Mamenchisaurus (Mamenxi lizard)

Short Info

Mamenchisaurus (Mamenxi lizard)

Phonetic : Ma-men-chi-sore-us.

Named By : C. C. Young – 1954

Diet : Herbivore

Size : Estimated 22 – 35 meters long

Type of Dinosaur : Sauropod

Type Species : M. constructus (type), M. anyuensis, M. hochuanensis, M. jingyanensis, M. sinocanadorum, M. youngi

Found in : China

When it Lived : Late Jurassic, 155-145 million years ago

Mamenchisaurus (/ma/mentSi/r@s/ mah/MUN-chi/SAWR-@s; or spelling pronunciation /m@mentSi/r@s/), is a genus that includes sauropod dinosaurs. It was known for its long necks, which accounted for nearly half of their total length. Many species have been assigned to this genus, but some of them may be suspect. In China, the Sichuan Basin has been home to fossils. Many species are found in the Upper Shaximiao Formation, whose geologic age remains unknown. Evidence suggests that this is not earlier than the Oxfordian Stage of the Late Jurassic. M. sinocanadorum is dated to the Oxfordian (158.7-161.2 mya), and M.anyuensis dates to the Aptian stage in the Early Cretaceous (114.4 mya). The majority of species were medium-large sauropods, ranging in size from 15 to 26 meters (49 ft to 85 ft). The two cervical vertebrae that are yet to be described could belong to M. Sinocanadorum. They were 35m (115ft) long and may have weighed 60 or 80 tonnes (66 or 88 short tons).

Mamenchisaurus in JapanKabacchi, CC BY 2.0, via Wikimedia Commons

It is not certain that all species assigned to Mamenchisaurus belong to this genus. Some Mamenchisaurus species have been found to be complete, while others are still unknown. Although the species are different in size and have specific skull and bone features, they share common sauropod traits like long tails and large bodies. Mamenchisaurids are known for their long necks that extend to half of their body. M. youngi and M. Hochuanensis have complete necks, with 18 and 19 vertebrae, respectively. Mamenchisaurus cervical vertebrae have a long, elongated shape and are highly pneumatic. Bifurcated neural spines are found on the anterior dorsal and posterior cervical vertebrae of Mamenchisaurus. Their shoulders were higher than their hips. Based on two unnamed vertebrae, the lengths of the different species range from 15 metres (49 feet) to at most 26 metres (85ft) and possibly up to 35 meters (115ft).

It is controversial to discuss the neck position of sauropod dinosaurs. Andreas Christian and his colleagues examined the neck of Mamenchisaurus Youngi. The neck was almost straight, with only a slight upward bend at its base and a slight downward bend towards its head when it is in neutral posture. The neck’s base has limited downward flexibility, but a high level of upward flexibility. The area near the head showed greater downward flexibility, but less upward flexibility. The mid-region had high downward flexibility, leading the authors to conclude M. youngi often ate at low levels. The flexibility of M. youngi may be limited by the presence of cervical ribs that are too long and overlap. The stress on intervertebral cartilage was also calculated by the authors. The results showed that the neck was mostly straight with possible exceptions at the base and near the head.

Mamenchisaurus have forked or sled chevrons that start around the middle part of their tails, much like diplodocids. These chevrons curve strongly in the backwards and have a forward projection. Gregory S. Paul argued that these chevrons were adaptations to rearing behavior. The tail acts as a prop in a tripodal stance. The forked chevrons help to distribute the weight evenly. Paul also points out that Mamenchisaurs’ pelvises are tilted (reversed) which may have allowed for slow-walking while bipedal.

Mamenchisaurus sp. referred to a large ulna (GPIT SGP2006/10) that measured >96 cm (38 in). A bone histology analysis was performed on the Shishugou Formation. The age at death was determined by dividing the bone and counting the growth rings.

Source: Wikipedia