The Oligo-Miocene flamingo Harrisonavis croizeti represents an intermediate form between the highly specialized extant flamingo cranial morphology and the more generalized ancestral phoenicopteriform one, characterized by the extinct taxon Palaelodus. However, the original description of H. croizeti lacked detail and the lectotypic skull was lost; thus, it is not known how the ancestral phoenicopterid cranial morphology differed from that of recent forms. Here, we describe new cranial material from Oligo-Miocene deposits of France, including a mostly complete skull with an articulated upper bill, a disarticulated upper bill, and pieces of lower bill. We assign this material to H. croizeti and compare it to all previously reported fossil flamingo cranial material as well as to all six living species. We also use 3D computed tomographic data to reconstruct the skull of H. croizeti in three dimensions. The skull and bill of H. croizeti are similar to those of living species, although they display less specialized filter feeding traits, including a straighter bill with less surface area for filtration lamellae and points of articulation with the lower bill which are less developed. The less specialized form of H. croizeti suggests the extant Phoenicopterus retains a skull morphology more similar to the ancestral condition of crown group flamingos, and the extant Phoenicoparrus form is more derived.