publications in 1966. The first was Rainer Zangerl's description of a new Carboniferous eugeneodont, Ornithoprion. This taxon had a highly specialized skull with a small tooth whorl in a symphysial position, i.e. at the midline of the base of the lower jaw. Although skull material had also been reported for Sarcoprion and Fadenia at the time, Ornithoprion was the first eugeneodont to have its skull described in detail. The other publication was Bendix-Almgreen's monograph on Helicoprion. His investigations reinterpreted the tooth-whorl as a symphyseal structure wedged between the meckelian cartilages, which were separated by a gap at the front. A pair of cartilage loops, the symphyseal crista, seems to develop as a paired extension of the jaw symphysis where the meckelian cartilages meet at the back of the jaw. Each loop arches up before curling back inwards, tracing over the root of the tooth whorl. The largest and youngest teeth form at the symphysis near the back of the jaw. Over time they are carried along the symphyseal crista, spiraling forwards, then downwards and inwards. The series of teeth accumulate into a spiraling structure, which is housed within the cavity defined by the symphyseal crista. The lateral and lower edges of the tooth whorl would have been obscured by skin during life. According to Bendix-Almgreen, the most likely use of the tooth whorl was as a tool for tearing and cutting prey against the upper jaw. In the 1994 book Planet Ocean: A Story of Life, the Sea, and Dancing to the Fossil Record, author Brad Matsen and artist Ray Troll describe and depict a reconstruction based on the information gleaned by Bendix-Almgreen (1966). They proposed that no teeth were present in the animal's upper jaw, besides crushing teeth for the whorl to cut against. The two envisioned the living animal to have a long and very narrow skull, creating a long nose akin to the modern-day goblin shark. A 1996 textbook by Philippe Janvier presented a similar reconstruction, albeit with sharp teeth at the front of the upper jaw and rows of low crushing teeth in the back of the jaw. In 2008, Mary Parrish created a new reconstruction for the renovated Ocean Hall at the Smithsonian Museum of Natural History. Designed under the direction of Robert Purdy, Victor Springer, and Matt Carrano, Parrish's reconstruction places the whorl deeper within the throat. This hypothesis was justified by the argument