general groups of vertebrates

Question 1

how diverse are vertebrates? what are the two main groups?

Answer 1

• Tremendous diversity and distribution 
	• Most are now extinct, approx. 63,000 extant species 
	• Two major groups: 
○ Non-amniotes (fishes and amphibians) 
○ Amniotes 
(sauropsids -reptiles/birds) 
 (synapsids - mammals)

Question 2

what are agnathans? what are the two extant groups?

Answer 2

jawless vertebrates
• Two extant groups:
○ Myxiniformes- hagfishes (approx 75 spp.); all marine; scavengers
○ Petromyzontiformes: lampreys (approx. 40 spp.); marine and fresh water; most adults are ectoparasites

Question 3

what are some features of agnathans?

Answer 3

• All lack jaws; body elongate
• Notocord in adult
• Incomplete cranium of cartilage
No vertebrae or bone

Question 4

describe Chondrichthyes (cartilaginous fishes)

Answer 4

• gnathostomes (jawed)
  • 1,201 extant species
  • Two groups:
  ○ Elasmobranchii - sharks, skates and rays
  § Range in size from 25 cm to over 15 m
  ○ Holocephali - ratfish or chimaeras
  § Rat like tail and large protruding front teeth
  Distinct head

Question 5

describe osteichthyes (bony fishes)

Answer 5

gnathostomes (jawed)
• Actinopterygii (ray finned fish)
○ Approx. 30,554 extant spp.
○ Thin finned fish
○ Polypteriformes - bichirs and reedfish
○ Acipenseriformes - sturgeons and paddlefish
○ Neopterygii - gars and bowfin
○ Teleostei - most fish
• Sarcopterygii (lobe finned fish)
○ 8 extant species
○ Heavy bodied , slow moving fish w/ broad based, muscular fins
○ Cladistically contain the tetrapods (tetraapoda)
§ Actinista - marine coelacanth; 2 extant spp.
□ Africa in 1938 and indonesia in 1998
§ Dipnoi - freshwater lungfish; 6 extant spp.
□ Australia (1 sp); south america (1 sp.), africa (4 sp)

Question 6

what are the three groups of amphibia? describe them

Answer 6

gnathostomes 
	• Approx. 6801 extant species 
	• 3 main groups: 
		i. Urodela or caudata 
		- Salamanders 
		- Tailed amphibians 
		ii. Anura 
		- Frogs and toads 
	- Tailless; large hind legs 
		iii. Gymnophiona 
		-Caecilians 
		- Legless

Question 7

what are the groups of reptiles? describe them

Answer 7

• Testudinia - turtles and tortoises 
		○ Approx 313 extant species 
		○ Carapace and plastron 
	• Lepidosauria - lizards and snakes 
		○ Approx. 9776 extant species 
		○ 3 main groups: 
			§ Sphenodontia - tuatara 
				□ Only one extant species 
			§ Lizards 
				□ Diverse and numerous 
				□ Many legless forms 
			§ Snakes 
				□ Diverse and numerous 
				□ Specialized jaw structure 
	• Archosauria - crocodiles, dinosaurs and birds 
		○ 3 main groups: 
			§ Crocodilia - crocodiles, alligators and gharial 
				□ 23 extant species 
				□ Semi aquatic predators 
				□ Dermal bone (osteoderms) embedded in skin 
				□ Extensive parental care 
			§ Dinosaurs 
				□ All extinct 
Aves - birds

Question 8

what are Aves? describe them

Answer 8

6. Gnathostomes - aves (birds) 
	• Approx. 10,000 extant species 
	• Archosaurian image 
	• Endothermic with feathers 
	• Many adaptations for aerial lifestyle

Question 9

what are mammals? what did they evolve from? 3 main groups?

Answer 9

7. Gnathostomes - mammalia (mammals) 
	• Approx. 5,488 extant species 
	• Evolved from synapsids 
	• Endothermic with hair 
	• 3 main groups: 
		○ Protoherians (monotremata) 
			§ Duck billed platypus and echidnas 
			§ Oviparous - lay eggs 
		○ Metatherians (marsupialia) 
			§ Kangaroos, wallabies, koalas, opposums, etc 
			§ Short gestation, simple placentae 
			§ Marsupium 
		○ Eutherians 
			§ The familiar mammals 
			§ Long gestation, complex placenta