Klamelisaurus (meaning "Kelameili Mountains lizard") is a genus of herbivorous sauropod dinosaur from the Middle Jurassic Shishugou Formation of China.

The type species is Klamelisaurus gobiensis, which was named by Zhao Xijin in 1993, based on a partial skeleton discovered in 1982 near the abandoned town of Jiangjunmiao.

Phylogenetic analyses have suggested that Klamelisaurus belonged to the Mamenchisauridae, a group of Middle to Late Jurassic and primarily Chinese sauropods, although its close relatives also include a mamenchisaurid from Thailand.

[1] In 1982, these excavations uncovered the skeleton of a sauropod dinosaur 35 kilometres (22 mi) north of the now-abandoned town of Jiangjunmiao, located in the eastern Junggar Basin.

[2] The specimen, which was catalogued under the specimen number IVPP V9492, consists of teeth, most of the vertebral column (save for the first seven cervical vertebrae (neck vertebrae) and the end of the tail), ribs, the right shoulder girdle and arm (scapula, coracoid, humerus, ulna, radius, and phalanges), and the right hip girdle and leg (ilium, pubis, femur, tibia, fibula, and astragalus).

The referral of the fragmentary teeth to the specimen was unexplained, and they can no longer be located along with two ribs, two carpals of the wrist, a calcaneum of the ankle, and some bones of the tail.

They noted that the specimen's reconstruction had been altered since Zhao's description, namely by the addition of a frontward-projecting process on the 15th cervical rib and the removal of a fabricated connection to the centrum (vertebral body).

They estimated a total of fifteen to seventeen cervicals, based on other sauropods with similar patterns of vertebral variation, and indicated that Klamelisaurus had a shorter neck than Omeisaurus tianfuensis, Mamenchisaurus hochuanensis, and M. sinocanadorum.

First, the spinoprezygapophyseal laminae (SPRLs), ridges of bone extending forward from the neural spines, bore irregular, plate-like extensions.

Second, below the SPRLs and in front of depressions called the spinodiapophyseal fossae (SDFs), the sides of the centra bore a set of deep foramina (openings).

Although these foramina were present only on the right side of the centra, Moore and colleagues considered them to be unique due to their consistency and the presence of similar structures in other sauropods.

However, for Klamelisaurus, Moore and colleagues interpreted the former to be an attachment for the intercristal muscles of the neck, based on the surface texture and comparisons with ostriches, while they considered the latter to be a pneumatic structure created by air sacs.

[1][2] Zhao's diagnosis for the hips and legs of Klamelisaurus included a robust ilium with an indistinct "laminar ridge" and a forward-projecting pubic peduncle (attachment to the pubis); a slender ischium; a robust, thin, flat, and weakly curved pubis (however, this bone appears to be reconstructed); a thick and flat femur with an indistinct head and a fourth trochanter (the attachment for the caudofemoralis muscle) located near the top of the bone; and a tibia shorter than the fibula (however, these bones are either incomplete or heavily reconstructed).

However, he noted that the combination of more than twelve cervicals, thirteen dorsals, five sacrals with four fused, and other characteristics in Klamelisaurus was distinct from these other groups, warranting the creation of a new subfamily.

Since previous analyses failed to find Mamenchisaurus and Omeisaurus species as unified (monophyletic) groups, their analysis focused on resolving the relationships of individual specimens rather than genera.

[2] Nearly all of their analyses found the "core Mamenchisaurus-like taxa" to be closely related to Euhelopus, Daxiatitan, and Dongbeititan, traditionally considered part of the more derived Macronaria.

They recovered this wider group — which they termed the Euhelopodidae — outside of the Neosauropoda; the implied-weights analysis on the Carballido dataset placed it as an early-diverging macronarian lineage, also including Bellusaurus, while the implied-weights analysis on the Gonzàlez Riga dataset found Euhelopus among macronarians as a somphospondyl (in which case they called the group Mamenchisauridae).

Meanwhile, based on comparisons with its relatives, Moore and colleagues inferred that Klamelisaurus likely had camerate air spaces (i.e., enclosed by bone[15]) in its cervicals.

[2] However, they also noted two characteristics on their list which may have varied with age: the bifurcated neural spines,[17] and the presence of wing-shaped processes that projected further outwards than the postzygapophyses on the rear dorsals.

[18] Using stratigraphic correlation, this rock layer was found to lie below a tuff from the Shishugou Formation at the Wucaiwan locality, which has been dated radiometrically to 162.2 ± 0.2 Ma, or the Oxfordian age of the Jurassic period.

[2] During the Callovian, the climate of the Shishugou Formation is considered to have been mesic (moderately and seasonally wet), with the environment at Wucaiwan having been an alluvial plain or marsh.

[20] Juliane Hinz and colleagues in 2010 reconstructed a petrified forest preserved in overlying Oxfordian rocks, located 17 km (11 mi) north of Jiangjunmiao.

[23] Meanwhile, the sauropods Bellusaurus, Mamenchisaurus sinocanadorum, and Tienshanosaurus are known from the "upper beds", above the level of the tuff at 162.2 Ma, and thus were not contemporaries of Klamelisaurus.

[11] Asides from these sauropods, Aorun, and Sinraptor, the Oxfordian portion of the Shishugou Formation preserves a diverse dinosaur fauna that also includes the theropods Haplocheirus, Shishugounykus, Zuolong, Guanlong, and Limusaurus; the ornithopod Gongbusaurus; the stegosaur Jiangjunosaurus; and the marginocephalians Yinlong and Hualianceratops.