Based on examination of molecular data and pelage patterns, it has recently been suggested that the island populations of the clouded leopard, traditionally considered a subspecies, may, in fact constitute a separate species. In this paper, I demonstrate that the island populations deviate strongly from the mainland populations in a large number of cranial, mandibular, and dental characters. The differences far exceed those that have been documented for subspecies within other pantherine felids, and are congruent with a separate species, to which the name Sundaland clouded leopard, Neofelis diardi, has been given, although the name Diard's cat has priority based on historical precedence. I suggest that the vernacular name Diard's clouded leopard be adopted for Neofelis diardi. In contrast, mainland populations diverge less from each other, and are congruent with 1 species (Neofelis nebulosa) and 2 subspecies, the western (N. n. macrosceloides) and eastern (N. n. nebulosa) clouded leopard. Neofelis deviates from other large felids in many aspects of craniodental morphology, and most likely also in several behavioral aspects. Diard's clouded leopard appears more derived with respects to saber-toothed craniodental features than the clouded leopard, indicating that the former may have gone farther than the latter in convergently evolving craniomandibular features traditionally considered characteristic of primitive saber-toothed felids.