What is a dragon lizard?
Dragon lizards belong to the scientific family Agamidae. Agamid lizards are found in Africa, the Middle East, Asia and Australia.
There are about 70 species of dragon lizards in Australia. They are easy to tell from other Australian lizards because they have:
- rough scales, sometimes with spines,
- strong legs,
- five toes on each foot,
- large slightly rounded heads, with distinct necks,
- a fleshy tongue that is not forked, and
- they are active during the day.
A Thorny Devil, Moloch horridus
Photographer: Alan Henderson / Source: Museum Victoria
Dragon lizards occur in most environments across Australia from tropical rainforests to alpine heaths but they have the largest number of species (highest diversity) in the deserts and semi-arid regions.
Dragon lizards come in many forms, such as the large, well-known Frilled-neck Lizard (Clamydosaurus kingii) from the tropical woodlands of northern Australia and the distinctive Thorny Devil (Moloch horridus) which is an ant-eating specialist from the sandy deserts of central Australia.
A male Nobbi Dragon, Amphibolurus nobbi coggeri, Lake Albacutya, Victoria.
Photographer: Peter Robertson. Source: Wildlife Profiles
Who are the dragon’s closest relatives?
The closest relatives of dragon lizards are the chameleons (Chamaeleonidae). Together the chameleons and dragons form a group known as Acrodont lizards, which refers to their unique teeth. Most lizards have teeth set individually in sockets in the jawbone (pleurodont teeth). In the dragons and chameleons, however, the teeth are fused directly to the jawbone without any sockets (acrodont teeth). Other similarities between chameleons and dragon lizards include intricate ornamentation, horns and elaborate crests.
DNA – the most important molecule in living things
DNA (deoxyribonucleic acid) is a molecule found in the cells of all living organisms. It carries the genetic code which determines who you are and what you look like. All DNA is made up of a combination of four chemical units called bases.
The four bases in DNA are:
- adenine (A)
- cytosine (C)
- thymine (T)
- guanine (G)
The particular order of As, Ts, Cs, and Gs is extremely important, because the order underlies all of life's diversity, even determining whether an organism is a human or another species such as an oak tree, an elephant or a grasshopper.
Did you know?
DNA is the only molecule in living organisms that makes copies of itself (replicates). This is important because when a cell divides the new cells need their own DNA to grow and divide further.
DNA sequencing – cracking the code
DNA sequencing is being used to decipher the DNA code – scientists can then work out how species are related to each other. The more similar an organism’s DNA is to another’s, the more closely related they are.
Did you know?
Unlike DNA in the nucleus, your mitochondrial DNA is inherited from only one parent – your mother. Scientists use mitochondrial DNA sequencing to trace the maternal lineage (the mother, grandmother, great-grandmother etc) and to find out where the common ancestor of all humans lived. The maternal common ancestor would be known as Mitochondrial Eve.
Discovering Dragon Diversity with DNA
Scientists at Museum Victoria are using DNA to unravel the extraordinary diversity of Australia’s dragon lizards.
In the past, scientists have used what an animal looks like (its morphology) to discover new species and to understand how species are related to each other. But morphology can often be misleading. Australia’s dragons have evolved in unusual ways and some lizards that are not closely related actually look very similar. Scientists now study patterns of DNA (DNA sequencing) to find out how closely related species are. Species with the most similar pattern of DNA are most closely related.
Researchers at Museum Victoria have been studying the DNA of three dragon species in Victoria: the Jacky Lizard (Amphibolurus muricatus), the Mountain Dragon (Tympanocryptis diemensis) and the Nobbi Dragon (Amphibolurus nobbi). This research has completely revised our understanding of how these species are related to each other. It has shown that the Mountain Dragon is not related to other species in the group “Tympanocryptis” but is really in the group of lizards known as “Rankinia”. Also DNA sequencing has shown that the two Victorian species belonging to the group Amphibolurus (the Jacky Lizard and the Nobbi Dragon) are not related to each other and the Nobbi Dragon will now be renamed.
Using DNA sequencing, Museum Victoria researchers have also found a number of new species of Australian dragons and these are now in the process of being described by the researchers.
Cogger H. 2000. Reptiles and Amphibians of Australia. Reed Books.
Wilson S. & Swan G. 2003. Reptiles of Australia. Princeton University Press.