primitive heron (Aves: Ardeidae) from the Miocene of Central Asia

A robust quadrate from the Middle Miocene of Mongolia represents a new genus of Ardeidae that combines the similarities to Nycticorax and Tigrisoma, both of which have been recovered in basal positions in recent phylogenies of the Ardeidae, and to cf. Pikaihao from the Middle Miocene of Africa. The confluence of mandibular facets on the medial condyle and pterygoid condyle in the new genus, Nycticorax, and cf. Pikaihao is likely to be symplesiomorphic, as it is shared with nearly all other waterbirds (except for the Ciconiidae), including the immediate outgroup (Threskiornithidae). However, the medial supraorbital crest is a likely synapomorphy of the new genus and cf. Pikaihao. The similarities to Trigrisoma support its basal position, as recovered from molecular sequences and proposed by a pre-cladistic morphological analysis. Since both the night herons and Tigrisoma have heads that are proportionally much larger than those of the large day herons, it appears that the Ardeidae started their evolution with relatively heavy heads, which may have contributed to the origins of the family-specific head retraction in flight.