Chimeras, "ghost sharks," are a part of class Chondrichthyes just like sharks, skates and rays. They share a common ancestor with modern-day sharks about 400 million years ago. There are 50 species of Chimera extant today. Because of the depth at which they reside, little is known about chimeras compared to their elasmobranch relatives. While there are a few coastal species, a majority of chimeras reside at depths at or below 500m (1,600ft). Because of the relative scarcity of food at these depths, chimeras are opportunistic feeders that consume a wide variety of invertebrates. Chimeras can be anywhere from 60 to 120cm in length. They are oviparous, which means they reproduce by laying eggs. Chimeras have very large pectoral fins, dorsal fins, and eyes. Uniquely, male chimeras possess a tentaculum on their forehead that attaches to the female to hold them in place during mating. Unlike sharks, chimeras only have one gill opening on each side.
Unlike the replaceable rows of teeth seen in their true sharks cousins, chimaeras have permanent tooth plates, and the upper tooth plate is fused to the neurocranium (skull). These are used to consume a variety of crunchy, benthic prey, such as crustaceans. As the chimaera grows, its jaw strength (and crushing force) increases substantially, allowing the chimaera to consume a wider variety of prey as adults
Rabbit Fish (Chimaera Monstrosa) Credit Andy Murch
Spotted ratfish (Hydrolagus colliei)
The spotted ratfish belongs to the “short-nosed” chimaera family, Chimaeridae
It can grow to nearly 1 m in length
Spotted ratfish are found in the northeast Pacific, from southeastern Alaska to Baja California, at depths of 0-913 m (most common 50-400 m). It is occasionally seen by divers.
You may recognize this species from your local aquarium – spotted ratfish are one of the few species of chimaera kept in captivity.
Like all chimaeras, the spotted ratfish has a long, pointed, and serrated dorsal spine. The dorsal spine is mildly poisonous and used for defense. Spotted ratfish are eaten by other sharks, some seabirds, and even seals. In Washington State, some seal deaths have been caused by internal trauma from ingesting chimaera spines