...a World of Dinosaurs

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Titanosaur
Tyrannosaurus rex

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Traditional Cladogram
2017 Proposed Cladogram

Dinosaur Teeth

SAURISCHIANS 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.
ORNITHISCHIANS 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. 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. 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.
Apatosaurus teeth
Tyrannosaurus rex teethImage caption
Hadrosaur teeth
Triceratops prorsus 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) 2. Triceratops teeth were made of five layers of tissue. In contrast, the teeth of plant-eating horse and bison have four layers of tissue. Crocodiles and other reptiles have just two. (More info: www.sci-news.com/paleontology/science-triceratops-teeth-02885.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) 4. Hadrosaurs had more teeth than any other dinosaur. These duck-billed dinosaurs had nearly 1,000 cheek teeth called grinders, which they used to eat plants. (More info: http://dinosaurs.about.com/od/typesofdinosaurs/a/hadrosaurs.htm) 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)(c) http://deltadentalazblog.com/5-fun-facts-about-dinosaur-teeth/ A DENTAL WEBSITE WITH AN EXCELLENT BREAKDOWN OF DINOSAUR TEETH: https://www.towncaredental.com/dinosaur-dental-discoveries/

Saurischians

OVERVIEW: http://www.ucmp.berkeley.edu/diapsids/saurischia/saurischia.htmlDINOSAUR MORPHOLOGY: http://www.ucmp.berkeley.edu/diapsids/dinomm.htmlSMITHSONIAN: https://www.smithsonianmag.com/science-nature/dinosaur-division-is-all-in-the-hips-20477310/OVERVIEW: https://en.wikipedia.org/wiki/Saurischia 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

Herrerasaurus ischigualastensis
Herrerasaurus ischigualastensis (Field Museum)
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 above].
SEE ALSO: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3088398/

Sauropods

Argentinosaurus
  • Sauropods: https://en.wikipedia.org/wiki/Sauropoda
  • Apatosaurus: http://www.prehistoric-wildlife.com/species/a/apatosaurus.html
  • Apatosaurus: https://www.livescience.com/25093-apatosaurus.html
  • Brachiosaurus: http://www.prehistoric-wildlife.com/species/b/brachiosaurus.html
  • Argentinosaurus: http://www.prehistoric-wildlife.com/species/a/argentinosaurus.html
  • TITANOSAURIA: https://en.wikipedia.org/wiki/Titanosaur
  • TITANOSAURIA: https://www.thoughtco.com/titanosaurs-the-last-of-the-sauropods-1093762
  • (Video) PATAGOTITAN MAYORUM: https://www.youtube.com/watch?v=dn1BW9tvq-I
  • (AMNH Videos) PATAGOTITAN MAYORUM: https://www.amnh.org/explore/amnh.tv/(category)/131058
  • Sauropoda, whose members are known as sauropods, is a clade of saurischian ("lizard-hipped") dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their body), and four thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known genera include Brachiosaurus, Diplodocus, Apatosaurus and Brontosaurus.
  • The oldest known unequivocal sauropod dinosaurs are known from the Early Jurassic. Isanosaurus and Antetonitrus were originally described as Triassic sauropods, but their age, and in the case of Antetonitrus also its sauropod status, were subsequently questioned. Sauropod-like sauropodomorph tracks from the Fleming Fjord Formation (Greenland) might, however, indicate the occurrence of the group in the Late Triassic. By the Late Jurassic (150 million years ago), sauropods had become widespread (especially the diplodocids and brachiosaurids). By the Late Cretaceous, one group of sauropods, the titanosaurs, had replaced all others and had a near-global distribution. However, as with all other non-avian dinosaurs alive at the time, the titanosaurs died out in the Cretaceous–Paleogene extinction event. Fossilised remains of sauropods have been found on every continent, including Antarctica. The name Sauropoda was coined by O.C. Marsh in 1878, and is derived from Greek, meaning "lizard foot". Sauropods are one of the most recognizable groups of dinosaurs, and have become a fixture in popular culture due to their impressive size. Complete sauropod fossil finds are rare. Many species, especially the largest, are known only from isolated and disarticulated bones. Many near-complete specimens lack heads, tail tips and limbs. (c) Wikipedia

Theropods

Allosaurus
What kind of feathers did a T. rex have?
Theropoda (from Greek meaning "beast feet") is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants (including modern birds). Dinosaurs belonging to the suborder Theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory. Theropods first appeared during the Carnian age of the late Triassic period about 230 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66.038 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by 9,900 living species. Among the features linking theropod dinosaurs to birds are the three-toed foot, a furcula (wishbone), air-filled bones, brooding of the eggs, and (in some cases) feathers. (c) Dinopedia
Oviraptor skeleton and eggs
Artist's rendering of an Oviraptor embryo

Dromaeosaurids and Oviraptosaurids

DROMAEOSAURIDS: https://en.wikipedia.org/wiki/DromaeosauridaeDROMAEOSAURIDS: http://www.dinosaur-world.com/feathered_dinosaurs/dromaeosauridae.htmRAPATORS: http://www.prehistoric-wildlife.com/species/r/rapator.htmlVELOCIRAPTOR: http://www.prehistoric-wildlife.com/species/v/velociraptor.html 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.
BUSTING SOME VELOCIRAPTOR MYTHS: https://www.thoughtco.com/things-to-know-velociraptor-1093806DEINONYCHUS: https://en.wikipedia.org/wiki/DeinonychusDEINONYCHUS: http://www.prehistoric-wildlife.com/species/d/deinonychus.htmlOVIRAPTOROSAURIDS: http://www.prehistoric-wildlife.com/articles/oviraptorosaurs.htmlOVIRAPTOROSAURIDS: http://www.dinosaur-world.com/feathered_dinosaurs/oviraptoridae.htmOVIRAPTOR: https://en.wikipedia.org/wiki/Oviraptor
Kulindadromeus
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.
FURTHER INFORMATION: http://palaeo.gly.bris.ac.uk/melanosomes/Kulindadromeus.html
Tianyulong confuciusi
Tianyulong confuciusi is a feathered ORNITHISCHIAN DINOSAUR 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.
Read more: http://www.smithsonianmag.com/smart-news/t-rex-skin-was-not-covered-feathers-study-says-180963603/
Anatotitan
Triceratops

Ornithischians


  • ORNITHISCHIAN OVERVIEW: https://en.wikipedia.org/wiki/Ornithischia
  • OVERVIEW FROM THE UNIVERSITY OF CALIFORNIA MUSEUM OF PALEONTOLOGY: http://www.ucmp.berkeley.edu/diapsids/ornithischia/ornithischia.html
  • VIDEO COMPARISON OF SAURISCHIANS AND ORNITHISCHIANS (Benjamin Burger): https://www.youtube.com/watch?v=qYsFVDj-65A
  • VIDEO OVERVIEW ABOUT ORNITHISCHIANS (Benjamin Burger): https://www.youtube.com/watch?v=RObirXm6DDU

  • 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.
Stegosaurus
Ankylosaurus

Thyreophorans

  • •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.

Triceratops
Centrosaurus

Marginocephalia

  • 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.

Iguanodon
Parasaurolophus

Ornithopods

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.
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