Fearsome Sharks

©Nobu Tamura, 2016; most recent accepted iteration of whorl location

Few animals are as frightening to humans, as primates, as large oceanic predators. The diversity of sharks is such that we could discuss almost any member of the shark family and have a "scary" animal for the final full week of October. What most anyone would imagine is the obvious choice for a scary shark would is something in the Carcharodon genus; that being the group that contains C. megalodon (Megalodon) as well as C. carcharias (Great white shark). Instead, because it is one of the most interesting of the odd members of the shark family tree, this week we will discuss the genus Helicoprion. Contrary to most popular knowledge, Helicoprion is not a single species, but rather a genus consisting of 3 acknowledged and accepted species and 3 questionable species. These species are: H. bessonowi Karpinsky, 1899; H. davisii Teichert, 1940; H. ergasaminon Bendix-Almgreen, 1966; ?H. karpinskii Obruchev, 1953; ?H. mexicanus Mullerried, 1945; and ?H. svalis Siedlecki, 1970. Helicoprion is better known as the "tooth whorl" shark, owing to their unique spiral arrangement of teeth. The shark is known from global deposits spanning North America, Europe, Asia, and Australia, but the cartilaginous elements of the skull, spine, and body are unknown because of their relative inability to fossilize well. The whorl of teeth was, because of a lack of associated material, at one time or another, thought to have been the nasal process, a throat structure, and teeth, of course, placed in different portions of the jaw. Different specimens are named from different regions and for having disparate tooth whorls; the only possible evidence for individual species given the lack of other skeletal elements for most of the specimens.