The natural world often employs similar blueprints to solve the same environmental challenges, a phenomenon known as convergent evolution. Among the most striking examples of this is the physical similarity between snakes and legless lizards. To the untrained eye, both appear as long, scaly, limbless reptiles slithering through the undergrowth. However, despite their shared aesthetic, they belong to entirely different evolutionary lineages. While snakes belong to the suborder Serpentes, legless lizards are scattered across several different lizard families that independently lost their limbs over millions of years to better navigate subterranean or dense vegetative habitats.

The Eyes Have It

1 of the primary anatomical distinctions lies in the eyes. Snakes lack moveable eyelids; instead, their eyes are protected by a transparent, permanent scale known as a “spectacle” or “brille.” This gives snakes their characteristic unblinking stare. In contrast, most legless lizards possess functional, moveable eyelids that allow them to blink. Regarding the Eastern glass lizard, the presence of these moveable eyelids is a definitive trait that identifies them as lizards rather than snakes, providing a clear visual cue for identification in the field.

What Did You Say? I Can’t Ear You

External ear openings offer another significant point of divergence. Snakes do not have external ear holes or eardrums; they “hear” primarily by sensing ground-borne vibrations through their jawbones, which are connected to their inner ear structure. Most legless lizards, however, retain the external ear openings typical of their legged relatives. The Burton’s legless lizard possesses these small ear holes, which are entirely absent in snakes, marking a fundamental difference in how these 2 groups perceive auditory information from their environment.

Jaws

The structure of the jaw further separates these 2 groups, particularly regarding their feeding capabilities. Snakes are famous for their “kinetic” skulls, where the lower mandibles are connected by flexible ligaments rather than a fixed chin bone, allowing them to swallow prey much larger than their heads. Most legless lizards have more rigid, fused jaw structures that limit them to smaller prey. However, there is an interesting exception: the Burton’s legless lizard has a specialized hinge made of cartilage that allows it to stretch its mouth to consume relatively large prey, though it still lacks the full independent mandible movement seen in snakes.

Speaking in Tongues

Tongue morphology is another subtle but telling difference. While both reptiles use their tongues for chemoreception—gathering scent particles to be processed by the Jacobson’s organ—the shapes differ. Snakes almost universally possess long, deeply forked tongues that they flick in and out of a small notch in their upper lip. Legless lizards typically have shorter, fleshier tongues that are notched rather than deeply forked. Even the specialized Burton’s legless lizard lacks the classic snake-like forked tongue, possessing a more “lizard-like” fleshy version instead.

The Tail End of Things

The proportions of the body relative to the tail provide a structural clue that is often overlooked. In snakes, the tail (defined as the portion of the body behind the cloaca) is relatively short, usually making up less than 1/3rd of the total length. Legless lizards are essentially the opposite; their tails are often significantly longer than their actual bodies. The tail of an Eastern glass lizard can account for up to 2/3rd of its total body length, making the animal’s “body” surprisingly short in comparison to its overall appearance.

An Emergency Escape

This long tail serves a vital defensive purpose known as caudal autotomy, or the ability to “drop” the tail when threatened. When a predator grabs a legless lizard by the tail, the lizard can fracture the vertebrae at specific points, leaving a wriggling tail behind as a distraction while the lizard escapes. This behavior is what gave “glass lizards” their name, as their tails seem to “shatter” like glass. While many legless lizards like the slowworm can regrow their tails, snakes lack this ability entirely; if a snake loses a portion of its tail to injury, it cannot regenerate.

Belly Up

The underside of these reptiles reveals a major difference in how they interact with the ground. Snakes possess wide, rectangular belly scales called “scutes” that provide traction, allowing them to grip surfaces and move efficiently even on flat terrain. Legless lizards lack these specialized scutes, possessing small, uniform scales all the way around their bodies. Because of this, legless lizards are often “helpless” on smooth, flat surfaces like paved roads where they cannot find the lateral resistance needed to push themselves forward, whereas a snake can navigate such surfaces with ease.

It’s What’s Inside That Counts

Internal anatomy also differs, particularly within the respiratory system. To accommodate their long, narrow body plan, most snakes have evolved to have only one functional lung (usually the right one), with the other being vestigial or absent entirely. Legless lizards, however, typically retain 2 more-or-less equal lungs, reflecting their closer relationship to other lizard species. This internal layout remains a vestige of their legged ancestors, even as their external limbs disappeared through the process of evolutionary reduction over time.

Movin and Groovin

Locomotion styles, while appearing similar, involve different muscular engagements. Snakes use a variety of movements, including lateral undulation, sidewinding, and rectilinear motion (using those belly scutes to move in a straight line). Legless lizards are largely limited to lateral undulation, where they push their bodies against objects in their environment to create forward momentum. This is why you will often find legless lizards like the slowworm in areas with plenty of leaf litter or dense grass, which is their preferred habitat for efficient movement and hunting.

What’s for Dinner?

Dietary habits often reflect these anatomical limitations. Because snakes can swallow large prey whole, they often target rodents, birds, and other sizable vertebrates. Legless lizards, with their more restrictive jaws, typically focus on smaller fare. The harmless slowworm primarily consumes soft-bodied invertebrates like slugs, worms, and garden snails. While some specialized legless lizards like the Burton’s hunt other lizards, the majority of the group occupies a niche more similar to insectivorous legged lizards than to apex-predatory snakes.

In Conclusion

Ultimately, the comparison between snakes and legless lizards is a masterclass in biological nuance. While they have arrived at a similar “tube-like” solution for moving through their environments, the details of their eyes, ears, jaws, and tails tell the story of their distinct origins. By observing these small characteristics—many of which are documented extensively by resources—one can appreciate the incredible diversity of reptilian life and the different paths evolution takes to reach a successful, specialized form.