Lecture 7

Question 1

What were Placodermi?

Answer 1

Armoured fish!
Head and thorax covered in large articulated bony plates 
Eggs were fertilised internally 
Give birth to live young 
Upper jaw formed from cheek bone

Question 2

What are the diagnostic features of jawed vertebrates?

Answer 2

1) opposing moveable jaws, mostly with teeth
2) paired nasal sacks (olfactory capsules)
3) complex gill arches for gill support
4) three semicircular canals
5) paired anterior and posterior fins or limbs
6) vertebral elements occurring underneath the notochord

Question 3

Name a good example of a model Gnathostome

Answer 3

Sharks!

Question 4

What are complex skulls made up of?

Answer 4

Splanchnocranium (viscerocranium) -jaws belong to this
Neurocranium
Dermatocranium

Question 5

Name a species with a complex jaw

Answer 5

The highly protrusible jaws of the Slingjaw Wrasse

Question 6

Where did jaws originate?

Answer 6

An anterior pharyngeal arch supporting gills

The use of jaws for feeding would have been a secondary function before coming the primary function in many vertebrates

Question 7

How does vortical cross-flow filtration work in bony fish?

Answer 7

Mainstream flow travels tangentially across the branchial arches and concentrate particles in the posterior oral cavity.
The filtrate exists between Gill rakers and passes to Gill filaments where gas exchange occurs

Question 8

How are gill filaments positioned in lampreys?

Answer 8

The gill arches lie external to Gill pouches, Gill filaments and blood vessels in lampreys