From Lexicanum

A Knarloc is any of several species of bipedal creatures native to the planet Pech, the homeworld of the Kroot. In appearance they resemble stocky theropod dinosaur with a frill of tough quills around the back of their head and a broad, jagged-edged carnivorous beak. Unlike Krootoxen and Kroot Hounds, Knarlocs are a distant relative of the Kroot, rather than the descendants of a degenerated kindred.

Varieties

There are two known varieties of Knarloc, the common or Riding Knarloc, roughly the size of a rhinoceros, are often employed by the Kroot Tracker Kindred as a riding beast, and the elephant-sized Great Knarloc^[1], rarely ridden but often trained as an attack beast and prodded into battle by a number of goads.

Sources

http://www.warmongerclub.com/articles/kroot/kroot5.html