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- shoulder joint faces backward
- three or more sacral vertebrae
- expanded ilium
- neck and ball on femur
- AM ankle
- modified hand
- Upright posture (limb socket orientations)
- -Humero-glenoid joint posteriorly oriented
- -Proximal femur - ball and neck at hip joint and a fourth trochanter
- Advanced mesotarsal (AM) ankle joint
- -Astragalus much larger than calcaneum
- -Astragalus and calcaneum fused to distal tibia
- -Provides rigid parasagittal hind limb motion
- Expanded ilium (three or more sacral vertebrae)
- Modified hand - three functional fingers
"lizard-hipped" - more primitive as in basal archosaurs
"bird hipped" new prepubic process
- Pelvic characters related to upright hind limb posture - legs close to vertical midline; parasagittal.
- Articulation at ball on femoral side, no longer top.
Ornithischian Dinosaur Characters
- ornithischian pelvis
- ossified tendons in back
- herbivores only
simplified dinosaur cladogram
- bipedal carnivores
- Ceratosaurs - fused hind limb elements
- Coelurosaurs - small, long-necked
- Carnosaurs - large, short-necked
- Prosaruopoda - small, slender, bipedal
- Sauropoda - large, heavy, quadrupedal
- Large lachrymal bone
- 5 or more sacral vertebrae
- Clawed hand
- Bowed femur
- Compact hind foot functional toes 2, 3, 4
- late Triassic ceratosaur
Cannibalism in Coelophysis
Coelophysis - small, late Triassic bipedal ceratosaur (early theropod) Hunderds of Coelophysis skeletons from Ghost Ranch, New Mexico bone bed. Colbert (1989) found juvenile bones inside rib cages of two adult skeletons and concluded this was evidence of cannibalism!
Potential murder mystery in Triassic
2002 and 2006 studies refuted cannibalism because juvenile Coelophysis bones under rib cage and that stomach bones not diagnostic - probably from late Triassic small crocodillian Hesperosuchus.
More Theropod Characters
- Curved, laterally-compressed, serrated teeth
- Anterorbital fenestra in skull
- Large eyes, sometimes pointed forward
- Largest brains among dinossaurs
- Flexible neck (similar to birds)
- Grasping forelimbs
- Hollow bones
- Stiff posterior tail
- Coelophysis - all theropod characters but lacks specializations of other groups.
- Ceratosaurs - more derived therapod group - often crests or horns on nasal or frontal bones.
- Among earliest dinosaurs, small
- Much bone fusion in hip and hind limbs
- Gap between premaxilla/maxilla skull bones
- Sexual dimorphism (females larger)
- Slender head crests (?=only males)
- one of the largest ceratosaurs; lower Jurassic of Arizona
- Fused tails
- Non-ceratosaur theropods have fused tails
- Anteorbital fenestra
- More flexible, spring like pelvis
- Includes coelurosaurs, carnosaurs and others
- Only two small, incomplete skeletons (Germany and France)
- All Tetanurae characters but lack of specific carnosaur and coelurosaurs
- All 5 meters long
- Lacrimal foramen
- Small vertebral spines in shoulder region
- Pronged chevrons in tail vertebrae
- Includes allosaurs and others such as Megalosaurus (first described dinosaur)
Allosaurus- at least 44 skeletons Morrison Formation, central Utah
- primitive top left
- derived bottom right
- Tyrannosaurus - "king" carnosaur - ? closely related to earlier carnosaur Allosaurus
- Further analysis - closer affinity between Tyrannosaurus and coelurosaurs - i.e., tight hind foot structure.
- Family Tyrannosauridae restricted to upper Cretaceous western North Aerica and Asia.
Tyrannosaurs hind foot matches coelurosaurs, not carnosaurs!
- least derived among tetanuran, most large carnivores.
- Distinct maxilla, ntout first metacarpal, and opistocoelus cervical vertebrae (posterior bulging centra).
- a) Magnasaurus
- b) Allosaurus
- c) Suchomimus
- d) Carcharodontosaurus
- Ancestral Saurischians (?Theropods)
- -Staurikosaurus - Upper Triassic, Brazil
- -Herrerasaurus - Upper Triassic, Argentina
- -Coelophysis - Upper Triassic, North America
- -Dilophosaurus - Lower Jurassic, Arizona
- Tetanurae undifferentiated
- -Compsognathus - Upper Jurassic, western Europe
- -Megalosaurus - Middle-Upper Jurassic, Europe
- -Allosaurus - Upper Jurassic, western United States
- Extra palatal fenestra
- Forelimbs >50% of hind limb length
- Slender hands - long digits 2 and 3
- Arctometatarsal (tight) hindfoot structure
- Some - bird-like features, including ? feathers
- all have arctometatarsal ankle
- Tyrannosaurus - reduced hand - two "functional" fingers.
- Ornithomimids - small toothless skulls.
- Ornithomimids ("bird mimics")
- long legs and necks
- small heads with large eyes
- Teeth replaced by horny bill
- Long arms with clawed hands
- Only from upper Cretaceous of North America and Asia
- Oviraptors ('egg stealers")
- short snouts, toothless jaws
- Large mandibular fenestrae
- Deep mandible
- Crest of sponge-like bone on tip of snout
- Fused clavicles (as in birds)
- probably relatives of Ornithomimosaurs
- Oviraptors now thought to have fed on freshwater clams abundant at lake margins in Mongolia in late Cretaceous.
- Dromaeosaurs ("raptors")
- Relatively large head; sharp serrated teeth
- Stiff tails - ossified tendons
- Posteriorly - directed (ornithischian) pubis
- Feet with large claw - digit two
- Velociraptor, upper Cretaceous, Asia
- Deinonychus, Lower Cretaceous, North America
- subgroup of coelurosaurs, includes birds and their closest relatives
- Most derived bird-like coelurosaurs - some consider birds. relationship is controversial.
- Mononykus - late Cretaceous (Mongolia)
- Either bizarre theropod or flightless bird. Reduced, specialized forelimbs obscure most evidence.
- Five feather types in modern birds
- Several types ?=on well-preserved dinosaur fossils from China.
- These are too late to be bird ancestors.
Dromaeosaur and Bird questions
- Various bird-like characters appear among many coelurosaurs: beaks, feathers, wishbones, posteriorly-directed pubis.
- Dromaeosaurs=most bird-like; ?=closest bird relatives.
- However, nearly all dromaeosurs appeared after first birds.
- Dromaeosaurs=odd; appear as large forms (utahraptor) and became progressively smaller (culminating in Velociraptor).
More Theropod Dinosaurs
- -Ornithomimus - Upper Cretaceous, W. North America
- -Struthiomimus - Upper Cretaceous, W. North America
- -Oviraptor - Upper Cretaceous, Asia
- -Deinonychus - Lower Cretaceous, W. N. Am.
- -Velociraptor - Upper Cretaceous, Asia
- -Tyrannosaurus - Western North America and Asia
- Head small relative to body
- Spatulate teeth
- Long necks - minimum ten cervical vertebrae
- Short, reduced elements in feet
- Large claw on first forefoot digit
- Largest land creatures of all time
- Late Triassic - latest Cretaceous
- Late Triassic prosauropod - Europe, a most abundant early dinosaur
- Small, head, uniform teeth - low, weak jaw joint suggest herbivory.
- Late Triassic - early Jurassic
- Largest dinosaurs of their time; small compared to later sauropods
- Quadrupedal - but could easily be bipedal for feeding
- Prosauropod Characters
- Intermediate state between bipedal and quadrupedal
Evolutionary position of Prosauropods
- Prosauropods typically considered direct saruropod ancestors because of intermediate traits, such as size and stance.
- But several unique prosauropod characters suggest they = sister groups
- Plants=easy to catch but hard to digest
- Plants must be ground into small pieces to increase the surface area.
- -Teeth frequently adapted for grinding plant food by having broad abrasive surfaces.
- -Some herbivores swallow stones (gastroliths) to grind up food in a large, muscular stomach.
- A large, long digestive track with special bacteria to break down cellulose is required.
Prosauropods as Herbivores
- Long necks allowed feeding from tall trees.
- Jaw articulation below tooth row as in herbivorous ornithischian dinosaurs.
- Variable offset upper and lower teeth permit grinding of plant food.
- Spatulate teeth similar to those of living herbivorous Iguana.
- gastroliths found with some skeletons for grinding plants.
Prosauropod life and death
- Infant prosaruopod skeleton less than a foot long.
- Associated eggs from the late Triassic of Argentina, shows that prosauropods laid eggs.
- Prosauropods disappeared at end of early Jurassic, just as sauropods and other large plant eaters (stegosaurs and ankylosaurs) appeared.
- largest land animals of all time
- Late Triassic - late Cretaceous
- Mostly appear after early Jurassic
- larger than prosauropods
- small heads and teeth only for cropping food
- extremely long necks and tails
- nasal openings high on skull
- E. D. Cope proposed that sauropods were aquatic
- -such large creatures could only exist under the buoyant force of water.
- -His model had long neck and dorsal nasal openings as a snorkel/periscope.
- -Hydrostatic pressure woudl have made it impossible to breath with deeply submerged lung, so this hypothesis is not feasible.
- -Sauropod food structure similar to elephants; they could easily have bone massive weight.
- Dorsal bony nasal openings may not represent the position of actual external openings.
- An extra skull nasal apparatus?
- Advantages - increased olfaction for locating mates or warning of approach of enemies
- Mechanism for cooling blood and brain.
- long, slender skull - elongate muzzle
- Nasal openings above and in front of eyes
- Peg-like teeth confined to front of mouth
- Very long but relatively lightly-built bodies
- Include largest (longest) dinosaurs
- Supersaurus, Ultrasaurus, and Seismosaurus competing for largest (longest or heaviest) dinosaur.
- Utah's "Dinosaur Jim" Jensen discovered the first two of these.
- Short, heavy skull with blunt snout
- Nasal openings lateral in front of eyes
- Long forelimb (humerus/femur=0.7)
- Paul Sereno's strange sauropod from North Africa with the shovel-like jaw and 600 teeth.
- longest forelimbs (humerus/femur>1.0)
- Camarasaur like skull and teeth but high forehead and smaller snout
- Could lift head to 40 ft above the ground
- Long neck (13 elongate neck vertebrae
- Tail short (50+ short tail vertebrae)
- Probablly heaviest dinosaur (~55 tons)!
- Appeared in Jurassic-Cretaceous boundary of western United States, Tanzania, and Portugal.
- Ultrasaurus probably a Brachiosaurus synonym.
sauropods classified by vertebral features
- six sacral vertebrae
- Procoelous tail vertebrae
- Some had body armor
- Mostly South American
- Alamosaurus-North America - late Cretaceous
- - one of the largest titanosaurids.
North American sauropods
- Greatest diversity late Jurassic.
- Diversity decreased in early Cretaceous.
- None known from late Cretaceous (100-75mya) despite good record ("sauropod hiatus")
- Alamosaurus appeared in latest Cretaceous, probably from South America, where Cretaceous sauropods flourished.
- -plateosaurus - Upper Jurassic, Western Europe
- Sauropods - Family Diplodocidae
- -Diplodocus - J-K boundary, w. US
- -Apatosaurus - Upper Jurassic, US
- -Supersaurus - Upper Jurassic, US
- -Seismosaurus - Upper Jurassic, US
- Sauropods - Family Camarasauridae
- -Camarasaurus - Upper Jurassic, US
- Sauropods - Family Brachiosauridae
- -Brachiosaurus - J-K boundary, widespread
- Sauropods - Family Titanosaruidae
- -Alamosaurus - Late Cretaceous, w. US
- appeared near end of Triassic
- "Bird-hipped" - Pelvic structure resembles modern birds.
- Both two-legged and four-legged types.
- Lacked front upper and lower teeth. Beak for cropping vegetation. Teeth limited to sides of jaws - well adapted for crushing and grinding vegetation.
- Front legs shorter, indicating descent from two-legged forms.
- Ornithopods, Stegosaurs, Ankylosaurs, Ceratopsians
- Ornithopods - bipedal, including ancestral ornithischians and hadrosaurs (duck-bills)
- Pachycephalosaurs - dome-headed dinosaurs
- Ceratopsians - horned dinosaurs
- Stegosaurs - plated dinosaurs
- Ankylosaurs - heavily-armored dinosaurs
- Early Ornithischians
- Possible 1st ornithischians - Argentina
- Predentary bone lacking teeth appeared
- Early forms all bipedal
- Known only from late Jurassic of south africa
- large canine-like anterior teeth (ecomorphy)
- distinct chisel-shaped cheek teeth
- mandibles moved apart while chewing
- Bipedal - long hindlimbs, short forelimbs
- Fused tibia and fibula
- bipedal and quadrupedal
- lacked body armor
- jaw joint below tooth row
- beak or offset tooth row in premaxilla and predentary
- early jurassic to latest cretaceous
- small sized but - diverse herbivores
- Jurassic and Cretaceous - several continents
- Ancestors of later, larger ornithopods
- Beak at front of skull, no tusks
- Battery of interlocking cheek teeth
- Jointed skull allowed upper jaws to move apart
- Bipedal with long hindlimbs, short forelimbs
- Ossified tendons (like dromeosaurs) stiffen tails
chewing in Ornithischians
- Lower jaws of heterodontosaurs slide outward as they close
- Later ornithopods have cheek hinge that allows maxillae to move outward as jaws close
- Both mechanisms produce grinding action for breaking tough plants
- Link (intermediate size) between small hypsilophodontids and large iguanodontids
- Beaks instead of premaxillary teeth
- Large, mostly bipedal
- Heavily built - heavy shoulders and forelimbs
- Mostly late Jurassic and early Cretaceous
- Large head; hose-like snouts
- Beak at front of skull, no tusks
- Spike-like thumb (weapon)
- Later forms developed a boxwork of ossified tendons to stiffen backs.
- Larger species tended to be quadrupedal
- horse-like skull with beak and grinding cheek teeth
- Expansion of anterior and reduction of posterior pubis
- Ossified tendons sitffened body
- Fused carpals, thumb spike on first digit of hand
- Middle Cretaceous of Niger
- Pointed skull with beak
- Long tendonized neural spines
- Hump may have stored fat as in modern bison
Hadrosaurs - Duck-billed Dinosaurs
- Middle - latest Cretaceous, very diverse
- Probably outcompeted other ornithopods
- Complete skeletons, nests, eggs, trackways and mummified skins and stomachs!
- Large skull with beak, no anterior teeth
- Cheek teeth in battery with 3+ per position
- Loss of first digit (thumb) on forelimb
- 8-10 sacral vertebrae
- Many species had elaborate head crests with nasal passages for loud vocalization
- Hadrosaur anatomy
- Ability to balance on two legs for running or four legs for climbing or ground feeding
- Cross-section through snout shows tooth replacement pattern
- Most hadrosaurs - tendons on neural spines to stiffen back
- Overlapping teeth formed powerful grinding surface.
- Stomach contents include conifer needles, twigs and seeds.
- other than size hadrosaur skeletons similar from species to species.
- Biggest differences in teeth and head crests.
- Two groups: Lambeosaurines had nasal tubes in head crests.
- hadrosaur head crests
- ability to make loud sounds goes hand in hand with herding behavior
- Ornaments for sexual display?
- Sexual dimorphism?
- Head crests acted as snorkels or air locks for use under water.
- Mummified skeletons show webbed hands.
- Hadrosaur tails tall and paddle-like.
- Most fossils found in river, lake, swamp and even shallow marine deposits.
- Most likely lived on land but were able to cross shallow water or retreat to water for temporary safety from predators.
- -Heterodontosaurus - Lower Jurassic, South Africa
- -Hypsilophodon - Early Cretaceous, Europe
- -Dryosaurus - Upper Jurassic, North America
- -Iguanodon - Early Cretaceous, Belgium
- -Edmontosaurus - flat heads - late Cretaceous, NA - Hadrosaurinae
- Lambeosaurinae - nasal head crests
- -Lambiosaurus - Late Cretaceous, NA
- One or more rows of dermal armor plates dorsal or parallel to vertebral column.
- Most armor plates dorsally keeled and excavated ventrally (^-shaped)
- Most primarily quadrupedal.
- Worldwide Jurassic and Cretaceous distribution.
- Stegosaurus, ankylosaurs, and others.
- primitive thyreophorans
- Early ornithischians developing body armor
- Scelidosaurus (left) mostly quadrupedal
- Scutellosaurus (right) mostly bipedal
- Primitive stegosaur - middle Jurassic of China
- Early development of stegosaurian plates on back.
- Deep skull with short snout.
- Forelimbs and hindlimbs of nearly equal size.
- Low skull, long snout and posterior eye sockets.
- Large size - massive skeletons.
- Hindlimbs much longer than forelimbs.
- Includes all stegosaurs except Huayangosaurus
- Lived throught Jurassic and Cretaceous, but most diverse and abundant in late Jurassic of North America, Asia, Africa
- most skin contained armor plates, arranged in two alternating rows. Contained numerous grooves for blood vessels.
- In spite of large body size, brain of Stegosaurus=less than 3 ounces!
- Small head, beak in front, leaf-shaped cheek teeth, eyes far posterior.
- Spiked tail=defensive weapon.