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Home , Gastrolith, Genasauria, Huayangosaurus, Kentrosaurus, Ornithischia, Scutellosaurus

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Ornithischia Intro,

I. - highly derived (appeared after ) & highly diverse

A. Shared derived characters: 1. back-prong on 2. long, thin forward process on 3. at least five sacral vertebrae 4. ossified around is connective tissue that connects muscle to bone (aka sinew) for further strengthening. Why would this group need further strengthening in its sacrum? 5. all 6. predentary = unpaired, scoop-shaped bone at front of lower 7. toothless tip of snout with "" 8. small, triangular teeth 9. jaw joint set below level of the upper row

B. Main Groups of Ornithischians 1. Fabrosaurids: most primitive ornithischians a. : upper : poorly known, lacks clear ornithischian characters b. : lower : least derived, well known ornithischian 2. Shared derived characters: Reduced mandibular foramen, muscular cheeks a. ("horned foot") Have a gap (diastema) between premaxilla and maxilla 5 or fewer teeth on premaxilla

i. ii. : bone shelf extends behind the skull Two main groups - Pachycephalosaurs and Ceratopsians

b. ("shield bearer") - named by Baron Franz Nopsca in 1915 Shared derived characters: Dermal armor (rows of keeled scutes on dorsal surface) i. Several less derived taxa: (small biped), (larger quadruped) ii. Eurypoda ("broad foot") Shared derived characters: enlarged anterior ilium, short ilium behind hip socket stocky foot/hand bones new bones around the eye

Two main groups - Stegosauria and

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II. STEGOSAURIA ("roofed ")

A. What? Shared Derived Traits: Rows of over the body that developed into spines and plates Parascapular spines = over shoulder blade, spines on tail Loss of ossified tendon Body sloped forwards due to short front legs (not in most primitive ones) Very tall neural arches on thoracic vertebrae (WHY? - more room for viscera) Feet with broad hooves Solid box-like (defense, defense, defense) Other features Five toes on front feet, three to four toes on back feet 3-9 meters long 300-6500 kg (to over 7 tons)

B. When? to early Late was heyday of Stegosauria Ultimately 11+ genera

C. Where? Cosmopolitan - earliest = in and western

D. Who? Many specimens in poor shape = difficult to classify group Only a couple of Chinese stegos + have relatively complete skeletons Most derived stegos have plates above all vertebrae + large nares

Huayangosaurus: basal stegosaur (14 feet, ), legs more equal in size - Tanzania, about 17 feet long, 2 tons Stegosaurus: largest and best-known member of , thanks to the Morrison Fm. Elongated snout End of snout covered by a horny beak Teeth are deeply set in from sides of face, suggesting cheeks

Many Chinese forms Only one known South American stegosaur

E. Physiology and Lifestyles : LIMITED INFO! A very successful group despite their bad wrap as idiotic microcephalics Present for over 100 million Lived in floodplains + coastal areas +?

Osteoderms/Plates: what is the deal? Some enlarged as spikes 3

All our embedded in the skin Plates probably related to + intimidation Mobile or immobile??? Probably evolved as midline armor, since (primitive) has midline spikes Shapes and pattern of spikes and plates -specific Plates vascularized, for heat control = solar panels + swamp coolers (rapid pumping of blood could cool dinos) Plates in paired, staggered rows. No dorsal plates in juveniles

Habitats: floodplains and coastal plains

Gait/Speed Not built to burn rubber, but like elephants were probably able to move quickly in bursts Hind limbs able to outrun forelimbs at high speeds - bipedal? Trackways suggest quadrupeds, not bipeds. Speed? 7km/hr max?

Feeding Cropped plants with sharp, toothless Tiny teeth and weak jaw muscles users? No evidence yet. Narrow heads, short legs = low browsers or, did they rear up at feed on higher parts of trees? (Hindlimbs supported 80% of wt.). Flexible tail could be third leg in tripod position

Brains Brains rot after death and burial, brain info comes from natural or lab-made Brain in verts. are proportional to body size, but brains grow in size at slower rate than bodies Only Kentrosaurus and Stegosaurs brain casts available - WHY? These relatively long, slightly bent, small (3 oz), with large olfactory bulbs, typically reptilian - as big as 3 walnuts Why small brains? They relied on armor rather than wily evasion to escape consumption Unhurried lifestyle and uncomplicated range of behaviors Large expansion of spinal cord in hip region = 20x size of brain DID NOT house a rear brain, but some other types of soft tissues

Behavior Some Mass accumulation of Kentrosaurus in Tanzania is hard to interpret! Defense