The Indus Dictionary Project
This motif is generally thought to be a markhor. This particular example is a chimaera which incorporates a human face, and a bull's body.
The key thing that you should notice about this motif is the lack of conformity in the markhor's horns. The horns have been deliberately splayed so that they resemble the Indus sign for water. They are an ideograph for a coracle, which is a small boat that sits on the water.
Moreover, the markhor is a large goat, and it is possible that markhor hide was used in the construction of coracles.
Mohenjo-daro: Seal: M-1186 A (You should note that this motif would have mirrored orientation in the sealing.): Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 425: Collections in Pakistan: Suomalainen Tiedeakatemia.
Coracle: Lynn Fawcett, 2017.