1) Amphibians first evolved from sarcopterygian fish in the Devonian period and became dominant during the Carboniferous and Permian periods before being displaced by reptiles. 2) The earliest amphibians, known as Labyrinthodontia, were the first vertebrates to live on land and were ancestral to modern amphibians and a bridge to reptiles. 3) Labyrinthodontia included various groups that lived from the Late Devonian to the Triassic period and could grow up to 4 meters long. They had characteristics intermediate between modern fish and reptiles.

1. CLASSIFICATION
Kingdom: Animalia
Phylum: Chordata
AMPHIBIANS
Subphylum: Vertebrata
Class: Amphibia (anamniote tetrapods)
Subclass: Labyrinthodontia (earliest tetrapods)
first terrestrial vertebrates
Subclass: Lepospondyli
Subclass: Lissamphibia

3. CLASS AMPHIBIA
- 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.

4. SUPERCLASS LABYRINTHODONTIA
→ Ichthyostegalia—primitive ancestral forms Late Devonian
only.
→ Temnospondyli—common, small to large, flat-headed forms
with either strong or secondarily weak vertebrae and limbs;
mainly Carboniferous to Triassic. May or may not be ancestral
to all modern amphibians
→Anthracosauria—deep skulls, strong vertebrae but weak
limbs, evolving towards and ancestral to reptiles; Carboniferous
and Permian (Now considered to be reptile-like tetrapods
separate from true amphibians)

5. SUPERCLASS LABYRINTHODONTIA

6. SUPERCLASS LABYRINTHODONTIA
→ oldest amphibians; earliest tetrapods
→ considered to include the first vertebrates known to
live on solid ground, and to have been ancestral to at
least some of the groups of modern amphibians and a
bridge to the reptiles.
→ constituted some of the dominant animals of Late
Paleozoic and Early Mesozoic times (350-210 mya).

7. SUBCLASS LABYRINTHODONTIA
→ Greek for "maze-toothed,"
→ up to four meters long.
→ They were short-legged and large headed
→ skulls were deep and massive
→ jaws lined with small, sharp, conical teeth. There
was a second row of teeth on the roof of the mouth.
→ vertebrae made of four pieces: an intercentrum, two
pleurocentra, and a neural arch/spine.

8. SUBCLASS LABYRINTHODONTIA
→ special sense organs in the skin, that formed a
system for perception of water fluctuations
→ some of them possessed well developed gills and
many seemingly had primitive lungs.
→ labyrinthodonts were probably similar to fishes. They
laid eggs in the water.

9. SUBCLASS LABYRINTHODONTIA
Strongly folded tooth surface, involving infolding
of the dentin and enamel of the teeth, so that a
cross section resembles a classical labyrinth (or
maze), hence the name of the group.
Cross-section of a labyrinthodont tooth

10. LIMBS

11. LIMBS

12. SIMILARITIES TO FISHES
→ anamniotic eggs
→ tail fins
→ lateral line system
SIMILARITIES TO REPTILES
→ vertebral column was strengthened, notochord
replaced by bony rings
→ limbs developed (more adapted for terrestrial
habitat)
→ development of lung structures

13. Lepospondyls

14. What are Lepospondyls?
 Small salamander-like amphibians from the
Carboniferous.
• Cardiocephalus Salamander (Eastern Mud)

15.  having simple, spool-shaped vertebra, which were not
preformed as cartilage, but rather grew as bony cylinders
around the notochord

17.  Six different groups are known, the
 Acherontiscidae,
 Adelospondyli,
 Aïstopoda,
 Lysorophia,
 Microsauria and
 Nectridea,
 between them they include newt-like, eel- or snake-like, and
lizard-like forms,
 Various species were aquatic, semi-aquatic, or terrestrial

18. • BRIEF OVERVIEW OF THE
DIFFERENT ORDERS

19. Order Adelospondyli
• is an order of elongate, presumably
aquatic, Carboniferous amphibians.
• skull is solidly roofed, and elongate, with
the orbits located very far forward

20. • limbs are well developed
• Adelospondylus.

21. Order Aïstopoda
• an order of highly specialized snake-
like amphibians.
• no trace of limbs or even limb girdles in
any known fossil
• the tail was short and primitive

22. • bones at the back of the skull were
reduced or absent.

23. Order Nectridea
• resembled modern newts or aquatic
salamanders.
• long flattened tails to aid in swimming,
• and well-developed hind limbs, with a full
set of five toes each.

24. Diplocaulus

25. Order Microsauria
• short tails and small legs
• group included lizard-like animals that were relatively well-adapted
to living on dry land, burrowing forms, and others that.
• possible ancestors of the newts and salamanders

26. Order Lysorophia
• resembled small snakes, as their bodies
are extremely elongate.
• are usually considered to be related to
the Microsauria, although the pattern of
bones of the skull is very different.

28. • Some features prompt the concept that at
least some specimens classified as
lepospondyls may have arisen directly
from crossoptergian ancestor.
• Some Urodeles may be descendants of
those specific lepospondyls.