Megapaloelodus

Its "knee" (actually ankle) joints had evolved to a peculiar form not known from modern flamingos and only incipient in Palaelodus; the function of this character is not known but possibly it enabled the bird to "lock" its leg in standing position when asleep in shallow water, out of the reach of most terrestrial as well as aquatic predators.[3] Megapaloelodus species were sized from equal to an average greater flamingo until 15 to 20% larger. Unfortunately, it is not known whether their bills were specialized for filter feeding as in the true flamingos, or whether they retained the less-specialized shape of Palaelodus which fed on small aquatic invertebrates and vertebrates.

The Miocene species M. connectens[4] is known from the Early Miocene of Bennett County, South Dakota; Rosebud Formation: late Arikareean, 23-19 mya and Hemingfordian Batesland Formation. The fossils comprise fragments of a femur and a tarsometatarsus), and from some bones of the early Late Miocene Temblor and Barstow Formations of San Bernardino County, California (c. 11 mya; UCLA 2303 & 2364). The latter may represent a distinct species due to the considerable difference in space and time between the two localities, but all these bones at least were from birds of similar size, about as large as a big greater flamingo.[5] The Californian population probably inhabited freshwater or saline lagoons or shallow lakes.

A later species, M. opsigonus, was found in the Clarendonian Juntura Formation at Juntura, Malheur County, Oregon.

Whether the species M. goliath[6] belongs into this genus or into Palaelodus is not quite certain; it surpasses all forms in the latter genus in size, but is generally similar. It is the earliest representative of Megapaloelodus, living from the Late Oligocene to the Middle Miocene, and has been found in a wide range of Central European localities, from France to Southern Germany (Ringingen-Frontal 1) and on to the Czech Republic and Hungary; it dwelled in the wetlands created by the rerouting of rivers due to the beginning uplift of the Alps.

Fossils referrable to this genus have also been found in the Huayquerian Ituzaingó Formation, Argentina. At least two additional undescribed species await description pending availability of more material.

Fossils have also been found in the Almejas Formation of Baja California, Mexico.