Mammals Flashcards
Mammals and mammal-like reptiles form which clade?
Synapsids
The non-mammalian synapsids include the…
Pelycosaurs (Earliest), Therapsids and Cynodont Therapsids (Last)
How many major adaptive radiations have the synapsids undergone?
3
The tertiary radiation of the mammals is associated with which event?
Dinosaur Extinction
Which region were the pelycosaurs mainly located
Laurasia (N. Hemisphere)
Which two key traits possessed by more derived synapsids did pelycosaurs lack?
1.High locomotor capacity, 2.
increased metabolic rate
What is the key defining feature of synapsids?
Temporal fenestra (hole accommodating jaw muscles behind the eyes)
Why are the sails many pelycosaurs had unlikely to have been used in display?
Lack of sexual dimorphism
What was the likely function of pelycosaur sails?
Temperature regulation
Where were the Therapsids mainly located?
Gondwana (S. Hemisphere)
What are the key features of the Therapsids?
- Increased metabolic rate
- Trough in roof of mouth indicates the evolution of a dedicated airway separate from rest of oral cavity
- Differentiation of teeth types
- Flexible neck
What major evolutionary trends can be observed in later Therapsids?
- Larger temporal fenestra
- Greater teeth specialization
- Development of bony secondary palate
- Change in limb position
- Dual gait locomotion
- Loss of lumbar ribs (diaphragm- higher rate of respiration
- Increased regulation of internal temps and chemical environments.
The Mesozoic radiation accounts for what fraction of mammalian evolutionary history
2/3
What were the key features of the Mesozoic mammals?
- Tiny
- Derived features of skull reflecting larger brain and inner ear
- Evolution of lactation and suckling
- Special Harderian gland- located in the nose, secretes insulatory lipid layer, suggests fur and preening
Tertiary radiation is characterized by what trend
Diversification of mammals into larger, more specialized forms