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What are the two groups of Dino's?
- Saurischians (Lizard Hip)
- Ornithischians (Bird Hip)
Defining Characters of Saurischians
- a) they have extra articular surfaces on the dorsal vertebrae
- b) they have twisted thumbs
What are the two groups of saurishians?
- 1) Theropods
- 2) Sauropodomorpha
What two groups are Sauropodomorpha divided into?
- 1) Prosauropods- Successive out groups of sauropods. They have a vestigal pinky toe.
- 2) Sauropods- They have a fully developed pinky
- Lanceolate teeth
- Long neck with at least 10 vertebrae
- Downward bent in front of lower jaw
- Robust, clawed thumbs
Sauropodomorph Body Plan
Long neck and tails, bulky body, very small head, and short front limbs relative to their hind limbs.
Throughout evolution there is a trend toward greater overall size with smaller heads at the end of longer necks.
Front limbs become nearly as long as the hind ones
When were Sauropodomorph found?
- Among the oldest of dino's with prosauropods found in late Triassic rock
- Youngest are sauropods from the late Cretaceous.
- Globally distributed
When were Prosauropods found?
- One of the two groups that went extinct before the end of the Cretaceous.
- Earliest found in Africa, suggesting they evolved there.
Prosauropod Body Plan
- Small to medium sized
- Ranged from 10m long and 8,800 lbs max in weight.
Prosauropods Posture and Locomotion
Small forearms and non weight bearing hand on many species suggest that they (especially small ones) were bipedal.
Large species are usually thought as quadrupeds based on their bulk and other skeletal proportions. Could not pronate their hands which means they were likely bipedal.
Hindlegs nearly as long as the front limbs. Suggested quadrupedality.
- -Some argue that they were omnivores (no direct evidence of meat eating is known but tooth shape is similar to that of living herbivorous and omnivorous iguanas)
- -Most food processing done in gut
- -Longer necks allowed them to access plants farther from the ground.
- -Some had a jaw joint below the teeth row (vice-like jaw closing action)
- - Other had rows of teeth in lone with the jaw joint, allowing for a scissor like cutting actions.
- -Not chewers
- -Had small coronoid process and the jaw only permitted up and down motion.
- -Teeth lacked grinding surface
Prosauropod Social Behavior and Reproduction
- -Some were social animals based on momospecific bone beds.
- -Eggs and nests have been found.
- -Multiple nests together suggest group egg laying behavior.
- -Nest also found in layers one on top of another. Suggest that the animals came back to the same site year after year. (Site Fidelity)
- -Embryos had large forelimbs and heads, held the neck horizontally, indicating they were quadrupeds when hatched.
- -Adults have relatively smaller skulls and arms and were bipedal.
- -Some were pro. At least went from a quad. to bipedal stage as they matured.
- -Done through Paedomorphois
- -Heavily vascularized (filled with blood vessels) more so than other dino's.
- -Grew faster than modern birds
- Retention of juvenile traits in adults
- Shut off developmental pathway that would make them bipedal
- Most closely related to prosauropods, together form sauropodomorphs.
- -Sister to the sauropodmrpha are the theropods
- Lanceolate teeth
- Long neck with at least 10 vertebrae
- Downward bend in front of lower jaw
- Robust, clawed thumb
When where Sauropods found?
- First occurred in Late Triassic and are abundant in the Jurassic
- -Went extinct at the end of the Cretaceous
- -Global distribution
Sauropods Derived Characters
- The front leg is 60% or more the length of the hind leg
- Ratio greater than .6
Derived Sauropods divided into:
- Macronairans (big nose)
- Dipodocoideans (means Diplodocus like)
- Have large nostrils
- Include Gamarosaurs, Brachiosaurs and Titansours
- Smaller nostrils on top of the skull
- Include: Apotasaurs, Nemegtosaurs and Diplosaurs
Why are Sauropods so big?
- Had to do with body shape and how food was processed.
- -Their teeth were simple and most did not chew their food
- -Allowed the head to remain small and the neck long
- -Only a few sauropods have gastoliths
- -Evolution favored larger body size to get more nutrients out of their food
- -Excess weight
- Used by Sauropods to solve the problem of weight and breathing
- Cavities in the vertebrae
- Probably had air sacs in them
- Makes their breathing similar to today's birds
Holes on the surface that the cavities which were probably filled with air was let out
- -Suggested that they used their necks to graze high in the trees, and that rearing up onto hind legs would increase their feeding range even further.
- -Others argue that they held their necks horizontally and ate at should height and lower
- -Evidence: Neck vertebrae, which have bifurcate neural spines
- Ran between the bifurcations and served as an elastic band holding up the head
- -Allowed the head to be held horizontally
Problems with Sauropod elevated necks and with rearing in particular:
- Enormous blood pressures would be required to push blood from heart to the head
- -Models suggest that they neck could only lift up 10 to 20 degrees while swinging 90 degrees to either side
- Obligate quadrupeds whose limbs were highly modified to bear weight
- -Narrow trackways indicate that the legs were column like and positioned directly under the body, not sprawled
- -Moved slowly (May have ran short distances)
- -Legs had no aquatic adaptions (H20 pressure would have crushed their lungs)
Bones between the wrist and fingers were fit tightly together and held off the ground, giving the front foot a horselike appearance.
Bones between the ankle and toes of the hind foot lay parallel to the ground and there was a big fleshy pad at the back of the foot
Sauropods Social Behavior
- At least some species were gregarious based on monospecific bone beds, mass nest accumulation for titanosaurids and parallel trackways.
- -Some localities the trackways all take the same turn, suggest group behavior.
Sauropod Reproductive Behavior
- No direct evidence on how they mated
- Suggested that males mounted females
- Argued that tail used for balance but no evidence
- Multiple layers containing nest show that they exhibited site fidelity
- Individual layers have large number of nest, indicating multiple individuals were involved.
- Once thought to have grown slowly
- Reach sexual maturity at 60 years and living to 100
- -Microscopic structure of bone indicates that they actually grew very rapidly and they may have reached maturity at 20 years old
- Immense size and group behavior was best defense
- -Some had whip like tail: May have been used to thrash molesters
- -Few developed dermal armor or clubbed tailed for defense
- Ex of convergent evolution: Thyreophorans
Why is it thought that Sauropods lived in water?
- -Noses on top of heads was one reason some thought they lived in water
- -Also gave rise to the idea that they had trunks
- -Unlikely to be true because reptiles do not have the needed face musculature for a trunk
- "Beast Feet"
- Saurischians (Forward pointing pubis, extra articular surfaces on the dorsal vertebrae and with a twisted thumb)
- -Sister group: long necked, Sauropodomorphia (divided into prosauropods and sauropods)
- Extreme hallowing of the bones
- -Hand with reduced ring and pinky fingers
- -Pits on the upper surface of the finger bones to allow extreme extension of finger
When were Theropods found?
- Longest living group
- 220-230 ma and continue today in the form of birds
- -All others died out at the end of the Cretaceous
- -Global distribution
- -Largest land predators ever (3 to 50 feet long)
- High diversity of ornithopods means their relationship are complicated
- -Have a semilunar carpal in the wrist, allowing the hand to fold against the forearm
- -Gave rise to birds
Theropod Body Plan and Posture
- All had long legs and short, sometime grasping arms, indicating they were bipedal
- -Ankles were held up so only toes touched the ground, called digitigrade posture
- -By contrast, humans have platigrade posture where the ankles rest on the ground
- -Held backbone horizontally and balanced the body over the hips with their long tails
- -Lack of tail drags in most trackways indicated that the tail was held off the ground
- -Sitting traces have been found that show resting posture
- -Whole foots touched the ground, as did the ischium
- -Occasionally the hands and belly touched and left traces too
- Footprints are best for determining how fast theropods could go
- -Calculation show that most theropods regardless of size walked only a few mph
- -Evidence for running is for small to medium sized theropods
- -Fastest: 25.6 mph
- Trackways suggest they could
- -Might have dispersed to islands by swimming
- -May have lived near water and fed on fish
- Most were carnivores based on sharp, pointed teeth and the claws on their hand and feet
- -In man teeth came together like shears
- -Sliced flesh had sharp, serrated teeth that were positioned in cross section and functioned like steak knives
- -Fish eaters: round in cross sections
Round teeth and a massive jaw for a bone crushing bite
- -Egg stealers
- -Lacked teeth
- -Tough beaks
- -Jaw mechanical studies show that they cracked open hard foods
- Bird mimic lizard
- Lost their teeth
- Gasoliths have been found in their stomachs and they may have been plant eaters
- Scythe lizards
- Lose their front teeth and the rear teeth have lost their sharp edges and points
- -Likely plant eaters
- -Pulled branches with long, clawed hands
Theropods Direct Evidence for Feeding
- Caught in act
- -Teeth scattered around "kill site" or left imbedded in bones
- -Trackways: provide evidence into hunting. Digging into mammal burrows
Theropods and Sense
- Large eyes indicate that they had good vision
- -Hearing well developed in troodonitds and ornithiminosaurs
t-Rex: eyes were set far apart so that they had steroscopic vision. Large olfactory bulbs indicate well-developed sense of smell.
Theropod Reproduction and Social Behavoir
- -At least some such as Oviraptor brooded their eggs the same way birds do
- -Suggest they may have been feathered
- -Many lived in packs
- -Had structures that would be used for matting and warding off rivals
Theropods Infraspecific Combat
- Number of them have been found with partly healed bite marks
- -marks and spacing match those of teeth of conspecific theropods
Once though to slash instead they were used to climb onto their prey
- Had large, heavy head for crushing bone
- -Extra weight of the head was offset by reducing the size of the arms so it wouldn't tip over
- Have a backbone=vertebrates
- Have four limbs=tetrapods
- Lay shelled eggs=amniotes
- Have antorbital fenestrae= diapsid archosaurs
- Considered to be highly derived theropod dino's.
- Large eyes and brain
- lack teeth
- Fingers are fused into a bone known as the carpometacarpus
The single bone that the bones between the ankle and toes are fused into
Bones that sacrai vertebrae are fused into
Vertebrae that the tail is reduced to
Flight attachment muscles
The first bird is....
- Late Jurassic
- Found in Germany
- -Known from 7 skeletons and 1 isolated feather
- -Shows a mix of theropods and bird characters
- -Upper and lower jaws have teeth
- -Long, bony tails
- -No synsacrum
- -Only small knell on the sternum (Suggest that its flight was not as strong as a modern bird)
- -Hand and foot lack the fused bones of modern birds
- -Had asymmetric feathers indicating that they flew, but how well is debated
- -Arrangement is much like that of modern birds
Archaeoteryx and Modern Birds Shared Characters
- Enlarged brain case
- Very long arms
- Narrow face
- Reduced fibula
The group formed from Arch. and modern birds is known as...
Archaeopteryx as a dino
- Has antorbital fenestrae=archosaur
- Has a four-toed food symmetric about toe three
- Foot type is charactersitci of omithdirans= omithdirans
- Has an inturned femur=dinosauropmorph
- Perforate acetbulum=dino
- Enlarged, three digit hand with pits on the metacarpals=theropod
- Emilunatr carpal=maniraptoran
Maniraptorans and Archacopteryx Characters
- Modern birds must also be this
- -Backward pointing pubis
- -Missing front part of pubic "boot"
- -Bowed, or bent, ulna (one of the lower arm bones)
Most closely related to Archacopteryx are...
- -Includes Dromacosauridae
- Replete with feathers
- -Has wings on both the arms and legs
- -From early Cretaceous
Why did feathers evolve?
- Insulation was most likely the reason.
- Dino's probably warm blooded
How did flight evolve?
- Two Ideas:
- 1) Cursoiral
- 2) Arborial
Cyrsorial Flight Theory
Suggest that flight evolved from a running ancestor
Arborial Flight Theory
Suggest that flight evolved from a gliding ancestor that lived in the trees
- Developed as a means of extending glides between trees until it became self-sufficient
- -Supported by Microraptor
Juvenile Birds Hypothesis
Young birds incapable of flight will flap their winds to help them scale steep slopes
Major Events in Bird Evolution
- 1) Perching and Flight
- 2) Fused Tail
- 3)Fused Hand with Alula
- 4) Pubic rotation complete
- 5) Loss of teeth
Primitive member of Pygostylia was...
Confusclusomis from the early Cretaceous of China
Had a carpometacarpus, an alula, series of feathers attached to 1st digit
Functioned like a slat on an airplane wind, extending during slow flight to increase lift and prevent stalling
- Major group of Ornithothraces.
- -Sparrow sized
- -Most abundant of Mesozoic Birds
- 1) Hesperomis
- West bird
- -Relatives are cretaceous flightless swimmers and divers
- -Cololites found in the body indicate that they ate fish
- Fish birds
- Relatives also cretaceous flight birds
- -Size of gulls
- -Excellent flyers
- First vertebrates known to have achieved powered flight, as opposed to gliding
- -Evolved in the Late Triassic and went extinct at the K/T Boundary
- -Existed for nearly 160 ma, during which they were diverse
- -Flight allowed them to achieve a global distribution
- Have an antorbital fenestra-archosaurs
- -Four toed feet symmetric about toe three- ornithidirans
- -They are not dinosaurs because they do not have the diagnostic characteristics of that group
- -"Sister" taxa within the Ornithodira
Pterosaurs Historically Divided into:
- 1) Rhamphorhyncoids
- -Small forms with long tails and short necks
- -Large number of teeth in the mouth
- -Most lacked head crests
- -First pterosaur
- -Went extinct by the end of the Jurassic
- -Some survive to Cretaceous
- -Small to large forms with short tails and long necks
- -Tended to reduce the teeth in the mouth
- -Many sported head crests
- -Appear first in the Jurassic Period
- -Go extinct at the end of the Cretacaeous
- Varied in size
- Some had only 1.3 feet wingspan
- -large wingspan- 34 feet
- -Largest flying vertebrates to have ever lived
- Based on footprints, structures of hip joints and computer simulations pterosaurs were quadrupedal
- -How they became airborne is not completely clear
- -Argued they ran bipedal and flapped wings
- -Others argue that they sprung forward with their legs and used the wings in a pole-vault like fashion
- Wings different from other flying vertebrates
- -Wings supported by arms and one extremely long finger
- -Finger lengthened by elongating individuals phalanx bones
- -Membrane stretched between the arm and the body to make an airfoil
- -Had layers of muscle, blood vessel and stiffening fibers in it
Airfoil Consisted Of
- 1) from shoulder to wrist was the propatagium
- 2)from fourth finger to the body was the brachipatgium
- 3)Between the legd was the uropatagium
- In rhamphohyneoids is stretched all the way to feet.
- -In pterodactyloids it stretched about to the knee
Bird Pulley System
Musculature that pulls the arms both up and down attaches the knell
- A small keel and did not have the birds pulley system.
- -Pulled the arm down using chest mussels, but unlike birds pulling the arms up required help from muscles on the back (like birds)
- -Have hallow and fused many bones together to strengthen the skeleton for flight
Pterosaurs Nervous System
- Had large eyes and enlargement in the brain to integrate flight info
- -One study showed that the brain region that integrates balance, the flocculus, was over 3x that of birds
Pterosaurs Habitat Preference and Diet
- Body fossils and footprints are found mostly in marine shoreline deposits (preferred)
- -Many thought to be piscivorous (fish eating) or that they ate other marine organisms (needle like teeth)
- -Some had no teeth or teeth used for sieving
- -Fish found in guts
- -Often fell prey to larger animals
Pterosaurs Daily Activity
- Active day and night
- -Wide lens and narrow bony ring is good for low light conditions
- -Narrow lens and wide bony ring is good for day light condition
Suggested that they are warm blooded due to the filaments attached to their bodies
- Laid eggs
- Eggs flattened without cracking during fossilization indicating that they were not leathery
- -Neonates had well developed wings, suggesting that parental care was minimal
Terminology of Extinction
- Abbreviated K/T
- K=German 'kreude' meaning chalk after the Cretaceous chalk cliffs of Europe
- T=Tertiray, an old name for the period after the dinosaurs until 2.6 ma
- Death of the last individual of a species
- Species approach extinction when birth rate drop below death rates
- Extinction of ind. species
- Occur all the time due to a variety of causes
- -Indv. ext. events are often indp. of each other
- -Factors: Competition, depletion of resources, climate change, change in geography, volcanic eruptions, flooding, humans.
- -Most Dino's
- Extinction of many species in a geologically short time
- -Result of one or a few causes
- -Only the dino's alive at the end of the Cretaceous experienced this
- -Ended in Mesozoic
Who died in K/T?
- On land= all non bird dino's, as well as pterosaus
- -Mammals and lizards= 88%
- -Fresh Water=10%
- Selective extinction
What causes mass extinction?
- -Same processes that cause background
- -It is clear that it is a sudden, unexpected events that may cause this
- -A comet impact with Jupiter is 1994 left no doubt that collisions of gigantic proportion occurs
Hypotheses for the K/T
- In Late Cretaceous of India huge volcanic eruption known as the Deccan Traps
- -Huge amount of lava. CO2 and SO@
- -Gas alters chemistry of the atmosphere
- -Sea level decreases
- -Loss of shallow seas
- -Could have played indirect role
- -Decrease in global temperatures
- Dino's still continued to live above the Arctic Circle
1980's and Asteroid
- Became clear an asteroid played a role
- -Clay layer at the K/T boundary containing Iridum
- -30x normal amount
- -Found world wide
- Two ways: extreme volcano or asteroid
Also found in clay and could be used to diff. between volcanism and asteroid
- Not exposed at surface (buried by sediment)
- -Impact crater 110 to 119 miles wide
- -Shock waves would have produced massive earthquakes and volcanic eruptions
- -Rocks under it contained sulfur
- -Produced tsunamis
- -Some say it may have killed dino's