| Eomamenchisaurus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Family: | †Mamenchisauridae |
| Genus: | †Eomamenchisaurus Lüet al., 2008 |
| Species: | †E. yuanmouensis |
| Binomial name | |
| †Eomamenchisaurus yuanmouensis Lüet al., 2008 | |
Eomamenchisaurus (meaning "dawnMamenchisaurus") is agenus ofmamenchisauridsauropoddinosaur from theMiddle JurassicZhanghe Formation ofYuanmou,Yunnan,China. Thetype species isE. yuanmouensis, described byLü Junchang and colleagues in 2008.
Eomamenchisaurus yuanmouensis was named byLü Junchang, Li Tianguang, Zhong Shimin, Ji Qiang, and Li Shaoxue in 2008 based on a partial skeleton found in Jiangyi Township ofYuanmou County,Yunnan. The genus name is derived from Greek ἠώς, "dawn" and the name of the related genusMamenchisaurus, referring to its status as an early mamenchisaurid, and the species name refers to its discovery in Yuanmou.[1]
Eomamenchisaurus yuanmouensis is only known from a single partial skeleton, theholotype CXMVZA 165, which includes incompletecervical vertebrae,dorsal vertebrae, a partialsacrum consisting of three preserved vertebrae, the rightilium,pubis, andtibia, and bothfemora andischia. The specimen was collected from theZhanghe Formation, which dates to theMiddle Jurassic. The specimen is stored in the Chuxiong Museum.[1]
Eomamenchisaurus was a mamenchisaurid, a group of sauropods typically characterized by a very long neck. However, in several respects,Eomamenchisaurus shows more primitive characteristics than other mamenchisaurids. Like some other mamenchisaurids, the posterior dorsal vertebrae are fused together. The dorsal vertebrae are unlike more derived mamenchisaurids in having only weakly convex anterior faces. The sacrum was probably composed of four vertebrae, as the first preserved sacral vertebra shows a missing sacral vertebra would have attached in front. The femur is 1.1 metres (3.6 ft) long,[1] similar in length to the 1.16 metres (3.8 ft) long femur of the 16 metres (52 ft) longMamenchisaurus youngi.[2] Thefourth trochanter, a ridge on the femur for muscle attachment, is located on the medial margin of the shaft, as in most early sauropods, rather than being on the midline of the shaft as inMamenchisaurus. The length of the tibia is approximately 64% of the length of the femur.[1]
Lü and colleagues, in their original description ofEomamenchisaurus, classified it as amamenchisaurid.[1] In 2015, Xing Lida and colleagues noted thatEomamenchisaurus was difficult to distinguish fromYuanmousaurus, another mamenchisaurid from the Zhanghe Formation.[3]
