Ceacilians

Caecilian

Blunt-headed, limbless,
elongate amphibians
• Fossorial (subterranean)
or aquatic lifestyle
• Live in moist soil near
water; some species
fully aquatic
• Segmented bodies encircled by annuli (rings) which each
contain one vertebra (usually)
• Heads are digging tools

Caecilian Family

Originated in the Jurassic

Anatomy

Oldest known fossil (from
the Jurassic) = Eocaecilia,
which had
– limbs and
– well-developed eyes
• Extant caecilians LACK
– pelvic girdles and
– pectoral girdles
(and thus limbs);
– Eyes are reduced
(for fossorial lifestyle)

Tails reduced or absent
• Eyes covered by skin
or bone
• Reduced left lung
• No external ear opening
• Dermal fish-like scales present in annular
grooves in some species—
***no other extant amphibians have scales,
but, many extinct species do have scales

Tentacle

Skull

Zygokrotaphic skull

Stegokrotaphic skull

Jaw under-slung (helps avoid a mouthful of dirt)
•Cartilage pad on nose buffers digging stress
• Cartilage between skull bones buffers stress

jaw

adductor mandibulae
interhyoideus posterior

Biomechanics of Burrowing

Vertebral column moves
independently of body wall

Caecilian moves via
internal concertina
locomotion

lateral undulation

Reproduction

Internal fertilization

Male everts phallodeum into female’s cloaca
• Viviparous (75% of species) or oviparous (25%)
reproduction

If viviparous, give live birth
– If oviparous, lay eggs, which will undergo either

Direct development (go through metamorphosis in egg) or
• Indirect development (go through metamorphosis in water
after hatching from egg)