A shark tooth is one of the numerous teeth of a shark. Sharks continually shed their teeth, and some Carcharhiniformes shed approximately 35,000 teeth in a lifetime. In some geological formations, shark’s teeth are a common fossil. These fossils can be analyzed for information on shark evolution and biology, especially because the teeth are often the only part of the shark to be fossilized, in fact fossil teeth comprise much of the fossil record of the Elasmobranchii, extending back hundreds of millions of years.
The most ancient types of sharks date back to 450 million years ago, during the Late Ordovician period, and they are mostly known from their fossilised teeth. The most commonly found fossil shark’s teeth are, however, from the Cenozoic (the last 66 million years).
Snaggle Tooth Shark Facts and Information – Behavior, Fossil History, and Evolution
The Hemipristis genus first appeared in the Eocene as H. curvatus. Their teeth are similar in shape to H. serra but are smaller. This genus is the direct ancestor of H. serra. It disappeared in the Oligocene as the first occurrence of H. serra appeared.
H. serra can be found in Tertiary deposits on the east coast from Maryland to Florida. These beautiful teeth are also a common find in Tertiary deposits worldwide, from both coasts of North and South America to Europe, Africa, and Australia. This shark clearly had a nearly global distribution in the Tertiary. However as the climate changed, from the warmer Miocene into the cooler climate of today, this species became extinct. They are deemed abundant in Miocene exposures. In Pliocene exposures, they are less numerous, and in the Pleistocene, they became restricted to the tropical waters around Indonesia before finally becoming extinct (Kent, p. 79).
H. Serras’ closest living relative is H. elongatus, which continues to swim in the tropical waters of the Eastern Hemisphere today. According to Bonfil, H. elongatus is an inshore and offshore shark with a distribution in the Indian Ocean, western Pacific, from South Africa to China and Australia, including the Red Sea and Gulf of Aden (Bonfil p.15). Sharks from the Hemigaleidae family have a long snouth, with horizontally oval eyes, and internal gill openings, and their first dorsal fin is slightly higher than their second dorsal fin (Compagno, p. 28). They also have a plain color pattern, except for light or dark fin edges or tips on some species (Compagno, p. 28). Figure 2 shows a sketch of H. elongatus.
Hemipristis elongatus primarily feed on small bony fish, sharks, and rays. They can reach lengths of up to 2.4 m (Bonfil p. 15). Based on tooth size comparisons between H. elongatus and H. serra, the fossil species could reach sizes between 3 to 5 m (Compagno, p. 486). Therefore, H. serra was most likely a larger version of H. elongatus, it may have looked and behaved similarly.
Source: The Fossil Guy