Lec 5 Synapsids & Mammals Flashcards
What are the 6 lineages of Pelycosaurs?
- Eothyrididae
- Caseidae
- Varanopidae
- Ophiacodontidae
- Edaphosauridae
- Sphenacodontidae
Which of the 2 pelycosaur lineages are herbivorous?
Caseidae, Edaphosauridae
What are the characteristics of both eothyridids and caseids?
- Wide, shortened skulls
- large supratemporal bones
- Large external nares
- Procumbent rostrum
What are the characteristics of caseids only?
Closely-packed leaf-like marginal teeth, palatine dentition
What are the characteristics of Varanopids?
long, slender limbs (like lizards), long tooth row extending behind orbit
What are the characteristics of Ophiacodontids?
long rostrum, sharply pointed teeth, stout limbs
What are the characteristics of Edaphosaurids?
small skull, dorsal sail (including hyperelongated neural processes and laterally oriented cross pieces), peg-like teeth, palatal teeth, sliding jaw joint for propalinal movements
What are the characteristics of Sphenacodonts?
reflected lamina of angular, differentiation of dentition (canine), increased coronoid region (suggesting powerful adductor musculature), 3 sacral ribs stabilizing pelvic girdle (efficient terrestrial locomotion)
List an example of Sphenacodont (or Sphenacodontid) and its characteristics
Dimetrodon: have sail, but no cross beams on neural spines like Edaphosaurs
When did Therapsida originate?
Middle Permian
What are the features of Therapsida?
a) Enlarged temporal fenestra
b) Increased coronoid region of lower jaw
c) more forward jaw joint
d) Reduction of palatal teeth
e) Enlarged canine
f) enlarged reflected lamina
g) Loss of supratemporal bone
h) Longer more gracile limbs -> increase mobility at shoulder and hip joints
i) raised body off ground -> efficient ventilation
What are the 6 major groups of Therapsids?
- Biarmosuchia
- Dinocephalia
- Anomodontia
- Gorgonopsia
- Therocephalia
- Cynodontia
What are the features of Biarmosuchians?
Resemble sphenacodontids but no supratemporal, well-developed canine
What are the characteristics of Dinocephalians
Pachyostosis of skull, heavy built, skull processes
What are the two groups of Dinocephalians?
Anteosauria, Tapinocephallia
What are the characteristics of Anteosauria?
Large canine, well-developed incisors, reduced postcanine teeth
What are the characteristics of Taphinocephalia?
Pschyostosis skull roof, temporal fenestra reduced, canine reduced, heels on incisors, post-canine teeth well-developed
What are the characteristics of Anomodontia?
Keratinous beak, large tusks as only teeth, long postorbital region -> massive adductor musculature, enlarged fenestra, mandibular fenestra
What are the characteristics of Gorgonopsia?
Huge canine, 90 degree gape
What are the features of mammals?
Cranial:
1. Dentary only lower jaw bone
2. Squamosal-dentary jaw joint
3. Dentary: high coronoid process and mandibular fossa
4. well-differentiated, marginal, diphyodont dentition
5. 3 ear bones: stapes, quadrate -> incus, articular -> malleus
6. Ectotympanic
7. Single bony naris
8. Double occipital condyle
9. Large temporal fenestra
10. Large zygomatic arch, dorsally bowed and laterally flared
11. No pineal foramen
12. No postorbital
13. Secondary palate
Postcranial:
1. Limbs erect, almost below body
2. Limbs move in parasagittal plane
3. girdles developed dorsally
4. Slender tail
5. No lumbar ribs -> have diaphragm
6. No cervical ribs
7. Vertebral column bends dorsoventrally, not laterally -> longer stride + ventilation
What are the characteristics of Therocephalia?
Derived: high coronoid process, secondary palate, no palatal teeth
Ancestral: have postorbital and postdentary elements
When did Amniota diversify
Late Carboniferous
What are the 2 key features of Cleidoic eggs
- Semi-permeable shell: keep fluid in, allow gas exchange
- Extra-embryonic membranes: chorion, amnion, allantois
What are the features of early amniote?
Astragalus, round occipital condyle, frontal contacts orbits,
What are the 4 types of skulls?
Anapsid, synapsid, diapsid, euryapsid
