Incomplete brachiocephalic trunk in a Korean water deer

The brachiocephalic trunk (Bct) branches from the aortic arch (Aa) and consists, in ruminants, of the common trunk of the left subclavian artery (LSb), the bicarotid artery (Bc) or left and right common carotid artery (LCc and RCc), and the right subclavian artery (RSb). This pattern differs from the primitive mammalian Aa pattern due to the fact that the analogs of the LCc and LSb migrate cranially and merge with the common trunk of the RCc and RSb in the embryonic stage. A Bct having a septal remnant that consisted of the tunica media was observed in a female Korean water deer (Hydropotes inermis argyropus), which was deemed to have resulted from an incomplete merging of the vessel walls between a carnivoran-type Bct and an incomplete LSb. This is the first report of an abnormal Bct in a Korean water deer.