From this, which is alone sufficient for diagnostic purposes, the group is often called the Cavicornia.
"Encyclopaedia Britannica, 11th Edition, Volume 4, Slice 3" by Various
They are included with the Sheep and Oxen in the family of the Cavicornia or 'Hollow-horned' Ruminants.
"The New Gresham Encyclopedia. Vol. 1 Part 2" by Various