crocorax, from which the family name Phalacrocoracidae is derived, is Latinised from Ancient Greek φαλακρ?ς phalakros "bald" and κ?ραξ korax "raven". This is thought to refer to the ornamental white head plumes prominent in Mediterranean birds of this species, or the creamy white patch on the cheeks of adult great cormorants, but is certainly not a unifying characteristic of cormorants. The cormorant family was traditionally placed within the Pelecaniformes or, in the Sibley–Ahlquist taxonomy of the 1990s, the expanded Ciconiiformes. Pelecaniformes in the traditional sense—all waterbird groups with totipalmate foot webbing—are not a monophyletic group, even after the removal of the distantly-related tropicbirds. Their relationships and delimitation – apart from being part of a "higher waterfowl" clade which is similar but not identical to Sibley and Ahlquist's "pan-Ciconiiformes" – remain mostly unresolved. Notwithstanding, all evidence agrees that the cormorants and shags are closer to the darters and Sulidae (gannets and boobies), and perhaps the pelicans or even penguins, than to all other living birds. In recent years, three preferred treatments of the cormorant family have emerged: either to leave all living cormorants in a single genus, Phalacrocorax, or to split off a few species such as the imperial shag complex (in Leucocarbo) and perhaps the flightless cormorant. Alternatively, the genus may be disassembled altogether and in the most extreme case be reduced to the great, white-breasted and Japanese cormorants. In 2014, a landmark study proposed a 7 genera treatment, which was adopted by the IUCN Red List and BirdLife International, and later by the IOC in 2021, standardizing it. Occipital crest or os nuchale in Phalacrocorax carbo The cormorants and the darters have a unique bone on the back of the top of the skull known as the os nuchale or occi
