amberSticky tree resin turned hard over millions of years. Insects and bits of plants caught in the resin are sometimes found inside. People have prized amber since the New Stone Age.
castA stone replica made when a mold fills in. It has the shape of the shell or bone that once lay there. Preparators make casts too, as copies of a fossil.
excavateTo free a fossil from the ground, bit by bit. Fossils come to light when the rock around them wears away. Paleontologists then dig them out with care and clean them.
extinctWiped out entirely, as trilobites and ammonites were. More than 99 percent of all the species that ever lived are extinct, over five billion of them.
fossilWhat is left of an ancient living thing, or its mark. The word comes from the Latin fossilis, obtained by digging. Bones, shells, stone imprints and insects in amber are all fossils.
moldAn empty space in rock shaped like a vanished shell. It forms when a buried shell or bone dissolves away. Snail shells are often found as molds because they dissolve easily.
Show all 36 terms (30 more)
Fossil basics, continued
paleontologistA fossil expert, at work at a dig or in a lab. Paleontologists use fossils to classify living things and to measure geologic time. Mary Anning, who collected on the south coast of England, was a famous early one.
paleontologyThe science that pieces together ancient life. Fossils are its main evidence. Georges Cuvier's studies of 1796 are counted as its start as a science.
prehistoricBelonging to the ages before written records. The earliest known writing is about 5,200 years old. The fossils that paleontologists study are far older.
sedimentThe mud, sand or ash that buries a dead animal. Quick burial keeps the remains from being scattered. More layers pile up on top, and in time the sediment turns to rock.
sedimentary rockThe kind of rock in which nearly all fossils lie. Sandstone, chalk and limestone are three kinds. It builds up layer by layer on the beds of seas, lakes and rivers.
skeletonAn animal's hard frame, left when soft parts rot. Bones, teeth and shells last long enough to be buried. Muscle and other soft parts usually rot away first.
Fossils and what they show 12
body fossilA fossil of the creature itself: bone, shell or leaf. Teeth, shells, bones and leaf imprints are all body fossils.
bone bedA rock layer crowded with fossil bones. The name is informal. The Ludlow Bone Bed of England is a thin layer made almost wholly of the spines, teeth and scales of fish.
carbon filmA thin dark outline left on rock by a leaf or fish. Heat and pressure drive off everything but a film of carbon. Leaves and animals with no hard skeleton are often preserved this way.
concretionA hard lump of mineral that grew inside sediment. It usually forms around a core such as a leaf, a tooth or a piece of shell. Odd-shaped ones have been taken for dinosaur eggs.
evolutionHow species change as traits are passed down. Fossils are important evidence for it, since rocks of different ages hold different kinds of fossils.
fossil recordAll the fossils known, taken as one history of life. It is incomplete, since most living things leave no fossil. It still gives a good picture of how life branched out over time.
index fossilA fossil found in rocks of only one short age. A good one lived for a short, well-known span of time. Ammonites are a classic example: layers far apart that hold the same kind are the same age.
living fossilA creature little changed from its ancient kin. Coelacanths were known only as fossils, the youngest 66 million years old, until a living one was found in 1938. Scientists now avoid the term.
permafrostEver-frozen ground, a natural freezer for mammoths. Frozen woolly mammoths have been found in Siberia and North America, some with their stomach contents.
permineralizationMinerals filling the tiny holes in bone or wood. Water carrying dissolved minerals seeps into the pores and cells of the buried remains. Petrified wood forms this way.
trace fossilA fossil of something an animal did or left behind. Footprints, burrows, feeding marks and fossil droppings, called coprolites, are trace fossils. They record how an animal behaved.
transitional fossilA fossil with traits of both an old group and a new. Archaeopteryx is the classic case. It had feathers and wings, and also sharp teeth, clawed fingers and a long bony tail.
Digs, labs and deep time 12
comparative anatomyComparing the body parts of different species. It began in classical times. Its findings help to classify animals and are evidence that they share ancestors.
dinosaurA reptile of the group that birds descend from. Dinosaurs first appeared in the Triassic period. Birds are living dinosaurs. The rest were gone by 66 million years ago.
fieldworkThe part of the job done outdoors, at the dig. Along with laboratory preparation and comparative anatomy, it is one of the classic parts of the science.
holotypeThe one specimen a species name is tied to. A better specimen found later does not replace it. The holotype of one dinosaur is a single leg bone kept in a London museum.
ice ageA time when glaciers reached far beyond the poles. The latest glacial period came to an end some 11,700 years ago. Woolly mammoths lived through it.
ichnologyThe study of tracks, burrows and other traces. It covers modern traces as well as fossil ones. A trace usually tells more about what its maker was doing than about what kind of animal it was.
mass extinctionThe dying out of many species in a short span. Counts of the major ones start at five. The one 66 million years ago killed off about three quarters of all plant and animal species.
matrixThe rock still clinging around a fossil. In other rocks the word means the fine material between the larger grains.
paleobotanyThe plant side of paleontology: leaves, wood, seeds. Fossil plants help rebuild ancient environments and climates. The study of fossil pollen and spores is a sister field, palynology.
preparatorThe lab worker who cleans and mends fossils. Preparation covers revealing, conserving and copying a fossil. Scientists and students do it too, but it is often left to professionals.
quarryA site where rock is cut away to reach fossil bones. In the Utah part of Dinosaur National Monument, a quarry wall on show to visitors still holds about 1,500 dinosaur bones.
rock hammerA pick-ended hammer for splitting rock open. It is also called a geologist's hammer. The head is flat at one end and a pick or a chisel at the other.
How this list was compiled: Term list chosen for this site on 2026-10-12. Each meaning is written in our own words and was checked that day against the article on the term in the English Wikipedia (https://en.wikipedia.org/), whose text is under the Creative Commons Attribution-ShareAlike license: Paleontology, Fossil, Mary Anning, Extinction, Amber, Prehistory, Sedimentary rock, Skeleton, Trace fossil, Biostratigraphy, Living fossil, Coelacanth, Transitional fossil, Archaeopteryx, Carbonaceous film (paleontology), Permineralization, Petrified wood, Bone bed, Concretion, Permafrost, Woolly mammoth, Evolution, Earliest known life forms, Quarry, Dinosaur National Monument, Field research, Matrix (geology), Fossil preparation, Fossil collecting, Geologist's hammer, Holotype, Comparative anatomy, Dinosaur, Extinction event, Cretaceous–Paleogene extinction event, Ice age, Holocene, Radiometric dating and Paleobotany. Excavate, fieldwork and prehistoric were also read in Wiktionary, the free dictionary (https://en.wiktionary.org/). How a fossil forms, molds and casts, body and trace fossils, permineralization, carbon films, amber, ammonites as guide fossils, fossils as evidence for evolution and the rocks fossils are found in were checked a second time against Fossils of the British Geological Survey (https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/fossils/) and against Fossils (https://www.bbc.co.uk/bitesize/articles/zt3ntrd) and How are fossils made? (https://www.bbc.co.uk/bitesize/articles/z2ym2p3) of BBC Bitesize. Fossil, mold, body fossil, trace fossil, coprolite, concretion, permafrost, matrix, stromatolite and sedimentary rock were read in the Glossary of Geologic Terms of the U.S. National Park Service (https://www.nps.gov/subjects/geology/gri-glossary-of-geologic-terms.htm), and the quarry wall of about 1,500 bones on its page for the Quarry Exhibit Hall of Dinosaur National Monument (https://www.nps.gov/dino/planyourvisit/quarry-exhibit-hall.htm). Index fossils are from Fossils, Rocks, and Time of the U.S. Geological Survey (https://pubs.usgs.gov/gip/fossils/). The fact after each meaning is from the same pages. Licence: own work
How it works
This vocabulary worksheet on paleontology prints fossil, excavate, sediment, cast, mold, extinct, amber and five more terms with their meanings mixed up on the right. The answer key is the last page. It has no fossil pictures to label.
Read the full guide
Fossils and what they show
Set opens on Fossil basics. The second set has body fossil, trace fossil, index fossil, living fossil, transitional fossil, carbon film, permineralization, bone bed, fossil record, concretion, permafrost and evolution.
Digs, labs and deep time
The third set has quarry, fieldwork, matrix, preparator, rock hammer, holotype, comparative anatomy, dinosaur, mass extinction, ice age, paleobotany and ichnology.
The geologic periods, from Cambrian to Quaternary, are on the fossil word search.
Questions and answers
Why are fossils found in sedimentary rock?
Because sedimentary rock is made of the very mud, sand or ash that buried the plant or animal. Fossils also turn up now and then in fine-grained rock that heat and pressure have changed only slightly.
What is the oldest fossil?
The oldest fossils known are stromatolites about 3.48 billion years old, found in Western Australia. A stromatolite is a layered structure built up by the growth of microbes.
How do paleontologists know how old a fossil is?
Mostly from the rock it lies in. The order of the layers and the index fossils found beside it place it in time, and radiometric dating of rocks turns that place into an age in years.
What tools do paleontologists use?
In hard rock, a geologist's hammer, cold chisels and a mallet split the layers apart. In soft sand or clay, a spade, a flat trowel and stiff brushes do the work, and sieves pick small fossils out of sand and gravel.