Shark tooth

Last updated
Fossil shark teeth (Cretaceous) from southern Israel CretaceousSharkTeeth061812.JPG
Fossil shark teeth (Cretaceous) from southern Israel
Elementorum myologiae specimen, 1669 Steensen - Elementorum myologiae specimen, 1669 - 4715289.tif
Elementorum myologiae specimen, 1669

Sharks continually shed their teeth; some Carcharhiniformes shed approximately 35,000 teeth in a lifetime, replacing those that fall out. [1] There are four basic types of shark teeth: dense flattened, needle-like, pointed lower with triangular upper, and non-functional. The type of tooth that a shark has depends on its diet and feeding habits.

Contents

Sharks are a great model organism to study because they continually produce highly mineralized tissues. [2] Sharks continually shed their teeth and replace them through a tooth replacement system. [3] Through this system, sharks replace their teeth relatively quickly with replacement teeth that are ready to rotate because their teeth often get damaged while catching prey. [3] They will replace teeth that are broken and young sharks can even replace their teeth weekly. [3] Although sharks constantly shed their teeth, factors such as water temperature affect the turnover rate. While warmer water temperatures produced faster rates, cold water temperatures slowed tooth replacement rates in nurse sharks. [4] They are only shed once new teeth are formed underneath and push them out of the connective tissue that was holding them in place. [5] The sex of the shark also plays a role in the development of teeth and the differences in teeth in species due to gender is called sexual heterodonty. [6] Usually, females have larger teeth because on average they are usually larger than males. [6] Also, age can change the shape of teeth in which "juvenile teeth start out more narrow and robust, while adult teeth are broader and thinner". [6]

In some formations, shark's teeth are a common fossil. These fossils can be analyzed for information on shark evolution and biology; they are often the only part of the shark to be fossilized. Fossil teeth comprise much of the fossil record of the Elasmobranchii, extending back to hundreds of millions of years. A shark tooth contains resistant calcium phosphate materials. [7]

The most ancient types of shark-like fish date back to 450 million years ago, during the Late Ordovician period, and are mostly known by their fossilized teeth and dermal denticles. [5] However, the most commonly found fossil shark teeth are from the Cenozoic era (the last 66 million years).

Types and functions

Though sharks often are highly specialized, as a category they have ranged widely in their adaptations. Their teeth reflect this, ranging widely in form and function.

There are a number of common types of shark teeth, that vary according to the diet of the shark. Examples include dense flattened teeth for crushing; long needle-like teeth for gripping; pointed lower teeth for gripping combined with serrated, triangular upper teeth for cutting, and teeth that are tiny, greatly reduced, and non-functional. [8]

Eastman1901-web Eastman1901-web.jpg
Eastman1901-web

Dense flattened teeth

Dense flattened teeth are used to crush prey like bivalves and crustaceans. [9] These sharks include nurse sharks and angel sharks. They are typically found at the bottom of the ocean floor.

Needle-like teeth

This was the first common style of shark tooth, present in the Devonian, four hundred million years ago. [10] Sharks with needle-like teeth commonly feed on small to medium-sized fish, sometimes including small sharks. These teeth are especially effective for such prey because they can easily grip their slippery and narrow bodies. Modern examples include the blue shark and bull sharks. These sharks specifically use their teeth to feed on small prey like squid, flounder, stingrays, and even hammerhead sharks. [11]

Pointed lower teeth and triangular upper teeth

This combination of pointed lower teeth, with triangular upper teeth are especially useful for cutting prey that consist of large mammals and fish. The combination of teeth entails serrated edges to cut the larger prey into smaller portions in order to easily swallow the pieces. [12] The most famously known shark with these teeth is the great white shark, which feeds on animals such as sea lions, dolphins, other sharks, and even small whales. [11]


Non-functional teeth

The teeth of plankton-feeders, such as the basking shark and whale shark, are greatly reduced and non-functional. These sharks filter feed on prey by opening their mouths to let tiny organisms get sucked into their mouths to feed without using their teeth at all, instead filtering the food when passing water through their gills. [11] Basking sharks feed by swimming towards their prey with their mouth open and straining their food. [12] Through this process the shark is able to successfully eat hundreds of pounds of zooplankton each day. [12] Whale sharks feed by using rakers on their gill bars and strain them from their gill slits after sweeping krill and other prey into their mouths. [12]

Transitional teeth

As one species evolves into another, its teeth may become difficult to classify, exhibiting characteristics of both species. (Example: teeth from Otodus auriculatus as it evolved into O. angustidens ) are difficult to definitively identify as coming from either species.

Otodus megalodon fossil shark jaw (reconstruction) (late Cenozoic) 2 Carcharodon megalodon fossil shark jaw (reconstruction) (late Cenozoic) 2.jpg
Otodus megalodon fossil shark jaw (reconstruction) (late Cenozoic) 2

A commonly referred to transition is the evolution of Isurus hastalis , the extinct giant mako, into the great white shark, Carcharodon carcharias. There exist teeth that are believed to represent the transition between the two species. These teeth, from Carcharodon sp. are characterised by the wider, flatter crowns of the extinct giant mako. However, they also exhibit partial, fading serrations, which are more pronounced near the root, and disappear towards the tip of the tooth - serrations being found in great whites but not extinct giant makos.

Special mention: Megalodon teeth

An O. megalodon tooth excavated from Lee Creek Mine, Aurora, North Carolina, United States. Carcharocles megalodon tooth.JPG
An O. megalodon tooth excavated from Lee Creek Mine, Aurora, North Carolina, United States.

Otodus megalodon teeth are the largest of any shark, extinct or living, and are among the most sought after types of shark teeth in the world. This shark lived during the late Oligocene epoch and Neogene period, about 28 to 1.5 million years ago, and ranged to a maximum length of 60 ft. [13] The smallest teeth are only 1.2 cm (0.5 in) in height, while the largest teeth are in excess of 17.7 cm (7.0 in). The smaller teeth ranging from 3+1⁄2" and 4+1⁄2" are more common finds, while teeth over 5", 6", and 7" are more rare. [13] These teeth are in extremely high demand by collectors and private investors, and they can fetch steep prices according to their size and deterioration. [13] The larger teeth can cost as much as 3,000 dollars. [14]

Deposits

Shark teeth cannot be collected from just any type of rock. Any fossils, including fossil shark teeth, are preserved in sedimentary rocks after falling from their mouth. [13] The sediment that the teeth were found in is used to help determine the age of the shark tooth due to the fossilization process. [15] Shark teeth are most commonly found between the Upper Cretaceous and Tertiary periods. [16] Only after about 10,000 years will a shark tooth fossilize. [17] The teeth commonly found are not white because they are covered with sediment from fossilization. The sediment prevents oxygen and bacteria from attacking and decaying the tooth. [16] [17]

Fossilized shark teeth can often be found in or near river bed banks, sand pits, and beaches. These teeth are typically worn, because they were frequently moved and redeposited in different areas repeatedly before settling down. Other locations, however, yield perfect teeth that were hardly moved during the ages. These teeth are typically fragile, and great care should be taken while excavating them. [16] Phosphate pits, containing mostly fossil bones and teeth, or kaolin pits, are ideal places to look for fossil shark teeth. One of the most notable phosphate mines is in Central Florida, Polk County, and is known as Bone Valley. Most of the teeth found here range from 3 to 10 million years old. [13] Near New Caledonia, up until the practice was banned, fishermen and commercial vessels used to dredge the sea floor for megalodon teeth. In the state of Georgia, shark teeth are found so often that they decided to make shark teeth the official state fossil in 1976. [18]

Counting

Megalodon lower jaw with 4 tooth rows and 4 tooth series labeled. "Series 1" contains the functional teeth at the front of the jaw. How to count shark teeth.png
Megalodon lower jaw with 4 tooth rows and 4 tooth series labeled. "Series 1" contains the functional teeth at the front of the jaw.

In taxonomy, shark teeth are counted as follows: rows of teeth are counted along the line of the jaw, while series of teeth are counted from the front of the jaw inward. [19] A single tooth row includes one or more functional teeth at the front of the jaw, and multiple replacement teeth behind this. [20] For example, the jaws of a bull shark can have 50 rows of teeth in 7 series, with the outermost series functional, but most sharks have five series with the average shark having about 15 rows of teeth in each jaw. [17] The small teeth at the symphysis, where the two halves of the jaw meet, are usually counted separately from the main teeth on either side. Sharks are also known to lose at least one tooth per week. Due to their specific arrangement of rows and series however, lost teeth can be replaced within a day. [17]

Research and identification

Identification of most sharks are found through a combination of tooth counts and tooth shapes. Teeth can even lead to the identification of shark species like the requiem shark. The fossilized records of teeth helps illustrate evolutionary history, and isolated teeth are used to study and analyze specific linear measurements of the species. [21] In order to identify teeth and specific information about the teeth, research can be done on a shark tooth. This research may uncover many different aspects about the tooth itself, and the shark species. This proves complicated, however, due to the fact that most fossilized teeth are found mixed and scattered. [15] To collect information on basic-life history and get dispersal estimates of a shark tooth, molecular-based technology is very efficient. To further shark population studies, collection of mtDNA can be extracted from shark jaws and teeth. [22] To study the caries-reducing effect in sharks, studies are done on the fluorine atoms that are bound covalently to calcium atoms in the teeth. Each tooth has a complex fluorapatite structure enameloid. [23] In order to reduce effects of deterioration in the teeth, it is useful to sample only the surface of the enameloid of the tooth for this specific research. [24] Studying and researching shark teeth betters our understandings of shark feeding behaviors, evolutionary changes, and mechanisms. [25] This helps us to identify the teeth, and even the species.

History of discovery

Scapanorhynchus texanus, Menuha Formation (Upper Cretaceous), southern Israel. ScapanorhynchusCretaceousIsraelTwo.jpg
Scapanorhynchus texanus, Menuha Formation (Upper Cretaceous), southern Israel.
Shark tooth Shark ododus fossil tooth.jpg
Shark tooth

The oldest known records of fossilized shark teeth are by Pliny the Elder, who believed that these triangular objects fell from the sky during lunar eclipses. [26]

According to Renaissance accounts, large, triangular fossil teeth often found embedded in rocky formations were believed to be petrified tongues of dragons and snakes and so were referred to as "tongue stones" or "glossopetrae". Glossopetrae were commonly thought to be a remedy or cure for various poisons and toxins; they were used in the treatment of snake bites. Due to this ingrained belief, many noblemen and royalty wore these "tongue stones" as pendants or kept them in their pockets as good-luck charms. [27]

This interpretation was corrected in 1611 by the Italian naturalist Fabio Colonna, who recognized them as ancient shark teeth, and, in 1667, by the Danish naturalist Nicolaus Steno, who discussed their composition and famously produced a depiction of a shark's head bearing such teeth. [28] He mentioned his findings in a book, The Head of a Shark Dissected, which also contained an illustration of a C. megalodon tooth, previously considered to be a tongue stone. [29]

Tool use by humans

Gilbertese weapons edged with shark teeth Shark-tooth weapons.jpg
Gilbertese weapons edged with shark teeth

In Oceania and America, shark teeth were commonly used for tools, especially on weapons such as clubs and daggers, but also as blades to carve wood and as tools for food preparation, such as the māripi of the Māori. For example, various weapons edged with shark teeth were used by the Native Hawaiians (see example here [30] ), who called them leiomano. [31] Some types were reserved for royalty. [32] The Guaitaca (Weittaka) of coastal Brazil tipped their arrows with shark teeth. [33] The remains of shark tooth-edged weapons, as well as chert replicas of shark teeth, have been found in the Cahokia mounds of the upper Mississippi River valley, more than 1,000 km (620 mi) from the ocean. [34] It is reported that the rongorongo tablets of Easter Island were first shaped and then inscribed using a hafted shark tooth. [35]

See also

Related Research Articles

<span class="mw-page-title-main">Frilled shark</span> Species of shark

The frilled shark, also known as the lizard shark, is one of the two extant species of shark in the family Chlamydoselachidae. The frilled shark is considered a living fossil, because of its primitive, anguilliform (eel-like) physical traits, such as a dark-brown color, amphistyly, and a 2.0 m (6.6 ft)–long body, which has dorsal, pelvic, and anal fins located towards the tail. The common name, frilled shark, derives from the fringed appearance of the six pairs of gill slits at the shark's throat.

<span class="mw-page-title-main">Megamouth shark</span> Species of shark

The megamouth shark is a species of deepwater shark. Rarely seen by humans, it measures around 5.2 m (17 ft) long and is the smallest of the three extant filter-feeding sharks alongside the relatively larger whale shark and basking shark. Since its discovery in 1976, fewer than 100 specimens have been observed or caught. Like the other two planktivorous sharks, it swims with its mouth wide open, filtering water for plankton and jellyfish. It is recognizable from its large head with rubbery lips. The megamouth is so unlike any other type of shark that it is usually considered to be the sole extant species in the family Megachasmidae, though some scientists have suggested it may belong in the family Cetorhinidae.

<span class="mw-page-title-main">Megalodon</span> Extinct giant shark species from 23 to 3.6 million years ago

Otodus megalodon, commonly known as megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Pliocene epochs. O. megalodon was formerly thought to be a member of the family Lamnidae and a close relative of the great white shark, but has been reclassified into the extinct family Otodontidae, which diverged from the great white shark during the Early Cretaceous.

<i>Cretoxyrhina</i> Extinct genus of shark

Cretoxyrhina is an extinct genus of large mackerel shark that lived about 107 to 73 million years ago during the late Albian to late Campanian of the Late Cretaceous. The type species, C. mantelli, is more commonly referred to as the Ginsu shark, first popularized in reference to the Ginsu knife, as its theoretical feeding mechanism is often compared with the "slicing and dicing" when one uses the knife. Cretoxyrhina is traditionally classified as the likely sole member of the family Cretoxyrhinidae but other taxonomic placements have been proposed, such as within the Alopiidae and Lamnidae.

<i>Helicoprion</i> Genus of fossil fishes

Helicoprion is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown. Fossils of Helicoprion are known from a 20 million year timespan during the Permian period from the Artinskian stage of the Cisuralian to the Roadian stage of the Guadalupian. The closest living relatives of Helicoprion are the chimaeras, though their relationship is very distant. The unusual tooth arrangement is thought to have been an adaption for feeding on soft bodied prey, and may have functioned as a deshelling mechanism for hard bodied cephalopods such as nautiloids and ammonoids. In 2013, systematic revision of Helicoprion via morphometric analysis of the tooth whorls found only H. davisii, H. bessonowi and H. ergassaminon to be valid, with some of the larger tooth whorls being outliers.

<i>Janjucetus</i> Extinct genus of mammals

Janjucetus is an extinct genus of cetacean, and a basal baleen whale (Mysticeti), from the Late Oligocene around 25 million years ago (mya) off south-east Australia, containing one species J. hunderi. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen, and so was likely to have been a predator that captured large single prey animals rather than filter feeding. However, its teeth may have interlocked, much like those of the modern-day filter-feeding crabeater seal, which would have allowed some filter-feeding behaviour. Its hunting behaviour was probably similar to the modern-day leopard seal, probably eating large fish. Like baleen whales, Janjucetus could not echolocate; however, it did have unusually large eyes, and so probably had an acute sense of vision. The only specimen was found on the Jan Juc beach, where the remains of the extinct whales Mammalodon, Prosqualodon and Waipatia have also been discovered.

<span class="mw-page-title-main">Spinner shark</span> Species of shark

The spinner shark is a type of requiem shark, in the family Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean. It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of the blacktip shark, with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin, which has a different shape and is placed further back, and by the black tip on the anal fin. It attains a maximum length of 3 m (9.8 ft).

<i>Otodus</i> Extinct genus of sharks (fossil)

Otodus is an extinct, cosmopolitan genus of mackerel shark which lived from the Paleocene to the Pliocene epoch. The name Otodus comes from Ancient Greek ὠτ- and ὀδούς – thus, "ear-shaped tooth".

<span class="mw-page-title-main">Viper dogfish</span> Species of shark

The viper dogfish or viper shark is a rare species of dogfish shark in the family Etmopteridae, and the only extant member of its genus. It has been found in the Pacific Ocean off southern Japan, the Bonin Islands, Pacific Ocean off northern Taitung County and the Northwestern Hawaiian Islands. This species inhabits upper continental slopes and seamounts. It may migrate vertically, shifting between bottom waters 270–360 m (890–1,180 ft) deep during the day and upper waters less than 150 m (490 ft) deep at night. A slender, black shark reaching 54 cm (21 in) in length, the viper dogfish can be recognized by its narrow, triangular jaws and well-spaced, fang-like teeth. It also has two spined dorsal fins, dermal denticles with faceted crowns, and numerous light-emitting photophores concentrated on its ventral surface.

<i>Thalassocnus</i> Extinct, aquatic ground sloth from South America

Thalassocnus is an extinct genus of semiaquatic ground sloths from the Miocene and Pliocene of the Pacific South American coast. It is monotypic within the subfamily Thalassocninae. The five species—T. antiquus, T. natans, T. littoralis, T. carolomartini, and T. yuacensis—represent a chronospecies, a population gradually adapting to marine life in one direct lineage. They are the only known aquatic sloths, but they may have also been adapted to a terrestrial lifestyle. They have been found in the Pisco Formation of Peru, the Tafna Formation of Argentina, and the Bahía Inglesa, Coquimbo, and Horcón formations of Chile. Thalassocninae has been placed in both the families Megatheriidae and Nothrotheriidae.

<i>Zygophyseter</i> Extinct genus of sperm whales

Zygophyseter varolai is an extinct sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. It is known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around 6.5 to 7 meters in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper and lower jaws which the modern sperm whale lacks. It also had a beak, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach 4 kilometers per hour (2.5 mph). These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day killer whale.

<span class="mw-page-title-main">Durophagy</span> Eating of hard-shelled or exoskeleton bearing organisms, such as corals, shelled mollusks, or crabs

Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil turtles, placodonts and invertebrates, as well as "bone-crushing" mammalian carnivores such as hyenas. Durophagy requires special adaptions, such as blunt, strong teeth and a heavy jaw. Bite force is necessary to overcome the physical constraints of consuming more durable prey and gain a competitive advantage over other organisms by gaining access to more diverse or exclusive food resources earlier in life. Those with greater bite forces require less time to consume certain prey items as a greater bite force can increase the net rate of energy intake when foraging and enhance fitness in durophagous species.

<i>Brygmophyseter</i> Extinct genus of toothed whale (fossil)

Brygmophyseter, known as the biting sperm whale, is an extinct genus of toothed whale in the sperm whale family with one species, B. shigensis. When it was first described in 1994, the species was placed in the genus Scaldicetus based on tooth morphology, but this was later revised in 1995. In 2006, it was classified into the genus Naganocetus, which is considered to be a junior synonym. The only known specimen, a nearly complete skeleton, was dated to be around 16–15 million years old. Brygmophyseter is thought to have been 6.5–7 meters (21–23 ft) long, and it probably had 11 or 12 teeth in the upper and lower jaws. Brygmophyseter is part of a group of macroraptorial sperm whales which tended to be apex predators using their large teeth to catch struggling prey such as whales. It had a spermaceti organ which was probably used for biosonar like in the modern sperm whale. The whale has made an appearance on The History Channel's TV series Jurassic Fight Club.

<span class="mw-page-title-main">Tooth</span> Hard, calcified structure found in the mouths of many vertebrates

A tooth is a hard, calcified structure found in the jaws of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the outermost embryonic germ layer, the ectoderm.

<i>Otodus chubutensis</i> Species of fossil sharks

Otodus chubutensis, meaning "ear-shaped tooth of Chubut", from Ancient Greek ὠτ and ὀδούς – thus, "ear-shaped tooth", is an extinct species of prehistoric megatoothed sharks in the genus Otodus, that lived during Early Miocene to Middle Miocene. The largest individuals were about 13.5 metres (44 ft) long. This shark is considered a close relative of the famous prehistoric megatoothed shark O. megalodon. However, as is the case with O. megalodon, the classification of this species is disputed.

<i>Livyatan</i> Extinct genus of sperm whale from the Miocene epoch

Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei. The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale. It is mainly known from the Pisco Formation of Peru during the Tortonian stage of the Miocene epoch, about 9.9–8.9 million years ago (mya); however, finds of isolated teeth from other locations such as Chile, Argentina, United States (California), South Africa and Australia imply that either it or a close relative survived into the Pliocene, around 5 mya, and may have had a global presence. It was a member of a group of macroraptorial sperm whales and was probably an apex predator, preying on whales, seals and so forth. Characteristically of raptorial sperm whales, Livyatan had functional, enamel-coated teeth on the upper and lower jaws, as well as several features suitable for hunting large prey.

<i>Cardabiodon</i> Extinct genus of sharks

Cardabiodon is an extinct genus of large mackerel shark that lived about 95 to 91 million years ago (Ma) during the Cenomanian to Turonian of the Late Cretaceous. It is a member of the Cardabiodontidae, a family unique among mackerel sharks due to differing dental structures, and contains the two species C. ricki and C. venator. Cardabiodon fossils have been found in Australia, North America, England, and Kazakhstan. It was likely an antitropical shark that inhabited temperate neritic and offshore oceans between 40° and 60° paleolatitude, similar to the modern porbeagle shark.

<i>Cretalamna</i> Extinct genus of sharks

Cretalamna is a genus of extinct otodontid shark that lived from the latest Early Cretaceous to Eocene epoch. It is considered by many to be the ancestor of the largest sharks to have ever lived, such as Otodus angustidens, Otodus chubutensis, and Otodus megalodon.

<span class="mw-page-title-main">Fish jaw</span>

Most bony fishes have two sets of jaws made mainly of bone. The primary oral jaws open and close the mouth, and a second set of pharyngeal jaws are positioned at the back of the throat. The oral jaws are used to capture and manipulate prey by biting and crushing. The pharyngeal jaws, so-called because they are positioned within the pharynx, are used to further process the food and move it from the mouth to the stomach.

<i>Cosmopolitodus</i> Extinct genus of mackerel shark

Cosmopolitodus is an extinct genus of mackerel shark that lived between thirty and one million years ago during the late Oligocene to the Early Pleistocene epochs. Its type species is Cosmopolitodus hastalis, the broad-tooth mako. In 2021, Isurus planus was reassigned to the genus, and thus became the second species C. planus. However, some researchers still consider both species of Cosmopolitodus as species of Carcharodon.

References

  1. ↑ "Shark teeth".
  2. ↑ Enax, Joachim (June 2012). "Structure, composition, and mechanical properties of shark teeth". Journal of Structural Biology. 178 (3): 290–299. doi:10.1016/j.jsb.2012.03.012. PMID   22503701 – via Elsevier Science Direct.
  3. 1 2 3 Kardong, Kenneth (2019). Vertebrates: Comparative Anatomy, Function, Evolution. McGraw-Hill. p. 96.
  4. ↑ Luel, Carl (1990). "Rate of Tooth Replacement in the Nurse Shark, Ginglymostoma cirratum". Copeia. 1 (1): 182–191. doi:10.2307/1445834. JSTOR   1445834.
  5. 1 2 "Ancient Sharks". Micronesian Conservation Coalition. 2015.
  6. 1 2 3 Purdy, Robert W.; Lonardelli, Diane (1995). "Fossil Shark Teeth" (PDF). The Paleontological Society. pp. 1–2.
  7. ↑ "Fossil folklore".
  8. ↑ "Shark Savers :: Shark Teeth".
  9. ↑ Summers, Adam (February 28, 2004). "Structure and function of the horn shark (Heterodontus francisci) cranium through ontogeny: Development of a hard prey specialist". Journal of Morphology. 260 (1): 1–12. doi:10.1002/jmor.10141. PMID   15052592. S2CID   4024283 – via Wiley Online Library.
  10. ↑ Long, John (May 28, 2015). "First Shark from the Late Devonian (Frasnian) Gogo Formation, Western Australia Sheds New Light on the Development of Tessellated Calcified Cartilage". PLOS ONE. 10 (5): e0126066. Bibcode:2015PLoSO..1026066L. doi: 10.1371/journal.pone.0126066 . PMC   4447464 . PMID   26020788.
  11. 1 2 3 "What Do Sharks Eat – The Shark Diet". Types of Sharks.
  12. 1 2 3 4 Kardong, Kenneth (2019). Vertebrates: Comparative Anatomy, Function, Evolution. McGraw-Hill. pp. 507–508.
  13. 1 2 3 4 5 The Zen Cart® Team; et al. "About Fossil Shark Teeth".
  14. ↑ "6 plus inch Megalodon Sharks Teeth". 23 February 2020.
  15. 1 2 "FLMNH Ichthyology Department: Fossil Sharks". 5 May 2017.
  16. 1 2 3 Hennemann, Ralf M. (2001). Sharks & Rays: Elasmobranch Guide of the World. IKAN-Unterwasserarchiv. pp. 266–269. ISBN   978-3-925919-33-6. OCLC   223251653.
  17. 1 2 3 4 "Sink your teeth into this: 20 facts about shark teeth". Beach Chair Scientist.
  18. ↑ "Georgia State Fossil - Shark Tooth". 24 May 2014.
  19. ↑ Case, Gerard (1967). "Fossil Shark and Fish Remains of North American". p. 2.
  20. ↑ Heemstra, P.C.; Heemstra, E. (2004). Coastal fishes of Southern Africa . NISC/SAIAB. pp.  47. ISBN   1-920033-01-7.
  21. ↑ Naylor, Gavin J. P.; Marcus, Leslie Floyd (1994). "Identifying isolated shark teeth of the genus Carcharhinus to species". American Museum Novitates. hdl:2246/4942. ProQuest   51542224.
  22. ↑ Ahonen, H.; Stow, A. J. (29 July 2008). "Shark jaws and teeth: an unexploited resource for population genetic studies". Journal of Fish Biology. 73 (2): 450–455. doi:10.1111/j.1095-8649.2008.01896.x.
  23. ↑ Chen, Chunlin; Wang, Zhongchang; Saito, Mitsuhiro; Tohei, Tetsuya; Takano, Yoshiro; Ikuhara, Yuichi (3 February 2014). "Fluorine in Shark Teeth: Its Direct Atomic-Resolution Imaging and Strengthening Function". Angewandte Chemie. 126 (6): 1569–1573. Bibcode:2014AngCh.126.1569C. doi:10.1002/ange.201307689.
  24. ↑ Becker, Martin A.; Seidemann, David E.; Chamberlain, John A.; Buhl, Dieter; Slattery, William (July 2008). "Strontium isotopic signatures in the enameloid and dentine of upper Cretaceous shark teeth from western Alabama: Paleoecologic and geochronologic implications". Palaeogeography, Palaeoclimatology, Palaeoecology. 264 (1–2): 188–194. Bibcode:2008PPP...264..188B. doi:10.1016/j.palaeo.2008.04.006.
  25. ↑ Whitenack, Lisa (7 November 2008). The Biomechanics and Evolution of Shark Teeth (PhD dissertation). University of South Florida. ProQuest   304460308.
  26. ↑ "Sharks' teeth are falling! - Dharma Beach Bum". Dharma Beach Bum. Archived from the original on 2014-11-13.
  27. ↑ Davidson, Jane (April 14, 2000). "Fish tales: Attributing the first illustration of a fossil shark's tooth to Richard Verstegan (1605) and Nicolas Steno (1667)" (PDF). Academy of Natural Sciences. 150: 329–344. JSTOR   4065077 – via JSTOR.
  28. ↑ Haven, Kendall (1997). 100 Greatest Science Discoveries of All Time . Libraries Unlimited. pp.  25–26. ISBN   1-59158-265-2.
  29. ↑ Bruner, John (1997). "The Megatooth shark". FLMNH. Archived from the original on 2007-12-28. Retrieved 2008-01-16.
  30. ↑ "Treasures of Hawai'i : Shark Tooth Weapon". Bishopmuseum.org. Archived from the original on 2008-12-04. Retrieved 2008-11-27.
  31. ↑ Taylor, Leighton R. (1993). Sharks of Hawaii: Their Biology and Cultural Significance. University of Hawaii Press. p. 28. ISBN   978-0-8248-1562-2.
  32. ↑ Anthony Meyer (1995) Oceanic Art, v. 2, p. 579.
  33. ↑ Métraux, Alfred (1946) Handbook of South American Indians, v. 1, p. 522, "The Guaitaca"
  34. ↑ Greg Perino, c. 1950, Cahokia Brought to Life, pp. 66-67
  35. ↑ Métraux, Alfred (1940), "Ethnology of Easter Island". Bernice P. Bishop Museum Bulletin (Honolulu: Bernice P. Bishop Museum Press) 160:404

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.