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Limnofregata
''Limnofregata'' ("Freshwater frigatebird") is an extinct genus of primitive frigatebird. The two known species were described after fossils from the Early Eocene Green River Formation (c.49 million years ago) of Wyoming. A number of good complete and partial skeletons, some with feather impressions, are known of the type species,''Limnofregata azygosternon'', and ''L. hasegawai'' is known from two skulls and most of one torso.
== Description==
Birds of the genus ''Limnofregata'' resembled modern frigatebirds, but had shorter less-hooked bills and longer legs, and longer slitlike nasal openings. They stood tall when on the ground and had a wingspan of about . The beak was shorter than that of modern frigatebirds, and lacked the typical hook at the end, resembling a strong booby beak more than that of today's frigatebirds. The species differ conspicuously in size, with ''L. hasegawai'' being as much larger when compared to ''L. azygosternon'' as today's largest species of frigatebird (''Fregata minor'') is compared to the smallest extant one (''Fregata ariel''). The bill of ''L. hasegawai'' was notably larger still than that of its congener, whereas its feet were smaller, echoing a pattern found in the extant ''Fregata'' species.
In 2014, a third species, ''Limnofregata hutchisoni'', was described from the Wasatch Formation, 2 million years older than the Green River Formation. Though the only remains are a coracoid and a humerus, these bones clearly identify it as part of the genus. It is of comparable size to ''F. magnificens''. It is at least 53 and possibly 54 or 55 million years old. The fossil beds have remains of crocodiles, large trionychid turtles and fish, indicating a sizeable body of water.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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