arterial pattern of the head;facial arterial supply;perissodactyla
Considerable consistency in the arterial pattern of the head has been observed in species of Artiodactyla, but few studies have examined the order Perissodactyla. Here, we describe arteries supplying the intermandibular, mental, masseteric, buccal, labial, and nasal regions in eight perissodactylans, including representing of all families comprising this order. Observations were made on a total of 45 preparations of head arteries, obtained by injection of arteries with acetone-dissolved stained vinyl superchloride or stained latex LBS3060. In the Equidae species alone it was found that the facial artery descends from the linguofacial trunk. In tapirs and rhinos the facial artery branches off directly from the main arteries of the head. In tapirs alone it was found that the inferior alveolar artery gives off the buccal and sublingual arteries, and then extends into the mental artery. In the rhino a specific feature of the arterial pattern of the head was the exit of the occipital artery from the superficial temporal artery. In all equines studied, the transverse facial artery gave off a larger blood vessel to the masseter muscle and ran along the facial crest, while in tapirs and rhinos the transverse facial artery fanned out branches in the masseteric fossa. The variations observed can be considered in future studies on the origin of Perissodactyla. In this context, we note that the most similar patterns of exit and course of the facial, mental, transverse facial and infraorbital arteries exist in tapirs and rhinos (Ceratomorpha suborder), at least among the perissodactylans studied here.