Final Cards Flashcards
what is a theropod?
= all saurschians that aren’t sauropods
- mostly bipedal
- claws
- serrated teeth
describe theropod walking
Harrow legs with one foot nearly in front the other
Horizontal, with head and tail balanced over pelvis
Tail never touched the ground: no tail trackmarks
femurs in theropods
some evolved short femurs compared to the tibia to increase speed (ornithomimids)
describe theropod grasping claws
semi-opposable thumbs that could grasp prey - in dromaeosaurs and troodontids, second digit held erect, until attacking (3 toes, 4th up and sticking backwards)
describe theropod arms
three fingered hands are most common
- four digits in more primitive theropods, and some derived forms only had 2
myths about theropod arms (3)
1) they are small
- only small related to body
2) they are weak
- might have been able to lift heavy and had huge claws
3) they were useless
- options such as mating, grasping prey
theropod jaws
carnivorous theropods had larger heads, with powerful bites compared to herbivores (theropods or not)
carnivore vs herbivore jaws
carnivores had slicing, scissor like jaw that was designed to cut through prey, not chew vegetation. Herbivorous ornithischians had grinding jaw for chewing
theropod teeth
- curved backward to hold prey
- serrated for greater cutting ability
- more rounded = less for slicing and more for crunching
not all had huge teeth:
- ornithomimids had beaks for grinding small vegetation
- short jaws for crushing (shellfish)
theropod vision
- theropods had generally excellent vision
- eyes facing forward and overlapping = stereoscopic (3D similar to us but worse)
- also has shortened snouts, to help increase range
theropod brains
had the largest brains compared to body size in dinos
sexual dimorphism
the difference in appearance (colour, size, shape, structure) between males and females of the same species
- some evidence of ornamentation, but could’ve also been colourful
- some medium and smaller theropods were multi coloured with feathers
feathers
many dinosaurs had some sort of feathers. the point when these evolved is continuously being pushed further back. most of the adaptations needed for flight happened for other reasons first.
some of these feathers are not flight feathers, but for display, insulation, and other reasons
types of feathers
1) hollow, hair like filaments (mono filamentous feathers)
2) loose, unconnected barbs (downy feathers)
3) hooked barbs on vane (contour feathers)
4) asymmetrical vane with hooked barbs (flight feathers)
uses for feathers
1) insulation
2) display
3) flight
limb to wing transition
in the fossil record, we can see changes in the size, number, and fusion in the digits of theropods
three main hypotheses for the origin of flight
1) tree down
- climbing and gliding
- claws used for climbing
2) ground up
- running and leaping
3) the compromise
- started by helping them run
what kind of hip structure is this?
saurischian
what kind of hip structure is this?
ornithischian
theropod diversity
- first dinosaurs may have been saurischians with the basic theropod appearance
- there was rapid diversification during late triassic
- sauropods split from theropods a bit later (still in late triassic)
the earliest theropod genus
herrasaurus
herrerasaurus description
walked on all four hind toes, but more advances theropods (neotherapoda) walked on only the middle three with digit 1 greatly reduced
- boxy shull and bad 3D vision
neotheropods
- one of the next clades after theropoda
- loss of fifth digit on feet and development of furcula (wishbone; two collar bones fused together)
only in birds today
coelophysis
- taxon of neotherapoda
- late triassic - early jurassic
- smallish, fast and agile, pack-hunting carnivore
- four digits on hand, but one was embedded in the hand
tetanurae
- clade after neotheropoda
- diverse group marked by stiffened tails, compared to coelophysis
- also loss of 4th digit in hand
tetanurae tails
one idea is that stiff tails helped balance bigger heads
spinosaurus
- 15 m long tetanurae theropod, with a stiff tail
- all of this points towards spending a lot of time in water
-> lived near shores, hunted fish - long snout with nostrils in middle, not front
- long, powerful arms
- dense (non-hollow) bones
- relatively weak pelvis
- flat toes
avetheropoda
- clade after tetanurae
- this group developed pneumatic (hollow) bones
- presumable, these were used to counter the increasing size in theropods, but also present in small avetheropoda too
- formed independently in other dinos
carnosauria
- taxon of avetheropoda
allosaurus
- was one of the most abundant large theropod carnivores in the jurassic
- tooth marks in stegosaurus plates and puncture wounds in allosauruses indicate they frequently fought
coelurosaurs general definition
remarkably diverse: everything from tyrannosaurs to hummingbirds
tyrannosauroidae
largest terrestrial carnivores in earths history
- at least 20 types including both big and small dinos
bite force of t-rex
= 12 800 ibs
- roughly its own weight
- 3-5 times greater than any other terrestrial carnivore
- other aquatic species have been even greater
- high bite force therefore thicker teeth
coelurosaur feet
had a middle metatarsal that tapered proximally, so that the two outer metatarsals made up most of the proximal surface
- this increased strength and agility in coelurosaurs
carnosaur feet
had 3 robust metatarsals making up much of the mid foot
ornithomimids
- very bird like (ostrich)
- long legs
- small skull, large eyes
- no teeth – plants and small animals for food
- fast runner
- evolved for speed
- mostly not carnivores
deinocheirus
- “marvelous terrible hands”
- only fossilized arms were found originally
- very long claws
- thought to look like a tyrannosaur
- no teeth
- long and skinny skull (weak)
- semi aquatic piscivore/herbivore
- gastroliths in stomach
examples of maniraptors
oviraptor
maniraptors
- clade after coelurosauria
- characterized by a modified wrist bone that allowed more movement
paraves
- clade after maniraptora
- loger arms and hands
- ‘wings’ with layered feathers
- backwards pelvis (more ornithischian - pubic bone still separated from ischium, but tilts backwards as in birds)
examples of paraves
troodontids and dromaeosaurs
dromaeosaurids
- highly predaceous and intelligent cretaceous meat eaters with serrated teeth
- fully functional front limbs (unlike many theropods)
- probably social
- called raptors informally
posture of dromaeosaur
- horizontal balanced posture
- claw lifted for running and dropped for attacking
- high degree of activity and some developed flight feathers
troodontids
- possibly entirely covered in feathers
- specimens found with melanosomes (colourful)
avialae
- clade after paraves
- characteristic: fairly long list of what makes a modern bird: full flight and loss of teeth (beak)
- feathers, stiff tail, bipedal, semi-lunate carpal, furcula, mesotarsal ankle, rear-facing pubis, hollow bones (not originally evolved for flying, but then used for flying
archaeopteryx
- taxon of avialae
- birds now known to be theropods
- jurassic bird
- found preserved in fine-grained limestone