Nipponosaurus
| Nipponosaurus | ||||||||||||
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Skeletal reconstruction of Nipponosaurus |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (late Santonium to early Campanium ) | ||||||||||||
| 85.2 to 80.6 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Nipponosaurus | ||||||||||||
| Nagao , 1936 | ||||||||||||
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Nipponosaurus is a little-known genus of ornithopod dinosaur from the group of Hadrosauridae .
The only known skeleton to date was discovered in southern Sakhalin in 1934 , which was under Japanese rule at the time. This is the first dinosaur to be discovered in Japan. The find is dated to the Upper Cretaceous (late Santonium to early Campanium ). The only species is Nipponosaurus sachaliensis .
features
Nipponosaurus is considered a representative of the Lambeosaurinae. While other representatives of this group often showed conspicuous head combs, such a possibly existing head comb in Nipponosaurus is not fossilized. The specimen found was a juvenile, as shown by not yet fused sutures of the vertebrae. Further indications of a young animal can be found in the jaw, among other things: the number of existing tooth positions was low, with the tooth batteries only having two teeth per tooth position in the lower jaw.
Find and differentiation from other genera
The found skeleton (holotype, copy number UHR 6590) of Nipponosaurus is 60% complete and consists of a few skull bones (including the upper and lower jaw), vertebrae (13 cervical, 6 back, two sacrum and 35 tail vertebrae), one Shoulder blade, most of the front legs, almost complete hind legs and pelvic bones (iliac and ischium). The skeleton is in a poor state of preservation because of the severely eroded bone surfaces, which is why Nipponosaurus is one of the least known lambeosaurins.
Nagao (1936) established the new genus Nipponosaurus , but could not differentiate it from other then known genera of Hadrosauridae due to the poor state of conservation on the basis of osteological characteristics, but only on the basis of the geographical distance of the sites. Daisuke Suzuki and colleagues (2004) were able to identify two autapomorphies in their first description - osteological features that distinguish the genus from all related genera - which confirms the status as a valid genus: The surangular, a bone of the lower jaw, showed a robust processus coronoid . In addition, the spinous process of the second cervical vertebra ( axis ) was only weakly developed, while the lateral edge of the first phalanx of the fourth finger of the hand was strongly indented.
Research history and naming
Parts of the only known skeleton were discovered and recovered in November 1934 during the construction of a hospital in southern Sakhalin, Japan (now Russia). The Japanese professor Takumi Nagao described the skeleton in 1936 as a new representative of the Trachodontidae (= Hadrosauridae). In 1937 Nagao organized an expedition with the aim of recovering further parts of the skeleton: The successful company brought out the front legs and both rear feet of the skeleton, among other things. Nagao described these additional finds in 1938. A new description of the genus by Suzuki and colleagues appeared in 2004.
The name Nipponosaurus means something like "Japanese lizard" ( Japanese Nippon - "Japan", Greek sauros - "lizard"). The second part of the species name, sachaliensis , refers to the place where it was found, the island of Sakhalin.
Systematics
Suzuki and colleagues (2004) assign Nipponossaurus to the Lambeosaurinae, one of two subfamilies of the Hadrosauridae. This assignment is based on two common features (synapomorphies): the nasal bone is excluded from the formation of the nostrils; In addition, the row of teeth of the dental is lengthened. Within the Lambeosaurinae, Nipponosaurus is mostly assigned to the group Corythosaurini. According to the phylogenetic analysis by Suzuki and colleagues, Nipponosaurus forms a clade with Hypacrosaurus altispinus ; both species form the sister group to Corythosaurus and Lambeosaurus . A more recent analysis according to Evans and Reisz (2007) sees Nipponosaurus as the most basic (most original) representative of the Corythosaurini.
The following is a cladogram according to Evans and Reisz, 2007:
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Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, p. 309, ISBN 978-0-691-13720-9 , online .
- ↑ a b c d e f Daisuke Suzuki, David B. Weishampel, Nachio Minoura: Nippponosaurus sachalinensis (Dinosauria; Ornithopoda): anatomy and systematic position within Hadrosauridae. In: Journal of Vertebrate Paleontology. Vol. 24, No. 1, 2004, ISSN 0272-4634 , pp. 145-164, doi : 10.1671 / A1034-11 .
- ↑ Takumi Nagao: Nipponosaurus sachalinensis. A new genus and species of trachodont dinosaur from Japanese Saghalien. In: Hokkaido University. Journal of the Faculty of Science. Series 4: Geology and Mineralogy. Vol. 3, No. 2, 1936, ISSN 0018-3474 , pp. 185-220.
- ↑ Takumi Nagao: On the limb-bones of Nipponosaurus sachaliensis Nagao, a Japanese hadrosaurian dinosaur. In: Annotationes Zoologicae Japonenses. Vol. 17, No. 3/4, 1938, ISSN 0003-5092 , pp. 311-319.
- ^ A b David C. Evans, Robert R. Reisz: Anatomy and Relationships of Lambeosaurus magnicristatus, a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta. In: Journal of Vertebrate Paleontology. Vol. 27, No. 2, 2007, pp. 373-393, doi : 10.1671 / 0272-4634 (2007) 27 [373: AAROLM] 2.0.CO; 2 .
