that the teeth supposedly had no wear marks, and the assumption that the whorl would have created a drag-inducing bulge on the chin of the animal if located in a symphysial position. They envisioned the tooth whorl as a structure derived from throat denticles and designed to assist swallowing. This would hypothetically negate the disadvantages the tooth whorl would produce if positioned further forward in the jaw. This reconstruction was criticized for the overly intricate and potentially ineffective design of such a structure, if solely used to assist swallowing. Lebedev (2009) found more support for a reconstruction similar to those of Bendix-Almgreen (1966) and Troll (1994). A tooth whorl found in Kazakhstan preserved radial scratch marks; the whorl was also found near several wide tuberculated teeth similar to those of the putative caseodontoid Campodus. Lebedev's reconstruction presented a cartilage-protected tooth whorl in a symphysial position at the front of the long lower jaw. When the mouth was closed, the tooth whorl would fit into a deep longitudinal pocket on the upper jaw. Both the pocket in the upper jaw and the edges of the lower jaw would have been lined with dense rows of Campodus-like teeth. This was similar to the situation reported in related helicoprionids such as Sarcoprion and Agassizodus. As for Helicoprion's ecology, it was compared to modern cetaceans such as Physeter (the sperm whale), Kogia (dwarf and pygmy sperm whales), Grampus (Risso's dolphin), and Ziphius (Cuvier's beaked whale). These fish- and squid-eating mammals have reduced dentition, often restricted to the tip of the lower jaw. Lebedev's reconstruction approximates modern views on Helicoprion's anatomy, though the hypothetical long jaw and Campodus-like lateral dentition has been superseded by CT data. References External links Agassizodontidae Prehistoric cartilaginous fish genera Cisuralian first appearances Permian cartilaginous fish Permian extinctions Prehistoric fish of Australia Permian fish of Asia Prehistoric fish of Europe Prehistoric fish of North America Fossil taxa described in 1899 Fossils of the United States Paleozoic life of Alberta Paleozoic life of British Columbia Paleozoic life of Nunavut