Megapaloelodus is an extinct genus of birds distantly related to flamingos. It belongs to the same family as the closely related genus Palaelodus, but was more specialized. Megapaloelodus represents a specialization of the lifestyle of Palaelodus, which apparently was more like a wading duck in behavior - long-legged but still able to swim with ease, possibly even diving a lot - than a modern flamingo. Megapaloelodus, on the other hand, seems to have been evolved into a true wading bird, convergent with the true flamingos.
Its "knee" (actually ankle) joints had evolved to a peculiary 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 (L. H. Miller, 1954). Megapaloelodus species were sized from equal to an average Greater Flamingo to 15-20% 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 is known from the Early Miocene of Bennett County, South Dakota (Rosebud Formation: late Arikareean, 23-19 mya: fragments of a femur and a tarsometatarsus), and from some bones of the early Late Miocene 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 (L. H. Miller, 1950). The Californian population probably inhabited freshwater or saline lagoons or shallow lakes.
Whether the species M. goliath 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 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 e.g. in the Late Miocene of northern Argentina. At least two additional undescribed species await description pending availability of more material.