Tympanocryptis

Tympanocryptis is a genus of Australian lizards in the family Agamidae, commonly known as earless dragons.

Description

The genus Tympanocryptis has the following characters. The tympanum is hidden (hence the common name earless dragon). The body is depressed, and it is covered dorsally with heterogeneous scales. There is no dorsal crest. There is no gular sac, but a strong transverse gular fold is present. The tail is round in cross section. There is a preanal pore on each side, which sometimes is absent in females. In most species there are no femoral pores,<ref>Boulenger GA (1885). Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume I. ... Agamidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xii + 436 pp. + Plates I-XXXII. (Genus Tympanocryptis, p. 392).</ref> Tympanocryptis tetraporophora being an exception.

Species

The following 23 species are recognized as being valid.<ref>Tympanocryptis. The Reptile Database. www.reptile-database.org.</ref><ref name=":2">Template:Cite journal</ref>

• Tympanocryptis argillosa Template:Small – claypan earless dragon
• Tympanocryptis centralis Template:Small – central Australian earless dragon
• Tympanocryptis cephalus Template:Small – blotch-tailed earless dragon
• Tympanocryptis condaminensis Template:Small – Condamine earless dragon (previously part of T. pinguicolla)<ref name="DD">"Dragons discovered on the Darling Downs". ABC local radio/online. (11 August 2014). accessed same date.</ref>
• Tympanocryptis diabolicus Template:Small – Hamersley pebble-mimic dragon
• Tympanocryptis fictilis Template:Small – Harlequin earless dragon
• Tympanocryptis fortescuensis Template:Small – Fortescue pebble-mimic dragon
• Tympanocryptis gigas Template:Small – Gascoyne pebble-mimic dragon
• Tympanocryptis houstoni Template:Small – Houston's earless dragon
• Tympanocryptis intima Template:Small – gibber earless dragon
• Tympanocryptis lineata Template:Small – lined earless dragon or Canberra grassland earless dragon (Canberra population previously part of T. pinguicolla)<ref name=":2" />
• Tympanocryptis macra (Template:Small) – savannah earless dragon
• Tympanocryptis mccartneyi Template:Small – Bathurst grassland earless dragon (previously part of T. pinguicolla)<ref name=":2" />
• Tympanocryptis osbornei Template:Small – Monaro grassland earless dragon (previously part of T. pinguicolla)<ref name=":2" />
• Tympanocryptis pentalineata Template:Small – five-lined earless dragon
• Tympanocryptis petersi Template:Small – lined earless dragon
• Tympanocryptis pinguicolla Template:Small – Victorian grassland earless dragon
• Tympanocryptis pseudopsephos Template:Small – Goldfields pebble-mimic dragon
• Tympanocryptis rustica Template:Small – Tennant Creek pebble dragon
• Tympanocryptis tetraporophora Template:Small – long-tailed earless dragon
• Tympanocryptis tolleyi Template:Small – Gawler earless dragon
• Tympanocryptis uniformis Template:Small – even-scaled earless dragon
• Tympanocryptis wilsoni Template:Small – Roma earless dragon (previously part of T. pinguicolla)<ref name="DD"/>

The "grassland earless dragons"

Several members of the T. lineata species complex (namely the Canberra population of T. lineata, T. mccartneyi, T. osbornei, and T. pinguicolla) are referred to as the "grassland earless dragons", being the only members of the family Agamidae to be restricted to natural temperate grasslands. These species are found at higher altitudes and in regions that have cooler temperatures than any other earless dragon, where they prefer sites with both taller tussock and shorter grasses. The species were formerly considered different isolated populations of T. pinguicolla, until a 2019 study found the Canberra population to actually be an isolated eastern population of T. lineata and the Cooma and Bathurst populations to represent distinct species, and thus restricted the definition of T. pinguicolla to refer to only the possibly-extinct Victorian population.<ref name=":2" />

The grassland earless dragons lay 3-6 eggs in late spring or early summer. Their young hatch in late summer (possibly disperse soon after hatching), grow to adult size rapidly (by late autumn-early winter), mate the following spring, and often die within one year of birth. They can reach the age of 5 within captivity.

All of the grassland earless dragons are highly endangered due to the heavy destruction and conversion of the temperate grasslands, of which less than 1% are said to remain. Overgrazing poses one of the most significant threats to them, especially when rocks are disturbed.<ref name=tympanocryptispinguicolla>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> These species are rarely found outside native temperate grasslands, and does not adapt well to changed environments, primarily due to the lack of food diversity found outside their native habitat. T. pinguicolla may already be extinct due to the heavy degradation that grasslands have received in Victoria, with the last known confirmed sighting being made in 1969.<ref name=":2" />

According to herpetologist Lyn S. Nelson, "Observations indicate that arthropod burrows, surface rocks, or other similar refuge sites may be necessary for the continued persistence of populations of dragons, by providing thermal refugia."<ref name=tympanocryptispinguicolla /> They are known to hide within abandoned arthropod burrows and underneath rocky outcrops in order to lay eggs and protect themselves from predators. Soil disturbance, such as ploughing or compaction, might also result in destruction of the essential arthropod burrows and possibly a reduction in the abundance, at least in the short-term, of burrow forming arthropods. A radio-tracking study found that "burrows excavated by arthropods are an important resource for grassland earless dragons, with individuals having one or two home burrows around which they maintained home ranges of between 925 m² and 4768 m²."<ref name=":1">Template:Cite journal</ref> According to Nelson, they "[m]ay survive short-term disturbance from fire."<ref name=tympanocryptispinguicolla/>

In early January 2014, media reported<ref>Canberra breeding program bolsters tiny endangered dragons, Kathleen Dyett, ABC News Online, 3 January 2014, accessed 6 January 2014</ref> that researchers Professor Stephen Sarre and Dr Lisa Doucette from the University of Canberra's Institute for Applied Ecology had succeeded in breeding the Canberran T. lineata in captivity, and had also hatched eggs gathered from field studies, with around 60 hatchlings being born. In June 2011, Professor Sarre's team won a four-year funding grant from the Australian Research Council to research and potentially save the species from extinction, and find a cause for the species recent collapse in numbers, thought to be associated with 10 years of drought in the species' range.<ref>New funding gives hope to endangered species, Claudia Doman, University of Canberra, 9 June 2011, accessed 6 January 2014</ref> In 2019, ecologist Brett Howard from the ACT Parks and Conservation Service said that "grassland earless dragons are at risk of extinction in the near future even though much has been done to improve their survival chances in the past five years." He then listed the threats posed to this species, saying "this species has suffered declines in recent decades likely due to a combination of drought, overgrazing and climate change.”<ref name="riot">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

External links

• Tympanocryptis. Zipcode Zoo.

• Grassland Earless Dragon.

Further reading

• Peters W (1863). "Eine Übersicht der von Hrn. Richard Schomburgk an das zoologische Museum eingesandten Amphibien, aus Buchsfelde bei Adelaide in Südaustralien ". Monatsberichte der Königlichen Preussischen Akademie der Wissenschaften zu Berlin 1863: 228–236. (Tympanocryptis, new genus, p. 230). (in German).