Earless monitor lizard
Borneo Earless Monitor ( Lanthanotus borneensis )
The Borneo Earless Monitor ( Lanthanotus borneensis ) is a domiciled on the island of Borneo lizard. The species is the only representative of Lanthanotidae family. Little is known about the apparently mainly underground fauna, in particular are almost no knowledge before about their lifestyle.
- 4.1 systematics
- 4.2 phylogeny
- 7.1 Notes and references
- 7.2 Literature
- 7.3 External links
Features
Borneo Taubwarane reach lengths of up to 55 (usually 42 or 43) centimeters, and are elongated and flat built. Of the total length of the tail makes up almost half. The relatively short legs with five clawed toes are very strong. The scalation consists mainly of many small scales. Between the small scales large, keeled, hump-like scales are arranged (heterogeneous scalation ) in longitudinal rows. These are located on Osteodermata mentioned, ossified documents received no connection with the skull on top of the head. The six to ten longitudinal rows of scales on the back put in smaller numbers continued on the tail.
The shifted backwards nostrils sit almost on the nose top. The very small eyes with movable lids have a closed window in the lid (so-called "glasses" ) made of horn, whereby the field of view is indeed very limited with closed eyelids, however, remains a visual perception possible. In Taubwaranen typically lack an external ear opening, as a Gularfalte (the latter is a contrast to the monitors ). The waranähnliche skull is very flat. The long, pointed and slightly curved teeth are at wide intervals. Taubwarane have nine cervical vertebrae, 27 dorsal vertebrae.
Special features of the skull are the palatine bone that contacts the prefrontal ( part of the frontal bone ), the postfrontal ( part of the frontal bone ) over the orbit ( eye socket ), a vertical and seam- like formation between Angular and Splenial on the medial side of the jaw, and the presence of palatal teeth. Characteristic is the complete separation of the osteoderms (embedded in the skin bone ) to the skull around, as well as the extremely strongly reduced Palpebralknochen.
Occurrence
The Borneo Earless Monitor is endemic to Borneo and settled there exclusively the north of the island. The species colonized underground rivers or other subterrestrische places and waters, but was detected in Sarawak in the irrigation ditches of rice fields.
Way of life
General
Over the life of Taubwaranen almost nothing is known. The little knowledge is based exclusively on a few observations specifically to held in terrarium animals. The light shy animals spend most of their time in underground tunnels or caves, or plants in the water and are probably nocturnal. They are mostly very lethargic and move rare; in captivity many Taubwarane lay for days in the same place, usually buried in the water or in the ground. The preferred temperature for captive animals is 24 to 28 ° C. Further adjustments to the aquatile life are probably the shifted far to the rear nostrils ( better breathing while swimming ) and the transparent lower eyelid. The eyelid is in addition to its transparency not water permeable, thereby Taubwarane can see while diving.
Nutrition
According to the assumptions Earless Monitor eats in its natural habitat mainly fish, but so far this has not been confirmed due to lack of field observations. In captivity came Taubwarane usually either refused any food or licking the contents of eggs of different animals, especially turtles and birds. However, eggs are probably not a natural food of Taubwarane. In Frankfurt am Main held Taubwarane ate only piece of meat Scholl. After seven years of entertainment in Frankfurt a Earless Monitor turned abruptly on earthworms, which were spurned before.
Reproduction
Females lay three to four more than three inches long eggs.
System
System
Since its first description in 1877, the species was placed in the vicinity of the beaded lizards and monitor lizards, as a close relationship was suspected. This systematic position was confirmed by a published study in 2001 of the mitochondrial DNA. Accordingly, the monophyly of the superfamily was Varanoidea ( families Helodermatidae, Lanthanotidae and Varanidae with only one genus ) reasonable; Lanthanotus was identified as the sister taxon of the Real lizards ( genus Varanus ).
In a recent study, the inclusion of other genome components and many additional species of reptiles, the above postulated composition of the superfamily Varanoidea was rejected as paraphyletic. The Chinese crocodile lizard tail ( Shinisaurus crocodilurus ) was the Helodermatidae therefore do not belong in this group, instead, assigned to the taxon Varanoidea. The sister group relationship between Lanthanotidae and Varanidae was confirmed again.
Phylogeny
Some conjectures assume that the Earless Monitor the transitional form of lizards could resemble snakes. Although the Earless Monitor is most likely none of the so-called " missing links", but many authors assume that snakes evolved from reptiles taubwaranähnlichen that existed in the Cretaceous period. In fact, he shows a lot of snake-like features, such as almost complete deafness. In addition, the eyes are not overly powerful, and the swirl number is greatly increased. Characteristics of a transitional form would also be shorter limbs and an elongated body in the case of Borneo Taubwaranes.
From Lanthanotus borneensis even no fossil is known. The only known fossil of a reptile is taubwaranähnlichen Cherminotus longifrons. It was found in 1984 by M. Borsuk - Bialynicka in the Late Cretaceous deposits in Mongolia.
Exploration History
The Viennese zoologist Franz Steindachner described in 1877 based on a single copy of a reptile from Borneo as Lanthanotus borneensis and reasoned with the genus and species, a new family. The type specimen is in a museum in Vienna.
By 1961, less than 10 Taubwarane came in museums, in no event with meaningful information about locality and Fund circumstances. Even after 1950 sought herpetologists to Borneo to Taubwaranen, but even locals interviewed were unaware of their existence. In January 1961, made by accident the first find for 45 years. A Dayak had discovered a Earless Monitor when cutting out a path and captured alive. Tom and Barbara Harrisson, two resident here herpetologists, the Earless Monitor could not keep alive long. Members of the Dayaks were pledged thereto premiums for catching live Taubwarane so were captured by circa 1970-1980 slightly more than sixty live animals are observed and dissected. Some came in zoos and museums in Europe and North America. To date, about 100 specimens were caught, both alive and dead
Etymology
The scientific genus name Lanthanotus comes from the Greek: hidden = λανθάνω, ώτός = ear, as it were "hidden ear " or ούς " ohrlos ". The " borneensis " stands for the spread of Taubwaranes in Borneo. The total name Lanthanotus borneensis therefore means " ear Loser of Borneo".