Class Mammals

Class Mammals

1. Reproduction

2. Evoltuion

   • Early synapsid
     • Pelycosaurs synapsids group
       • therapsids synapsid group
         • Cyndont synapsid group
           • Only group survived Mesozoic
           • evolved several characteristics to support a high metabolic rate
         • First to have an efficient erect gait with upright limbs beneath body
     • First synapsid had homodont dentition teeth

3. Features

   • Body
     • Synapsid skull
   • Endothermic
   • skin generally thinker than other vertebrates
   • Hair
     • All Hair at some point
       • grow from hair follicle
     • Different Types
     • Hair stop growing at a certain length

4. Cyndodonts features

   • 1) Specialized jaw musculature permitted a stronger bite
     • Changes to jaw
   • 2) Heterodont teeth improved food processing for variety of foods
     • Changes to teeth
       • Diphyodont
       • Polyphyodont
   • 3) Turbinate bones in nasal cavity aided body heat retention
     • Heat retantion
   • 4) Secondary palate enabled breathing while eating
     • Help breath while eating
   • 5) Loss of lumbar ribs correlated with evolution of diaphragm
     • Lost ribs