Thursday, December 4, 2008

Image(s) of the Day

Cassowary, originally uploaded by jesuitjason.

Flightless bird of Queensland--any doubts as to the claim that birds are descended from dinos should end here, with this large and aggressive bird.

Scientific classification
Kingdom: Animalia
Class: Aves
Order: Struthioniformes
Family: Casuariidae
Genus: Casuarius
Brisson, 1760

Casuarius casuarius
Casuarius unappendiculatus
Casuarius bennetti

Cassowaries (from the Indonesian name kasuari) are part of the ratite group, which also includes the emu, rhea, ostrich, and kiwi, and the extinct Moa and Elephant Bird. There are three species recognized today:

* Southern Cassowary or Double-wattled cassowary C. casuarius of Australia and New Guinea.
* Dwarf Cassowary C. bennetti of New Guinea and New Britain.
* Northern Cassowary C. unappendiculatus of New Guinea.

The evolutionary history of cassowaries, as of all ratites, is not well known. A fossil species was reported from Australia, but for reasons of biogeography this assignment is not certain and it might belong to the prehistoric "emuwaries", Emuarius, which were cassowary-like primitive emus.

A cassowary's three-toed feet have sharp claws; the dagger-like middle claw is 120 mm (5 inches) long. This claw is particularly dangerous since the Cassowary can use it to kill an enemy, disemboweling it with a single kick. They can run up to 50 km/h (32 mph) through the dense forest. They can jump up to 1.5 m (5 feet) and they are good swimmers.

All three species have horn-like crests called casques on their heads. These consist of "a keratinous skin over a core of firm, cellular foam-like material".[3] Several purposes for the casques have been proposed. One possibility is that they are secondary sexual characteristics. Other suggestions include that they are used to batter through underbrush, as a weapon for dominance disputes, or as a tool for pushing aside leaf litter during foraging. The latter three are disputed by biologist Andrew Mack, whose personal observation suggests that the casque amplifies deep sounds.[4] However, the earlier article by Crome and Moore says that the birds do lower their heads when they are running "full tilt through the vegetation, brushing saplings aside and occasionally careering into small trees. The casque would help protect the skull from such collisions."[3] Mack and Jones also speculate that the casques play a role in either sound reception or acoustic communication. This is related to their discovery that at least the Dwarf Cassowary and Southern Cassowary produce very-low frequency sounds, which may aid in communication in dense rainforest.[4] This "boom" is the lowest known bird call, and is on the edge of human hearing.[3]


Females lay three to eight large, pale green-blue eggs in each clutch. These eggs measure about 9 by 14 cm (3½ by 5½ inches) — only ostrich and emu eggs are larger. The female does not care for the eggs or the chicks; the male incubates the eggs for two months, then cares for the brown-striped chicks for nine months, defending them fiercely against all potential predators, including humans.

They call 55-million-year-old Diatryma gigantean a terror bird. And the evidence is compelling.

This flightless species stood some seven feet (two meters) tall and was armed with a strong beak and powerful clawed feet. In North America and western Europe, scientists say, Diatryma likely took over as top predators once the dinosaurs had died offpossibly even hunting ancestors of today's horses.

Convergent evolution? Cousins? Surely joined by a common ancestor... but which one (and was it flightless)?

Information source and first photo credit: Wikipedia
Remaining Cassowary images: Flickr
Terror Bird: National Geographic, info and picture

No comments: