Ornithischia: pelvis in the opisthopubic position, presence of the predentary (scoop shaped bone that caps the front of the lower jaws), toothless and roughened tip to the snout, presence of a narrow bone (palpebral) that crosses the outside of the eye, jaw joint set below the level of the upper tooth row, check teeth with low, subtriangular crown, teeth set in from jaw edge, at least 5 sacral vertebrae, ossified tendons along the back and the tail | Basal member: Pisanosaurus: late Triassic Argentina, small and lightly built, small light skull with large eyes, a horn covered beak (used as a bill to crop vegetation) |
Ornithischia in group Genasauria, derived characteristics: reduction in the size of the opening on the outside of the lower jaw, muscular cheeks, snout shaped front to the mandibles, asymmetrical enamel on teeth | Hypacrosaurus: high ridged back + radiator, laid eggs and placed vegetation on top | Parasaurolophus: 2m long crest w/ internal nasal passage | Locomotion: hands became more robust and the claw like fingers became more hoof like, some can be bipedal when running | Defense: camoflouge, living in herds, well developed thumb spike, acute hearing and sight | Feeding and Food: twigs, berries, coarse plant matter, beak or bill attached to diastema to crop vegetation, robust process on jaw to attach masticatory muscles, tooth row set in from edge jaw (muscular cheek), Hadrosauids and others appeared to chew back to front, propalinal jaw movement (both sides of mouth at the same time) | Characteristics that made Iguanodonts different from Hypsilophodonts: longer length, larger nares, 6 or more sacral vertebraes | Iguanodon found in large numbers in Bernissart Belgium 1878 | Terrestrial Lifestyle: dental battery, desiccated foot, rigid crest not used for breathing (underwater), stiffened duckbills don’t have body for swimming | Head structure: sexual dimorphism, distinctive headgear to prevent confusion, head crest used for visual and auditory signals, warming air, enhancing sense of smell
Hadrosauridae: duck bill dinosaurs, distinguished from the basal members of Iguanodon and Hypsilophodonts with: expansion of the end of the snout, increase of the number of tooth position, more closely packed dental battery, loss of their thumb = 4 fingers, last group of ornithopods to evolve, split into two groups: Hadrosaurinae (flat heads) and the crested Lambeosaurinae | Nasal arched forms: Gryposaurus (elephant-sized plant eater and known for large bump on nose), Maiasaurus (was found near nests containing remains of juveniles in “Egg Mountain”, Montana), and Brachylophosaurus (found in river deposits, small solid crest at the top of the skull behind eyes shows its relationship to other crested hadrosaurines like Prosaurolophus), Solid crested forms: Saurolophus, Prosaurolophus (had large crest that goes on and off the skull), True flat headed forms: Edmontosaurus ( largest hadrosaur to live in AB, had balloon like flaps of facial skin), Anatotitan (one of the last large duck billed dinosarus), Shantungosaurus | Lambeosaurinae: hollow crest that nasal passages went into, crests vary between visual and aural display: Corythosaurus: helmet lizard, tall rounded crest on top of its narrow head, Hypacrosaurs: below the top lizard, high ridged back acted as a radiator, Lambeosaurus: Lawrence Lambe, first duck bill found in NA, had a large hollow hatchet shaped crest -> may have been used to produce sounds or improve its sense of smell, Parasaurolophus: had hollow crest with internal nasal passages that were up to 2m backwards from the skill, Magnapaulia laticaudus: broad tail, had elongate chevrons and dorsal vertebrae, high cordal vertebrae, fan shaped over back and a broad tail
Maiasaura “rookery”: nest spacing approximates adult body length, caring for offspring is k selective, young delay their maturation and get more help from adults - “altrical”, young that behave as small adults (need no care) are “precocial” (r selective)
Thyreophora (shield bearers) : osteroderms (keratin over scoots), armor plates in the skin above or alongside the vertebral column | Basal member is Scutellosaurus: smaller size, lighter armor (plates only on the back), extensive body covering bony plates set in the skin, had sinuous lower cheek tooth row | Another Basal member is Scelidosaurus: limbs were massive, fore and hind limbs were almost equal length, skull lacked armor, back covered by bony plates embedded in skin
Eurypoda: Stegosauria and Ankylosauria, short and stocky metacarpal and metatarsal bones, spike osteoderms protruding from the scapular region, special bones that fuse in the margins of the eye socket, enlarging front part of illium, reduction of holes in skull
Stegosauria: roof lizard, parascapular spines over shoulder blades, parallel rows of osterderms along the back, comprised of plates: mediolaterally flattened tall osteoderms, spikes: conical tall osteroerms, quadrupedal limb position, long thin relatively small heads w/ simple teeth, short, massive forelimbs and long columnar hind limbs, toes ended in broad hooves, 3-9m length, 300 to 6500 kg, mid jurrasic to early late cretaceous (170-95 my)