The Borneo Pygmy Elephant

This species of elephant has only recently enjoyed a solid classification of which species it belongs to, or more specifically, whether or not it is a sub-species of elephant of its own. The point is moot, however, if we let this majestic line of creatures disappear from the earth, and they're well on the way to that ignominious fate. Perhaps 1,500 Borneo Pygmy Elephants remain in the wild today.
Maybe the most fascinating tidbit of information about this elephant is the mythology of their arrival on Borneo. It was thought by some that the Sultan of Sulu (from the Phillipines) brought a herd of domesticated pygmy elephants to the island of Borneo in the 17th century. It wasn't until 2003 that this myth was completely debunked: the WWF found that the Borneo Pygmy Elephants were different, genetically, from other elephants. At least 300,000 years separate this elephant, the smallest in Asia, from its cousins on Sumatra and the Asian mainland.

The Borneo Pygmy elephant sports larger than usual ears for an Asian elephant, its tail is longer and its tusks are straighter, too. But their numbers are dwindling fast, due for the most part to the rampant deforestation in their of the world. These gentle animals require wide, continuous swathes of forest to feed their voracious need for at least 150kgs of vegetation daily. Where the forests aren't being destroyed for urban expansion or for commercial farms, they are being converted to commercial logging plantations. This loss of habitat represents for the most part the same fate that nearly all the endangered species of this region (and many others) face.
The loss of this elephant species isn't a certainty, and there are research and conservation organizations that are striving to save it. You can help, too (see below). If the Borneo Pygmy Elephant does disappear, the ecosystems it once called home will lose a vital "keystone species". The concept of a keystone species, and how valuable they are, is best summed up by this bit from Think Elephants International:

"The loss of elephants [the Keystone Species in question] from one particular site would mean that all the biological interactions and ecosystem processes in which they are involved, would also be lost."
These "architects" and "gardeners" of the forests of Borneo are disappearing quickly, and without them, that ecosystem will likely never be the same.

Resources:

http://thinkelephants.blogspot.com/2012/10/elephants-ecosystems-engineers.html
http://wwf.panda.org/what_we_do/endangered_species/elephants/asian_elephants/borneo_pygmy_elephant/

Organizations dedicated to helping Asian elephants:

http://worldwildlife.org
http://www.wcs.org/saving-wildlife/elephants/asian-elephant.aspx