How do caecilians differ from frogs and salamanders in body shape and limbs?

Caecilians differ significantly from frogs and salamanders in their body structure and lack of appendages. While frogs and salamanders typically possess limbs, caecilians are characterized by their long, limbless, and wormlike bodies.123

The primary structural distinctions include:

• Limbs: Unlike salamanders, which generally have two pairs of limbs of roughly equal size, and frogs, which are identified by their long hind limbs, caecilians are entirely limbless.2
• Body Shape: Caecilians have cylindrical, segmented bodies marked by annular grooves and a short, blunt tail. In contrast, frogs are distinguished by the absence of a tail, while salamanders are characterized by the presence of a long tail.12
• Cranial Structure: Caecilians possess a compact, bony, and spadelike skull with fused ossification centers, which provides strength for burrowing. This differs from the cranial structure of anurans and salamanders, which retain a greater number of independent cranial bones.14

These specialized adaptations allow caecilians to thrive in subterranean environments, utilizing concertina locomotion to move through soil.14