Ghost Sharks? Rat fish? Rabbit fish? No, Chimaera!
Chimaeras are cartilaginous fish related to sharks, skates and rays. Most of them live in great depths under the sea, but some species live in small depths, and in multiple parts of the globe.
Even though they look very scary, ghost sharks are only 60 to 200 cm long (24 - 79 inches). They are popularly called ghost sharks (or rat fish, spook fish and rabbit fish) but they aren’t real sharks. They are weak swimmers and are delicate when caught, dying quickly out of water. So you may find it in your nightmares but in real life it is just a nice fish that fits perfectly with Halloween trends.
They are related to sharks, skates and rays but they diverged from their relatives long ago, for about 360-400 million years. The differences from a chimaera to a shark are: Upper jaws that are fused to their skull, 4 gills with one external opening, 3 pairs of large permanent grinding tooth plates (permanent meaning that the teeth of sharks falls like the first human teeth do, but chimeras have permanent teeth that keeps growing)
Chimaeras have cartilaginous skeletons, like their relatives. The dots on their faces are sensory organs that detect electrical fields in the water, helping them find their prey. The males possess external reproductive organs, they also have tentacles on the forehead and in front of each pelvic fin. They have long tapering bodies (it starts big and becomes smaller and smaller as it approaches the end of its body) with a big head. Their colors can be black, pale blue, and brownish grey. And they have large translucent-green eyes that help them to see in the dark deep-sea.
There are about 50 species of chimaera known, and they are separated into 3 groups by their body shape: Plow-nose chimaera, Long-nose chimaera, and Short-nose chimaera. It can be hard to differentiate one species from another because of the subtle differences.
They can be found in different depths going between 400 - 2000 meters deep (1312 - 6562 ft), and smaller depths living in 3 meter deep (10 ft). Chimaera live in all the world’s oceans, except the Antarctic. They also can live in different habitats, such as volcanic boulders and cobbles, high rocky relief, and soft sediments such as sand and mud.
Chimaera have an ecological importance, they eat invertebrates, such as crabs, mollusks, octopuses, marine worms and sea-urchins. If it wasn’t for them eating these small creatures, there could be negative impacts on the populations of other species.
Sources: https://www.forbes.com/sites/melissacristinamarquez/2018/10/30/what-everyone-ought-to-know-about-ghost-sharks-this-halloween/?sh=4804f23b3e1f https://www.britannica.com/animal/chimaera https://www.sharktrust.org/chimaera https://oceantoday.noaa.gov/creaturesofthedeep_chimaera/