Complex sentence: In addition to the 10 subspecies listed below, some have recognized "O. h. crooki" from northern Mexico, but it is invalid, as it is based on a hybrid between the mule deer and white-tailed deer.
Split into simpler sentences: In addition to the 10 subspecies listed below, some have recognized "O. h. crooki" from northern Mexico. However, it is invalid, as it is based on a hybrid between the mule deer and white-tailed deer.