Phatfossils - Shark Fossils

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Megalodon Shark Facts

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What is a Fossil?

Shark Fossils

Fossil shark remains are the most common Vertebrate fossil and are found around the world. The first sharks appeared around 450 million years ago during the Ordovician period. With sharks being cartilaginous not much of their body typically fossilizes. Despite this fact you can from time to time find Vertebrae, and far less frequently cartilage and rostral notes. Items that are much harder such as teeth and denticles made of dentine are the most common to fossilize. Denticles are small, almost microscopic and cover the animals body. They assist it in various ways such as reducing drag when moving through the water. Various species of sharks have protective spines on their dorsal din.

Fossil Shark Teeth

Sharks continually replace their teeth over their life time in a conveyor type system. With teeth constantly being replaced a single shark can drop thousands of teeth in a life time helping propel fossil shark teeth to the most common Vertebrate fossils around the world.

Lower Great White Jaws showing the conveyor like system of teeth.

Close up from the upper jaw of a great white shark showing rows of teeth forming stacked on top of each other

During the beginning shark teeth were non-descript and small such as the two Devonian teeth show below. Over time as the species diversified and grew larger teeth off all shapes and sizes started to evolve to fit evolutionary niches as can be seen in the pic on the right with various modern species

Devonian shark teeth measuring 1mm and .5mm respectively
Various fossil shark tooth designs still in use today. Top left to right, sand tiger, snaggletooth, mako. Bottom left to right, tiger, cow , nurse

Don't let the size of the teeth fool you, just because they are small doesn't mean they came from a small shark. This biggest shark alive today, the whale shark has some of the smallest teeth. Maxing at around fourty feet you would expect the whale shark to have some monster compers, instead the measure under a quarter of an inch. Now, the Megalodon that's a different story. Maxing out at around sixty feet this beast had teeth that could reach over seven inches in slant height. The whale shark tooth is greatly increased in size for viewing detail in comparison to the megalodon shark tooth

Just under 6" slant height Megalodon Shark Tooth from the Lee Creek Mine, Aurora, NC

.19" Fossil Whale Shark Tooth, Lee Creek Mine, Aurora, NC

Fossil Shark Vertebrae

Outside of teeth Vertebrae are the most common found fossils from sharks. There are tones of different shark Vertebrae out there, a cast majority of them maintain the same shape and structure, the biggest difference being the foramen or openings on the side. There are two basic types of commonly identified shark vertebra, lamnoid and scyliorhinoid. Lamnoid are generally flatter and have many poramen on teh sides as seen in the vert on the left. The scyliorhinoid verts typically are less compressed and are smooth outside of the main foramen on the sides as seen in the massive tiger shark vert on the right.

Fossil Shark Lamnoid Vertabrae

Huge Tiger shark vertabra from The lee Creek mine in Aurora North Carolina. This thing is bigger around then a soda can. Check out the bite marks on it as well. Another shark at it.

Every once and a while you will get lucky and find some associated shark verts, when you do you hope you get teeth with them as well but that usually is not the case around here. Sometimes it is the material they are fossilised in that keeps them together and other times you just get lukcy and find a bunch stickgin out of the formation. Below are an example of each, a string of verts found sticking out of the base clay at a miocene river site non articuladed, and three verts that were fused together by th epungo lime they fossilised in. Shark verts can possess pathologies as well as seen below.

Arthritic shark vertebra

Shark verts fused together after death bu the pungo lime it fossilised in

Twenty Three plus shark verts found disarticulated in the base clay of a river

Fossil Shark Fin Spines

Various species of shark have what are refered to as fin spines. They can be found on genus such as Heterodondus, Squalus, Hybodus and many other. These spines sit on the leading end of dorsal fins and are used as a defense mechanism. A hungry predator might let go if it gets a mouthful of a shark fin spine. The spines can vary in size and shape, some are smooth while others have knobby protrusions. Not all fin spines found are attributed to sharks, such as, the Chimaera fin spin shown below.

Fossil shark fin spine, Miocene, from Bakersfield California.

Fossil Chimaera fin spine, Paleocene, from Charles County MD.

Fossil Shark Dermal Denticles

Sharks entire body are covered with dermal denticals made the same material as their teeth, dentine. The derminal denticles are extremely small, typically measuring in under a millimeter and can vary in form. They are so small and tightly packed together across the skin that a single animal has tens of thousands of them. This small size typically creates a collecting bias when it comes to fossil specimens. The varying desing and tight packing can be seen in the two close ups of a modern Mustelus fin below. The close up of the fossil shark derminal denticle give you an idea as to what one type looks like.

Close up of dermal denticles on the fin of a Mustelus.

Close up of dermal denticles on the fin of a Mustelus.

Individual fossil shark dermal denticle

Fossil Shark Cartilage

Cartilage is not one of the best things when it comes to fossilization. When you factor in that sharks are cartilaginous you can understand why the study of fossil sharks can sometimes be difficult. Despite the low odds some cartilage does survive the test of time and become a fossil. There are instances where entire sharks fossilize but typically you only come across small, disarticulated and indescript pieces. Shark cartilage has a distinct honey comb like structure making it quite easy to identify fossil cartilage. You can see the small circular structures stacked on top of each in the image below

Fossil Shark Cartilage from the Lee Creek Mine Aurora NC

Fossil Shark Rostral Nodes

Another portion of the shark that can be found fossilized is the rostral node. The rostral node is located in tip of the snout, not the very tip but the tip and is the very tip piece of the cartilagineus skeleton of the shark. Like other cartilage, rostral nodes do not fossilize as often making them less common to find. There are various types of rostral nodes out there but for the most part they all are comprised of three solid tube like structures coming together at the tip.

Fossil Shark Rostral Node, Lee creek Mine Aurora NC. Found in two pieces and glued back together