Palaeognathae

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Paleognaths
Temporal range: Paleocene - Recent
A kiwi
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Subclass:
Carinatae
Infraclass:
Neornithes
Superorder:
Paleognathae

Pycraft, 1900
Orders

Primary classification

Alternate classification


see text for more info

Synonyms

Palaeognathia Huxley, 1867

Look up ratite in Wiktionary, the free dictionary.

The Paleognathae or paleognaths ("old jaws") are one of the two living superorders of birds. The other living superorder is Neognathae.

The paleognaths contain several living orders of birds, the Tinamiformes (tinamous), the Apterygiformes (kiwis), Casuariiformes (cassowaries and emus), Rheiformes (rheas), and the Struthioniformes (ostriches). All but the tinamous are flightless. There are also many extinct orders: the Lithornithiformes, the Ambiornithiformes, the Gansuiformes, the Paleocursornithiformes, the Dinornithiformes (moas), and the Aepyornithiformes (elephant birds).

Most paleognaths have long necks and long legs, and are specialized for running rather than flight; indeed, the ratites are all completely flightless. The group is not separated because of this though, it is rather based on the form of the jaw. Paleognaths other than tinamous are commonly known as ratites from the Latin word for raft, ratis, because they have a breastbone shaped like a raft.

Anatomy and characteristics

Ratite birds are the easiest birds to distinguish - they are mostly large, flightless, have extended necks, a breastbone shaped like a raft (with the exception of tinamous), they have a simpified wing bone structure, strong legs, and no feather vanes, making it unnecessary to oil their feathers. And as a direct result of this they have no preen gland that contains preening oil.

Ratite sizes range from 10 inches (25 centimeters) to 9 feet (2.7 meters) and weight can be from 2.86 pounds (1.3 kilograms) to 345 pounds (155.25 kilograms). Ostriches are the largest struthioniforms (members of the Struthioniformes order), with long legs and neck. They range in height from 5.7 to 9 feet (1.8 to 2.7 meters) and weigh from 139 to 345 pounds (63 to 157 kilograms). They have loose-feathered wings. Males have black and white feathers while the female has grayish brown feathers. Emus are about 6.5 feet in height and weigh 51 to 120 pounds (23 to 55 kilograms). They have long, strong legs and can run up to 30 miles per hour (48 kilometers per hour). They have short wings and the adults have brown feathers. Rheas are 4.5 to 5.6 feet (1.3 to 1.7 meters) and weigh 55 to 88 pounds (24.75 to 40 kilograms). Their feathers are gray or spotted brown and white. Cassowaries are 3.3 to 5.6 feet (1 to 1.7 meters) in height and weigh 30 to 130 pounds (14 to 59 kilograms). They have tiny wings with black feathers. Kiwis are the smallest of ratites, ranging in height from 14 to 22 inches (35 to 55 centimeters) and weight 2.6 to 8.6 pounds (1.2 to 3.9 kilograms). They have brown and black hair-like feathers. The tinamous have a keeled breastbone (shaped like a wishbone) and can fly. They range in size from 8 to 21 inches (20 to 53 centimeters) and weigh 1.4 ounces to 5 pounds (43 grams to 2.3 kilograms). The basic anatomy of ratites is simple in principle and there are few exceptions to the rules stated.

Evolution

Paleognaths probably descended from a common ancestor in the late Cretaceous period on the supercontinent of Gondwana.[citation needed] As the continents separated several forms of paleognaths reached different parts of the world, to support this idea all the continents where living (ostrich, cassowary, kiwi, tinamous, emu, and the rhea) and various fossil forms are found were connected during the late Cretaceous.[citation needed] Recent genetic evidence seems to also point towards this theory, DNA shows that they may not be descended from one common ancestor, but two or more.[citation needed] The results also show that ratites probably didn't lose the ability to fly until the middle Eocene.[citation needed] Many similarites in morphology and genetic analysis show that there is probably no convergent evolution between ratite birds.[citation needed] Currently, there is no exact way to say where, why, or when the paleognaths diverged.[citation needed]

Systematics and taxonomy

As told in the Evolution section of this article, the exact evolutionary history of the paleognaths is unresolved presently. Despite this many taxonomists try to place them in the grand scheme of the Aves. As a result two main branches developed, they are shown in the classification part below.

Early taxonomy

Initially the ratites were placed in a single group Ratita. Later it was realized that they were too different to be placed in a single order, so they were split into the several orders in the infobox at the top of this article. Then they were split into two orders, the Struthioniformes and the Lithioniformes. Although the first classification is adopted in this article, either one is commonly used in sources.

Classification

Alternate classification

  • Superorder Paleognathae
    • Order Struthioniformes
    • Order Lithioniformes
    • Order Tinamiformes

Sometimes placed here

Paraphysornis is a phorusrhacid.

Ootaxa

  • Gobioolithus (Late Cretaceous) - paleognath?
  • Incognitoolithus (Eocene of North America) - ratite?
  • Type A ("aepyornithoid") eggs (Tsondab Early Miocene of Namibia - Pliocene of Asia)
  • Namornis (Middle Miocene of Namibia - Late Miocene of Kenya) - ratite?
  • Diamantornis (Middle Miocene of Namibia - Late Miocene of UAE and Kenya) - ratite?
  • Psammornis - may be from Eremopezus

Locomotion

Many of the larger ratite birds have extremely long legs and the largest living bird, the ostrich, can run at speeds over 60 km/h. Cassowaries, emus, and rheas show a similar likeness in agility and some extinct forms may have reached speeds of 75 km/h. Moas, the largest birds, had legs over 3 feet high and may have been the fastest land animals to live outrunning even the cheetah.

Reconstruction of two moa species, Otago Museum, Dunedin. Otago Museum holds the world's largest collection of moa remains.

Paleognaths and humans

Paleognaths probably first interacted with Australopithecines about 3 million or so years ago in the middle Pliocene in the form of an ancient ostrich or elephant bird. As Homo erectus evolved and left Africa for other continents not much contact was made with ratites, until the Maori and Aborigines arrived in New Zealand and Australia. Like many other native species, they were not well-adapted to environments containing humans, and many ratites (and other Oceanic species) became extinct during this period. Worldwide, most giant birds became extinct by the end of the 18th centurys and most surviving species are now endangered.

Today, ratites such as the Ostrich are farmed and sometimes even kept as pets. Ratites play a large part of human culture- they are farmed, eaten, raced, protected, and kept in zoos.

See also

References

Perrins, Christopher (1979). Birds: their life, their ways, their world. Pleasantville, New York: The Reader's Digest Association, Inc. pp. 8–412. ISBN 0-89577-065-2. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

Wyse, Elizabeth (2001). Dinosaur Encyclopedia: from dinosaurs to the dawn of man. New York, New York: DK publishing, inc. pp. 138–145. ISBN 0-7894-7935-4. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

Animal: the definitive visual guide to the world's wildlife. New York, New York: DK publishing, inc. 2005. pp. 260–265. ISBN 0-7894-7764-5. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

Charles, Sibley (1993). A World Checklist of Birds. New Haven: Yale University Press. ISBN 0-3000-5547-1. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

Elwood, Ann (1991). Ostriches, emus, rheas, kiwis, & cassowaries. Mankato, Minnesota: Creative Education. ISBN 0-8868-2338-2. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

Wexo, John (2000). Zoobooks: Ostriches and other Ratites. Poway, California: Wildlife Education. ISBN 1-8881-5357-1. {{cite book}}: Unknown parameter |author link= ignored (|author-link= suggested) (help)

The Ratite Encyclopedia. Charley Elrod. 1996. ISBN 0-0642-9402-8. {{cite book}}: Check |isbn= value: checksum (help)

External links

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