Borneo Deaf Monitor

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Borneo Deaf Monitor
Real Lanthanotus borneensis.jpg

Borneo deaf monitor ( Lanthanotus borneensis )

Systematics
Order : Scale reptiles (Squamata)
without rank: Toxicofera
without rank: Sneaky (Anguimorpha)
Family : Lanthanotidae
Genre : Lanthanotus
Type : Borneo Deaf Monitor
Scientific name of the  family
Lanthanotidae
Steindachner , 1877
Scientific name of the  genus
Lanthanotus
Steindachner, 1877
Scientific name of the  species
Lanthanotus borneensis
Steindachner, 1877

The Borneo deaf monitor ( Lanthanotus borneensis ) is a lizard native to the island of Borneo . The species is the only member of the Lanthanotidae family . Little is known about the animals, which apparently predominantly live underground, and there is almost no information about their way of life.

features

Borneo deaf monitors reach lengths of up to 55 (mostly 42 or 43) centimeters and are elongated and flat. The tail makes up almost half of the total length. The relatively short legs with five clawed toes are very strong. The scaling consists mainly of many small scales. Large, keeled, hump-like scales are arranged in longitudinal rows between the small scales (heterogeneous scaling). These are located on ossified surfaces called osteodermata, which do not enter into any connection with the skull on the top of the head. The six to ten longitudinal rows of these scales on the back continue in smaller numbers on the tail.

The nostrils, which are shifted backwards, sit almost on the top of the snout. The very small eyes with movable lids have a closed window (so-called "glasses") made of horn in the lower eyelid, whereby the field of vision is severely restricted when the eyelids are closed, but optical perception is still possible. Typically, deaf monitor lacks an outer ear opening, as well as a gular fold (the latter is a difference to the monitor lizards ). The waran-like skull is very flat. The long, pointed and slightly curved teeth are far apart. Deaf monitors have nine cervical vertebrae and 27 trunk vertebrae.

Special features of the skull are the palatine bone , which touches the prefrontal (part of the frontal bone ), the postfrontal (part of the frontal bone) over the orbit (eye sockets), a vertical and seam-like formation between the angular and splenial on the medial side of the jaw, and the presence of palatal teeth. Characteristic is the complete separation of the osteoderms (bones embedded in the skin) around the skull, as well as the extremely reduced palpebral bones.

Occurrence

The Borneo deaf monitor is endemic to Borneo and only inhabits the north of the island. The species inhabits underground rivers or other subterrestrial places and bodies of water, but has also been found in the irrigation ditches of rice fields in Sarawak .

Way of life

General

Almost nothing is known about the way of life of deaf monitors. The little knowledge is based exclusively on a few observations specifically on animals kept in terrariums. The light-shy animals spend most of their time in underground passages or caves, under plants or in water and are probably nocturnal. They are usually very lethargic and rarely move; In captivity, many deaf monitors lay in the same place for days, mostly in the water or buried in the ground. The preferred temperature for animals kept in captivity is 24 to 28 ° C. Further adaptations to aquatic life are probably the nostrils moved far back (better breathing when swimming) and the transparent lower eyelid. In addition to being transparent, the eyelid is not permeable to water, which means that deaf monitors can see when diving.

nutrition

It is assumed that the dead monitor eats mainly fish in its natural habitat, but this has not yet been confirmed due to a lack of field observations. Deaf monitors that were taken into custody mostly either refused to eat anything or licked the contents of the eggs of various animals, especially turtles and birds . However, eggs are probably not a natural food for the deaf monitor. Deaf monitors kept in Frankfurt am Main only ate pieces of plaice meat. After seven years in Frankfurt, a deaf monitor abruptly switched to earthworms , which had previously been spurned.

Reproduction

The females lay three to four eggs more than three centimeters long.

Systematics

Systematics

Since the first description in 1877, the species has been placed in the vicinity of the crusty lizards and monitor lizards, as a close relationship was assumed. This systematic position was confirmed by a study of mitochondrial DNA published in 2001 . Accordingly, the monophyly of the superfamily Varanoidea (families Helodermatidae , Lanthanotidae and Varanidae each with only one genus) was well founded; Lanthanotus has been identified as the sister taxon of the real monitor lizards (genus Varanus ).

In a more recent study including further genome components and many additional reptile species, the composition of the superfamily Varanoidea postulated above was rejected as paraphyletic . The Helodermatidae therefore do not belong to this group, instead the Chinese crocodile tail lizard ( Shinisaurus crocodilurus ) was assigned to the taxon Varanoidea. However, the sister group relationship between Lanthanotidae and the Varanidae was confirmed again.

Tribal history

Some speculations assume that the deaf monitor could resemble the transitional form from lizards to snakes . Although the deaf monitor is most likely not one of the so-called " missing links ", many authors assume that snakes evolved from deaf monitor-like reptiles that existed in the Cretaceous period . In fact, it shows many snake-like features, such as almost complete deafness. In addition, the eyes are not overly efficient and the number of vertebrae is greatly increased. In the case of the Borneo Taubwaran, features of a transitional form would also be shorter limbs and an elongated trunk.

From Lanthanotus borneensis itself a fossil is known. The only known fossil of a deaf monitor- like reptile is Cherminotus longifrons . It was found in 1984 by M. Borsuk-Bialynicka in Late Cretaceous deposits in Mongolia .

Exploration history

The Viennese zoologist Franz Steindachner described a reptile from Borneo as Lanthanotus borneensis on the basis of a single specimen and founded a new family with the genus and species . The type specimen is in a museum in Vienna.

Up to 1961 fewer than 10 deaf monitors had come to museums, in no case with meaningful information on the location and the circumstances of the find. Herpetologists were still looking for deaf monitor lizards on Borneo after 1950 , but even the locals interviewed knew nothing about their existence. In January 1961, the first find in 45 years was made by chance. A Dayak had discovered a dead monitor while cutting a path and caught it alive. Tom and Barbara Harrisson , two scientists based here, could not keep the deaf monitor alive for long. Members of the Dayaks were then guaranteed bonuses for catching live deaf monitor lizards, so from around 1970 to 1980 a little more than sixty live animals were caught, observed and dissected. Some ended up in zoological gardens and museums in Europe and North America. To date, around 100 specimens have been caught, both alive and dead. In the meantime, deaf monitors are successfully kept in some zoological gardens, in German-speaking areas in the Neunkirchen zoological garden , Schönbrunn Zoo in Vienna and in Turtle Island in Graz .

etymology

The scientific generic name Lanthanotus comes from the Greek: λανϑάνω = hidden, ούς ώτός = ear, to a certain extent "hidden ear" or "earless". The " borneensis " stands for the distribution of the deaf monitor in Borneo. The overall name Lanthanotus borneensis means something like "earless from Borneo".

swell

literature

  • Eric Pianka: Lanthanotus borneensis . In: Eric R. Pianka, Dennis R. King, Ruth Allen King: Varanoid lizards of the world. Indiana University Press, Bloomington IN 2004, ISBN 0-253-34366-6 , pp. 535-538.
  • Konrad Klemmer : Taubwarane family. In: Bernhard Grzimek (ed.): Grzimeks animal life. Encyclopedia of the Animal Kingdom. Volume 6: reptiles. Bechtermünz, Augsburg 2000, ISBN 3-8289-1603-1 , p. 337 f. (Unchanged reprint of the original edition from 1979/80).

Web links

Commons : Borneo Taubwaran ( Lanthanotus borneensis )  - Collection of images, videos and audio files
  • BorneoTaubwaran page about keeping - breeding and rearing of Lanthanotus borneensis (German)

Individual evidence

  1. Jennifer C. Ast: Mitochondrial DNA Evidence and Evolution in Varanoidea (Squamata). In: Cladistics. Vol. 17, No. 3, 2001, pp. 211-226, doi : 10.1111 / j.1096-0031.2001.tb00118.x .
  2. ^ Ted M. Townsend, Allan Larson, Edward Louis, J. Robert Macey: Molecular Phylogenetics of Squamata: The Position of Snakes, Amphisbaenians, and Dibamids, and the Root of the Squamate Tree. In: Systematic Biology. Vol. 53, No. 5, 2004, pp. 735-757, doi : 10.1080 / 10635150490522340 , PMID 15545252 .
  3. Tom Harrisson, Neville S. Haile: Notes on a Living Specimen of the Earless Monitor Lizard, Lanthonotus borneensis. In: Journal of the Ohio Herpetological Society. Vol. 3, No. 2, 1961, pp. 13-16, doi : 10.2307 / 1562598 .
  4. ^ After: Konrad Klemmer: Taubwarane family. In: Bernhard Grzimek (ed.): Grzimeks animal life. Encyclopedia of the Animal Kingdom. Volume 6: reptiles. Bechtermünz, Augsburg 2000, ISBN 3-8289-1603-1 , p. 337 (unchanged reprint of the original edition from 1979/80).
  5. After: David Burnie (Ed.): Animals. (The big making encyclopedia with over 2000 styles). Dorling Kindersley, Munich 2001, ISBN 3-8310-0202-9 , p. 419. Note: Popular science source.
  6. www.Zootierliste.de. Retrieved July 3, 2018 .