Mamenchisaurus hochuanensis. （The front dinosaur） Symtemtic position: Mamenchisauridae, Sauropodomorpha, Saurischia Locality: Hongqi, Zigong, Sichuan, China. Age: Late Jurassic (about 150 million years ago). An extra large long-necked sauropod dinosaur up to 20m long. Its elongated neck consists of 19 cervical vertebrae. It is a dinosaur taxon with the most cervical vertebrae.