How do caecilians move through soil?

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Zoom in on the serpentine locomotion of the limbless, amphibious caecilian over soil — Gymnophiona Caecilian moving over soil.

Caecilians are specialized for a subterranean existence, utilizing a compact, bony, and spadelike cranium to assist in tunneling through the soil.1

To move through this environment, they employ a method known as concertina locomotion. In this process, the animal's long, muscular body alternately folds and extends along its entire length. This movement is facilitated by the axial musculoskeletal system, where the skin is attached to the axial muscles, forming a tough sheath that encases the body and covers the rear of the skull. This structural arrangement allows for both internal flexures within the skin envelope and broader flexures of the entire body to navigate through the earth.1