a large skeleton

• -75, 805, 4 (seen once)
• -45, 714, 4 (seen once)
• -83, 710, 4 (seen once)
• -61, 598, 4 (seen once)
• -23, 550, 4 (seen once)
• -87, 515, 5 (seen once)
• -47, 506, 4 (seen once) (1 of 3 spawns here)
• 63, 495, 4 (seen once)
• -17, 484, 5 (seen once)
• 60, 469, 4 (seen once)
• -37, -160, -25 (seen once)

As /loc gives them: Y, X, Z, the most used first; nearby spawns share a spot, and one seen in a single visit may be where the mob had been pulled to.