Tarchia, scientifically known as "Tarchia kielanae," is classified as an ankylosaur dinosaur. Tarchia derives from Mongolia and translates to “the brainy one”. The specific name, "kielanae" honors the Polish paleontologist, Zofia Kielan-Jaworowska.

The discovery of Tarchia fossils occurred in the 1960s in the Nemegt Formation of Mongolia. Although incomplete, the well-preserved remains have provided paleontologists with important information about the anatomy and characteristics of Tarchia.

Tarchia was a medium-sized ankylosaur, characterized by its heavily armored body, short legs, and distinctive tail club. It measured around 13 to 18 feet (4 to 5.5 meters) in length. Its entire body, including its head, was covered with thick, bony plates known as osteoderms, providing protection against predators.

One of the most notable features of Tarchia was the presence of a large, knob-like structure at the end of its tail, known as the tail club. This club was composed of fused vertebrae and acted as a formidable weapon against potential predators.

As an ankylosaur, Tarchia was a herbivorous dinosaur, relying on a plant-based diet to sustain itself. Its low-slung body and stout legs suggest that it was primarily a quadrupedal animal, moving on all fours. Its heavy armor and tail club would have offered defense against predators, making it a formidable presence in its ecosystem. Tooth marks identified as belonging to the tyrannosaurid, Tarbosaurus, have been found on one skull of Tarchia, indicating that the theropod likely hunted the ankylosaurid.

Tarchia's unique tail club is believed to have been used in defense against predators. It could swing its tail with great force, delivering powerful blows to deter attackers. Additionally, the armor plating covering its body acted as a natural shield against predators, providing further protection.