They include 316 species of shark, rays and skates, and chimaeras.
The latest list has 31 new extinctions including several frogs and more than a dozen freshwater fish.
And an Amazon river dolphin has become newly endangered.
“This really shows that the world is under huge pressure," said Craig Hilton-Taylor, head of the Red List Unit.
“The idea of the Red List is to try to draw attention to species and stop them from going extinct but sometimes the process goes too quickly."
Simon Walmsley, chief marine adviser at WWF-UK said: “We’ve been witnessing the alarming decline in sharks and rays for the last two decades and yet the unsustainable fishing of these crucial species has continued unabated.
“These animals have evolved over 400 million years, and sadly we’re now pushing them to the brink of extinction.
“Our ocean is in crisis and if we’re going to secure a healthy future for our seas, we need urgent action from the global community to stop this destruction of our marine life.”
It’s been known for several years that the world is in a sixth mass extinction process, accelerated by loss of habitat and the climate crisis.
Last year, the UN warned humans were risking wiping out a million species.
And earlier this year scientists found nature is racing faster towards the point of collapse than previously thought. Research published in the Proceedings of the National Academy of Sciences warned the critical window for preventing mass losses is only 10 to 15 years.
The “lost shark" of the heavily fished South China Sea was only formally discovered last year based on decades-old specimens. But there have been no sightings and it has not shown up in surveys, prompting the IUCN to list it as critically endangered (possibly extinct).
Sharks have survived previous mass extinction events such as the asteroid strike believed to have wiped out most dinosaurs. But this might be the first shark extinction in human times, according to Will White, an ichthyologist at the Australian National Fish Collection.
“Unfortunately, what makes a species a great survivor in the natural world doesn't equate to making them great survivors against man," he said.
The IUCN tends to be conservative on extinctions, since declaring them can spell an end to any remaining protection efforts. So species it calls “possibly extinct" often already are.
The organisation also moved an Amazon dolphin with a pinkish belly called the tucuxi to its endangered list, meaning that all the world's freshwater dolphins are now threatened.
It is being killed by dams, pollution and gillnets – vast curtains of fishing nets that dangle in the current.
IUCN described the decline in frog populations in Central and South America as drastic. It cited a disease caused by a fungus linked to climate change.
The organisation also said European bison populations had grown more than threefold since 2003 to 6,200 last year, thanks to conservation efforts, and bumped it up one category from endangered to vulnerable.
The bison were decimated by hungry armies in the First World War in current-day Poland and Belarus, and vanished from the wild before later being reintroduced.
“There are glimmers of hope, little stories that show us what can be done," said Mr Hilton-Taylor.
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