Synapsid Amniotes

Question 1

What two groups are within the synapsids?

Answer 1

• Pelycosaurs

- Therapsids (further divided into cynodonts and mammals)

Question 2

What are some features of the pelycosaurs?

Answer 2

• reptiles from carboniferous that led to modern mammals
• single temporal fenestrae like modern mammals
• sprawling posture, some had broad ‘sail’ of spines along back
• one occipital condyle
• hindlimbs semi-erect and closer to body=longer strides

Question 3

What are some features of the cynodonts?

Answer 3

• mammal-like reptiles
• changes in jaw allowed chewing in multiple directions
• muscles expanded into larger areas of skull
• double condyles=greater neck mobility
• nasal turbinates for heat and water exchange regulation
• secondary palate divides food and air passages

Question 4

What are some features of the first mammals?

Answer 4

• small insectivores
• fast and agile
• enlarged brain and endothermy, better hearing and smell

Question 5

What are basic features of all mammals?

Answer 5

• feed young milk from mammary glands
• extended parental care
• large brain compared to body
• hair

Question 6

What glands are present in mammals? Give a brief description of them.

Answer 6

Sebaceous: alveolar glands, waterproof hair and protect skin from drying
Sweat: tubular, secrete water, salts, urea, role in thermoregulation
Mammary: develop along milk line, number and location of nipples varies among species, provide for young
Scent: for defense, recognition

Question 7

What are examples of derivatives of integument?

Answer 7

• claws, hoofs, nails
• antlers (shed, bone)
• horns (most not shed, keratin over bone)
• hair

Question 8

How does the hyomandibular bone vary between fishes and amphibians/reptiles?

Answer 8

• fish: hyomandibula supports jaws

- amphibians/reptiles: becomes stapes, involved in sound transmission within ear

Question 9

What were some structural changes in the bones within the skull from reptiles to mammals?

Answer 9

• lower jaw=single bone: dentary
• jaw joint between dentary ad squamosal
• quadrate and articular part of middle ear
• middle ear=three bones: stapes, incus, malleus

Question 10

T or F: the incus bone within the middle ear in mammals was formerly the articular within reptiles

Answer 10

False

the incus was formerly the quadrate, and the malleus was formerly the articular

Question 11

T or F: mammalian diversity increased after the loss of the dinosaurs in the K-T extinction

Answer 11

True

Question 12

What three groups of mammals were present around the time of the K-T extinction?

Answer 12

• monotremes
• metatherians: marsupials
• eutherians: placentals

Question 13

What are some features of the mammalian group, monotremes?

Answer 13

• hair, endothermy, suckling young
• no nipples or external ears
• embryos develop in leathery eggs
• limited diversity

Question 14

What are some features of the marsupials?

Answer 14

• predominantly found in Oceania, also in Americas
• birth tiny young, suckle until they grow larger
• specialized pouch of mother
• likely arose in what became N America

Question 15

What are some features of the placentals?

Answer 15

• most diverse and widespread group
• extensive diversification after extinction but limited last 50my
• longer gestation of embryo in uterus with placenta
• likely arose in Asia

Question 16

What are 4 possible explanations for the rapid adaptive radiation of mammals?

Answer 16

• extended parental care
• greater intelligence
• versatile feeding mechanisms
• locomotory adaptations