Mammal Origins Flashcards
What is a mammal?
Milk producing glands
Live birth (viviparity)
Hair or fur
How many species of mammals are there?
4,500
How much heavier is the largest mammal from the smallest
53 million’s x heavier
What is an amniote
A tetrapod with a membrane shelled egg
What are eutherians?
New mammals
What defines the nodes in a cladogram?
Synapomorphies - the shared derived character states
What are the pelycosaurs?
An extinct group of mammal like reptiles
Very abundant in Carboniferous/ Permian
Many forms, small, herbivores and carnivores
Relatively long limbed with parasagittal gait
Elongated neural spines on vertebrae (weight bearing)
Dorsal sail (temp regulation?)
What are therapsids?
Worldwide occurrence before break up of Pangea
Longer limbed, more upright stance
Rib reduction (lumbar ribs reduced)
Diaphragm possibly
What are cynodonts?
Complete loss of lumbar ribs Secondary palate, creating nasal passage with turbinal bones More similar in form to early mammals Multiple types of teeth Development of zygomatic arch
What are the advantages for having a secondary palate and therefore long nasal passage?
Heat exchanger
Allows breathing while eating - very important for sucking mammals
Development of an articular quadrate jaw articulation
What is a zygomatic arch for?
allows mastication muscles to attach, gives more power to bite
What is the distinction between a cynodont and a mammal?
The jaw structure
What separates marsupials/eutheria from old mammals?
Development of a placenta
What are tribosphenic cheek teeth?
Basically molars
Very specialised surfaces, fit together very well
deep routed
Allows diversification of diet
What are the 3 bones in the mammalian ear?
Malleus
Incus
Stapes
