Practical Specimens

Question 0

What facial components does the splanchnocranium form in cartilaginous fish?

Answer 0

The upper and lower jaws plus the gills.

Question 1

In cartilaginous fish, what forms the skull?

Answer 1

The neurocranium (or chondrocranium) that forms the braincase.

The splanchnocranium (or viscerocranium) that forms the facial skeleton.

Question 2

What are the 2 hypotheses for the origin of jaws?

Answer 2

1. The first 2 gill plates migrated forwards to form the upper/lower jaws and the hyoid, and the gill slit became the spiracle.
2. The gills are a completely unrelated structure derived from the velum.

Question 3

What components form the skull in bony fish?

Answer 3

The neurocranium, splanchnocranium and the dermatocranium.

Question 4

What is the dermatocranium?

Answer 4

Forms the bones of the roof of the skull, the palate and the upper jaw. Bones often cover the eye and nostril regions.

Question 5

In bony fish, what 5 parts is the splanchnocranium composed of?

Answer 5

1. The hyomandibular
2. The quadrate
3. The articular
4. The angular
5. The branchiostegal rays

Question 6

What is NOT part of the splanchnocranium?

Answer 6

The operculum.

Question 7

In bony fish, where does the angular insert?

Answer 7

Into the dentary (lower jaw bone).

Question 8

In bony fish, which are the teeth-bearing bones?

Answer 8

The premaxilla, dentary and vomer.

Question 9

What is the vomer?

Answer 9

A bone in the roof of the mouth at the anterior of the skull.

Question 10

In bony fish, are there teeth on the maxilla?

Answer 10

No. Well not in the cod (a teleost).

Question 11

What is the jaw articulation in bony fish?

Answer 11

Between the quadrate and the articular.

Question 12

What kind of dentition do reptiles have?

Answer 12

Homodont.

Question 13

What is the jaw articulation in diapsids?

Answer 13

Between the quadrate and articular.

Question 14

In diapsids, what is the purpose of the temporal fenestrae?

Answer 14

For muscle attachment and to make the skull lighter.

Question 15

In reptiles, where do the pectoral and pelvic girdles sit and why?

Answer 15

Below the vertebral column to facilitate a sprawling gait.

Question 16

What is the purpose of a sprawling gait? Give 3 reasons.

Answer 16

1. Lowers the centre or gravity for stability
2. May aid camouflage
3. Allows the ribcage to extend back to the hind limbs to facilitate respiration

Question 17

In reptiles where does the pectoral girdle attach?

Answer 17

The thoracic vertebrae.

Question 18

In reptiles where does the pelvic girdle attach?

Answer 18

The lumbar and sacral vertebrae.

Question 19

How does the ribcage differ in reptiles and mammals?

Answer 19

Reptiles = extends to the hind limbs, no diaphragm

Mammals = gap between the ribs and hind limbs, have a diaphragm

Question 20

Why do mammals have a gap between their ribs and hind limbs? Give 2 reasons.

Answer 20

1. Mammals have an erect stance and the gap increases stride length as must swings the limbs forwards.
2. Mammals are v. active and require a diaphragm/increased lung capacity

Question 21

Where do the pectoral and pelvic girdles attach to the vertebral column in mammals?

Answer 21

To the sides of the spine.

Question 22

In which plane does the spine flex in mammals and why?

Answer 22

Vertical - the erect stance means more weight bares down on the spine. Having zygopophyses in a vertical plane prevents the spine collapsing under the downward force.

Question 23

How does the erect stance of mammals facilitate respiration?

Answer 23

The lungs are NOT compressed in locomotion as they would be in a sprawling gait.

Question 24

In some mammals, the orbit is congruent with the single temporal fenestra. How is this loss of the temporal bar advantageous?

Answer 24

Leaves a bigger space for jaw-closing muscle attachment over the zygomatic arch.

Question 25

What is the jaw articulation in mammals?

Answer 25

Between the dentary (lower jaw) and the squamosal bones.

Question 26

What has happened to the articular and quadrate in mammals?

Answer 26

They have migrated backwards in the skull to form the inner ear bones.

Question 27

In mammals, what has the articular become?

Answer 27

The malleus.

Question 28

In mammals, what has the quadrate become?

Answer 28

The incus.

Question 29

What kind of dentition is characteristic of mammals?

Answer 29

Heterodont.

Question 30

Which 2 animal groups are the ONLY ones to have secondary bony palates?

Answer 30

The crocodiles and the mammals.

Question 31

What do the nasal turbinal bones do?

Answer 31

Support the nasal passages.

Question 32

What is the shell formed from in turtles?

Answer 32

Carapace and plastron = expanded flattened ribs, fused vertebrae with external body armour (dermal bone). There is also an epidermal covering of keratin.

Question 33

What kind of teeth are characteristic of lepidosaurs?

Answer 33

Palatal teeth.

Question 34

What kind of teeth are typical of venomous snakes and why?

Answer 34

Small, conical teeth with long fangs. Bite prey and wait to venom to take effect.

Question 35

What teeth are characteristic of constricting snakes and why?

Answer 35

Large, recurve teeth that further impales the prey/pushes it down the throat.

Question 36

How many digits (and which ones) do birds have?

Answer 36

Digits 1-3.

Question 37

In crocodiles, what is the secondary palate made of?

Answer 37

The palatine, premaxilla and maxilla

Question 38

Why is the vomer exposed in teleosts?

Answer 38

Because they have no secondary palate.