Troodon

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Troodon
Skeletal reconstruction of Troodon

Skeletal reconstruction of Troodon

Temporal occurrence
Upper Cretaceous (late Campanium )
76.4 to 72 million years
Locations
Systematics
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Theropoda
Deinonychosauria
Troodontidae
Troodon
Scientific name
Troodon
Leidy , 1856

Troodon is a genus of theropod dinosaur from the Late Upper Cretaceous North America and Asia.

So far only one species has been described, the type species T. formosus . The species Stenonychosaurus inequalis has been a synonym of Troodon formosus since 1987 . Rehabilitation is currently being discussed.

The first finding is a tooth that was discovered in 1856 and given the name Troodon ("tearing tooth") for the animal. After the first find one was surprised at later finds (1979/1980) that it belonged to the teeth of a bird-like dinosaur.

features

Sculptural life picture of Troodon

It is a dinosaur with large eye sockets , which suggests it may have been nocturnal . In addition, the eyes were partially directed forward, which most likely already enabled stereoscopic vision . Some scientists consider Troodon formosus to be the most developed species of dinosaur and suspect an intelligence similar to that of today's birds. The dinosaur had a relatively large brain (0.1% of body weight) and large nostrils, which indicate a keen sense of smell.

The body length was about 2.5 to 3 meters and the estimated weight about 35 to 45 kg. The arms had three fingers that could be grasped, the legs three toes, one toe bearing a sickle-shaped claw like Deinonychus .

Discovery story

First find

The holotype consisted of a single tooth and was found in Santonium by Joseph Leidy in 1856 - although it was still described as a troödon . The official name was coined by Sauvage in 1876. Leidy found the tooth in the Judith River group , but thought it was a lizard's. In 1877 Troodon was identified as a dinosaur . Because of the sparse fossil record, the classification of Troodons was the subject of heated debate for several decades .

Synonyms

In the early 1930s, two fragmentary dinosaur skeletons were found in Alberta's Dinosaur Provincial Park . The first of the two, consisting of a metatarsal bone, fragments of the hand bones and some caudal vertebrae, was described by Charles M. Sternberg as Stenonychosaurus inequalis and assigned to the Coeluridae family . The second skeleton was also attributed to a new species - in this case a lizard: Charles W. Gilmore described Polyodontosaurus grandis in 1932 using an only partially preserved lower jaw . In 1951, Sternberg was the first to propose the thesis that P. grandis was synonymous with Troodon , while at the same time he suspected a close relationship between the latter and the S. inequalis described by him .

Also due to the identification of another more complete dinosaur skeleton than Stenonychosaurus by Dale Russell , the species remained scientifically recognized until the 1980s and has now been assigned to the group of Saurornithoididae as a result of more recent studies . In 1987, however, Phil Currie showed that the jaw and tooth structure previously mentioned as the main difference between Saurornithoididae and Troodontidae was not based on belonging to different species, but only on different ages of the animals. Therefore he synonymized both Stenonychosaurus , as well as Polyodontosaurus and Pectinodon bakkeri with Troodon , whereby the name of the latter was retained according to the rules of nomenclature , since this was described first. Furthermore, he synonymized the group of Saurornithoididae with the Troodontidae . However , the redefinition of Saurornithoides mongoliensis as Troodon mongoliensis proposed by Gregory S. Paul in 1988 hardly met with approval in the research world. Curries investigations also led to the fact that relatively quickly all Troodontid remains found in North America and dated to the Upper Cretaceous were assigned to Troodon formosus informally.

Revision of the universal generic model

This approach met with criticism from some researchers (including Currie himself). It was stated that troodontid finds that did not come from the Judith River group could well belong to a different species. For example, the designation Troodon bakkeri for the finds in the Lance Formation , or Troodon inequalis for those in the Dinosaur Park (based on the Pectinodon bakkeri and Stenonychosaurus inequalis, which were previously found there and later synonymous ) were proposed.

Lindsay Zanno et old followed in 2011. Nicholas Longrich, who postulated in 2008 that Pectinodon bakkeri should be regarded as an independent genus, and also advocated using Troodon formosus as a noun dubium . As justification, they stated that the tooth found in 1856 alone was insufficient as a holotype, since different Troodon species could not be distinguished from one another based on the tooth morphology.

2017 attacked Evans et old. made this request and also recommended that fossil material from troodontids from Dinosaur Park should be entirely ascribed to Stenonychosaurus . In the same year, Aaron J. van der Reest and Currie went one step further: From the significant differences in size, as well as deviations in skull and pelvic bones between Troodontid remains in the upper and lower part of Dinosaur Park, the authors concluded that this was the case must act two different ways. While they newly described the larger specimens in the upper part as the Latenivenatrix mcmasterae , they also pleaded for a rehabilitation of Stenonychosaurus inequalis as a name for the smaller individuals found in the lower part. Although the reintroduction of S. inequalis is particularly controversial, the fact remains that ultimately only the tooth found in 1856 can be ascribed with certainty to Troodon formosus .

Systematics

The classification of Troodon has been an active point of contention in research since its discovery. After Leidy attributed the tooth he found to a lizard, Franz von Nopcsa said in 1901 that it must be a megalosaurid . In 1924 Gilmore put forward the thesis that the tooth would belong to the herbivorous Stegoceras , so that Stegoceras was merely a synonym for Troodon . However, Sternberg rejected this classification in 1945 and identified Troodon as a theropod .

Today Troodon is considered to be one of the most developed representatives of the Troodontidae.

Paleobiology

Troodon teeth found in Alaska are considerably larger than comparable finds from other areas of North America. It is therefore estimated that the so-called "Alaska Troodon" could be twice as large as an average member of its genus, which also indicates the validity of Bergmann's rule . In addition, due to the lack of larger predators in the Cretaceous Arctic , the "Alaska Troodon" probably assumed the role of the top predator , while populations elsewhere competed for prey, especially with representatives of the tyrannosaurs .

In addition, a study suggests that Troodon's tooth structure suggests a rather soft diet. Bones break but also eating hard plant parts was hardly possible.

It is assumed that the species laid two eggs at a time, each day or over longer periods, and hatched them using body and geothermal heat.

literature

  • David J. Varricchio, Frankie Jackson, John J. Borkowski, John R. Horner : Nest and egg clutches of the dinosaur Troodon formosus and the evolution of avian reproductive traits. In: Nature . Vol. 385, No. 6613, January 16, 1997, pp. 247-250, doi : 10.1038 / 385247a0 .

Web links

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

Individual evidence

  1. ^ Alan H. Turner, Diego Pol, Julia A. Clarke, Gregory M. Erickson, Mark A. Norell : A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight. In: Science . Vol. 317, No. 5843, 2007, pp. 1378-1381, doi : 10.1126 / science.1144066 , PMID 17823350 .
  2. ↑ H.-E. Sauvage, 1876, Notes sur les reptiles fossiles , Bulletin de la Société Géologique de France, 3rd series 4 : 435-444
  3. ^ Edward Drinker Cope: Report on the geology of the region of the Judith River, Montana, and on vertebrate fossils obtained on or near the Missouri River . In: Bulletin of the United States Geological and Geographical Survey . 3, No. 3, 1877, pp. 565-597.
  4. ↑ CM Sternberg: The lizard Chamops from the Wapiti Formation of Northern Alberta: Polyodontosaurus grandis is not a lizard . In: Annual Report of the National Museum of Canada Bulletin . 123, 1951, pp. 256-258.
  5. ^ DA Russell: A new specimen of Stenonychosaurus from the Oldman Formation (Cretaceous) of Alberta . In: Canadian Journal of Earth Sciences . 6, No. 4, 1969, pp. 595-612. bibcode : 1969CaJES ... 6..595R . doi : 10.1139 / e69-059 .
  6. ^ P. Currie: Theropods of the Judith River Formation . In: Occasional Paper of the Tyrrell Museum of Palaeontology . 3, 1987, pp. 52-60.
  7. ^ GS Paul: Predatory Dinosaurs of the World . Simon and Schuster, New York 1988, ISBN 978-0-671-61946-6 , pp. 398-399.
  8. ^ P. Currie. (2005). "Theropods, including birds." in Currie and Koppelhus (eds). Dinosaur Provincial Park, a spectacular ecosystem revealed, Part Two, Flora and Fauna from the park. Indiana University Press, Bloomington. Pp 367-397.
  9. ^ N. Longrich, 2008, "A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: implications for the study of dissociated dinosaur remains", Palaeontology 51 (4) 983-997
  10. ↑ Lindsay E. Zanno, David J. Varricchio, Patrick M. O'Connor, Alan L. Titus, Michael J. Knell: A new troodontid theropod, Talos sampsoni gen. Et sp. nov., from the Upper Cretaceous Western Interior Basin of North America . In: PLoS ONE . 6, No. 9, 2011, p. E24487. doi : 10.1371 / journal.pone.0024487 . PMID 21949721 . PMC 3176273 (free full text).
  11. ↑ DC Evans, TM Cullen, DW Larson, A. Rego: A new species of troodontid theropod (Dinosauria: Maniraptora) from the Horseshoe Canyon Formation (Maastrichtian) of Alberta, Canada . In: Canadian Journal of Earth Sciences . 54, No. 8, 2017, pp. 813–826. bibcode : 2017CaJES..54..813E . doi : 10.1139 / cjes-2017-0034 .
  12. ↑ Aaron J. van der Reest, P. Currie: Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America . In: Canadian Journal of Earth Sciences . 54, No. 9, 2017, pp. 919-935. bibcode : 2017CaJES..54..919V . doi : 10.1139 / cjes-2017-0031 .
  13. Jump up ↑ DJ Varricchio, M. Kundrát, J. Hogan: An Intermediate Incubation Period and Primitive Brooding in a Theropod Dinosaur . In: Scientific Reports . 8, No. 1, 2018, p. 12454. doi : 10.1038 / s41598-018-30085-6 . PMID 30127534 . PMC 6102251 (free full text).
  14. ^ Franz von Nopcsa: Synopsis and descent of the dinosaurs . In: Foldtani Kozlony . 31, Budapest, 1901, pp. 247-288.
  15. ↑ Gilmore, CW, 1924. On Troodon validus , an orthopodous dinosaur from the Belly River Cretaceous of Alberta, Canada. Department of Geology, University of Alberta Bulletin 1: 1-43
  16. ↑ Charles M. Sternberg: Pachycephalosauridae proposed for domeheaded dinosaurs, Stegoceras lambei n. Sp., Described . In: Journal of Paleontology . 19, 1945, pp. 534-538.
  17. ↑ The Dino Planet (2/3)
  18. ^ Anthony R. Fiorillo: On the Occurrence of Exceptionally Large Teeth of Troodon (Dinosauria: Saurischia) from the Late Cretaceous of Northern Alaska In: Palaios, No. 23, 2008, pp. 322-328