A frilled shark sounds like an animal that would be at home at a tea party, with frills and ruffles, right?
The frilled shark, Chlamydoselachus anguineus, is actually a terrifying, serpentine shark with 300 needle-sharp teeth lining its mouth in neat rows. It’s also a shark that has been around for a long time. According to the Wikipedia article, “belongs to one of the oldest still-extant shark lineages, dating back to at least the Late Cretaceous (about 95 Mya) and possibly to the Late Jurassic (150 Mya).” There are possibilities that perhaps it’s not quite that old, however.
Some scientists speculate that when nineteenth-century sailors reported seeing “sea serpents,” they may actually have been seeing frilled sharks. Frilled sharks are typically deep-sea dwellers, but in recent months, a large number of these beasties have turned up, 28 (!) in Tokyo Bay, and the most recent off the coast of Portugal. In the latter case, at least, scientists were looking deep beneath the ocean waves (at around 2,300 ft, or almost half a mile down). But clearly, nineteenth-century sailors must have seen such critters surfacing, since they were not doing any deep-sea diving while sailing the oceans.
So while you likely won’t come across a frilled shark during your day at the beach, you never know!