lecture 15 Flashcards
What does theopoda mean?
beast foot
What are the characters of the therapoda? (5)
- are bipedal
- active runners
- have knife-like teeth
- have extra openings in front of the antorbital fenestrae called the promaxillary fenestrae
- have large hands with grasping abilities
How do therapods move away from the classical characteristics we think of them having?
They evolve omnivory and herbivory, are very toothy to toothless, have diverse ecology and morphology, range from the size of a small bird to a t.rex
Are birds living theropod dinos? How?
Yes, they are the lineage of therapods that survived the end cretaceous mass extinction 65 million years ago
What is the most diverse group of terrestrial vertebrates? How many species?
birds, have nearly 10,000 species
How did hollow bones help therapods as predators? Do birds also have these?
The limb bones of theropods were hollow and likely housed air sacs, the combo of light skeleton and unidirectional breathing made them very active predators
Why are therapods so diverse?
They were around the entire age of the dinos so Diversity in therapod habitats led to diversity in morphology of theropods
What is the global distribution of therapods?
They have been found on every single continent, rom virtually every kind of terrestrial environment
What are the seven main groups of therapods, start from primitive to most derived?
Therapoda
Neotheropoda
Tetanurae
Avetheropoda
Coelurosauria
Maniraptoriformes
Maniraptora
All other therapods outside the herrerasaurus are what?
neotheropoda
What are the three characteristics of the neotheropods?
Lose digit 5 (pinky) on hand
functionally 3-toed foot (fourth toe suspended in air)
have the furcula present
What is the difference between the theropod and the ornithopod footprint?
Theropod footprint has claws, slender toes, longer foot then wide, more of a v shaped outline
The ornithopod footprint has blunt rounded tips, wider toes, wider foot than long, and has a more u shaped foot outline
What is the furcula? What does it do?
Is a wishbone/clavicle, it strengthens the thorax but also acts as a spring which allows for efficient flight
How does the furcula act like a spring and allow for more efficient flight?
When breast muscles contract, the furcula expands, energy is released when the furcula snaps back to normal position which helps lift wings
What else does the furcula aid in outside of strengthening thorax and helping flight?
Aids in respiration, helps to pump air through the air sacs.
Why was it hard to identify dinos as the ancestors of modern birds?
Because we couldn’t see the furcula preserved
What did the discovery of the furcula do to change our perception of the therapod body plan?
moved the arms from out to the side towards the front of the body
Large neotherpods frequently had what on their heads?
elaborate head ornamentation
The ceratosauria belong to which clade? What were they named for?
They’re named for having cranial ornamentation and belonged to the neotheropoda
What were the characters of the tetanurae?
All have an inflexible tail, all have interlocking zygopophyses on tail vertebrae
What are zygopophyses?
projections from neural arches
What group of dinosaurs are within the tetanurae?
The megalosauroidea and spinosaurus
What dinosaur was the first to be named? What clade is it in?
Is in the tetanurae, is the megalosaurus
Spinosaurus and it’s relatives (belonging to tetanurae) are considered what? Why?
crocodile mimics, because they have a croc like snout and conical teeth- the teeth are not laterally compressed
What did spinosaurus likely feed on and why?
probably fish/small terrestrial animals, couldn’t resist tortional stresses
What are the characteristics of the spinosaurus? (4)
- Is the longest theropod
- Has aquatic features, such as the position of nares and dense leg bone
- Had a sail or hump on it’s back- maybe for thermoregulation or display
- May be partially quadrapedal (only therpod to be this)
What were the characteristics of the avetheropoda?
Had a three fingered hand, loss digit 4, meat eaters
What were the features of the allosauroids (belonging to avetheropoda clade)? (4)
-Were the major predator group across most of the world for most of the jurassic and cretaceous)
- Some got very big
- Hunted sauropods
-Have poor fossil record in north america
What are the characteristics of the coelurosauria? (2)
have an enlarged brain and long, narrow foot
What species does the coelurosauria contain?
Tyrannosauroidea
Did Tyrannosauroidea always act as dominant predators?
No , only did after allosauroids extinction
How long did the tyrannosauridae last?
85-66 ma (not long)
Were the tyrannosauridea diverse? What trait was preserved among them?
yes, but they all had small two fingered forelimbs
Are T.rexes native to north america?
No, they’re native to asia
What clade do the compsognathidae belong to?
Coelurosauria
What are the traits of the compsognathids?
are small, lightly built runners
Why do the comsognathidae have low diversity?
due to preservation bias
What dinosaur had a color-banded tail?
The sinosauropteryx (belonged to comsognathidae->Coelurosauria)
What are the traits of Maniraptoriformes? What species belong to this clade?
Maniraptoriformes are dinosaurs with pennaceous (bird-like) feathers and wings, includes Ornithomimisauria
What are Ornithomimosaurs referred to as?
bird-mimic dinosaurs
How did Ornithimimsauria use their feathered wings?
display/courtship
What were the characteristics of the maniraptora? What species belonged to this?
Had elongate forelimbs and a semi-lunate wrist bone, species Therisinosauroidea, and Oviraptorsauria belonged to this clade
What was the semi-lunate wrist bone?
Was a wrist bone that had a half moon shape, allowed motion of the wrist so that the hand could be rotated laterally
Why is the semi-lunate wrist bone important for birds?
Important because it is that bone that allows modern birds to fold their wings.
What unique characteristics did the therizinosaurs (clade: Maniraptora) have?
Huge with long claws- were herbivores and only neotheropods with four toe tracks
What are the characteristics of the maniraptora?
- Small (<1 m) to large (8 m)
- Parrot-like head with or without crest, toothless in derived forms.
- Peg-like spine at top of mouth (for
eating eggs?) - Short tail
- Feathers on forelimbs
- Tail fan of feathers on pygostyle-fused bones (vertebrate) at end of tail…like a bird!
What are the characteristics of Alvarezsaurs (closest to maniraptora)
small, with short arms, small teeth, and seem to be covered in feathers.
Hands are fused.
What are the characteristics of the eumaniraptora? What do they include?
Includes the raptors with killing claws- have both species Troodontids (e.g. Anchiornis)
* Dromaeosauridae (e.g. Velociraptor)
What are the features of the dromaeosauridae? (5)
- Generally small bodied predators
- Well known from Asia (e.g. Velociraptor)
- Fighting dinosaurs
- Some larger forms
- have feather preening teeth
What is the last known step leading upto the birds? What are they?
The archaeopteryx, they are the trnasition between non avian dinos and birds as they have features of both (feathers, long tail and hands with claws)
What are the evolutionary trends in therapoda?
Overall decrease in body mass
When did down-like feathers become common, when did wing like feathers become common? When did omnivory and herbivory develop?
down-like feathers became common in Coelurosauria, winglike feathers first evolved in maniraptoriformes. Omnivory and herbivory evolved around maniraptoiformes.
Redraw the traits refer to slide 52
Look at slide 52
