Heterodontosauridae
| Heterodontosauridae | ||||||||||||
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Heterodontosaurus tucki fossil |
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| Temporal occurrence | ||||||||||||
| Norium ( Upper Triassic ) to Aptium ( Lower Cretaceous ) | ||||||||||||
| 228 to 112.9 million years | ||||||||||||
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| Heterodontosauridae | ||||||||||||
| Romer , 1966 |
The Heterodontosauridae ("lizards with different types of teeth") are a group of two-legged , herbivorous or omnivorous dinosaurs that lived from the Upper Triassic to the Lower Cretaceous . The group is classified within the bird pelvic dinosaur (Ornithischia), the exact systematic position is however controversial. The best known genus, Heterodontosaurus , comes from the Lower Jurassic South Africa ; however, the group is documented with mostly very fragmentary finds from North and South America, Europe and Asia. A characteristic and eponymous feature was the heterodontics , the presence of different types of teeth in the dentition, including both molars and often greatly enlarged "tusks". Heterodontosaurids are among the smallest known bird pelvic dinosaurs; For example, Fruitadens is only 65 to 75 centimeters long. The skeleton of the Chinese Tianyulong shows filamentous structures that have been interpreted as proto-feathers .
features
With a maximum body length of one to two meters, the various genera of the Heterodontosauridae are the smallest known representatives of the bird pelvic dinosaur (Ornithischia). They were herbivores or omnivores and moved bipedally , i.e. H. only walk on the hind legs.
The main synapomorphism of the group is the presence of differently formed groups of teeth ( heterodontics ) in their teeth. This feature is typical for synapsids (Synapsida) and their descendants, the mammals ; However, reptiles usually have homodontic teeth with only one type of tooth. On the maxillary and in the middle and rear part of the dental there were high-crowned molars with cusps, suitable for grinding vegetable food. In the front part of the lower jaw and on the premaxillary in the upper jaw there were large fang-like teeth ("tusks"). The tusks of the lower jaw reached into a toothless gap ( diastema ) between the tusks and the front molars of the upper jaw.
In the case of the Heterodontosauridae, cheeks appeared for the first time in the tribal history of the bird pelvic dinosaur . This made it easier to hold back the food in the mouth and improved the preparation of the food before digestion.
In the Chinese Tianyulong , which was only described in 2009 , feather-like structures on the skin have been preserved in fossil form. Protofeathers have previously only been found in advanced theropods .
Systematics
External system
The position of the Heterodontosauridae within the bird pelvic dinosaur is controversial. Originally, the group was considered the original bird pelvic dinosaur. Later there was broad consensus to place them as a basal group in the ornithopoda . In a more recent phylogenetic study, they are compared as sister taxons to almost all other ornithic groups grouped as taxon genasauria . Only Pisanoaurus has a more basal position.
Kladogramm of Butler et al. 2008:
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Internal system
The current version by Paul Sereno (2012) summarizes the South African representatives (Heterodontosaurus, Lycorhinus, Pegomastax, Abrictosaurus) and the South American Manidens in the subfamily Heterodontosaurinae, while the Heterodontosaurids (Echinodon, Fruituladens) from the northern land masses ( Laurasia ) and classified outside of this group, whereby he cannot resolve whether these genera themselves form a clade .
Cladogram from Sereno et al. 2012:
| Heterodontosauridae |
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literature
- 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) .
Web links
- The Paleobiology Database Heterodontosauridae
Individual evidence
- ^ A b Paul C. Sereno : Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs (= ZooKeys. No. 226, Special Issue). Pensoft, Sofia 2012, ISBN 978-954-642-652-9 , pp. 1-2, 30, doi : 10.3897 / zookeys.226.2840 .
- ↑ Xiao-Ting Zheng, Hai-Lu You, Xing Xu , Zhi-Ming Dong: An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. In: Nature . Vol. 458, No. 7236, 2009, pp. 333-336, doi : 10.1038 / nature07856 .
- ↑ z. B. Robert L. Carroll : Paleontology and evolution of vertebrates. Thieme, Stuttgart et al. 1993, ISBN 3-13-774401-6 , p. 319.
- ↑ z. B. in David B. Norman et al .: Basal Ornithopoda. 2004, p. 394.
- ^ Richard J. Butler, Paul Upchurch , David B. Norman: The phylogeny of the ornithischian dinosaurs. In: Journal of Systematic Palaeontology. Vol. 6, No. 1, 2008, ISSN 1477-2019 , pp. 1-40, doi : 10.1017 / S1477201907002271 , digitized version (PDF; 761.65 kB) .