Temporal range: Late Cretaceous - Recent, 65–0Ma
Cariamiformes is an order of primarily flightless birds that have been around for 63 million years. The group includes the family Cariamidae (Seriemas) and the extinct families Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae. Though traditionally considered as a suborder of the Gruiformes, based on both morphological and genetic studies they may belong to a separate group of birds whose other living members would be the Falconidae, the Psittaciformes and the Passeriformes.
The earliest known fossil belonging to this group is an isolated femur from the Cape Lamb Member of the Lopez de Bertodano Formation, Vega Island, Antarctica. This specimen, which dates to the late Cretaceous period about 65 million years ago, is indistinguishable from the femurs of modern seriemas, and belonged to a large bird about 1 metre (3.3 ft) tall. Because of its age and geographic location, this unnamed species may have been close to the ancestry of both cariamids and phorusrhacids.
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