CollectA 88908 Deluxe (1:100) - Mamenchisaurus 40 x 24 cm Mamenchisaurus is a genus of sauropod dinosaurs known for their remarkably long necks which made up nearly half the total body length. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species are from the Upper Shaximiao Formation whose geologic age is uncertain. However, evidence suggests that this was no earlier than the Oxfordian stage of the Late Jurassic. Most species were medium- to large-size sauropods, 15 to 26 meters (49 to 85 ft) in length. Two as-yet-undescribed cervical vertebrae suggest one of the largest dinosaurs known; estimated at 35 meters (115 ft) in length and possibly weighed 60 and 80 tonnes (66 and 88 short tons).