Amphibians

1. AMPHIBIANS
The First Terrestrial Vertebrates

2. Amphibians
– Review the general taxonomy and biology of
amphibians, as well as global patterns of distribution
and diversity.
– Discuss important groups of amphibians:
• Order: Gymnophyona
• Order: Caudata
• Order: Anura
– For the amphibians, what are major evolutionary
pressures?

3. Amphibians
(L. amphibia, living a double life)
“These foul and loathsome animals are
abhorrent because of their cold body,
pale color, cartilaginous skeleton, filthy
skin, fierce aspect, calculating eye,
offensive smell, harsh voice, squalid
habitation, and terrible venom; and so
their Creator has not exerted his powers
to make many of them.”
- Linnaeus, 1758

4. Amphibians
• General characteristics:
– Amphibians (L. amphibia, living a double life)
are ectothermic
– Tetrapod vertebrates
– All living amphibians belong to the group Lissamphibia
– They inhabit a wide variety of habitats, with most
species living within terrestrial, fussorial, arboreal or
freshwater aquatic ecosystems
– Thus amphibians typically start out as larvae living in
water, but some species have developed behavioural
adaptations to bypass this.

5. Amphibians
• Evolution:
– The earliest amphibians evolved in
the Devonian period from sarcopterygian fish with
lungs and bony-limbed fins, features that were helpful
in adapting to dry land
– They diversified and became dominant during
the Carboniferous and Permian periods, but were
later displaced by reptiles and other vertebrates.
– Over time, amphibians shrank in size and decreased in
diversity, leaving only the modern subclass
Lissamphibia.

6. Amphibian Evolution
– Approximately 8,100 species of living amphibians are
known.
– First appearing about 340 million years ago during
the Middle Mississippian Epoch
– Of the living vertebrates, amphibians were the first to
adapt to extended periods of time on land.
– Most still need fresh water at some point in life cycle.
– These multiple habitat requirements are reflected in the
complex life cycle of most (but not all) species.

7. The Complex Life Cycle
Costs and Benefits?

8. Classification of Amphibians
– Divided into:
• Order: Gymnophyona (caecilians)
• Order: Caudata (newts & salamanders)
• Order: Anura (frogs & toads)

9. Order Gymnophiona
(aka, Caecilians/apoda)
– Gymnophiona (Gk: naked snake)
–162 species
– Limbless
– Up to 1.5 m long
– Tentacle between eye and nostril – sensory organ
– Oviparous and viviparous

10. Order Gymnophiona
• Gymnophiona, also called Apoda one of the
three major extant orders of the class Amphibia
– Its members are known as caecilians, a name
derived from the Latin word caecus, meaning
“sightless” or “blind.”
– wormlike amphibians live underground in humid
tropical regions throughout the world.
– Because of their relatively hidden existence,
caecilians are unfamiliar
– There is very little known about this group

11. Gymnophiona Life History, Reproduction,
and Ecology
–Not known much
– Extended breeding in tropics,
across multiple seasons
– Primarily fossorial, but also
aquatic

12. Order Caudata
– Caudata (L, cauda:tail, ara:bear)
–352 species
– North America is home to greatest diversity!
Hynobiidae
Salamandridae
Cryptobranchidae

13. Order Anura/Salientia
– Anura (gk, a:without, oura:tail)
generally called tail-less amphibians
–4000 species!!
– No scientific distinction between
frogs and toads
– Frogs are typically smooth-skinned,
have long hind limbs for leaping, and
live in or near water
– Toads have warty, drier skin, with
shorter hind limbs , and live on land –
but most still return to water to breed