A second species historically pertained to "Hainosaurus" was described by in 1988 by Elizabeth Nicholls based on a partial skeleton consisting of a partial skull, lower jaw, a near-complete vertebral column, and some limb bones recovered from the Pembina Member of the Pierre Shale in Manitoba, Canada. This skeleton resides in the Miami Museum in Miami, Manitoba cataloged as MT 2. Although "Hainosaurus" was previously only known in Europe, Nicholls (1988) argued that the new species differed from the more locally known "Tylosaurus" based on a higher count of pygal vertebrae, longer external nares, and femur longer than the humerus. The species was named "Hainosaurus pembinensis", the specific epithet referring to the Pembina Member the skeleton was found in.