It isn't often that the northern hairy-nosed wombat, the finger-sized slender loris and the mountain pygmy possum share the spotlight. But these odd creatures are the focus of a conservation program launched Tuesday to safeguard some of the world's rarest mammals.

The Zoological Society of London 's program highlights 100 species selected because of the peculiarity of their genetic backgrounds and the degree of danger they face.

The species' lack of close relatives make their preservation particularly urgent, society scientist Jonathan Baillie said. He described them as natural masterpieces.

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"Would we just sit there and watch the Mona Lisa disappear?" he said. "These are things that are just irreplaceable."

Many of the species are the only representative of groups that have otherwise died out. West Africa's pygmy hippopotamus, known for its thick, oily "blood-sweat," is the only member of its genus.

Others, like the Yangtze River dolphin, are thought to represent an entire genetic family. The dolphin may already be gone, like some others on the list.

Those that remain act as living fossils, offering glimpses into how the animal world looked millions of years ago.

That's the case of the Andean mountain monkey, the only marsupial in an otherwise extinct lineage that dates back more than 40 million years.

New Guinea's long-beaked echidnas, anteater-like creatures that lay eggs like reptiles, are even older, remaining unchanged since the time of the dinosaurs.

Donors are invited to sponsor a species and track its conservation progress through blogs and discussion groups on the Web site www.edgeofexistence.org. About $1 million is needed to fund the conservation projects, Baillie said.

Researchers hope the catalog of bizarre creatures might attract younger donors.

"The younger generation is more interested in the weird and wonderful," Baillie said.

There's no lack of either. Many of the mammals are freakishly large, or small, or just long-lived. Australia's hairy-nosed wombat can grow bigger than a dog, while the Sri Lankan slender loris's 5-inch-long frame is dominated by huge night vision eyes.

The mountain pigmy possums of Australia can live 12 years, a remarkable age for a one-ounce creature.

Others, like Madagascar's aye-aye, are just weird. The oddly-shaped primate sports an unsettlingly long, skeletal middle finger it uses to scrape insect larvae from holes in trees.

Central Asia's long-eared jerboa, a small jumping rodent, boasts the largest ear-to-body ratio of any mammal, while the volcano rabbit of Mexico barely has any ears at all.

Still, some have undeniable charm, like the half-once bumblebee bat or the hairy-eared dwarf lemur, the world's smallest primate.

"There's nothing like them when they go," Baillie said.