Mamenchisaurus: Dinosaurs in the Mist

Setting our sights via the Dino Cam to the Jurassic Period of 160 million years ago, in what is now the Sichuan Basin of China, we witness a small herd of giants slowly traversing the sandy plains of a misty river delta environment. The heavy rains of the wet winter season are easing-up as the dry summer months approach. These ambling long necked sauropod dinosaurs are, in fact, Mamenchisaurus - the genus comprising the longest-necked animals of all time. As a group, the sauropods are famous for their long necks, which includes Apatosaurus, Brachiosaurus, Diplodocus, Titanosaurus, and the apparently recently resurrected "Brontosaurus". 

However, Mamenchisaurus species had exceptionally long necks - even by sauropod standards. We're not sticking our necks out with such claims - the 7 known species of Mamenchisaurus include 2 species described with necks exceeding 45 feet long alone: a specimen of Mamenchisaurus constructus had a neck estimated at 15 m (49 ft) in length, and Mamenchisaurus sinocanadorum (with substantial material discovered, yet remaining to be formally described), may have been among the largest dinosaurs of all time, reaching 35 metres (115 ft) in total length and possessing a neck 18 metres (59 ft) long (!)

These extraordinary numbers reflect the unique proportions of Mamenchisaurus: the mamenchisaur neck comprises half the total length of the animal. As mamenchisaurs evolved longer necks it seems their tails compensated by getting proportionally shorter. This is in stark contrast to most other sauropods, where long necks were balanced by even longer tails. The one exception is Brachiosaurus, which shared similar long neck/short tail proportions with Mamenchisaurus. Consequently, it's not surprising that Mamenchisaurus is now considered closely related to the brachiosaur genus.