Saichania

***Saichania*** (Mongolian meaning "beautiful one") is a genus of herbivorous ankylosaurid dinosaur from the Late Cretaceous period of Mongolia and China.

The first fossils of *Saichania* were found in the early 1970s in Mongolia. In 1977 the type species *Saichania chulsanensis* was named. The description of this species has been based on limited fossil material; especially the rear of the animal is not well known.

*Saichania* was over five metres long and weighed over two tonnes. It was more robustly built than other members of the Ankylosauridae. Neck vertebrae, shoulder girdle, ribs and breast bones were fused or firmly connected. Its body was flat and low-slung, standing on four short legs. The forelimbs were very powerful. The head was protected by bulbous armour tiles. It could defend itself against predators like *Tarbosaurus* with a tail-club. On the torso keeled osteoderms were present. *Saichania* bit off plants in its desert habitat with a horny beak and processed them in its wide hindgut.

*Saichania* was a large ankylosaurid. Maryańska estimated its length at seven meters.[1] Other estimates roughly confirmed this, stating a maximum length of about 6.6 metres (22 ft) long.[5] However, Gregory S. Paul in 2010 gave a lower estimate of 5.2 metres, with a weight of two tonnes.[6] Finds of tail clubs of gigantic individuals suggest larger sizes but their reference to *Saichania* cannot be substantiated as the holotype, the only specimen sufficiently described, only consists of the front of the animal.[3]

*Saichania* shared the general ankylosaurid build, being a low-slung, broad, heavily armoured dinosaur, with short forelimbs. Even for an ankylosaurid however, *Saichania* is exceptionally robust, its rump strengthened by ossifications and fusions of the vertebral column, ribs, shoulder girdle and breast bones.[1]

Arbour in 2014 established a revised list of distinguishing traits. The osteoderms on the skull are bulbous. The first and second neck vertebrae are fused into a single element, a syncervical. The upper side of the humerus is very broad, equalling 70% of the total length of the bone. The rib shafts are expanded by intercostal ossifications, the cartilage connecting the ribs having been turned into bone sheets. The cervical halfrings, protecting the neck, have each an underlying continuous band of bone and the borders between the segments of these rings are covered by extra armour plates entirely hiding these connections from view.

The skull of *Saichania* is broad, 455 millimetres long and 480 millimetres wide with the holotype.[1] The top of the snout is covered with strongly convex osteoderms. These armour tiles on the snout comprise a central large *caputegula*. A large "loreal" osteoderm covers much of the top edge and the side of the snout. The *caputegula* on the prefrontal is of moderate size and not strongly protruding sideways. The osteoderms on the upper eye socket rim are continuous, not forming two peaks. An extra osteoderm on the rear supraorbital, as in *Tarchia*, is lacking. The pyramid-shaped squamosal horns on the rear skull corners are broad, not narrow as with *Tarchia*. These horns have a uniform surface texture, not a division into a smooth and rough surface as in *Zaraapelta*.[3] On the cheek, large triangular quadratojugal horns are present.