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title: "20 Most Common Fossils and How to Identify Them" description: "A beginner-friendly visual guide to the 20 fossils you're most likely to find, including brachiopods, crinoid stems, coral, shark teeth, ammonites, and trilobites." category: "Identification" date: "2026-03-30"

A Beginner's Guide to Common Fossils

Fossil hunting, or "fossil collecting," is a rewarding hobby that connects us directly to the deep history of our planet. It’s a treasure hunt through geologic time, where the prize is a tangible piece of a long-lost world. While spectacular dinosaur skeletons are the stuff of museums, countless smaller, more common fossils are waiting to be discovered by amateur paleontologists in local quarries, road cuts, and creek beds. This guide introduces 20 of the most frequently found fossils, organized from the easiest to find to the more challenging, providing tips on how to identify them and where to look.

Level 1: The "Can't-Miss" Fossils

These fossils are incredibly abundant in sedimentary rocks of the right age and type. If you are in a fossiliferous Paleozoic marine deposit, you are almost guaranteed to find some of these.

1. Crinoid Stems (Sea Lilies)

What It Is: Crinoids are marine animals, not plants, despite their nickname "sea lilies." They are echinoderms, related to starfish and sea urchins. The most common fossilized part is the stem, which was made of numerous stacked, disc-like plates called columnals.
How to Identify It: Look for small, circular or star-shaped discs, often about the size of a small button (typically 2-10 mm in diameter). They have a hole (lumen) in the center. You may find individual columnals or articulated sections of the stem, which look like a screw or a stack of poker chips.
Where Found: Extremely common in Paleozoic marine limestones and shales worldwide, especially from the Ordovician through the Permian periods. The Midwestern United States (e.g., Indiana, Ohio, Iowa) is famous for its crinoid-rich deposits.
Age Range: Ordovician to present, but most common in Paleozoic rocks (485–252 million years ago).
Collecting Tips: Scan the surfaces of weathered limestone slabs or search through gravel in creek beds that cut through these formations. They are durable and often wash out of softer rock.

2. Brachiopods (Lampshells)

What It Is: Brachiopods are marine animals with two shells (valves), similar to clams. However, their internal anatomy is very different, and their shells are symmetrical from left to right, but the top and bottom valves are different shapes. Clams, by contrast, have left and right valves that are mirror images.
How to Identify It: Look for shell fossils that have bilateral symmetry running from the "beak" (the pointed end where the shells hinge) to the front edge. They often have fine radiating ribs. Common shapes include D-shapes, circular forms, and winged forms.
-Where Found: Abundant in Paleozoic marine sedimentary rocks globally. They are excellent index fossils for dating rock layers.
Age Range: Cambrian to present, but they dominated the Paleozoic seafloor.
Collecting Tips: Like crinoids, they are often found weathering out of shales and limestones. Look for whole shells or impressions left in the rock.

3. Horn Coral (Rugosa)

What It Is: Horn corals were a group of solitary corals that are now extinct. They built a cone- or horn-shaped skeleton (corallite) in which the single coral polyp lived.
How to Identify It: These fossils look like small, curved horns, often with fine lines (growth lines) wrapping around the outside and thin vertical ridges (septa) visible at the wide, open end. They can range from less than an inch to over a foot long.
Where Found: Common in Silurian and Devonian marine limestones, such as those found in the Great Lakes region of North America and parts of the UK.
Age Range: Ordovician to Permian (extinct at the end-Permian mass extinction).
Collecting Tips: Check limestone outcrops and gravel beds. Their robust shape helps them survive weathering. Sometimes they are silicified (replaced by silica), making them harder than the surrounding limestone and easy to spot as they weather out.

4. Bryozoans (Moss Animals)

What It Is: Bryozoans are colonial animals that live in interconnected structures called zooids. The colonies can take many forms: branching like twigs, encrusting like a net, or forming fan-like shapes.
How to Identify It: Look for delicate, net-like patterns on rock surfaces or small, twig-like fossils covered in tiny pores. The "Archimedes" bryozoan is a famous example, with a screw-shaped central axis. A hand lens is very helpful to see the tiny individual pores where the animals lived.
Where Found: Very common in Paleozoic marine rocks, particularly Ordovician, Silurian, and Carboniferous limestones and shales.
Age Range: Ordovician to present.
Collecting Tips: Their delicate structures are often best preserved as impressions on shale surfaces. Look for the distinctive lacy or branching patterns.

5. Petrified Wood

What It Is: This is fossil wood where the original organic material has been replaced by minerals, most commonly silica (quartz). The replacement process, called permineralization, can be so precise that the cellular structure, growth rings, and bark are perfectly preserved.
How to Identify It: It looks like wood but is as heavy and hard as rock. The colors can be vibrant, ranging from red and yellow (from iron oxides) to black (from carbon). The wood grain and rings are often clearly visible.
Where Found: Found worldwide in terrestrial sedimentary deposits. Famous locations include the Petrified Forest National Park in Arizona (collecting is illegal here) and deposits in the western United States, Argentina, and Egypt.
Age Range: Devonian to present, but most common from the Mesozoic and Cenozoic eras.
Collecting Tips: Search gravel bars in rivers and desert washes in areas known for terrestrial deposits. It is very durable and accumulates in these settings.

Level 2: Common, But Requiring a Sharper Eye

These fossils are also widespread but may be smaller, more fragmented, or found in more specific types of rock, requiring a bit more patience to find.

6. Bivalves (Clams, Oysters, Scallops)

What It Is: Bivalves are mollusks with two hinged shells (valves), like modern clams. Unlike brachiopods, their two valves are typically mirror images of each other.
How to Identify It: Look for shells that are asymmetrical from the hinge to the edge but have symmetrical left and right valves. You will often find just one valve. Oysters have thick, irregular shells, while scallops have the classic fan shape with radiating ribs.
Where Found: Common in marine and freshwater deposits from the Mesozoic and Cenozoic eras. The Cretaceous chalks of Europe and North America are famous for bivalve fossils.
Age Range: Cambrian to present.
Collecting Tips: Coastal cliffs, especially those made of sandstone or chalk, are excellent places to look. They are often found in dense beds.

7. Gastropods (Snails)

What It Is: Gastropods are mollusks with a single, usually coiled, shell. They are one of the most successful animal groups in history, living in marine, freshwater, and terrestrial environments.
How to Identify It: Look for the characteristic spiral or conical shell shape. They can be high-spired (like a turret) or low-spired (like a garden snail). Most are found as internal molds, called steinkerns, which preserve the shape of the inside of the shell.
Where Found: Found in almost all fossil-bearing sedimentary rocks. Marine forms are common in Paleozoic limestones, while terrestrial and freshwater forms are found in Cenozoic lake and river deposits.
Age Range: Late Cambrian to present.
Collecting Tips: Search carefully on weathered slopes. Their three-dimensional shape makes them stand out from the flat rock fragments.

8. Ammonites

What It Is: Ammonites were predatory, shelled cephalopods related to modern squid and octopus. They had a coiled, chambered shell that they used for buoyancy.
How to Identify It: They have a distinctive, typically flat, coiled shell, often resembling a ram's horn. A key feature is the intricate suture pattern—the wavy line where the internal chamber walls (septa) meet the outer shell wall. These patterns became more complex over time.
Where Found: Exclusively marine. They are extremely common in Mesozoic rocks worldwide and are a primary index fossil for that era. The Jurassic Coast in the UK and the Cretaceous shales of the Western Interior Seaway in North America are classic hunting grounds.
Age Range: Devonian to Cretaceous (extinct with the dinosaurs).
Collecting Tips: Look for them weathering out of shale and limestone cliffs. Often, you will find fragments first. Splitting shale layers can reveal beautifully preserved, flattened specimens.

9. Belemnites

What It Is: Belemnites were another group of squid-like cephalopods. The most commonly fossilized part is the guard, a dense, bullet-shaped internal shell that acted as a counterbalance.
How to Identify It: These fossils are cigar- or bullet-shaped, usually dark brown or black, and have a pointed tip and a conical cavity at the blunt end where the soft body attached. They are typically 5-15 cm long.
Where Found: Abundant in Mesozoic marine sediments, often found alongside ammonites.
Age Range: Carboniferous to Cretaceous.
Collecting Tips: Their robust, dense shape means they weather out of rocks easily and accumulate in gravel deposits. They are very common on the beaches of the UK's Jurassic Coast.

10. Shark Teeth

What It Is: Sharks have skeletons made of cartilage, which rarely fossilizes. However, their teeth are made of dentin and enamel, making them hard and easily preserved. A single shark could shed tens of thousands of teeth in its lifetime.
How to Identify It: Look for triangular, blade-like, or pointed objects with a glossy enamel surface. They can range from a few millimeters to over 15 cm for a Megalodon tooth. The root is typically darker and rougher than the shiny blade.
Where Found: Common in Cenozoic and late Mesozoic marine deposits. Phosphate mines (e.g., in Florida and Morocco) and coastal rivers or beaches that erode these formations are prime spots.
Age Range: Devonian to present, but most commonly found are from the Cretaceous onward.
Collecting Tips: Sift through gravel and sand in creeks and on beaches. Their dark color often stands out against lighter sand. "Shark Tooth Hill" in California is a famous Miocene locality.

11. Trilobites

What It Is: Trilobites were a highly successful group of extinct marine arthropods, distant relatives of modern insects and crustaceans. Their body was divided into three lobes, giving them their name.
How to identify It: Look for a segmented, oval-shaped body with a distinct head (cephalon), a middle section (thorax), and a tail (pygidium). The compound eyes are sometimes visible on the head. They are often found enrolled, like a modern pill bug.
Where Found: Exclusively in Paleozoic marine rocks. Famous locations include the Wheeler Shale in Utah (Elrathia kingii), deposits in Morocco, and the Emu Bay Shale in Australia.
Age Range: Cambrian to Permian.
Collecting Tips: Finding a complete trilobite often requires carefully splitting layers of shale or limestone. Look for fragments first, as they are much more common than whole specimens.

Level 3: Requires Location and Luck

These fossils are still "common" in a geological sense but are either restricted to specific environments, are more fragile, or require more specialized searching techniques.

12. Plant Impressions

What It Is: These are carbon films or impressions of leaves, stems, and bark left in fine-grained sedimentary rock. The most famous examples are from the Carboniferous Period, when vast coal swamps covered much of the globe.
How to Identify It: Look for dark, carbonaceous films in the shape of ferns, scale trees (like Lepidodendron, which has a diamond-patterned bark), or seed ferns on the surfaces of shale, siltstone, or sandstone.
Where Found: Common in terrestrial deposits associated with coal seams, such as the Carboniferous coal measures of the eastern US and Europe. A famous locality is Mazon Creek, Illinois.
Age Range: Silurian to present.
Collecting Tips: Carefully split layers of shale and sandstone, especially those found near coal deposits. The impressions are very fragile.

13. Graptolites

What It Is: Graptolites were colonial marine animals that floated in the Paleozoic oceans. The colony, called a rhabdosome, was built from a protein called scleroprotein.
How to Identify It: They typically look like tiny, black, carbonaceous markings on the surface of dark shales, resembling pencil marks or miniature hacksaw blades. Some were branching, others were straight.
How to Identify It: Ordovician and Silurian deep-water black shales. Their rapid evolution and wide distribution make them excellent index fossils.
Age Range: Cambrian to Carboniferous.
Collecting Tips: You need to find the right kind of rock—dark, fine-grained shale. Split the rock along its bedding planes. A hand lens is essential to see the detailed structure.

14. Sea Urchin Spines and Plates (Echinoids)

What It Is: Sea urchins (echinoids) have a spherical or flattened shell called a test, made of interlocking calcite plates, and are covered in spines. Both the spines and the plates can fossilize.
How to Identify It: The test, when found whole, is a distinctive round or heart-shaped fossil with a five-fold symmetry pattern. More commonly, you'll find individual spines, which are small, cylindrical, and often have fine ridges, or hexagonal plates from a broken test.
Where Found: Common in Mesozoic and Cenozoic marine rocks, especially chalk and limestone formations.
Age Range: Ordovician to present.
Collecting Tips: Scan the surfaces of chalk or limestone exposures. The spines are small and easily overlooked.

15. Trace Fossils (Ichnofossils)

What It Is: Trace fossils are not remains of the organism itself, but rather evidence of its behavior. This includes tracks, trails, burrows, and borings.
How to Identify It: Identification depends on the type. Look for patterns that are clearly biological in origin and not just cracks in the rock. Examples include networks of burrows on a bedding plane, footprints with distinct toes, or winding trails left by a crawling invertebrate.
Where Found: Very common in many sedimentary environments, from deep sea muds to terrestrial sandstones.
Age Range: Precambrian to present.
Collecting Tips: Look at the surfaces of sedimentary layers (bedding planes), as this is where tracks and trails are preserved.

16. Coprolites (Fossilized Feces)

What It Is: Coprolites are fossilized dung. They provide direct evidence of an ancient animal's diet.
How to Identify It: They are often phosphatic and have a lumpy, oblong, or spiral shape. They can contain fragments of bone, scales, or plant matter. They are distinct from regular stones (geofacts) by their texture, shape, and inclusions.
Where Found: Can be found in marine or terrestrial deposits. Some shark-rich marine deposits are known for spiral-shaped coprolites.
Age Range: Paleozoic to present.
Collecting Tips: This is a tricky one for amateurs, as many "coprolites" are just suggestively shaped rocks. Look for tell-tale inclusions or a distinctive fine-grained, phosphatic texture.

Level 4: The Specialist's Finds

These fossils are common only in very specific, often rare, types of deposits. Finding them usually requires targeting a known locality.

17. Foraminifera (Forams)

What It Is: Foraminifera are single-celled protists that build a shell, or test, typically out of calcium carbonate. Most are microscopic, but some can be several centimeters across.
How to Identify It: You will need a microscope or a good hand lens. They look like tiny shells, often resembling miniature ammonites or grains of rice. Some limestones, like the Eocene limestones used to build the Egyptian pyramids, are composed almost entirely of them.
Where Found: Abundant in most marine sediments, especially chalk and fine-grained limestone.
Age Range: Cambrian to present.
Collecting Tips: Collect a sample of soft chalk or limestone, wash and sieve it in the lab, and examine the residue under a microscope.

18. Ostracods (Seed Shrimp)

What It Is: Ostracods are tiny crustaceans with a two-valved, bean-shaped carapace that encloses the body.
How to Identify It: Like forams, they are typically microscopic. They look like tiny beans or seeds, often less than 1 mm long.
Where Found: Found in both marine and freshwater deposits. They are very useful for biostratigraphy and paleoenvironmental reconstruction.
Age Range: Ordovician to present.
Collecting Tips: Use the same lab preparation techniques as for foraminifera.

19. Fish Scales

What It Is: The individual scales of bony fish can be preserved as fossils, even when the rest of the skeleton is not.
How to Identify It: Look for small, thin, often iridescent or shiny flakes on the surface of shales or sandstones. They can be circular (cycloid), diamond-shaped (ganoid), or comb-like (ctenoid).
Where Found: Common in lake, river, and marine deposits, especially in fine-grained shales like the Green River Formation in Wyoming.
Age Range: Silurian to present.
Collecting Tips: Scan bedding planes of shales under good light. The scales' shininess can make them stand out.

20. Insect Inclusions in Amber

What It Is: Amber is fossilized tree resin. Insects and other small organisms can become trapped in the sticky resin, which then hardens and preserves them in three-dimensional detail.
How to Identify It: Look for translucent to transparent, yellowish to reddish-brown fossil resin. The inclusions can be tiny, so a hand lens is essential.
Where Found: Found in specific deposits around the world. The most famous are the Cretaceous amber from Myanmar, the Eocene Baltic amber from Europe, and Miocene amber from the Dominican Republic.
Age Range: Carboniferous to present, but most insect-bearing amber is from the Cretaceous and Cenozoic.
Collecting Tips: This is not a fossil you stumble upon randomly. You must visit a known amber-producing region. Amber is very light and can be found washed up on beaches in the Baltic region.