Most people are familiar with these big, showy, eye catching animals. They are common in zoos, frequently seen images in popular media, and recently have even gained popularity as livestock (drumstick, anyone?). Ostriches commonly appear in documentaries, such as this recent appearance (as cat food) in the latest BBC series, Life (see below).
As you may have already noticed, Ostriches aren't just some stretched out version of your typical bird. So what makes them so distinct? To fully appreciate what makes these towering descendants of dinosaurs so darn interesting, it helps to look into their evolutionary history -- one that is shared with their closest living relatives, the other ratites.
Ratites are a group of flightless birds (order Struthioniformes, though some elevate the families below to order status) spread out over South America, Africa and Australasia. They're a great example of allopatric speciation, with the different species having diverged from one another as the continents spread apart during the past hundred million years or so.
Figure 1: Pangea breaking up starting at ~225 million years ago.
As a group, the taxonomic relationships within the ratites falls cleanly over their geographic distributions. Excluding extinct species like the freakishly huge Moas, and other groups that have recently been associated with the ratites (i.e., the Tinamous), their distributions are as follows:
1. Family Cassuariidae
- Emu (Dromaius novaehollandiae)
- Cassowary (3 species; Southern Casuarius casuarius, Dwarf C. bennetti, Northern C. unappendiculatus.)
2. Family Apterygidae
- Kiwis (5+ species, all in the genus Apteryx)
3. Familiy Struthionidae
- Ostrich (Struthio camelus)
South American Ratites
4. Family Rheidae
- Rheas (2 species; Greater Rhea americana, and Lesser R. pennata)
If that's news to you, lets just say it out loud one more time: Ostriches have claws!!
Figure 2: Details of the wingtip of the Ostrich, drawn circa 1898.
[Source: The structure and classification of birds (full text).]
Fortunately for zoo visitors and Ostrich farmers, they didn't retain TOO many of their ancestors' other dinosaurian features. Imagine getting a bite from one of these!
Figure 3: The ostrich farmer's worst