Lec 13 - Mammals Flashcards
Final Exam (15 cards)
Why are early mammal groups thought to have evolved in different directions?
They show different adaptations, suggesting broad adaptive radiation
What makes the jaw joint important in mammal evolution?
Mammals shifted from a reptile jaw joint (quadrate-articular) to a dentary-squamosal joint
Which two animals show the transitional stages of jaw evolution?
Diarthrognathus (reptile-like joint still dominant), Morganucodon (mammal joint dominant)
What is heterodont dentition?
Having different kinds of teeth (incisors, canines, premolars, molars)
What was the typical dental formula of early mammals like triconodonts?
4 incisors, 1 canine, 4 premolars, 5 molars = 14 teeth per side (56 total)
What was unique about symmetrodont molars?
They had 3 cusps arranged in a symmetrical triangle
What group likely gave rise to marsupials and placentals?
Pantotheres
What are multituberculates known for?
Herbivory, rodent-like teeth, and long survival from Jurassic to early Cenozoic
Which modern animals are monotremes?
Platypus and echidna
Name two primitive traits monotremes retain
Cloaca and no external ears
How do monotremes reproduce and feed their young?
Lay eggs and secrete milk from modified sweat glands
Which three groups survived past the Cretaceous?
Monotremes, marsupials, and placentals
Why did multituberculates likely go extinct?
Competition with rodents
What were the three phases of mammalian radiation?
Triassic–Jurassic (early orders), Cretaceous (marsupials/placentals arise), Cenozoic (dominance of modern mammals)
