Galeamopus was first known from a partial skeleton discovered by fossil hunter William H. Utterback in 1902 near Sheridan, Wyoming, in the Red Fork Powder River Quarry A. In 1906, the skeleton was referred to Diplodocus by William Jacob Holland when he described its braincase.
The specimen was classified by Holland as a new species of Diplodocus, Diplodocus hayi, in 1924.
The specific name honoured Oliver Perry Hay.

In 2015, it was renamed as the separate genus Galeamopus by Emanuel Tschopp, Octávio Mateus and Roger Benson.
The generic name is derived from Latin galeam, the accusative of galea, "helmet", and opus, "need".
The combination is intended as a translation of Wil-helm, literally "want helmet", in reference to the first name of both Utterback and Holland.
The name is at the same time an allusion to the fact that the brittle braincase of the type specimen is in need of a helmet.

The genoholotype is HMNS 175 (previously CM 662), the original skeleton.
It was found in layer of the lower Morrison Formation dating from the Kimmeridgian.
This specimen is also the holotype of Galeamopus hayi, the combinatio nova of the type species D. hayi.
Several other specimens were referred to the genus Galeamopus but not to Galeamopus hayi.
These included specimen AMNH 969, a nearly complete skull discovered in 1903 at the Bone Cabin Quarry by Peter Kaisen; and specimen USNM 2673, a partial skull excavated in 1884 by Marshall P. Felch at Garden Park in Colorado.

SMA 0011, a skeleton nicknamed "Max" and found in June 1995 at the Howe-Stephens Quarry, was considered sufficiently different from the others to consider naming a separate species for it.
In 2017, the "Max" specimen was made the type specimen of a second Galeamopus species, G. pabsti, by Tschopp and Mateus.
It was named after the Swiss paleontologist Dr. Ben Pabst, who discovered the specimen and helped mount the skeleton at Sauriermuseum Aathal.
Galeamopus was first known from a partial skeleton discovered by fossil hunter William H. Utterback in 1902 near Sheridan, Wyoming, in the Red Fork Powder River Quarry A. In 1906, the skeleton was referred to Diplodocus by William Jacob Holland when he described its braincase. The specimen was classified by Holland as a new species of Diplodocus, Diplodocus hayi, in 1924. The specific name honoured Oliver Perry Hay.
In 2015, it was renamed as the separate genus Galeamopus by Emanuel Tschopp, Octávio Mateus and Roger Benson. The generic name is derived from Latin galeam, the accusative of galea, "helmet", and opus, "need". The combination is intended as a translation of Wil-helm, literally "want helmet", in reference to the first name of both Utterback and Holland. The name is at the same time an allusion to the fact that the brittle braincase of the type specimen is in need of a helmet.
The genoholotype is HMNS 175 (previously CM 662), the original skeleton. It was found in layer of the lower Morrison Formation dating from the Kimmeridgian. This specimen is also the holotype of Galeamopus hayi, the combinatio nova of the type species D. hayi. Several other specimens were referred to the genus Galeamopus but not to Galeamopus hayi. These included specimen AMNH 969, a nearly complete skull discovered in 1903 at the Bone Cabin Quarry by Peter Kaisen; and specimen USNM 2673, a partial skull excavated in 1884 by Marshall P. Felch at Garden Park in Colorado.
SMA 0011, a skeleton nicknamed "Max" and found in June 1995 at the Howe-Stephens Quarry, was considered sufficiently different from the others to consider naming a separate species for it. In 2017, the "Max" specimen was made the type specimen of a second Galeamopus species, G. pabsti, by Tschopp and Mateus. It was named after the Swiss paleontologist Dr. Ben Pabst, who discovered the specimen and helped mount the skeleton at Sauriermuseum Aathal.
Galeamopus