Archosaurs (Crocodilia, Pterosauria, Dinosaurs) Flashcards
Superorder Archosauria
- Late Permian/Early Triassic
- 2 main clades:
1. Crocodilians and relatives
2. Pterosaurs, dinosaurs, and birds - Synapomorphies:
1. Teeth in *sockets
2. Antorbital and mandibular *fenestrae (in skull)
3. *Fourth trochanter (on femur)
Age of Reptiles: The Mesozoic
- Synapsids (mammal-like reptiles) replaced by Archosaurs after the Permian extinction
1. Erect limbs
2. Water conservation (uric acid)
Order Crocodilia Descent
- Descended from Thecodonts
- Modern crocodilians are the only surviving non-avian reptiles of the archosaurian lineage
- This linage gave rise to the Mesozoic diversification of the dinosaurs and to birds
- Modern crocodilians differ little from primitive crocodilians of the early Mesozoic
Order Crocodilia
- 28 spp.; lineage appeared 250 mya (Early Triassic)
- Large, solid reptiles with a flattened snout, powerful jaws, and laterally-compressed tails
- Eyes, ears and nostrils on top of head
- Semi-aquatic
Order Crocodilia Families
- Family Crocodilidae
- The Crocodiles (18 spp.)
- Family Alligatoridae
- Alligators (2 spp.) and Caimans (6 spp.)
- Family Gavialidae
- Gharial (1 sp.) & False Gharial (1 sp.)
Secondary Palate
- Crocodilians Have a complete secondary palate!
- Allows these animals to breath while eating (or suckling in mammals) or while opening their mouth underwater
Crocodilian Mating
- Male alligators emit loud bellows during mating season
- Oviparous
- Female parental care
- Temperature-dependent sex determination (>34C = males; <30C = females; *opposite of turtles)
Archosauria -> Order Pterosauria
- “Wing + Lizard”; late Triassic/end-Cretaceous
- 1st flying “Reptile” (and 1st flying vertebrate)
- Range of sizes (9m wingspan!)
- Wings = thin membrane; no feather; elongated 4th digit;anchored to body/leg
- Strong sternums
- Some lost teeth = beak
- Not bird lineage; parallel evolution of flight
- E.g., Pterodactyles, Rhamphorynchoids
“Dinosaurs” Lineage
- Triassic to Cretaceous
- 1000+ spp. non-avian Dinosaurs
- Extinct Archosaurs with limbs held erect beneath the body
- Thecodonts & Crocodiles are not Dinosaurs
Clade Dinosauria:
Characteristics:
- Strong knee & ankle joints
- Upright stance
- Ancestrally bipedal, but also quadrupedal (in both groups!)
2 main Lineages:
1. Ornithischians
2. Saurischians:
I. Sauropods
II. Theropods
-> Modern Birds! (extant avian
Archosaurians)
Standing Tall - Dinosaurs
Sprawling gait
- Hip sockets face sideways
*Carrier’s constraint:
- Having limbs to the sides of the body: Flexing side to side when moving
- Hard to breathe and run at the same time: Expands one lung and compresses the other
Instead… Evolution of an erect gait with two main hip types
Clade Dinosauria -> Herrerasaurus
- 231 mya
- Among the oldest known “dinosaurs”
- Mixture of characteristics
- walking upright
- Pillar-like legs
Classification?
- Early/ancestral Saurischian?
Hips
Saurischia = “liazrd-hipped”
Ornithischia = “bird-hipped”
Clade Dinosauria -> Order Ornithischia
“bird hipped”
Beaked, herbivorous Dinosaurs
- Predentary bone
Often in large herds
- Often prey for many Saurishcian Theropods
- Bipedal (e.g., Iguanodon, Hadrosaurs) & quadrupedal (e.g., Triceratopds, Stegosaurs)
Clade Dinosauria -> Order Saurischia
- “lizard-hipped”
1. Herbivorous, quadrupedal Sauropods
2. Carnivorous, bipedal Theropods - Not all are carnivorous, but all carnivores were Saurischians!
