Indiana University Paleontology Collection

This is a spine fragment from Crawford County, Indiana, possibly from the shark Orthacanthus, and is a part of the IUPC’s Mississippian period (~358.9-323.2 Ma) collection. This spine would have come from the back of the head of an Orthacanthus. Many sharks during this period (and today) had spines coming off their bodies that were likely useful in preventing them from being eaten by larger fish and other sharks.

Orthacanthus was a part of a group of sharks known as xenocanths (meaning, “strange spine”) that had long, more eel-like bodies with long dorsal fins. Additionally, some species of xenacanth sharks might have been able to live in saltwater, brackish water, freshwater or a combination of the three.

Another highlight from our Shark and Fish Fossil Inventory in the IUPC from one of our undergraduate hourly workers: This tooth belongs to perhaps the most infamous prehistoric shark, Otodus megalodon (Order Lamniformes, family Otodontidae). Its species name translates to "giant tooth", and it certainly lives up to this title. This fossil belongs to the largest macropredatory fish to have ever terrorize the Earth's ocean, living from the Miocene to the Pliocene epochs of the Cenozoic era (23-2.5 million years ago). Its size estimates are around 16 meters (52.5 ft) long on average, with a mass of 35-70 US tons. The fossils of this colossal shark are mostly comprised of teeth like this one that are commonly found on coastlines and in former ocean basins. This is due to the constant replacement of the O. megalodon's teeth throughout it's lifespan - a characteristic shared by its many chondrichthyan relatives. Fossil teeth like this have been found from the coasts of the United States, South Africa, Japan, and Australia, suggesting it could have migrated throughout global waters in pursuit of its cetacean prey.

The shape of this tooth is very reminiscent of modern-day mackerel sharks like the great white, a triangular shape with many serrations along the sides to maximize its capability to rip and tear flesh. Coupled with one of the strongest bite forces of the animal kingdom, these teeth made for jaws that were extremely effective at hunting the whales of its time. A 6-foot (1.83 meter) tall man could walk straight through its jaws when its mouth was completely open! Despite its immense size and ferocity, O. megalodon would become extinct towards the end of the Pliocene epoch. This extinction is likely due to a variety of factors such as a rapidly changing climate as the Earth transitioned into the Pleistocene, being outcompeted by other sharks and macropredatory whales, and the extinction and/or relocation of its primary food sources.

Since its formal discovery in 1835 by Swiss-American geologist Louis Agassiz, O. megalodon has had quite the number of taxonomic changes. At first it was placed under the genus Carcharodon, understood as a close relative of the extant Great White Shark (Carchardon charcarias). However, it has recently been placed under the Otodus genus, within the family of extinct mackerel sharks Otodontidae. Some paleontologists claim it belongs to another genus, Carcharocles. In 2022, a rare vertebral column of megalodon was discovered in Belgium, leading to a reanalysis of its body shape suggesting the shark was more slender than previously thought.