Theropods AND some Ornithiscian dinosaurs had feathers, proto-feathers, "fuzz," or a combination of scaly skin and feathers. In addition to the presence of "hollow" bones in Theropods and some smaller Ornithischian dinosaurs, the presence of feathers (or feather-like structures), gives weight to the idea that both groups of dinosaurs might more properly belong to the proposed group called Ornithoscelida.
DISSENTING VIEWS: PERHAPS A COMBINATION OF BOTH FEATHERS AND SCALES?
An international team of researchers studied skin impressions taken from Tyrannussaurus rex fossils found in Montana. They then compared those impressions to fossilized skin patches of other tryannosaurs, like the Albertosaurus, Daspletosaurus, Gorgosaurus, and Tarbosaurus. The samples represented parts of the dinosaurs’ stomach, chest, neck, pelvis, and tail, according to Ben Guarino of the Washington Post. And none bore any traces of feathers. These findings indicate “that most (if not all) large-bodied tyrannosaurids were scaly,” the authors of the study write. They add that the Tyrannusaurus rex may have had some feathers, but the plumage was likely limited to the dinosaur’s back. Since there is ample evidence to suggest that earlier tryannosaurs had feathers, the study’s conclusions would mean that tyrannosaurs evolved a feathery coat, only to eventually lose it. The study’s authors believe that the Tyrannusaurus rex’s size can help explain the evolutionary shift, Bittel reports.
What makes an ornithischian dinosaur? All terrestrial animals and even marine animals derived from terrestrial stocks have hip girdles, or pelvises, and all hip girdles are composed of three bones: the ilium, ischium, and pubis. All ornithischians are united by a pubis pointing backward, running parallel with the ischium. The name "Ornithischia" means "bird-hipped," and birds also have pelvises in which the pubis points backwards. However, birds are more closely related to the Saurischia, or "lizard-hipped" dinosaurs, than to the ornithischian dinosaurs featured on this page. There were many kinds of ornithischian dinosaurs, dating back to the early Jurassic. The Ornithopoda included the hadrosaurs ("duck-billed dinosaurs"), the iguanodontids, the heterodontosaurs, the hypsilophodontids, and various other dinosaurs. The Ceratopsia included the horned dinosaurs, the Ankylosauria and Stegosauria (now usually grouped together in the Thyreophora) included various types of armored dinosaurs, and the Pachycephalosauria, the extremely thick-skulled pachycephalosaurs.
•Thyreophorans represent the armored dinosaurs, and are a clade of (predominantly) quadrupedal ornithischians.
•There are characterized by the presence of osteoderms (armor plates) in their skin. Different clades of thyreophorans express these osteoderms in different patterns.
•Beyond a few basal taxa, thyreophorans are divided into the plated Stegosauria and the tank-like Ankylosauria.
•Armor in thyreophorans seem to have functions beyond simple defense: they served as display structures and (in the case of the stegosaurs and the club-tailed ankylosaurine ankylosaurs) as active weapons.
Marginocephalia is a clade of ornithischian dinosaurs that is characterized by a bony shelf or margin at the back of the skull. These fringes were likely used for display. There are two clades included in Marginocephalia: the thick-skulled Pachycephalosauria and the horned Ceratopsia. All members of Marginocephalia were herbivores. They basally used gastroliths to aid in digestion of tough plant matter until they convergently evolved tooth batteries in Neoceratopsia (or "new Ceratopsia") and Pachycephalosauria. Marginocephalia first evolved in the Jurassic Period and became more common in the Cretaceous. They are basally small facultative quadrupeds while derived members of the group are large obligate quadrupeds. Primitive marginocephalians are found in Asia, but the group migrated upwards into North America.
Ornithopods are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape. Their major evolutionary advantage 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 in the duck-bills (hadrosaurs), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known from all seven continents, though they are generally rare in the Southern Hemisphere.
BONE STRUCTURE IN DINOSAURS
DISCLAIMER: I do not represent the Museums mentioned on this website. My photos, links, and comments are personal points of view that do not necessarily reflect any official position by the administration of those Museums or their curators.