FIG. 4. — Most likely relationships of the mephitids. Main apomorphies are: Node 1, expansion of the epitympanic recess into a mastoid sinus, extraroots on m1; Node 2 (Mephitidae), rhinal sulcus higher, P2 smaller, P4 protocone much reduced, P4 hypocone large; Promephitis, face short, broad, and inflated, anterior premolar series much shortened, strong basal cingulum on canines, P4 hypocone long and tall, M1 very large, with strong buccal cingulum; Node 3 (Mephitinae), shallow fossa subarcuata, slender zygomatic arch, angular region of the mandible somewhat expanded, masseteric fossa shallow, distinct sylvian sulcus, long supra-sylvian sulcus (less so in Mephitis), arched lateral sulcus, cruciate and post-cruciate sulci present; Mydaus, long and narrow skull and face, long premolar row, choanae far behind M1, indistinct tensor tympani fossa, incisors in broad arch, lower ones procumbent and spatulate, M1 buccal cingulum absent, femur trochanter low, shallow intertrochanteric fossa; Mephitini, no protocone on P4, angular region of the mandible more expanded, loss of epitrochlear foramen on the humerus.