The gemsbok shofar has been gradually making its way onto the shofar market in recent years. According to Rabbi Natan Slifkin, it is made from the horn of an antelope, the southern African oryx (Oryx gazella), known in Afrikaans as the “gemsbok.”
The horns are about two and a half feet long, straight, ridged along half their length, and dark brown or black in color, lending the shofar a striking appearance that can command a hefty price. They are considered kosher, but according to halacha are not preferred, because they are not bent. However, for the Jubilee year, the Mishna states that a straight horn is ideal (Rosh Hashana 3:2).
Another exotic shofar appearing on the shofar market is the eland shofar, which is straight, but has a twist (not a curve) along part of its length. Ibex shofars and pronghorn shofars are also sometimes sold, and are kosher, but not preferable. (According to the Pri Megadim, the ibex shofar is preferable to the eland shofar, because the ibex is from the goat family and the Torah uses the same terminology for goats and sheep.)