Sharks that use a whip-like tail to stun their prey, rays with saws on their faces, and river rays half the length of a bus are among the most unique species at risk of extinction according to the latest ranking from international conservation charity Zoological Society of London’s pioneering EDGE of Existence program.

The new list revealed on Tuesday ranks the world’s 50 most Evolutionarily Distinct and Globally Endangered (EDGE) sharks, rays and chimeras – known collectively as Chondrichthyes.

These mythical-sounding (but very real) creatures have no bones in their bodies, only cartilage and appeared more than 400 million years ago, roaming the seas when dinosaurs lived. Each species on this list has few or no remaining close relatives, effectively representing distinct branches of the tree of life and making each of them truly irreplaceable. If they go extinct, we will have nothing like them left on the planet.

Topping the new list, at number one is the largetooth sawfish (Pristis pristis), which also holds the distinction of being the highest-ranking EDGE species in the world. Using an elongated snout (rostrum) lined with teeth on each side to slash at its prey, the large-tooth sawfish is facing threats from unsustainable fishing activities as it’s often caught as by-catch in nets.

Despite the fearsome reputation of the great white shark and the well-recognised appearance of the hammerhead, sharks are one of the least-studied groups of animals – some so elusive they’ve never been captured on camera. Many of these species are threatened by targeted fishing, driven by a desire for shark fins or other body parts, as well as being unintentionally caught (bycatch).

Habitat degradation, due to coastal development, mangrove deforestation, water pollution and trawling, is also to blame for the steep decline in many of these populations. However, the new EDGE List gives conservationists another tool to identify and prioritise species where there is a most pressing need for action.

EDGE Sharks co-ordinator and marine biologist, Fran Cabada said: “Sharks, rays and chimeras – making up the cartilaginous fish, have been around since the age of the dinosaurs, but due to human activities, their modern relatives are facing threats all over the world. They’re found in almost every aquatic environment and as many are apex predators, i.e., at the top of the food chain – they’re crucial to maintaining healthy ecosystems.

“Unfortunately, sharks have a bad image. This means people often can’t see beyond the negative, and usually exaggerated stories, and don’t understand just how threatened and important they are.

“The new EDGE Sharks and Rays list gives us the opportunity to highlight the most unique sharks and rays on our planet which are also the most endangered, so that we can target conservation efforts where it’s needed most. Many are overlooked and poorly known, so conservation actions targeted at these survivors of ancient lineages should be prioritised.”

ZSL’s Marine and Freshwater Conservation Programme Manager, Dr. Matthew Gollock added: “The EDGE Sharks and Rays list comprises some of the most interesting and unique fish we have on this planet. The modern extinction of a single species from this list would cause the loss of millions of years of evolutionary history.

“Since 2013, we have been working in collaboration with partner organisations in the Canary Islands for the conservation of the angel shark (Squatina squatina), #5 in the EDGE list, increasing our knowledge of this species and working with divers, fishers and policymakers to improve management and policy.

“Our successes from this project have allowed us to expand our work to Wales, UK, where we have taken a similar stakeholder-lead approach to collect sightings and community memories of the angel shark in order to better understand and conserve this Critically Endangered species across its range.”

First established in 2007, the EDGE of Existence programme has previously published lists for amphibians, birds, corals, mammals and reptiles. The EDGE lists provide conservationists worldwide with a scientifically rigorous method of focusing their conservation efforts on animals and plants that represent a significant amount of threatened evolutionary history.

ZSL’s EDGE of Existence programme works with partners including the National Geographic Photo Ark and Fondation Segré to fund early-career conservationists striving to secure the future of EDGE species all around the world, through the EDGE Fellowship initiative. The first ever EDGE Fellowships on Sharks and Rays will begin in early 2019, implementing conservation actions for the largetooth sawfish and the pelagic thresher shark (Alopias pelagicus) in Asia.

ZSL is highlighting ten of the most unique and threatened EDGE Sharks and Rays:

The largetooth sawfish (Pristis pristis) – Is not only number one on EDGE Sharks and Rays, but also has the highest-ranking score across all EDGE species. They have been sought after for their meat and as curios for many years. Ancient Mayas were buried with sawfish teeth and cowboy boots were once made from sawfish skin. Their rostra were also used as ceremonial weapons in some countries.

– Is not only number one on EDGE Sharks and Rays, but also has the highest-ranking score across all EDGE species. They have been sought after for their meat and as curios for many years. Ancient Mayas were buried with sawfish teeth and cowboy boots were once made from sawfish skin. Their rostra were also used as ceremonial weapons in some countries. Caribbean electric ray (Narcine bancroftii) – Like all electric rays, they use an electrical charge to deter or stun their prey. Unusual to rays, the females can reproduce at around two years old (that is very fast for a ray or shark!). Caribbean electric rays are active during the night, eating sandy worms on the bottom of the seabed.

– Like all electric rays, they use an electrical charge to deter or stun their prey. Unusual to rays, the females can reproduce at around two years old (that is very fast for a ray or shark!). Caribbean electric rays are active during the night, eating sandy worms on the bottom of the seabed. Whale shark (Rhincodon typus) – Whale sharks are the biggest fish in the sea, with the largest individual recorded reaching 20m in length. Even though these sharks are filter feeders eating plankton, fish and shrimp, scientists can’t figure out why they still have a row of tiny mysterious teeth inside their mouth. Although we see them often in pictures, very little is known about how they reproduce and where. Only one pregnant female has ever been successfully examined.

– Whale sharks are the biggest fish in the sea, with the largest individual recorded reaching 20m in length. Even though these sharks are filter feeders eating plankton, fish and shrimp, scientists can’t figure out why they still have a row of tiny mysterious teeth inside their mouth. Although we see them often in pictures, very little is known about how they reproduce and where. Only one pregnant female has ever been successfully examined. Zebra shark (Stegostoma fasciatum) – The zebra shark gets its name from the colouration of its babies, that have striking black and white stripes on them, which changes to spots as they get older and is also the reason why they are also known as leopard sharks. They are also solitary and spend most of their life hanging around in the same spot – a creature of comfort you might say.

– The zebra shark gets its name from the colouration of its babies, that have striking black and white stripes on them, which changes to spots as they get older and is also the reason why they are also known as leopard sharks. They are also solitary and spend most of their life hanging around in the same spot – a creature of comfort you might say. Giant freshwater whipray (Urogymnus polylepis) – An enormous ray usually found feeding on the shores of rivers. They reach sizes half the length of a bus! Populations are declining due to increasing demand for the aquarium trade.

– An enormous ray usually found feeding on the shores of rivers. They reach sizes half the length of a bus! Populations are declining due to increasing demand for the aquarium trade. Angel shark (Squatina squatina) – The angel shark family (Squatinidae) has been declared the most threatened of all sharks and rays’ families, following sawfishes. Their ability to camouflage themselves might rival that of a chameleon! They generally enjoy eating fishes, skates, crustaceans and molluscs but one account recalls them trying the likes of a cormorant.

– The angel shark family (Squatinidae) has been declared the most threatened of all sharks and rays’ families, following sawfishes. Their ability to camouflage themselves might rival that of a chameleon! They generally enjoy eating fishes, skates, crustaceans and molluscs but one account recalls them trying the likes of a cormorant. Ornate eagle rays (Aetomylaeus vespertilio) – An uncommon ray, being one of the few without a stinging barb. These rays are very strong swimmers, jumping out of the water and reaching several meters high. They are utilised for their meat and cartilages and are a magnificent sight in some coral reefs.

– An uncommon ray, being one of the few without a stinging barb. These rays are very strong swimmers, jumping out of the water and reaching several meters high. They are utilised for their meat and cartilages and are a magnificent sight in some coral reefs. Honeycomb izak (Holohalaelurus favus) – This catshark can only be found off the coasts of South Africa and Mozambique. Once regularly caught in trawl fisheries, it has not been seen since the 1970s. This includes commercial fisheries and scientific surveys.

– This catshark can only be found off the coasts of South Africa and Mozambique. Once regularly caught in trawl fisheries, it has not been seen since the 1970s. This includes commercial fisheries and scientific surveys. Blackchin guitarfish (Glaucostegus cemiculus ) – This species reaches almost 2 metres, with females achieving greater lengths than males. A common sight in markets in the 18 th century, they are now extremely rare in waters off the Balearic Islands and in the Alboran and Aegean seas. Their fins are highly priced in the Asian fin market, surpassing £90/Kg (USD $114/Kg).

) – This species reaches almost 2 metres, with females achieving greater lengths than males. A common sight in markets in the 18 century, they are now extremely rare in waters off the Balearic Islands and in the Alboran and Aegean seas. Their fins are highly priced in the Asian fin market, surpassing £90/Kg (USD $114/Kg). Sand tiger shark (Carcharias taurus) – Sand tiger sharks have a rather gruesome reproductive technique called intrauterine cannibalism; embryos reach 17cm long and develop teeth; the largest embryo in each uterus kills and eats its siblings, leaving a litter of just two pups, one in each uterus, each measuring around a meter long. The pups are born as effective hunters in an extreme version of survival of the fittest!

Take action

One way that people can help sharks is by learning more about them and their plight and sharing that new-found knowledge and interest with their friends and family. To learn more about sharks visit www.edgeofexistence.org/sharks-and-rays or https://www.zsl.org/conservation/regions/uk-europe/angel-shark-conservation or http://www.iucnssg.org/.

International conservation charities like ZSL are actively researching and implementing conservation initiatives to bring back sharks on this list from the brink of extinction. By supporting ZSL’s Edge of Existence programme you’ll be making a huge difference. Donate now at https://donations.zsl.org/edge/