Omeisaurus

Skeletal reconstruction of Omeisaurus tianfuensis in Hong Kong.

• Sichuan, China ( Shaximiao Formation)

Omeisaurus is a genus of dinosaur from the group of sauropods, whose fossils date from the Middle Jurassic of China. Significantly for this sauropod was a relative extremely long neck, which was one of the longest of all sauropods. The skeleton of this species is almost completely known due to numerous discoveries, which she is one of the best surviving sauropods - a full description of the skeleton is still pending. In addition to the type species Omeisaurus junghsiensis six other species have been described, of which are currently recognized, however only three.

The name Omeisaurus (Ch Omei or Emei, gr saurus - " lizard" ) has the Emei Shan, one of the four sacred Buddhist mountains in China, about 100 kilometers west rises the locality of the first skeleton.

Features

Omeisaurus was a medium to large sauropod. The type species, Omeisaurus junghsiensis, reaching body lengths of about 10 to 15 meters; the type Omeisaurus tianfuensis was larger, measuring 16 to 20 meters. Weight estimates of Omeisaurus tianfuensis vary depending on the study from 9.8 to 11.8 tons.

The blueprint for this sauropod was characterized by a relatively short torso and short legs, and by a relative extremely long neck that measured at Omeisaurus junghsiensis a length of about 8.5 meters. Thus, the neck was one of the longest of all proportion sauropods. The cervical spine consisted of 16 to 17 cervical vertebrae, the individual cervical vertebrae were greatly extended - the middle cervical vertebrae were almost five times as long as deep. The dorsal spine consisted of 12 vertebrae, the sacrum of 4 fused sacral vertebrae; the tail spine, however, is not fully known. Unlike Mamenchisaurus all spinous processes were ungegabelt, the spinous processes of the cervical vertebrae were very low. From the 16th or 17th caudal vertebrae forked chevron bones are found. It is unclear whether Omeisaurus carried a club-like ossification at the end of the tail, as it is known from the contemporary Shunosaurus: Although such tail lobes Omeisaurus were attributed, but these were not found in direct connection with the skeletons.

The skull resembles that of Shunosaurus, but is shorter and higher. The pine wore on each side 4 teeth in the premaxillary bone, 11 teeth in the upper jaw and 13 to 15 teeth in the lower jaw. The spatula-shaped teeth were significantly greater than that of Shunosaurus in proportion.

Systematics and species

Omeisaurus deemed to be an original representative of Eusauropoda, but the exact relationships of this genus are controversial. Many researchers suggest a closer relationship with the also very long-necked Mamenchisaurus and take both classes in a Mamenchisauridae said group together; occasionally, this grouping is referred to as Omeisauridae or Euhelopodidae. Other researchers suggest, however, that Omeisaurus and Mamenchisaurus split off independently of the main line of advanced sauropods ( the Neosauropoda ).

Although so far about seven different species have been described, are just two through full findings known and generally accepted as valid - the type species Omeisaurus junghsiensis as well as the larger type Omeisaurus tianfuensis. Two other species, Omeisaurus maoianus and Omeisaurus jiaoi were in 2001 and 2011 scientifically described, both types are based on nearly complete skeletons. Three other species, Omeisaurus changshouensis, Omeisaurus luoquanensis and Omeisaurus fuxiensis, however, are known, and probably invalid only by fragmentary remains. Omeisaurus fuxiensis is sometimes treated as a separate genus - Zigongosaurus - or classified as a type of Mamenchisaurus.

History of Research

The first skeleton was discovered in 1936 in the district in Zigong Rong and in the summer of that year by the paleontologist Yang Zhongjian (aka CC Young) salvaged and Charles Camp. The partially enclosed by rock fossils still weighed a total of 2.3 tons and had in 24 boxes of coolies to the nearest, are transported about 200 Li (approx. 100 km) distant road. Subsequently, the fossils were prepared in the Cenozoic Research Laboratory in Beijing and 1939, scientifically described by Yang Zhongjian as a new species and genus, Omeisaurus junghsiensis.

Since then further skeletons and species have been described. The second day very well known type, Omeisaurus tianfuensis was described in 1984 by researchers at Hey Xinluhai based on an incomplete skeleton, which was discovered in Dashanpu in Zigong, about 40 kilometers east of the Omeisaurus junghsiensis locality. These researchers mentioned about 10 other skeletons, which are probably also attributable to this type. He Xinluhai (1988 ) Omeisaurus introduced himself as a rather slow animal that perhaps aquatic lived. A mass accumulation of Omeisaurus fossils confined space saw these researchers also as an indication of a possible hearth life.

In the recent past, the types Omeisaurus maoianus and Omeisaurus were jiaoi described. The former is based on a discovered in Leshan in a circle Jingyan skeleton, while the second is known by a discovered in Zigong skeleton.