Megapaloelodus

Megapaloelodus Temporal range: Late Oligocene–Early Pliocene PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Phoenicopteriformes
Family:	†Palaelodidae
Genus:	†Megapaloelodus A. H. Miller 1944[1]
Species
M. connectens Miller, 1944 (type) M. goliath Milne-Edwards, 1863 M. opsigonus Brodkorb, 1961 M. peiranoi Agnolin, 2009
Synonyms
Megapalaelodus Wetmore 1951

Megapaloelodus is an extinct genus of

The name Megapaloelodus combines the Ancient Greek word "mega" meaning "great" with a misspelling of the name Palaelodus, roughly translating to "ancient inhabitant of marshes",^[4] after the closely related genus primarily known from European deposits. The name was chosen to reflect the fact that the first discovered Megapaloelodus remains, belonging to M. connectens, appeared to have been larger than the already big Palaelodus goliath.^[1][2] This is rendered somewhat ironic as subsequent research has placed Palaelodus goliath in Megapaloelodus as well.

Species

• M. connectens

The

San Bernardino County, California.^[2][3]

The species name connectens was chosen by Alden H. Miller in the belief that this species bridged the gap between Palaelodus and extant flamingos.

It is the earliest representative of Megapaloelodus, living from the Late Oligocene to the Middle Miocene, and is the only named species outside of the Americas. It was described based on several remains from France, with more material being later identified from Germany.^[7] While it was initially described as a species of Palaelodus, it was later transferred to Megapalaelodus by Cheneval.^[6] This has been called into question however, with some researchers arguing that the referral is largely dependent on the animal's size.^[7]

• M. opsigonus

A later species, M. opsigonus, was found in the Pliocene^[7] Juntura Formation at Juntura, Oregon.^[4] Brodkorb described the species as being smaller than Megapaloelodus goliath and Palaelodus crassipess (at times considered to simply be a large Palaelodus ambiguus), but larger than the other Palaelodus species. Hildegarde Howard also tentatively assigned material from the Miocene to Pliocene Almejas Formation of Cedros Island (Baja California) to this species.^[5] The species name means "born in a later age" in reference to its appearance during the Pliocene.^[4]

• M. peiranoi

The most recently described species, M. peiranoi was discovered in the strata of the Late Miocene Andalhualá Formation of Catamarca, Argentina. The holotype consists of a coracoid, sacrum and multiple wing bones, with a variety of other bones referred to the species as well. Unlike Palaelodus and modern flamingos, the forearm of M. peiranoi appears to have been short and robust rather than elongated. The notarium meanwhile appears to have been more similar to the basal Juncitarsus than to other phoenicopterids. Agnolin proposes that M. peiranoi may have been one of the more basal species of Megapaloelodus. It was named after Abel Peirano, a paleontologist who initially found and recovered the bones of this species.^[8][9]

Various scant remains possibly belonging to Megapaloelodus are also known from across America. For instance, some remains were found in the Sharktooth Hill Bonebed of

In many regards the bones of Megapaloelodus closely resembles those of Palaelodus. Both genera for instance share many characteristics of the tibiotarsus. Both have noticeable furrows along the edge of the pons supratendinous and lack the pits on the cranial surface that are noted for P. kurochkini (which may present a distinct genus of palaelodid). Megapaloelodus differs from its relatives through the pronounced tubercle located on the trochlea that articulates with the carpal bones, this tubercle is present as a rounded point that is located on the upper rim of the bone.^[13] The articulation point between the coracoid and the clavicle overhangs two distinct pits that are much shallower in Palaelodus and missing entirely in modern flamingos, yet also present in the early Adelalopus.^[14]

When compared to the same bones in other modern forms, "straight-legged" birds such as

Fossils assigned to this genus are oftentimes identified based on their greater size relative to Palaelodus species, which are generally smaller than those of Megapaloelodus.[1]^[7] There is however overlap between some of the species, for example between Palaelodus ambiguus and Megapaloelodus goliath^[13] that add to the doubts around the latter's genus designation. Megapaloelodus opsigonos likewise overlaps in size with the larger Palaelodus species.^[5] The Belgian Adelalopus, the oldest known palaelodid, is similar in size to Megapaloelodus and was described as slightly larger than M. goliath.^[14] Megapaloelodus species were generally similar in size to the greater flamingo.^[2]

Phylogeny

Megapaloelodus is placed in the family

Although the exact function of the pronounced notches and hooked processes on the leg bones of Megapaloelodus is not known, Miller mentions the possibility that they may have anchored powerful ligaments. According to him, a colleague suggested that this may have allowed these birds to "lock" their legs in an upright standing position while sleeping, thus stabilizing their resting posture.[2]

It is possible that Megapaloelodus, much like many other phoenicopteriforms, inhabited lakes which at times may have been highly saline or brackish. The shallow lake that formed the sediments of the Barstow Formation may have been freshwater given the presence of freshwater molluscs and the absence of any salts in the deposits, but has been suggested to have undergone cycles of dry periods that concentrated the water. Still conditions are not fully understood, as the local climate may have been wetter than today to allow the presence of palm trees.