This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Lecture 19 – 2/26/10 Origin of Mammals: what are we, where did we come from, and when? What are mammals? Three groups to make up mammalia- Placentalia- Marsupialia- Monotremata Monotremes- Only live in Australia- Lay eggs- Babies drink milk- Almost extinct Marsupials- Do well around the world- Settle in Australia- Have pouches- Tiny babies Placentalia- Have placenta to make baby stronger and larger Most mammal fossils can’t be traced into cretaceous (except possibly opossum group) Mammals probably first appeared middle Jurassic, around the same time as birds What characters do mammals have? Features seen in mammals- Only one bone in the lower jaw- Three year ossicles (reptiles only have one)- Secondary palate + nasal turbinate- “erect” posture- Mammary glands – suckling- No “third eye” Locomotion, food processing, senses, metabolism What are mammalian “ancestors”? Pelycosaurs: look more reptilian; carboniferous Therapsids: more mammalian; permian Cynodonts: more mammalian; shorter tail; some even had lumbar area (w/o ribs); had one huge bone in...
View Full Document
This note was uploaded on 08/30/2011 for the course GEL 3 taught by Professor Motani,r during the Spring '08 term at UC Davis.
- Spring '08