Topic 21

Question 1

What are synapsids?

Answer 1

have one “hole” in the skull (contrasts with anapsid (0) and diapsid (2))

clade includes mammals

all non-mammalian members extinct

Question 2

What are therapsids?

Answer 2

characterized by enlargement of the dentary bone in the jaw

development of a secondary palate (a partition to separate the nasal passages from the oral cavity, allows chewing and breathing at the same time)

Question 3

What are the characteristics of mammals?

Answer 3

1. Endothermic
2. Dentition much more differentiated than reptile dentition (greater diversity of diet)
3. Mammalian teeth also occlude more closely than those of reptiles
4. Two sets of teeth over lifespan
5. Vertical placement of limbs beneath the body
6. Mammals have hair
7. Diaphragm (dome-shaped muscle at base of rib cage, helps with breathing)

Question 4

What is the clade monotremata?

Answer 4

only 5 extant species (1 platypus, 4 echidnas)

Australia and New Guinea

Matrotrophic Oviparity (lay eggs), but provide milk for young after they hatch (no nipples, just patches of specialized hairs)

cloacas

lack teeth as adults

feed on invertebrates

Question 5

What are the clades of marsupials and eutherians?

Answer 5

viviparous = give birth to “live” young

placenta provides nourishment to young initially

after birth: nursed on milk from nipples

Question 6

What are eutherians?

Answer 6

eutherians are non-marsupial mammals

nourish young via placenta until very well-developed, then suckle young with milk

have separate urinary and anal opening (no cloaca)

Question 7

What are the characteristics of the order primates?

Answer 7

thumb and toe widely separated from other digits (allows grasping)

flat nails rather than narrow claws on some digits

large brain, short jaws

forward-facing eyes (stereoscopic vision)

pentadactyl appendages