Table 1.

Presence and number of visible entrances from nasal cavity to rostral and caudal maxillary sinus (N = 12)

Pony number	Rostral nasomaxillary aperture		Caudal nasomaxillary aperture
	left	right	left	right
1	+	-	-	-
2	+	++	-	-
3	-	-	+	+
4	+	+	-	+
5	-	-	-	-
6	+	++	+	-
7	+	+	+	+
8	-	-	-	-
9	+	-	-	-
10	++	++	-	-
11	-	-	-	-
12	+	-	+	-

- no entrance, + one entrance, ++ split entrance