The first
Bactrosaurus remains recovered from the
Iren Dabasu Formation in the
Gobi Desert of
China were composed of partial skeletons of six individual
B. johnsoni. The specimens collected appear to come from a variety of age groups, from individuals that may be hatchlings to full-sized adults. The fossils were described in 1933 by
Charles W. Gilmore, who named the new animal
Bactrosaurus, or "club lizard", in reference to the large club-shaped neural spines projecting from some of the vertebrae. The Iren Dabasu Formation has been dated to the
Cenomanian stage, around 95.8 ± 6.2
million years ago. No complete remains have yet to be uncovered, but
Bactrosaurus is still better known than most of the early hadrosaurs. Known parts of the anatomy of
Bactrosaurus include the limbs, pelvis, and most of the skull (although the crest is notably absent). "Bakesaurus" is an informal name based on a
maxilla from the
Majiacun Formation of China assigned to
Bactrosaurus in 2001. The
nomen nudum was created and pictured in a Chinese-language book by Zhou (2005) and first surfaced on the
Internet during February 2006 when it was mentioned on the
Dinosaur Mailing List by Jerry D. Harris. ==Description==