The unicorn in the Indus valley seal was an unknown creature. Today I found similar unknown creature in the Hittite excavations.
Late Hittite (Aramaean) Basalt relief sculpture of a Bull from 9th Cent B.C, excavated from the west side of the citadel gate of Sam'al (Hittite: Yadiya) located at Zincirli Höyük in the Anti-Taurus Mountains of modern Turkey's Gaziantep Province. Istanbul Archaeological Museum Inv. No 7709.. Photography by © Paul E Williams 2016.
More search on these two creatures are needed to find the exact species in those seals.