Thorny devil

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Moloch horridus
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Iguania
Family: Agamidae
Subfamily: Amphibolurinae
Genus: Moloch
Gray, 1841
Species: M. horridus
Binomial name
Moloch horridus
Gray, 1841
Thorny Devil Area.png

Acanthosaura gibbosus

The thorny devil (Moloch horridus) is an Australian lizard, also known as the mountain devil, the thorny lizard, or the moloch. This is the sole species of genus Moloch. The thorny dragon grows up to 20 cm (7.9 in) in length, and can live for 15 to 20 years. The females are larger than the males. Most of these lizards are coloured in camouflaging shades of desert browns and tans. These colours change from pale colours during warm weather and to darker colours during cold weather. These animals are covered entirely with conical spines that are mostly uncalcified.


A thorny dragon in Western Australia

An intimidating array of spikes covers the entire upper side of the body of the thorny dragon. These thorny scales also help to defend it from predators. Camouflage and deception may also be used to evade predation. This lizard's unusual gait involves freezing and rocking as it moves about slowly in search of food, water, and mates.[1]

The thorny devil also features a spiny "false head" on the back of its neck, and the lizard presents this to potential predators by dipping its real head. The "false head" is made of soft tissue.[2]

The thorny dragon's scales are ridged, enabling the animal to collect water from any part of its body by simply touching water, usually with their limbs; via the capillary principle water is transported to the mouth through their skin.[1]

Taxonomy and naming[edit]

The names given to this lizard reflect its appearance: the two large horned scales on its head complete the illusion of a dragon. The name Moloch was used for a deity of the ancient Near East. The thorny dragon also has other nicknames people have given it such as the "devil lizard", "thorny devil", "horned lizard", and the "thorny toad".[3]

The thorny dragon was first described in writing by the biologist John Edward Gray in 1841. While it is the only one contained in the genus Moloch, many taxonomists suspect another species might remain to be found in the wild.[1] The thorny dragon is only distantly related to the morphologically similar North American horned lizards of the genus Phrynosoma. This similarity is usually thought of as an example of convergent evolution.


Illustration from Lydekker's The Royal Natural History
Thorny dragon underside, Western Australia

The thorny devil usually lives in the arid scrubland and desert that covers most of central Australia, sandplain and sandridge desert in the deep interior and the mallee belt.

The habitat of the thorny devil coincides more with the regions of sandy loam soils than with a particular climate in Western Australia.[4]


The thorny dragon is covered in hard, rather sharp spines that dissuade attacks by predators by making it difficult to swallow. It also has a false head on its back. When it feels threatened by other animals, it lowers its head between its front legs, and then presents its false head.


The thorny dragon mainly subsists on ants, especially Ochetellus flavipes and other species in the Iridomyrmex or Ochetellus genera.[5] Thorny dragons often eat thousands of ants in one day.[1]

Thorny dragons collect moisture in the dry desert by the condensation of dew on their bodies at night. This dew forms on its skin, and then it is channelled to its mouth in hygroscopic grooves between its spines.[6] During rainfalls, capillary action allows the thorny dragon to absorb water from all over its body.

Breeding and reproduction/survival[edit]

The females lay a clutch of three to ten eggs between September and December. They put these in a nesting burrow about 30 cm underground. The eggs hatch after about three to four months.[7] Predators that consume thorny dragons include wild birds and goannas.

Popular reference[edit]

The popular appeal of the thorny dragon is the basis of an anecdotal petty scam. American servicemen stationed in Southwest Australia decades ago (such as during World War II) were supposedly sold the thorny fruits of a species of weeds, the so-called "double gee" (Emex australis), but those were called "thorny devil eggs" as a part of the scam.[citation needed] Thorny dragons have been kept in captivity.[1]

Further reading[edit]

  • Clemente, Christofer; Thompson, Graham G.; Withers, Philip C; Lloyd, David (2004). "Kinematics, maximal metabolic rate, sprint and endurance for a slow-moving lizard, the thorny devil (Moloch horridus)". Australian Journal of Zoology. 52 (5): 487–503. doi:10.1071/ZO04026.
  • Meyers, Jay (2005). "Prey capture kinematics of ant-eating lizards". Journal of Experimental Biology. 208: 115–127. doi:10.1242/jeb.01345. PMID 15601883. Retrieved 1 May 2015.


  1. ^ a b c d e Browne-Cooper, Robert; Brian Bush; Brad Maryan; David Robinson (2007). Reptiles and Frogs in the Bush: Southwestern Australia. University of Western Australia Press. pp. 46, 65, 158. ISBN 978-1-920694-74-6.
  2. ^ Bell, Christopher; Mead, Jim; Swift, Sandra (2009). "Cranial osteology of Moloch horridus (Reptilia: Squamata: Agamidae)". Records of the Western Australian Museum. 25 (Part 2): 201–237. Retrieved 25 May 2015.
  3. ^
  4. ^ Pianka, E. R.; Pianka, H. D. (1970). "The ecology of Moloch horridus (Lacertilia: Agamidae) in Western Australia". Copeia. 1970: 90–103. doi:10.2307/1441978.
  5. ^ Australia's Thorny Devil, retrieved 2007-10-31
  6. ^ Bentley, P. J.; Blumer, F. C. (1962). "Uptake of water by the lizard, Moloch horridus". Nature. 194: 699–700. doi:10.1038/194699a0.
  7. ^ Pianka, E. R. (1997). "Australia's thorny devil". Reptiles. 5 (11): 14–23.

External links[edit]