Mononykus

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Mononykus
Skeletal reconstruction of Mononykus

Skeletal reconstruction of Mononykus

Temporal occurrence
Upper Cretaceous ( Campanium )
83.6 to 72 million years
Locations
Systematics
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Theropoda
Coelurosauria
Alvarezsauridae
Mononykus
Scientific name
Mononykus
Perle et al. , 1993

Mononykus is a relatively small, bird-like genus of theropod dinosaur in the Alvarezsauridae family. The only species assigned to this genus is Mononykus olecranus . She lived at the time of the Upper Cretaceous in what is now Mongolia .

description

The 90 cm long animal ran biped (two-legged) on long hind legs. Similar to his relatives, he had very short, stubby front extremities. Each of these had a single claw that was about five cm long ( Greek : Mononykus = "single claw"). The other claws had receded. The purpose of these highly specialized arms is controversial. One study suspects a similar way of life as that of the anteater . The claw was used to break insect nests such as B. Termite mounds , served. The fused carpal bones (carpalia) and the structure of the breastbone (sternum) are reminiscent of the anatomy of birds. The metatarsus was designed as an arctometatarsus , which means, among other things, that the middle of the three large metatarsal bones (metatarsal III) tapers sharply towards the tarsus.

Mononykus may have been a feathered dinosaur .

Finds

Finds attributed to the genus Mononykus come from the Dshadochta Formation and the Nemegt Formation of Mongolia and from the Iren-Dabasu Formation of China.

The holotype material (GI N107 / 6; Geological Institute of the Mongolian Academy of Sciences) comprises an incomplete skeleton, which consists of the skull, upper jaw parts, fore and hind limbs, a few fragments of ribs and vertebrae. It was found in 1987 by a "dinosaur hunter" from the Mongolian Natural History Museum during the Soviet-Mongolian Paleontological Expedition . When it was discovered, the bones were in an anatomical context. The type locality is Bugin-Tsav, a 13 square kilometer locality in the Nemegt basin ( Gobi , southern Mongolia), which is famous today for its spectacular finds. The corresponding find horizon is in the Nemegt formation. Turtles and the remains of the tyrannosaurid Tarbosaurus bataar were discovered in the vicinity .

Kinship relationships

Drawing reconstruction of Mononykus ' life , the fletching shown is based on assumption

The holotype material was described in 1993 by Altangerel Perle , Luis M. Chiappe , Rinchen Barsbold , James Matthew Clark and Mark Norell , as a representative of a new basal bird genus, briefly mentioned in the journal Nature . A comprehensive description followed a year later (see literature, below). They consider Mononykus a sister taxon to all other birds, with the exception of the Archeopteryx . According to this, Mononykus would be a side branch of the birds that had the Archeopteryx as an ancestor, but soon developed back to an inability to fly.

However, the avian status of this genus is controversial and has been heavily questioned by various other researchers. Heated debates broke out between the two opinions. Criticisms are especially the unusual forelegs. Wellnhofer (1994) said:

"(...) it would be very difficult to imagine how a primitive bird wing, such as that of Archeopteryx , could have evolved into a forelimb like that of Mononykus ." (In German for example: "It would be very difficult to imagine how such a primitive wing as that of Archeopteryx could develop into a fore limb like that of Mononykus . ").

However, those who believe Mononykus is a bird defended their views (Chiappe, Norell & Clark, 1997; Padian & Chiappe, 1998).

After the South American Patagonykus was described in 1996 , commonalities between this, Mononykus and the more primitive Alvarezsaurus were recognized . Alvarezsaurus was already, as the only representative, classified in the family of the Alvarezsauridae within the Ceratosauria . All three species have now been classified as Alvarezsauridae within the Coelurosauria . Shortly afterwards, Parvicursor joined the family, Shuvuuia followed in 1998.

The majority of researchers today assume that they are bird-like coelurosaurs, but not birds.

literature

credentials

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ 2010, ISBN 978-0-691-13720-9 , p. 127, online .
  2. ^ Phil Senter: Function in the stunted forelimbs of Mononykus olecranus (Theropoda), a dinosaurian anteater. In: Paleobiology. Vol. 31, No. 3, 2005, ISSN  0094-8373 , pp. 373-381, doi : 10.1666 / 0094-8373 (2005) 031 [0373: FITSFO] 2.0.CO; 2 , abstract .
  3. ↑ David E. Fastovsky , Mahito Watabe, Demchig Badamgarav, David B. Weishampel : Late Cretaceous dinosaur-bearing paleoenvironments of Bugin-Tsav, south-central Gobi Desert, Mongolia. In: The Geological Society of America. Abstracts with Programs. Vol. 34, No. 1, 2002, ISSN  0016-7592 , p. A62, abstract .
  4. ↑ According to Middleton, Gatesy: theropod forelimb design and evolution. 2000, these were “Ostrom, 1994; Wellnhofer, 1994; Zhou, 1995; Feduccia, 1996; Chatterjee, 1997 ".
  5. ↑ Zhonghe Zhou : Is Mononykus a Bird? In: The Auk. Vol. 112, No. 4, 1995, ISSN  0004-8038 , pp. 958-963, digitized version (PDF; 528.14 kB) .
  6. ↑ Middleton, Gatesy: Theropod forelimb design and evolution. 2000.
  7. ↑ Luis Chiappe , Mark Norell , James Clark : Mononykus and Birds: Methods and Evidence. In: The Auk. Vol. 114, No. 2, 1997, pp. 300-302, digitized version (PDF; 272.59 kB) .