15: Amphibians

Question 1

When did amphibians split into two main evolutionary lines?

Answer 1

300mya

Question 2

What are the two main evolutionary lines of amphibians?

Answer 2

Ancestors of reptiles

Ancestors of modern amphibians

Question 3

How many species of amphibian are there?

Answer 3

Around 6000

Question 4

What is their water/land relationship?

Answer 4

Adapted for life on land, but still depended on water

Question 5

Why move onto land?

Answer 5

Competition/predation with other aquatic species
More food sources- metamorphosis, so exploit different niches
Can get back into the water under arid conditions

Question 6

Amphibian fossil record

Answer 6

None found from before early Jurassic- gap in fossil record

Question 7

Why is the fossil record so bad?

Answer 7

Burrowing species
Lived in fertile environments
Had a reduced skeleton
Had soft, delicate bodies

Question 8

What happened in the Triassic?

Answer 8

Lots of environmental change
Huge rise in CO2 concentration at the end of Triassic
Deserts expanded their range
No recorded glacial activity
These could have impacted the potential for fossilisation

Question 9

What were Stereospondyl?

Answer 9

A group of extinct amphibians

Eg. Mastodontosaurus, Peltobatrachus

Question 10

Features of Stereosponyli compared to other tetrapods

Answer 10

More simplified backbones and weak vertebrae-
couldn’t support own body weight, could only crawl on land
Appeared in Late Permian

Question 11

When were amphibian ancestors from?

Answer 11

The Permian

Question 12

Two theories of the ancestry of modern amphibians

Answer 12

1. Single phylogenetic group due to similarities in soft tissue and physiology
2. Frogs and amniotes evolved from different groups of fishes than those that gave rise to salamanders

Question 13

Tooth similarities between frogs, salamanders and caecilians

Answer 13

All have pedicellate teeth- base of tooth is separated from crown by fibrous tissue that is softer than dentine or enamel

Question 14

Importance of pedicellate teeth

Answer 14

Unique, probably only evolved once

Suggests that extant amphibians are monophyletic

Question 15

Characteristics of modern amphibians

Answer 15

Bony skeleton
2 types of skin glands
Ectothermal
Ribs do not encircle body
Pedicellate teeth
Fat bodies
Green rods in eyes
Presence of operculum

Question 16

Name for all extant amphibians

Answer 16

Lissamphibia

Question 17

Shared characteristics with tetrapods

Answer 17

Fenestration of skull
Loss of posterior skull bones
10 cranial nerves

Question 18

Amphibian heart features

Answer 18

3 chambered hearts

Incomplete separation of the ventricles

Question 19

Examples of salamanders

Answer 19

Great Crested Newt, Britains largest and most endangered newt species
Giant salamander

Question 20

Salamander’s ties to water

Answer 20

Aquatic larvae
Metamorphosis to terrestrial adults
Some are entirely aquatic
So not separate from water

Question 21

Ancestry of salamanders

Answer 21

Possibly from Triassic

Don’t see transition fossils due to Romer’s Gap (Cretaceous)

Question 22

Common characteristics of salamanders

Answer 22

500 species
Limbs at a right angle (sprawling gait)
Aquatic and burrowing limbs
Carnivorous- worms, arthropods, molluscs
Have gilled larvae

Question 23

Characteristics of salamander skulls

Answer 23

Loss of primitive bones at the back of the skull
Large orbits
Pedicellate teeth
Lower jaw consists of Meckel’s cartilage
No bony connection between pterygoid and maxilla

Question 24

Characteristics of salamander skeleton

Answer 24

Single sacral vertebrae
Short ribs
Extensive tail
Loss of dermal bone on the shoulder girdle
Small pubis

Question 25

What are axolotyls?

Answer 25

They can metamorphose under certain conditions into salamander-type things
Gills become lungs
Look very prehistoric
Don’t live long after transformation

Question 26

How do salamanders capture prey?

Answer 26

Use tongue prehension
Very sticky tongue
Rapid projection/retraction
Modify speed and angle of attack based on prey size

Question 27

What are Caecilians?

Answer 27

Amphibians that totally lack girdles and limbs
Weird slimy snake things
Eg. blue caecilian

Question 28

How many Caecilian fossils are there?

Answer 28

Only 3 well preserved enough to be named

Question 29

How many species of Caecilian are there?

Answer 29

160

Question 30

Caecilian characteristics

Answer 30

Elongated body
Small scales
Limbless
Burrow
Internal fertilisation
Aquatic larvae
Eat worms and small invertebrates

Question 31

What is skin feeding?

Answer 31

Parents grow bits of skin very high in nutrients

Babies eat this

Question 32

Jurassic frogs

Answer 32

Look a lot like modern frogs

Question 33

What is Prosalirus bitis?

Answer 33

The oldest known frog (Jurassic)
Known from post cranial skeleton
Bones indicate that it was capable of jumping

Question 34

What is Vieraella?

Answer 34

Nearly complete frog fossil
From the Lower Jurassic
10 vertebrae
Fused tibia and fibula

Question 35

What are Shomronella?

Answer 35

Cretaceous tadpoles

Fossil record of tadpoles is quite good

Question 36

Extant Anuran (frogs) features

Answer 36

Aquatic reproduction
Tailed larvae form with gills
No tails in adult, lungs
Specialised for jumping
If frogs go, so will everything else

Question 37

How many species of Anuran are there?

Answer 37

4840

Question 38

Frog anatomy

Answer 38

Large orbits
Pedicellate teeth
No ribs
Loss of scales
No hyoid bone
Fused ulna and radius and tibula and fibula- to prevent breaking when jumping

Question 39

Why do snakes need lots of venom to kill frogs?

Answer 39

They have low metabolic rates

Question 40

How do some frogs fly?

Answer 40

Glide using webbed hands and skin flaps