A tiger shark tooth can tell a story about a prehistoric world. These teeth, from the extinct shark Galeocerdo cuvier, reveal details about their environment in the same way that a human tooth does.
These teeth (G. cuvier) were collected from sediments at Lee Creek, Florida, and Calvert Cliffs, Maryland. Oxygen atoms in the outer enameloid hydroxyapatite can tell us about the temperature and salinity of the water where sharks lived.
Origins
Sharks have a long evolutionary history and, like many carnivores, are often characterized by the presence of sharp serrations on their teeth. The teeth of tiger sharks are efficient tools to pierce and grip small to medium-sized prey. They are also used to crush bone and shells of other fish and reptiles. The teeth of tiger sharks, along with other members of the genus Galeocerdo, have been found in a variety of marine Oligocene to Recent deposits including those from the Chesapeake Bay area (Calvert Cliffs sites) and Florida (Pensacola and Peace River).
A tiger shark tooth can be easily recognized because it is triangular in shape and has an upward-pointing slant tip with small serrations. These serrations are highly efficient and can cut through flesh, skin, and even turtle shells. Like most sharks, tiger sharks continuously shed and replace their teeth throughout the course of their lives.
Because of this, fossil tiger shark teeth are relatively common. The teeth are the most commonly collected fossils from tiger sharks because they are more likely to survive fossilization than other bones of the skeleton. Additionally, fossil shark skeletons are extremely rare because the skeletal anatomy is composed of cartilage which does not fossilize well. Therefore, most of what we know about extinct sharks is derived from their well-mineralized teeth.
Despite the fact that complete shark skeletons are rarely preserved, tiger shark teeth can provide a wealth of information about a shark’s evolution. In addition to revealing details about the shark’s overall morphology, isolated teeth can help distinguish different species and even individual individuals within a species.
This tiger shark tooth has been identified as belonging to the species Galeocerdo aduncus. It dates back to the Oligocene and is one of the most common Tiger Shark teeth collected from the Calvert Cliffs of Maryland. The tooth has a wide root base, slender twisted crown, and a shallow nutritive groove that are typical of G. aduncus.
A study based on the comparison of the teeth of the tiger shark +Galeocerdo clarkensis with those of the modern Sand Tiger Shark (Carcharias taurus) revealed that the differences between these two species are statistically significant. This includes the mesial cutting edge of the anterior teeth which is evenly convex rather than sigmoidal, the shoulder of the lingual edge is more pronounced, and the distal notch has a more distinct development.
Functions
As the name suggests, tiger sharks are a powerful predatory fish. They have a highly-serrated teeth that are used to cut through tough sea turtle shells and other bony fishes. Their unique notch tips are also very effective at shearing through fish flesh. The tiger shark is a cosmopolitan species, occurring in all oceans worldwide. Their striped pattern helps them blend in with their environment, and they are often found around shallow waters near reefs where they can ambush smaller fishes. Tiger sharks are one of the most active marine predators, consuming a wide variety of prey. They are known to eat everything from sea turtles, other sharks, bony fishes, crustaceans, and even dolphins.
The tiger shark is one of the few fishes that can crush the hard shells of sea turtles, which makes this fish a major threat to their populations. Its teeth are so strong that they can also tear chunks out of larger marine animals, including other sharks, sea turtles, rays, and various sea birds. Their specialized serrations and saw-like action from shaking their head back and forth are what give them their legendary killing power.
A tiger shark’s jaws open wide to reveal teeth with striking notch tips that point in opposite directions. The tiger shark’s teeth are very effective at cutting through the toughest skin, and their distinct shape gives them a distinctive look. Unlike other sharks, tiger shark jaws are square in shape rather than circular, making them more stable than the round shapes of other sharks.
Tiger sharks have a high level of genetic diversity, and the fossil record of this group includes many different extinct species. However, the morphological similarities of these teeth have been a major barrier to the recognition and taxonomy of extinct tiger sharks. This study aims to overcome this limitation by using quantitative geometric morphometrics to distinguish between the teeth of different Galeocerdo species. The results also provide insights into the evolutionary history of this unique genus.
A total of 569 teeth were photographed in labial view and used for this analysis. These included the teeth of the six valid extant tiger shark species +Galeocerdo cuvier, +G. aduncus, +G. clarkensis, +G. eaglesomei, +G. mayumbensis, and +G. rosaliaensis. In addition, the teeth of the two extinct tiger sharks +Hemipristis and +Physogaleus were also used to validate the application of these methods in separating similar-looking shark tooth taxa.
Habitat
Tiger sharks are apex predators that feed on a wide variety of marine animals. They are a dark gray to black on the dorsal side and pale on the underside. They have two large, broad-based dorsal fins set back beyond the pectoral fins. They are able to move through shallow waters as well as deep channel areas, but primarily dwell in tropical and subtropical coastal habitats. They may also occur in the lagoons and coral atolls of oceanic island chains.
Tiger Sharks are generally solitary hunters that only come together during mating or feeding periods. They typically live for 12 years on average. They are a diurnal, fish-eating animal that hunts by ambush in open water. The tiger sharks’ sharp pointed teeth are well-adapted for puncturing and tearing open hard shelled prey items like turtles.
In some cases, tiger sharks will eat other sharks, bony fish, lobsters, crabs, porpoises, squid, sea snakes, terrestrial birds, mammals, and even human beings. This shark’s teeth have a deep primary notch and serial cusplets along the serrated edge, which is ideally suited for piercing and ripping open these tough chelonians.
The outer layer of shark teeth is composed of enameloid hydroxyapatite, the same substance that makes up our own teeth. By analyzing oxygen atoms in shark teeth, scientists can determine the temperature and salinity of the water(s) in which the shark lived. This information is helpful in determining Earth’s climate change during the ice age.
In the Oligocene, the tiger shark G. latidens appeared with other sharks, such as the extinct G. aduncus and the less common G. eaglesomei, which had simpler serrations. P. contortus, which appeared in the Miocene and was common at the Calvert Cliffs of Maryland, had an entirely different tooth form. Its roots were thicker and its crowns were curved and slender.
The morphology of the tiger shark’s teeth provides clues about how these animals fed. The interior angle of the root base to the mesial cutting edge is acute, so excessive stress would quickly sheer off this part of the teeth’s structure. The twisted crown shape would also allow the shark to grasp prey.
Predators
The tiger shark is one of the ocean’s most powerful predators. Its awe-inducing teeth have been used to crack sea turtle shells, and its ability to swallow entire prey animals is testament to its innate adaptability and predatory plasticity. Despite its name, the Tiger Shark (Galeocerdo cuvier) does not exclusively eat sea turtles, as multiple studies have shown that this species consumes a wide range of marine reptiles and fishes, with a greater focus on teleosts at larger sizes.
The teeth of the tiger shark are triangular and blade-like, with a pointed crown and complex serrations. Their roots are flattened, and their mesial cutting edges have a strongly notched profile. These characteristics make tiger shark teeth unmistakable, even in the fossil record.
Unlike most sharks, the tiger shark is capable of generating significant acceleration with its fins, making it quick to change directions or move up or down the water column. This flexibility, combined with the shark’s thick hide — once described as having the strength of an ox — allows it to ambush unsuspecting prey and survive potentially fatal injuries.
Like most cartilaginous fishes, tiger sharks are primarily a carnivores. However, they also eat bony fishes and small crustaceans, as well as marine mammals.
The tiger shark’s large mouth allows it to eat whole prey animals, including sea turtles, and it has a highly effective system of gill rakers to pierce the soft body of its prey and draw the animal into the jaws. This is especially true for squid, which the tiger shark devours in its native Hawaiian waters.
Although the tiger shark is known to ambush its prey, it can also rely on its swift swimming abilities and the agility of its fins to scavenge for dead or injured animals. This ability, coupled with its relatively slow metabolism, makes the tiger shark an important scavenger in its natural habitat.
The tiger shark is a keystone predator of its region, and it is an important part of the food chain for many smaller species. It is also a popular target for sport fishing and diving.