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Going out on a limb, or not!

Slender and sinuous, a rapid flick of the body and a long thin tail disappears into the grass. Most people could be forgiven for mistaking it for a snake. I mean after all it was a long wriggly reptile with no legs. But a snake it is not, in fact it’s a lizard, a legless lizard.

Slow Worm, Anguis fragilis (c) George Madani

Last year I was fortunate enough to meet up with Andrew and we spent a great day in the Lake District in search of the UK’s very own legless lizard; Anguis fragilis – the Slow Worm. On seeing one I could not help but remark on the similarities between this and the legless lizards we have back home in Australia.

Flap foot of a Common Scaly-foot - Pygopus lepidopodus[1]

Flap foot of a Common Scaly-foot – Pygopus lepidopodus (c) G. Madani

Correctly referred to as Flap-footed Lizards of the family Pygopodidae, Australia is home to a great diversity of these creatures with over 40 species from 7 different genera. They are found throughout the mainland from temperate woodlands, humid savannas, across the arid heart of the continent and reaching their greatest diversity in the south west corner of Western Australia where the most ideal habitat of grasslands and heath on sandy substrates dominate. But what is it that sets these reptiles apart from serpents? For starters they are not entirely legless. If you were to look closely enough at the vent part of the animal you would notice tiny vestigial limbs, mere flaps flattened against the body. These flaps are the all that remain to hint at what once were legs in this lineage of lizards. In some species they are barely discernible whereas in others they are slightly more prominent and give rise to common names such as ‘Scaly-foots’.

Pygopus steelescotti - Northern Hooded Scaly-foot tongue cleaning its eye[1]

Northern Hooded Scaly-foot, Pygopus steelescotti – tongue cleaning its eye (c) G.Madani

Unlike snakes, flap footed lizards have external ear openings, broad fleshy tongues that they use to lick their eyes clean as they can not blink and unlike snakes which tend to have relatively short tails, the tails of legless lizards are sometimes more then two thirds the length of their bodies! In fact the Australian pygopods are most closely related to geckos! They share a number of similarities with them including only producing two eggs per clutch, immovable, transparent eye-lids which they lick clean with their tongues (pictured right), and the ability to drop their tail should they feel threatened by a predator.

Like skinks, both geckos and pygopods can also regrow their tails. One of the most interesting similarities however is that both groups of lizards are able to vocalise! Yes that’s right they can squeak, bark and even hiss! Most often in alarm or as part of a threat display in some gecko species.

Lialis burtonis - Burton's Snake-lizard[1]

Burton’s Snake-lizard, Lialis burtonis                 (c) George Madani

Different species of legless lizards have different diets, some species feed solely on ant pupae and larvae whilst others almost exclusively spiders. The Burton’s Snake Lizard- Lialis burtonis has a fascinating adaptation where its skull is hinged at eye-level in order to help it to suffocate and swallow larger prey of predominately small skinks which are grabbed from its hidden point of ambush.

Lialis burtonis showing ear opening[1]

Lialis burtonis showing ear opening C) G. Madani

With the Slow Worm and Australian flap footed lizards a great example in convergent evolution can be witnessed. That is; different species independently evolving similar physical adaptations due to similar environmental driving forces. Both these forms of legless lizards have external ear openings, broad tongues, and elongated bodies with heavily reduced hind limbs or in the case of Anguis fragilis entirely limbless.

Pygopus lepidopodus - Common Scaly-foot[3]

Common Scaly-foot, Pygopus lepidopodus (c) G.Madani

Across the world, many other groups of reptiles have evolved a similar body plan in order to best survive in their habitats. Across Asia, Europe and even North Africa are the Anguids or Glass Lizards, some of which such as the European Glass Lizard, Pseudopus apodus can grow up to nearly a metre and half long!

Delma inornata - Patternless Delma[3]

Patternless Delma, Delma inornata (c) G. Madani

Representatives of this family are found from the Mediterranean to the sub continent of India as well as the humid tropical jungles of South-east Asia! In North America there are the Anniellids – American legless lizards and in South Africa members of the genus Chamaesaura – Grass Lizards. Also legless and which are distantly related to the tail biting, four-legged armour plated girdled lizards of the Cordylid family to which they both belong. The need to move fast within a dense matrix of low vegetation, as well as to feed and hide within has no doubt been the facilitator to evolving such an elongate and limbless or limb reduced body form.

All in all, legless lizards from around the world provide a fascinating insight into the processes of natural selection and adaptation. And we are all lucky to each have our very own representatives to appreciate.


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