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Flightless birds are birds that cannot fly, as they have, through evolution, lost the ability to. [1] There are over 60 extant species, [ 2 ] including the well-known ratites ( ostriches , emus , cassowaries , rheas , and kiwis ) and penguins .
Phorusrhacos was part of the group called the Phorusrhacidae, which is an extinct group of flightless, cursorial carnivorous birds that occupied one of the dominant, large land-predator niches in South America from the lower Eocene to the Pleistocene. They dispersed into North America during the Great American Biotic Interchange (~3 Ma).
With the emergence of the Isthmus of Panama 2.7 million years ago, carnivorous dogs, bears, and cats from North America were able to cross into South America, increasing competition. [52] They had been preceded by procyonids as early as 7.3 million years ago. [ 7 ] )
Their wings are large for a flightless bird (250 cm (8.2 ft)) [13] and are spread while running, to act like sails. [15] Unlike most birds, rheas have only three toes. Their tarsus has 18 to 22 horizontal plates on the front of it. They also store urine separately in an expansion of the cloaca. [13]
And it turns out the moa's closest relative is another chicken-sized bird called the tinamou, which lives - get this - in South America. Another twist: some of them can even fly.
Gastornis is an extinct genus of large, flightless birds that lived during the mid-Paleocene to mid-Eocene epochs of the Paleogene period. Most fossils have been found in Europe, and some species typically referred to the genus are known from North America and Asia.
The basal metabolic rate of flighted species is much higher than that of flightless terrestrial birds. [34] But energetic efficiency can only help explain the loss of flight when the benefits of flying are not critical to survival. Research on flightless rails indicates the flightless condition evolved in the absence of predators. [35]
Struthionidae is a member of the Struthioniformes, a group of paleognath birds which first appeared during the Early Eocene, and includes a variety of flightless forms which were present across the Northern Hemisphere (Europe, Asia and North America) during the Eocene epoch.