Thorntail agamas

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Thorntail agamas
Decorated thorntail (Uromastyx ocellata)

Decorated thorntail ( Uromastyx ocellata )

Systematics
Superordinate : Scale lizards (Lepidosauria)
Order : Scale reptiles (Squamata)
without rank: Toxicofera
without rank: Iguana (Iguania)
Family : Agamas (Agamidae)
Subfamily : Thorntail agamas
Scientific name
Uromastycinae
Theobald , 1868

Thorn- tailed agamas (Uromastycinae) are a subfamily within the agam family (Agamidae). These stocky agamas are pronounced desert inhabitants. Representatives of this genus can be found in the dry belts of Africa and Asia .

features

Compared to other agamas, thorntail agamas are relatively large and plump with a body that appears flattened from above. The legs are short and strong. The head with a vertical ear is small and is reminiscent of the heads of tortoises . The short, thick tail is densely covered with strong prickly scales. Depending on the amount of sunlight (see chapter on adaptation to the arid environment), they are dark, brown-gray or bright yellow, orange and green in color. The Egyptian thorntail is by far the largest representative of the genus with a length of up to 75 cm and a weight of 1.5 kg. All other species are between 25 and 50 cm tall.

There is a gender dimorphism. Adult males are significantly larger and have a larger head with a sharper snout. There are also differences between the sexes in terms of coloration: the males are more contrasting and sometimes also differently colored than the females. The preanofemoral pores of the males ready to mate are enlarged.

Habitat and distribution area

Total distribution area of ​​the thorntail agamas

Thorntail agamas live exclusively in arid areas, more precisely semi-deserts, but also the vegetation points that are sparsely planted in the full desert.

The total distribution area of ​​the thorn-tailed dragons stretches from West Africa to the West Indies.

There are two major distribution areas in Africa :

The Egyptian thorntail is found in Egypt east of the Nile, on the Sinai, Israel, Jordan and on the Arabian Peninsula, making it the only thorntail agam that is common on both continents.

The distribution area of ​​the Asian thorntail agamates can also be roughly divided into two larger units:

Way of life and behavior

Thorn-tailed dragons are only active during the day and hide at night, in the greatest midday heat and when there is disturbance under stone slabs and in caves. Species that live in areas where winter temperatures can drop to 0 ° C retreat into deep caves to hibernate from a few weeks to several months. Thorntail agamas are pure herbivores , at best the young animals also feed on insects . Since thorntail agamas have hardly any natural enemies, they also become trusting to humans relatively quickly. If you stay still or move slowly, they will come so close even in the wild that you can feed them. Nevertheless, they are quickly stressed by too much movement and too many people in terrariums, as their natural habitat is very sparsely populated and there are hardly any encounters with conspecifics and other desert inhabitants. The males occupy territories of several hectares.

Thorntail dragons are sexually mature when they are three to four years old. The male shows his willingness to mate through his impressive behavior. It walks around the female with a nod and secretes a whitish liquid. When the female is pregnant, she becomes more aggressive. Four to six weeks after mating, they lay up to 25 eggs, which they scratch with soil and defend for weeks. The young hatch after about 90 to 100 days.

Adaptation to the arid environment

As distinct desert dwellers with a small radius of action, the thorntail agamas have special adaptations to their surroundings. Even if they can endure a very strong heating of their body up to 47 ° C, they hide in the greatest midday heat in rock crevices or caves during the summer. Their changeable skin color, hence the name "changeable thorn tail", helps them to use the different intensity of radiation and to regulate their body temperature accordingly. In the cool morning hours, the skin is darkly colored so that it can absorb as much heat as possible, while at noon it is colored orange to bright yellow so that a lot of radiant heat is reflected and the body does not heat up additionally. In addition, thorntail agamas change their body position in order to let the sun's rays work particularly well or as little as possible.

Since thorntails meet their water needs exclusively through their vegetable food, they also have adaptations that minimize water loss and make the best possible use of the liquid they have absorbed. As much water as possible is withdrawn from the excretions in the sewer . The salts that are concentrated in the body as a result are excreted via glands in the nose. In addition, the animals can absorb moisture through the skin and remove water from the fat stored in the tail by burning it.

Tribal history and systematics

For a long time, the opinion was widespread in research that the African and Arabian taxa of the thorn-tailed dragons share a common tribal history, but that the Indian thorn-tail must be separated from it. New molecular biological studies have shown that Macfadyen's thorntail cannot be placed in the group of Arab taxa despite its similar morphology . On the basis of these investigations as well as geological and palaeontological studies, it can be assumed that thorn-tailed agamas developed in Central Asia during the Eocene and were only able to colonize Africa after its connection with Eurasia in the early Miocene .

Position of the thorn-tailed agamas within the family of the Agamidae (after Macey et al. 2000):

  Iguanas  

 Pleurodonta  ( iguanas and relatives)


  Acrodonta  

 Chameleons  (Chamaeleonidae)


  Agamas  

 Thorntail agamen (Uromastycinae)


   

 Butterfly  agamas (Leiolepidinae)


   

 Amphibolurinae


   

 Sailing lizards  ( Hydrosaurus )


   

 Draconinae


   

 Agaminae









Template: Klade / Maintenance / Style
South Saharan thorntail
Decorated thorn tail
Geyr's thorntail dragon

Today the subfamily Uromastycinae comprises 18 species in two genera:

swell

  • Thomas Wilms: thorntail dragons. Way of life. Maintenance. Breed. 2nd, revised, greatly expanded edition. Herpeton, Offenbach 2001, ISBN 3-9806214-7-2 .
  • Beate Löhr: Geyr's thorn-tailed dragon. Uromastyx geyri. Natur-und-Tier-Verlag, Münster 2004, ISBN 3-937285-09-1 .
  • Sayed AM Amer, Yoshinori Kumazawa: Mitochondrial DNA sequences of the Afro-Arabian spiny-tailed lizards (genus Uromastyx; family Agamidae): phylogenetic analyzes and evolution of gene arrangements. In: Biological journal of the Linnean Society. Vol. 85, No. 2, 2005, pp. 247-260, doi : 10.1111 / j.1095-8312.2005.00485.x .
  • Sönke Frahm: The decorated thorn-tailed dragon. Uromastyx ocellata. Natur-und-Tier-Verlag, Münster 2006, ISBN 3-937285-80-6 .
  • Thomas M. Wilms , Wolfgang Böhme , Philipp Wagner , Nicolà Lutzmann, Andreas Schmitz: On the Phylogeny and Taxonomy of the Genus Uromastyx Merrem, 1820 (Reptilia: Squamata: Agamidae: Uromastycinae) - Resurrection of the Genus Saara Gray, 1845. In: Bonn zoological contributions. Vol. 56, No. 1/2, 2007, ISSN  0006-7172 , pp. 55-99, digital version (PDF; 1.34 MB) .

Individual evidence

  1. ^ J. Robert Macey, James A. Schulte II, Allan Larson: Evolution and phylogenetic information content of mitochondrial genomic structural features illustrated with acrodont lizards. In: Systematic Biology. Vol. 49, No. 2, 2000, pp. 257-277, doi : 10.1093 / sysbio / 49.2.257 .

Web links

Commons : Uromastycinae  - collection of images, videos and audio files