Frequently Asked Questions

What is a fossil?

Fossils are the remains of organisms from before history. Anything from a plant, animal, fungus, bacteria, any piece of anything (bones, teeth, shells, soft parts) imprint, mold, or trace such as burrows, excrement, and footprints that was once alive or made by something alive during prehistoric times. This does not include things made by prehistoric man though, so arrowheads, pottery shards, and stone tools are not fossils, they are artifacts. However, the remains of prehistoric man are fossils.

How old does something have to be for it to be a fossil?

For example, are Egyptian mummies fossils? What about the bones from an archeological site three thousand years old? Generally speaking, no because the soft parts are still (kinda) soft. Now, soft parts like skin and tissue can fossilize, but when they do they are turned to stone by a process called permineralization, where the organic molecules (proteins, amino acids, carbohydrates, all the really complex molecules that are vital to life) are replaced by inorganic molecules (minerals) from the surrounding rock. So the answer is however long it takes for the organics to be replaced or at least mostly replaced by minerals, several thousand years at a minimum. Usually, this means before recorded history, about five thousand years ago, but it depends much more on the chemistry aspect than any cut off point in time.

How do fossils form?

Fossils form whenever any piece or trace of an organism is preserved too today. It all comes down to preservation. Anything no matter how delicate can be fossilized under the right conditions. Usually this involves being buried very quickly in an environment where bacteria responsible for decomposition don’t do so well so mineralization can begin. Some conditions are of course rarer than other though. Hard parts such as bones, teeth, and shells don’t decompose quickly so they have plenty of time to be buried, they also have minerals in them (Calcium phosphate for teeth and bones and calcium carbonate for shells usually) as the body makes them so they have a head start. Soft tissue needs to be dried out and buried immediately so it doesn’t have a chance to decompose and won’t decompose while buried. This happens a lot less often which is why fossils of skin and tissue are very rare. There are several different types of fossilization process:

Permineralization: The organic molecules (proteins, amino acids, carbohydrates, all the really complex molecules that are vital to life) are replaced by inorganic molecules (minerals) from the surrounding rock. The primary way that soft parts are preserved, also fossilizes bones, teeth, and wood.

Unaltered: The organic molecules have long since decomposed or been replaced by minerals but the natural minerals that the bone or shell were made of by the living organism remain. Very rare.

Imprint/ mold: The organism’s remains held of decomposition just long enough to leave an imprint in mud or silt. The mud or silt hardens and then turns to rock before it is disturbed. Footprints, skin impressions, and impressions of shells are formed this way.

Cast: An imprint is filled in with sediment making a natural cast of the original. Most fossil bivalves and snails are casts that filled in the shell and remained after the shell dissolved.

Recrystallization: The natural minerals in bones and teeth dissolve and are replaced by other minerals.

How do we know how old fossils are?

There are two main ways that age is determined, relative dating and radiometric dating.

Relative dating all boils down to one simple fact, a layer of rock on top of another layer will be younger than the layer it is on top of. Unfortunately, there is no perfect sequence of rock layers anywhere on the planet. Perhaps a layer was eroded in the distant past at a spot, or there was a period of time where there just wasn’t any rock forming in that area. So, geologists and paleontologists have to piece together a perfect sequence from different outcrops. Let’s say you have two outcrops, in outcrop 1 layer A is on top of layer B, in outcrop 2, layer B is on top of layer C. Between these two outcrops, you can infer that layer A is younger than layer B which is younger than layer C. Now, scale that up to layers and outcrops all over the world and you get an idea of how relative dating works. This was the only way to date rocks and the fossils within them until the twentieth century when radiometric dating was invented.

Radiometric dating is a lot more accurate and a LOT more complicated. I’ll have to explain a bit of chemistry first. Everything from rocks to planets to people is made up of atoms, all atoms are composed of particles called protons, neutrons, and electrons. Protons and neutrons are in the center of an atom while electrons orbit the edge like the Earth orbits the sun. The particles act like magnets. Electrons are negatively charged, protons are positively charged, and neutrons are neutral. Different elements have different numbers of protons. You can see this by looking at a periodic table. Hydrogen atoms have one proton, Helium has two, etc. Isotopes are atoms that have the same number of protons, and are therefore the same element, but have different numbers of other particles. Because protons are all positive, they don’t like being near each other just like trying to put the positive sides of two magnets together. So over time the protons break free and the atom becomes another element because the number of protons changed. This process is called radiometric decay. This happens primarily in isotopes. As it turns out, this process happens at a very stable rate. What I mean by that is that every isotope with the same number of protons, neutrons and electrons will break down at exactly the same rate no matter what you do to it. Pressure and heat have ZERO effect on radiometric decay. As a rock, fossil, whatever forms, some isotopes are going to find their way into it. The amount of time it takes for half the isotopes in something to break down is called a half-life. Scientists can measure how many isotopes have broken down into another element (called daughter isotopes) and compare that to how many of the original isotope (called the parent isotope) there are and from that determine the age of whatever it is they are looking at.

Scientists will usually combine these two techniques to figure out things like how long it takes a layer to form, which layers were formed at the same time but in different environments, and what fossils are found at what times. The latter is how fossil age is determined and also how new fossils are aged by looking at the known age range of fossils found with it.

How do I know it is real?

There is only one way to know with absolute 100% certainty that the fossil is 100% authentic and that is to dig it up and prep it yourself. There is no authentication process like with artwork, everything in the world of fossil dealing is based on trust and an understanding that if you are caught engaging in funny business that word travels really fast. When you buy a fossil from anyone whether a museum or a small dealer you are trusting their word that they are, to the best of their knowledge, selling you what they believe they are selling you (I say that because misidentification does happen sometimes). A trained eye can tell if the “fossil” in front of them is a fossil or a replica made of resin usually, but even then there are some really convincing fakes out there. Fortunately, making a truly convincing fake is so expensive that it’s usually more profitable to just sell the actual fossil. Or they’ll put out a really bad fake that can be easy to spot. One thing I always ask myself when looking at other dealers’ fossils is “Is it worth it to fake?” isolated bones and teeth are usually okay since making a truly convincing fake of them would take more resources than it would to go out and find one. It’s actually pretty rare for someone to put out a complete fake of a vertebrate fossils and straight up claim it’s real (happens all the time with trilobites though). What is more common is a “restored” fossil being sold as having no repair or restoration. To be clear, there is nothing wrong with selling a fossil that was glued back together, had a ding repaired, or even sell one that is replica so long as you are up front about it. Here are a few things to keep an eye out for when purchasing fossils;

Repaired: The texture and luster on one part of the fossil doesn’t match the rest (very common on repaired megalodon teeth).

Identical fossil: A lot of fossils that are almost identical (mass produced Trilobites, usually Moroccan).

Franken fossils: When multiple pieces from different specimens are glued together to make a whole one. Usually found on fossil plates like crinoids and trilobites. Check the back of the plate to see if there are a bunch of cracks that were filled in. A black light helps to show where a fossil was glued together. Another common one is the Moroccan “Mosasaur jaws” with real (often janky) teeth in an artificial matrix with bits of modern bone in the shape of two long rectangles which form the upper and lower “jaws”.

“Too perfect”: Fossils are NEVER uniform in color since minerals don’t seep in every part in the exact same concentrations. Also be wary of completely flat Moroccan symmetrical trilobites. Remember, if it looks like it was painted on, it probably was.

Moroccan and Chinese fossils: The two worst offenders. 99.999% of the time when I see or hear about a fake it’s from either Morocco or China. This isn’t to say that all Chinese and Moroccan fossils are fake, most are fine such as isolated teeth and shells. It’s the fossil plates you have to keep an eye out for. Usually the rock the “fossil” is on is used to mask that it’s a fake. Fortunately, the Moroccans don't usually make decent forgeries. Google fake Moroccan fossils to get an idea of what they look like, it’s not subtle. Chinese stuff on the other hand is tricky. Look out for the small Triassic reptiles like Keichousaurus that have been painted on or partially painted on.

Outdated classification: Not so much a sign of forgery as a sign that the fossil might be worth less (or more!!!) than it’s listed as. Paleotaxonomy changes more often than the average person changes their socks. Species thought to be distinct get lumped together and two seemingly identical fossils can be classified in completely different families quite regularly as new discoveries are made. This isn’t a sign of malice or even laziness, it is REALLY difficult to keep up with across the entire spectrum of extinct species. It is something to keep an eye out for if for no other reason that a fossil might get listed a lot cheaper than it actually is.

Misidentification: It happens. We’ve all done it. Fossil dealers and paleontologists are people too. If you see a misidentified fossil for sale it usually isn’t a sign of malice as it is humanity. A gentle explanation in private with the dealer is usually pretty appreciated in these circumstances. Just keep in mind that you might be the one misidentifying it.

How and where do I find fossils?

Fossils are a lot easier to find than you might think. Just follow the following steps.

Research the location: If there are fossils to be found at a site, chances are someone else has already found a few there. Google “(your location) fossil collecting” or something similar and see what’s around you, you’ll probably be surprised. If you’re looking for a specific type of fossil, ex. shark teeth, you might want to broaden your search area to “(state or country) fossil shark teeth”. You can also just look for famous sites with that type of fossil and plan a fossil vacation there! Florida gulf coast beaches are excellent places to find fossil shark teeth, there are also ranchers in Montana, Wyoming, etc. who advertise letting you onto their property to look for dinosaur fossils!

Make sure it’s legal: Just because there are fossils there doesn’t mean you can collect them. NEVER collect on private property without the owner’s permission. Most state and national parks are also a no go. Some countries will arrest you for collecting ANY fossils.

Make sure it’s safe: Hey! You wanna go collect dinosaur teeth in that mountain range full of man-eating cougars? How about that remote outcrop in the middle of the territory of indigenous cannibals/drug cartels/terrorists? No, no you don’t. No fossil is worth your life. Make sure you know what type of wildlife, plant life, natural hazards like floods and tornados, and insane nut cases are in an area before you go and be prepared for them. Or don’t go if you can’t be prepared. DON’T BE A CANDIDATE FOR A DARWIN AWARD!

What are some common mistakes to avoid while searching for fossils?

Don’t push yourself too hard:

It’s very easy to get carried away while out in the field doing what you love. Overloading your pack with too many finds, getting lost, or traveling too far from your group or your vehicle can easily happen if you’re not paying attention and lead to serious injury or worse. When you hunt for fossils you are going out into the wilderness; make sure you know your physical limitations and pay close attention to your supply of liquids and location relative to safety.

Don’t look where you can’t dig:

This won’t kill you, but it will haunt your nightmares. In the world of paleontology there is nothing more frustrating than seeing a rare well-preserved fossil in a location you can’t access. I’ve heard stories of finding a trilobite on a huge boulder, seeing a Plesiosaur skull sticking out of a vertical cliff several stories above the ground, and stumbling across a rare artifact in a national park (that last one happened to me). All these finds are either impossible to extract or illegal to collect and leaving them behind HURTS. Save yourself the heartache, and don’t look in locations you can’t collect from.

Don’t hit the rock next to the fossil:

You’re out fossil hunting. You find a pristine shark tooth on a large rock. Which of the following do you do?

  1. Carry the rock back to your vehicle and prep the tooth using the proper tools.
  2. Break away small pieces of the rock away from the fossil in the field making it easier to transport.
  3. Bring your rock hammer down, right next to the fossil because “ain’t nobody got time for that!”

If you go with c, you’re not going to like what happens next. Unfortunately, a LOT of people go with c in these circumstances and every time without fail the rock breaks right through the fossil. Haste makes waste and regret.


The last tip is about not being stupid. This one is about accepting that no matter how smart and careful you are you will make mistakes and you need to learn to deal with it. You will break something. Everyone has broken something. Anyone who says they haven’t either hasn’t spent a lot of time working with fossils or is outright lying through their teeth. It sucks, but that’s part of the trade. So, when it does happen, don’t be down on yourself. Learn from your mistakes and accept that you don’t have total control. If you do let the fear and trauma from breaking something consume you, you’ll move too slowly to get anything done.

Don’t fossil hunt while drunk:

You’d think this one would be common sense, or at least self-explanatory but personal experience has shown otherwise so here it is. You are in the wilderness while fossil hunting, you need your wits about you to identify both fossil treasures and potential dangers. Booze makes it much harder to do those things, so save the six pack for after you’ve found your prize AND driven home ESPECIALLY IF YOU ARE A PART OF A GROUP SINCE YOUR DRUNK BUTT IS PUTTING OTHER PEOPLE IN DANGER!!!!!  Don’t drink and fossil hunt PERIOD!

What makes a dinosaur a dinosaur?

It never ceases to amaze me how many educated people mislabel things as dinosaurs. I’ve personally witnessed science graduate students, professors, and professionals talk about all manner of prehistoric creatures as their “favorite dinosaur”. Usually it’s a prehistoric reptile, which is kind of understandable, but I’ve also been told woolly mammoths, sabre tooth “tigers”, and Megalodon! You can’t be to upset though; the exact definition of a dinosaur has never been clear in popular media and even paleontologists have been debating what exactly qualifies as a true dinosaur and even if dinosaurs are true reptiles (birds being reclassified as true dinosaurs made the taxonomy really complicated). So in the spirit of educating the masses I’ll give an in-depth definition of dinosaur taxonomy and list common, well known animals that are dinosaurs, and others that are confused with dinosaurs.


First I have to define the group of animals that include dinosaurs and their kin, Archosaurs. Archosaurs are animals descended from the reptile evolutionary tree that are distinguished from other reptiles by having teeth with deep roots (assuming it has teeth), holes in the jaw and in the skull in front of the eye socket, and a prominent ridge on the femur bone. Dinosaurs are a type of archosaur with erect limbs positioned directly underneath their body, they are also believed to be warm blooded.

Therefore, a dinosaur is defined as an animal descended from reptiles with deep rotted teeth, a hole in the jaw and right in front of the eye socket, a prominent ridge on the femur bone, has erect limbs positioned directly underneath its body, and is (probably) warm blooded.

The following are dinosaurs:

Theropods: Carnivorous dinosaurs including T-rex, raptors, and birds.

Sauropods: long neck plant eating dinosaurs like Apatosaurus (Brontosaurus).

Ceratopsians: Dinosaurs with boney frills on the back of their head and parrot-like beaks. Many have horns. The most well-known is Triceratops.

Ornithopods: Plant eating dinosaurs with hard bills and three toed feet such as Iguanodon. The duck billed dinosaurs such as Edmontosaurus are a type of Ornithopod.

Pachycephalosaurs: Dome headed dinosaurs like Pachycephalosaurus.

Ankylosaurs: Armored dinosaurs, some had large clubs on the end of their tail like Ankylosaurus.

Stegosaurs: Dinosaurs with two rows of plates or spikes going down their back such as Stegosaurus.

The following are NOT dinosaurs although they are often called dinosaurs:

Pterosaurs: AKA Pterodactyls. Pterodactyls are another type of archosaur and very closely related to dinosaurs, they are not dinosaurs, however.

Crocodiles and Alligators: Often called living dinosaurs, crocodilians are the only other living group of archosaurs besides birds. They are not dinosaurs, but closely related.

Mosasaurs: Large carnivorous marine reptiles that lived during the latter half of the Cretaceous period. They’re not dinosaurs but are actually marine lizards.

Plesiosaurs: Another group of carnivorous marine reptiles, there are several different varieties. The most well-known type of plesiosaur, the Elasmosaurs, had a long neck like the sauropods.

Ichthyosaurs: A different group of marine reptiles that bared a striking resemblance to modern dolphins. Also, not dinosaurs.

Dimetrodon: A large reptile with a sail on its back that lived about 290 million years ago. The existence of Spinosaurus, a large carnivorous dinosaur with a sail on its back makes this one an easy mix-up. One look at Dimetrodon’s limbs tells the whole story as they are sprawled off to the side like a crocodile. Dimetrodon is actually part of the group of reptiles that eventually evolved into mammals.

Ice age mammals: I blame the Flintstones for this. Woolly mammoths, Sabre Tooth Cats, and all the other large mammals from the Ice Age are just that, mammals. They are not dinosaurs.

Megalodon: “What’s your favorite dinosaur? Mine’s Megalodon!” These words actually came out of the mouth of a senior level geology undergrad in complete seriousness just outside Big Bend national Park in the spring of 2013. The look of shock on her face when I (politely) corrected her is seared into my memory. Megalodon is a species of giant shark that lived between 20 and 2.5 million years ago in all the world’s oceans. Never in my life have I seen anyone mistake a shark of any kind for a dinosaur. Even those with ZERO science background know the difference as sharks and dinosaurs have always been two separate categories of cool scary monsters to the general public and media. It never had a starring role in any kids cartoon where it could be confused with surrounding dinosaurs (I mean, I think there was a big shark in one of the Land Before Time movies but that’s about it as far as I know, and it wasn’t called anything beyond “swimming sharp tooth”). Fascinating animal, not a dinosaur, not even close, to this day I haven’t figured out why she thought it was a dinosaur.

How do I identify fossils?

Identifying fossils is more of a process of elimination than anything else, starting with three pieces of information that narrow down what a fossil can be; the type of fossil, age, and location. Different fossils have different characteristics, different fossils are found in different formations, and different formations are found at different locations from different ages.


The first thing you’re going to do is figure out what type of fossil you’re dealing with. Is it a tooth, a shell, a bone, an imprint, etc.? What type of organism is it from, shark, snail, dinosaur, plant, trilobite, etc.? There really aren’t any sort of shortcuts with this, you’re going to need at least some knowledge of biology. Google is your best friend for this kind of thing especially if you lack experience. Research a wide variety of fossils and what they look like and try to narrow down what you are dealing with as much as possible. Even just determining plant or animal can make a huge difference. A paleontologist once misidentified a huge log of petrified wood as a bone from a new species of dinosaur.

Location and age:

I lumped these two together because you use both to find out what rock formation a fossil is from. I really can’t stress enough how important it is to have this information since fossils from closely related species can be very similar even if they lived millions of years and hundreds of miles apart in different formations. One example is T-rex. T-rex lived from 68 to 66 million years ago in North America, however there were other large Tyrannosaurs who lived in north America such as Albertosaurus, Gorgosaurus, and Daspletosaurus. An isolated Tyrannosaur tooth from the late Cretaceous of north America could be from any of them. During the last part of the Cretaceous however the choices narrow as from 68-66 million years ago the only Tyrannosaur that lived in North America was T-rex and wouldn’t you know it there is a formation in North America from that narrow range. If you know that the tooth came from the Hell Creek formation, a formation dated to 68-66 million years old, you can positively identify the tooth as being from a T-rex. Location is something you are either going to know or don’t unfortunately. Whenever you find a fossil make sure to write down where you found it. Also make sure you know where a fossil was found before purchasing it as that can help you to know if it has been identified correctly. T-rex is an example of the later again, as teeth from Carcharodontosaurus are often sold as “African T-rex” teeth on ebay when as I mentioned before T-rex only lived in North America. Figuring out age from location is easy thankfully, just google the age of the rock in the area the fossil was found. There are some locations that have multiple rock layers from different times however, so you’re going to have to compare the different formations to the type of fossil you found. For example, if a marine limestone formation is found next to a terrestrial sandstone and you’re trying to identify a large shark tooth than you’re probably dealing with the marine limestone. Having a sample of the rock to compare the formations to also helps since you can in the example just tell from that if it is a sandstone or limestone.

Once you have the type of fossil, its age and location, and by extension the rock formation it’s from you can try to identify the species or at least a narrower definition than “shark tooth” or “ammonite”. You do this by looking at the fossil’s distinguishing characteristics and compare it to each fossil of that type found in the formation. By distinguishing characteristics, I mean details such as shape, size, presence of features like serrations if it’s a tooth or spines/ridges if it’s a shell.

Putting everything together, let’s say you find a shark tooth on an outcrop on a river. Google the area on the river it was found on and something like fossils or rock formation and compare the outcrop to different formations found in that area until you find a match for the type of rock and fossils. Then google “(formation) shark teeth”. Then compare features like the size, shape, presence of serrations or cusps to known shark teeth from that formation until you find a match.

Also, never be afraid to ask for help. Local fossil clubs and online fossil forums are a fantastic resource especially if you don’t have a lot of experience.