Hypsilophodontidae

Hypsilophodontidae
Atlascopcosaurus , live reconstruction
Temporal occurrence
Middle Jurassic to Upper Cretaceous ( Bathonian to Maastrichtian )
168.3 to 66 million years
Locations
Worldwide
Systematics
Archosauria Dinosaur (dinosauria) Pelvic dinosaur (Ornithischia) Cerapoda Ornithopoda Hypsilophodontidae
Scientific name
Hypsilophodontidae
Dollo , 1882

The Hypsilophodontidae were smaller ornithopod dinosaurs. Their fossils were found almost worldwide in sediments from Central Jurassic to Upper Cretaceous .

Genera of the Hypsilophodontidae, such as Leaellynasaura and Qantassaurus , make up more than half of the "polar dinosaurs" found in southeast Australia. The site in today's state of Victoria was in the Lower Cretaceous , 115 to 105 million years ago, near the southern polar circle and must have had a significantly colder climate with average annual temperatures just below freezing point.

features

They were built quite primitively and resembled the heterodontosaurines , but they were the first dinosaurs to have the ability to chew plant food. Later this ability was even more pronounced in Iguanodontids and Hadrosaurs . In addition, the ceratopsids are likely to have had higher chewing skills. The molars had elevations ( Hypsilophodontiden = dt. "Teeth with elevations") and should probably cut the food better when chewing. The skull did not have the enlarged canines of the Heterodontosauridae and the midline of the skull was narrower. In the ventral view you can see that the cheek regions were very extended outside the rows of teeth due to the wide lower jaw . The prerequisites for chewing in hypsilophodontids were well-fitting upper and lower rows of teeth due to the development of secondary chewing surfaces. In addition, the skull was particularly mobile.

Earlier views that the hypsilophodonts were tree dwellers and that the feet clasped branches is rejected because the foot had no gripping function, but rather a typical "walking foot" with claws. The tail end was ossified and was probably used for balancing, similar to the dromaeosaur Deinonychus . The whole limb structure, but especially the long shin and the foot, resembled a gazelle . They were probably quite nimble animals and were up to five meters long, the smaller species reached up to two meters.

Systematics

External system

Earlier theories claimed that the Hypsilophodontidae was a sister taxon of the Iguanodontia . However, modern analyzes have shown that the Hypsilophodontidae is paraphyletic , with some authors, such as Michael J. Benton , still classifying this taxon as a sister group of the Iguanodontidae and the Hadrosauridae .

Cladogram according to Benton (2007):

Ornithopoda	Heterodontosauridae   Euornithopoda    Hypsilophodontidae      Iguanodontidae      Hadrosauridae

The following cladogram (Boyd et al. 2009) shows the Hypsilophodontidae paraphyletically. The Hypsilophodontidae would in this case be all taxa from Agilisaurus or Hexinlusaurus to Hypsilophodon or Gasparinisaura .

	Scutellosaurus      Lesothosaurus      Heterodontosaurus      Agilisaurus      Hexinlusaurus      Othnielosaurus      Oryctodromeus      Orodromeus      Zephyrosaurus      Parksosaurus      Thescelosaurus      Hypsilophodon      Gasparini aura      Tenontosaurus      other ornithopods

Genera

Leaellynasaura

Parksosaurus

• Agilisaurus
• Alocodon
• Anabisetia
• Atlascopcosaurus
• Bugenas aura
• Daurosaurus
• Drinker
• Fulgurotherium
• Gasparini aura
• Hypsilophodon
• Jeholosaurus
• Leaellynasaura
• Notohypsilophodon
• Orodromeus
• Oryctodromeus
• Othnielia
• Parksosaurus
• Qantassaurus
• Thescelosaurus
• Yandusaurus
• Zephyrosaurus

literature

• Reinhard Rieger , Wilfried Westheide (ed.): Special zoology. Volume 2: Vertebrates or Skull Animals. Spectrum - Akademischer Verlag, Heidelberg et al. 2004, ISBN 3-8274-0900-4 .
• Michael J. Benton : Paleontology of the vertebrates. Translation of the 3rd English edition by Hans-Ulrich Pfretzschner. Pfeil, Munich 2007, ISBN 978-3-89937-072-0 , p. 222.

1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 273-278, online ( memento of the original of July 13, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . 
2. ^ Thomas H. Rich , Patricia Vickers-Rich , Roland A. Gangloff: Polar Dinosaurs. In: Science . Vol. 295, No. 5557, 2002, pp. 979-980, doi : 10.1126 / science.1068920 .
3. ^ David B. Norman , Hans-Dieter Sues , Lawrence M. Witmer , Rodolfo A. Coria : Basal Ornithopoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 393-412, digitized version (PDF; 2.66 MB) .
4. ↑ Clint A. Boyd, Caleb Marshall Brown, Rodney D. Scheetz, Julia A. Clarke: Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura. In: Journal of Vertebrate Paleontology. Vol. 29, No. 3, 2009, ISSN  0272-4634 , pp. 758-770, doi : 10.1671 / 039.029.0328 .
5. ↑ Владимир Р. Алифанов, Сергей В. Савельев: Два новых птицетазовых динозавра (Hypsilophodontia, Ornithopoda) из поздней юры России. In: Палеонтологический Журнал. No. 4, 2014, ISSN  0031-031X , pp. 72-82, doi : 10.7868 / S0031031X14040023 .

Web links

Commons : Hypsilophodontidae  - Collection of images, videos and audio files