The lobe-fins are osteichthyans that have at least some characteristics of the first
terrestrial vertebrates
● Lobe-fin fishes include the coelacanth, Latimeria, a fish within the Actinistia
with paired fins at the end of appendages with internal bony elements (rather
than the fin rays of the Actinopterygii) and the lungfishes
○ In addition to the presence of fins supported by substantial skeletal
elements, coelacanths retain the notochord as the primary anterior-
posterior support and the primitive trait of a jointed braincase.
○ Into the early 1900’s it was thought that the coelacanth had been extinct
for 65 million years
○ In 1938 the crew of a fishing vessel working at the southern tip of Africa
captured a coelacanth
● Lungfishes retain a prominent notochord but have well developed vertebrae as
well
○ Lungfish have functional lungs and can withstand drying of their habitat
○ Lungfish can enter estivation, a state of reduced physiological activity
during drought for months, buried in a mucous cocoon
■ Air-breathe
■ Lower heart rate
■ Retain urea and other wastes
■ Break down body fat and protein
The tetrapods are the ancestrally terrestrial and four-limbed vertebrates. Amphibia is
the earliest diverging living group
Chordates on Land
● Oxygen is 20 times more concentrated in air than in water
● Air is 1000x less dense and 50x less thick than water
● Air experiences far greater temperature extremes
, ● Terrestrial environments comprise a much greater diversity of habitats than do
marine environments
Modern Amphibians
● There are over 6,000 species of predatory salamanders, frogs, and caecilians
● Their skeleton is mostly bones (rather than cartilage)
● Usually amphibians have four limbs
● Their skin is moist and functional in respiration (oxygen and carbon dioxide
diffuse across the skin)
● The extant amphibians include frogs, salamanders, and caecilians
● Amphibians have three distinct forms
○ Frogs
■ Anurans
○ Salamanders
■ Urodeles
○ Caecilians
■ Gymnophionanas
Amphibian Skin
● Mucous glands keep the skin moist so that it functions as a respiratory surface
(cutaneous respiration) and can also produce adhesives that function in
locomotion and defense
● A great diversity of other defensive substances are produced by the skin
including caustic and toxic poisons
Salamanders
● There are over 600 salamander species which are found mostly in North and
Central America
● The salamanders are elongate and tailed and, except for some fully aquatic forms,
have four limbs
, ● Metamorphosis
○ Amphibians have a diversity of life cycles with the typical form that of an
aquatic larva and terrestrial adult
○ Larvae have adaptations to aquatic habitats including external gills and
laterally flattened tails
○ The most fully terrestrial salamanders, the lungless plethodontids, include
species that hatch from eggs as miniatures of the adult with no aquatic
larval stage
○ Paedomorphosis is the evolution of retention of larval characteristics into
adulthood. Many salamanders reach sexual maturity while retaining
external gills and an aquatic habitat
○ All amphibians have cutaneous respiration - at various life stages
salamanders may have gills, lungs, both or neither
○ Newts have aquatic larva followed by a terrestrial juvenile stage (called an
eft) then by a second adult aquatic stage
● Reproduction
○ Most salamander eggs are fertilized internally by sperm passed to the
female in a packet or spermatophore
○ Eggs are either deposited on the spermatophore or it is drawn into the
female’s cloaca (common opening of the digestive and reproductive tracts)
○ A few species are viviparous (birth live young)
● Defense and Offense
○ To be effective, poison must be fast acting on lips or epithelial tissue of
mouth so as to rapidly deter predation
○ Both salamanders and frogs exhibit warning (aposematic) coloration
accentuated by display
○ The Iberian ribbed newt has tubercles along its side through which the
ribs can protrude as a defense
Frogs
, ● Frogs occur on every continent except Antarctica and include more than 6000
species in over 50 families
● Skeletal features specialize anurans for locomotion by jumping with the
hindlimbs generating the power to propel the frog through the air or water
● The pelvis is elongate and reaches far anteriorly and the posterior vertebrae are
fused into a urostyle
● The vertebral column is short and overlapping projections restrict side to side
bending
● Circulatory System
○ Anurans have an efficient, closed circulatory system with a three-
chambered heart and separate pulmonary (lung) and systemic (body)
circuits
● Reproduction
○ Anurans have external fertilization of typically huge masses of eggs (10,000
by cane toads) deposited in aquatic habitats
○ The larval tadpoles first have external then internal gills, the full process
of metamorphosis takes 2-3 years in some species
Caecilians
● The caecilians are a group of entirely limbless amphibians
● Body muscles work against the hydrostatic (balloon-like) skeleton of the body
cavity
● Less is known of caecilians because most are burrowers and seldom seen
● They have highly variable forms of reproduction with some larvae having
extensive external gills
Amphibian Declines
● Many amphibian species have gone extinct in the last 50 years, at least 40% of
species are in decline
● Causes of the declines include
terrestrial vertebrates
● Lobe-fin fishes include the coelacanth, Latimeria, a fish within the Actinistia
with paired fins at the end of appendages with internal bony elements (rather
than the fin rays of the Actinopterygii) and the lungfishes
○ In addition to the presence of fins supported by substantial skeletal
elements, coelacanths retain the notochord as the primary anterior-
posterior support and the primitive trait of a jointed braincase.
○ Into the early 1900’s it was thought that the coelacanth had been extinct
for 65 million years
○ In 1938 the crew of a fishing vessel working at the southern tip of Africa
captured a coelacanth
● Lungfishes retain a prominent notochord but have well developed vertebrae as
well
○ Lungfish have functional lungs and can withstand drying of their habitat
○ Lungfish can enter estivation, a state of reduced physiological activity
during drought for months, buried in a mucous cocoon
■ Air-breathe
■ Lower heart rate
■ Retain urea and other wastes
■ Break down body fat and protein
The tetrapods are the ancestrally terrestrial and four-limbed vertebrates. Amphibia is
the earliest diverging living group
Chordates on Land
● Oxygen is 20 times more concentrated in air than in water
● Air is 1000x less dense and 50x less thick than water
● Air experiences far greater temperature extremes
, ● Terrestrial environments comprise a much greater diversity of habitats than do
marine environments
Modern Amphibians
● There are over 6,000 species of predatory salamanders, frogs, and caecilians
● Their skeleton is mostly bones (rather than cartilage)
● Usually amphibians have four limbs
● Their skin is moist and functional in respiration (oxygen and carbon dioxide
diffuse across the skin)
● The extant amphibians include frogs, salamanders, and caecilians
● Amphibians have three distinct forms
○ Frogs
■ Anurans
○ Salamanders
■ Urodeles
○ Caecilians
■ Gymnophionanas
Amphibian Skin
● Mucous glands keep the skin moist so that it functions as a respiratory surface
(cutaneous respiration) and can also produce adhesives that function in
locomotion and defense
● A great diversity of other defensive substances are produced by the skin
including caustic and toxic poisons
Salamanders
● There are over 600 salamander species which are found mostly in North and
Central America
● The salamanders are elongate and tailed and, except for some fully aquatic forms,
have four limbs
, ● Metamorphosis
○ Amphibians have a diversity of life cycles with the typical form that of an
aquatic larva and terrestrial adult
○ Larvae have adaptations to aquatic habitats including external gills and
laterally flattened tails
○ The most fully terrestrial salamanders, the lungless plethodontids, include
species that hatch from eggs as miniatures of the adult with no aquatic
larval stage
○ Paedomorphosis is the evolution of retention of larval characteristics into
adulthood. Many salamanders reach sexual maturity while retaining
external gills and an aquatic habitat
○ All amphibians have cutaneous respiration - at various life stages
salamanders may have gills, lungs, both or neither
○ Newts have aquatic larva followed by a terrestrial juvenile stage (called an
eft) then by a second adult aquatic stage
● Reproduction
○ Most salamander eggs are fertilized internally by sperm passed to the
female in a packet or spermatophore
○ Eggs are either deposited on the spermatophore or it is drawn into the
female’s cloaca (common opening of the digestive and reproductive tracts)
○ A few species are viviparous (birth live young)
● Defense and Offense
○ To be effective, poison must be fast acting on lips or epithelial tissue of
mouth so as to rapidly deter predation
○ Both salamanders and frogs exhibit warning (aposematic) coloration
accentuated by display
○ The Iberian ribbed newt has tubercles along its side through which the
ribs can protrude as a defense
Frogs
, ● Frogs occur on every continent except Antarctica and include more than 6000
species in over 50 families
● Skeletal features specialize anurans for locomotion by jumping with the
hindlimbs generating the power to propel the frog through the air or water
● The pelvis is elongate and reaches far anteriorly and the posterior vertebrae are
fused into a urostyle
● The vertebral column is short and overlapping projections restrict side to side
bending
● Circulatory System
○ Anurans have an efficient, closed circulatory system with a three-
chambered heart and separate pulmonary (lung) and systemic (body)
circuits
● Reproduction
○ Anurans have external fertilization of typically huge masses of eggs (10,000
by cane toads) deposited in aquatic habitats
○ The larval tadpoles first have external then internal gills, the full process
of metamorphosis takes 2-3 years in some species
Caecilians
● The caecilians are a group of entirely limbless amphibians
● Body muscles work against the hydrostatic (balloon-like) skeleton of the body
cavity
● Less is known of caecilians because most are burrowers and seldom seen
● They have highly variable forms of reproduction with some larvae having
extensive external gills
Amphibian Declines
● Many amphibian species have gone extinct in the last 50 years, at least 40% of
species are in decline
● Causes of the declines include
