Fossil of the month: Saivodus sp.
What did Saivodus eat?
Modern sharks have a wide range of diets. What they eat is partly a function of the shape and size of their teeth (as well as mouth gape size, bite force, tooth position in the jaw, etc.). Scientists can infer the diet of extinct ancient sharks by comparing the size and shape of their teeth to those in modern sharks (and other fish). Saivodus had teeth shaped like long, rounded spikes or spears (central cusp). Teeth with spike-like shapes in modern sharks tend to function as clutching/grasping or piercing/gouging tools to hold onto wriggling prey, rather than slicing or chewing (Frazetta, 1988; Williams, 2001; Ciampaglio et al., 2005). Prey caught with this type of teeth are often swallowed whole. Many of the Saivodus teeth in the KGS collection have a long edge between the inner and outer side of the medial cusp, which may also have helped to slice prey if the shark shook its head.
Whitenack and Motta (2010) tested a variety of modern shark teeth and fossil teeth to determine the forces required to puncture and tear a variety of different prey/food. They also tested a fossil Cladodus tooth (with a shape similar to Saivodus). They found the Cladodus tooth functioned similar to modern shark teeth and was able to puncture a variety of different prey/food types.
Several modern sharks have narrow, tall, pointed, clutching/grasping teeth. The modern Sand tiger shark (Carcarias taurus) has a tall slender, pointed medial cusp, but also 1-2 small cusplets on either side of the medial cusp. Sand tiger sharks feed on smaller fish, squids, and sometimes crustaceans (Williams, 2001). Sand tiger sharks have different-sized teeth in different positions in their mouth, with slightly different curvature on the medial cusp. This allows them to grab and hold prey with their front teeth, and then pass that prey back to the rear of the jaw for more puncturing and processing before being swallowed (Applegate, 1965). Saivodus also appears to have had different size teeth with different angles of inclination on their medial cusps. Perhaps Saivodus had similar eating habits to modern Sand tiger sharks.
Saivodus striatus had somewhat similar shaped teeth to the modern Sand tiger shark, so perhaps had a similar diet.
Smaller fish, squid-like cephalopods (squids with shells), and crustaceans existed during the Late Mississippian when Saivodus lived and may have been part of Saivodus’ diet. Studies in Mammoth Cave are currently increasing our knowledge of the many kinds of smaller fish (including other sharks) which also shared the seas with Saivodus. These fish may have been part of Saivodus’ normal diet, but in the case of the Mammoth Cave fossil, they appear to have turned the tables and made the Saivodus carcass part of their diet!
Text, photographs, and illustrations by Stephen Greb