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1-3: Three Long-Beaked EchidnasScientist Kris Helgen holds an Eastern long-beaked echidna in Indonesia's Foja Mountains (map) in a file picture. The elusive egg-laying species is one of the rarest and most genetically unique mammals on the planet, according to the Zoological Society of London's 2010 EDGE (Evolutionarily Distinct, Globally Endangered) list, released November 19. (Take an endangered-animals quiz.)Of the 100 species on this year's list, 49 are new additions since the last EDGE update, in 2007—and some may already be extinct. In addition to the Eastern long-beaked echidna, the Western long-beaked and Attenborough's long-beaked echidna topped EDGE's list this year. All three—and most of the other EDGE species—are deemed critically endangered by the International Union for Conservation of Nature (IUCN).The EDGE project calculates a score for a species' uniqueness by looking at a so-called supertree, a "huge family tree showing the evolutionary relationships between all mammals," said Carly Waterman, program manager for EDGE. That number—combined with the animal's scarcity according to the IUCN—determines a species' rank on the EDGE list. ZSL created a separate EDGE list for weird and rare amphibians.Though a 2010 expedition to Indonesia's Papua Province did not reveal any live echidnas, the team did find telltale holes that the creatures poke in the earth while searching for worms."And everybody we spoke to that had encountered one had eaten one," Waterman said. "Every single person said they're really, really tasty." (Related: "New Snub-Nosed Monkey Discovered, Eaten.")While experts suspect that hunting is the biggest danger to echidnas, "we don't really know what the relative impacts of the threats are," Waterman added.—Rachel Kaufman

Photograph by Tim Laman, National Geographic