Excerpt from the book Animals Evolution Avoided. This book describes 40 animals that ought to exist but don’t, because I made them up.
The Poodle Shark is so called because of the round knobs of cartilage that were found at the top and bottom of its tail, on the top of its dorsal fin, and on the ends of its pectoral fins. These round protuberances hindered the shark’s passage through the water, slowing its progress by about 20% due to the resistance of the water against the knobs.
Where the knobs did come in useful was during a feeding frenzy. Most Sharks attack with their teeth, which are their only weapon. Poodle sharks are different. Not only do they have sharp teeth, they are also able to attack with their tail and fins, which are very flexible. A poodle shark is able to swish its tail and hit its competitors in the face with its tail knobs, as well as hitting other sharks with the pectoral knobs and biting yet more sharks with its teeth.
Although the poodle sharks are fearsome fighters they tend to be rather delicate and discerning eaters, tearing off only as much flesh as they thought they could eat at any time. They took this flesh to deep water where it is chewed thoroughly before returning to the fray.
The number of Poodle Sharks declined dramatically once other sharks realised that biting off the knobs of cartilage on the tail and fins disabled the Poodle Shark and meant it had difficulty swimming with injured fins and a badly bitten tail. Poodle Sharks are seldom seen in shore these days, but are undoubtedly still found in the deep waters of the southern oceans where food is plentiful and where swimming quickly is not that important.