By Richard Black
Environment correspondent, BBC News website
Discoveries of hugely diverse fish and coral species in the Indonesian archipelago have amazed researchers.
The Bird's Head region in Papua may be the most biologically diverse in all the oceans, say scientists from Conservation International (CI).
Among 50 species believed to be new are bottom-dwelling "walking" sharks and "flasher" wrasse, which feature colourful male courting displays.
CI is working with the Indonesian government to protect the ecosystem.
"Five years ago we ran our first expedition to Raja Ampat [islands off the Bird's Head], and this revealed what we felt to be the epicentre of marine biodiversity on the planet," said Mark Erdmann, a CI scientist on the project.
Researchers have just returned for a more detailed survey, which revealed 20 corals, 24 fish and eight mantis shrimp believed to be new to science.
Highlights included two apparently new species of epaulette sharks, which spend most of their time walking across the sea floor, swimming away when danger looms.
Unspectacular, dull brown male wrasse transform into a spectacular blaze of yellow, blue and purple to impress females in their harem and persuade them to mate.
"We were simply blown away by what we found," Dr Erdmann told the BBC News website.
Reefs in the "coral triangle" - an area rather un-triangular in shape which includes tracts of water off the coasts of Indonesia, Malaysia, the Philippines, Papua New Guinea, the Solomon Islands and East Timor - are home to about 600 species of reef-building coral.
That is more than exist along Australia's Great Barrier Reef which covers an area 10 times larger.
What makes the region special, it seems, is a combination of its topography and its history.
It contains a mixture of deep basins and shallower waters. As global sea levels have risen and fallen over the millennia, the basins would have become isolated, allowing species to evolve differently in each, before being returned to the open sea when waters rose.
This pattern has very likely been amplified by the region's active tectonics, creating regular earthquakes and other upheavals.
Another contributing factor could be the region's isolation from large centres of human population, making it easier for unique species and ecosystems to survive.
That has certainly helped in the preservation of land animals in the region, which has seen several finds of new forest species in recent years.
CI believes that without protection, the unique marine creatures of the Bird's Head area will not survive intact; human activities, in particular fishing using explosives and cyanide, will have their inevitable impact.
"The other thing we are afraid of is economic development plans for Papua, which involve increased fisheries exploitation," said Dr Erdmann.
"There are relatively few people living there, but they are dependent on their coastline; and we think development plans need to be revisited."
CI and its conservation partners are now working with the Indonesian government to protect the special areas of the Bird's Head peninsula and Raja Ampat islands, and to manage development in a sustainable way.