Terrific Trilobites
Trilobita is one of the most recognizable, and successful, groups of animals of all time. UAlberta has over 15000 trilobite fossils. "Terrific Trilobites" compliments the trilobite displays in the UAlberta Paleontology Museum. By exploring the museum virtual tour and this website, you can experience the entire exhibit from wherever you are. See the built-in displays, view over 100 images of trilobites from infancy to adulthood, watch trilobites grow, engage with 3D models of trilobites, and challenge yourself to solve 3D trilobite puzzles. Enjoy!
Fantastic forms
The images below demonstrate the breadth of form of trilobites. The head end of the trilobite is to the left. The size and shape of the parts of the exoskeleton varies greatly. Some lack ornamentation, whereas others are covered in spines, or bumps. One hypothesis is that trilobites developed spines in response to the evolution of jawed fishes. The Huntoniatonia fossil shows spots of white which may be the actual colour pattern on the exoskeleton. The captions include the species name, the geologic time period during which the species lived, the country the fossil was found in, and the length of the trilobite from the tip of the head region to the tip of the tail, not including the tail spines.
Acanthopyge, Devonian, Morocco, 2.2 cm
What are trilobites?
Trilobita is an extinct group of three-lobed arthropods that lived in ancient oceans. Arthropoda is the group of animals with jointed and segmented exoskeletons made of the organic material chitin. Insects, shrimps, crabs, spiders, and millipedes are examples of arthropods.
Trilobites had an exoskeleton made of the mineral calcite underlain with chitin. Trilobites were the first group of animals to have compound eyes, the same kind of eyes that crustaceans and insects have. A trilobite’s body parts were underneath the exoskeleton, like a horseshoe crab.
Trilobites had multiple lifestyles and feeding habits Some adults lived on the sea floor whereas others had adaptations that helped them swim in the water column. Trilobites would either hunt and eat worms or other invertebrates, scavenge and eat bits of edible material on the ocean floor, or filter food from the water. Paleontologists interpret what trilobites ate by looking at parts of the exoskeleton that could be used for feeding.
How did trilobites grow?
Trilobites reproduced through sexual reproduction. It is thought that trilobites had at least four different lifecycles. One involved laying eggs in a nest on the seafood; the larval stages and the adult stage live on the sea floor. Another supposed eggs were spawned into the water column; there were early swimming larval stages and bottom living later larvae and adults. Fossil evidence also suggests that eggs were sometimes brooded externally underneath the cephalon, like in horseshoe crabs. Early trilobite life stages lacking a calcified exoskeleton haven't been found in the fossil record yet.
Like other arthropods, trilobites went through several developmental stages until maturity. The first mature exoskeleton was small enough to fit on the end of a piece of spaghetti. As mature bodies aged, there would come a time when the growing soft parts would no longer fit within the exoskeleton. The too tight exoskeleton was shed, and a new one formed to cover the soft parts. The exoskeleton would crack along suture lines between parts of the cephalon so that the soft bodied animal could escape the old exoskeleton. Most trilobite fossils are moulted exoskeletons, most of which are incomplete.
Complete trilobite exoskeleton. Not a moult.
Trilobite moult. Cephalon parts separated along suture lines.
When did trilobites live?
Trilobites lived in the oceans from 521 million years ago to 250 million years ago. Trilobites were around more than 100 million years longer than the dinosaurs which lived from about 245 million years ago to 66 million years ago.
Why did trilobites go extinct?
The diversity and geographic range of Trilobita was impacted by five mass extinction events. The most significant occurring 375 million years ago. After which, only one group of trilobites remained. Trilobites went extinct by 250 million years ago during the biggest die off in Earth’s history when 96% of the species on the planet were lost. It is no wonder this event is called "The Great Dying".
Mass extinctions are caused by dramatic and persistent changes to the environment. Volcanism, shifts in tectonic plate positions, ocean circulation changes, atmospheric changes, climate change, meteorite impacts, new predators or competitors, may all lead to conditions responsible for extinction events. All of the processes listed may be associated with different extinctions that impacted trilobites.
How many trilobites existed?
Over 21000 species of trilobite have been described. Most trilobite fossils are moulted exoskeletons shed when the trilobite was growing. It is impossible to estimate the number of individuals of any species that has lived because the fossil record preserves a tiny fraction of those that lived in the past. Plus, only a fraction of the fossil record is accessible to paleontologists to study.
At times, trilobites lived in oceans around all ancient continents. The fossil record suggests that trilobites reached the peak number of species alive at one time, and abundance, by 485 million years ago. Long lived, diverse, everywhere. There is no doubt that trilobites were one of the most successful groups of animals of all time.
Why does UAlberta have so many trilobite fossils?
UAlberta is home to over 15000 trilobites in its museum, research, and teaching collections. Most of the trilobites were collected by UAlberta researchers and students. Over 150 species of trilobites have been named by the research group led by Professor Emeritus Dr. Brian Chatterton, who worked in the department from 1970 – 2010. The UAlberta Museums Invertebrate Paleontology Collection has the finest collection of Devonian trilobites from Morocco in the world.
More fantastic fossils
UAlberta is home to over 2 million fossils of invertebrate animals (those without a backbone). Part of the UAlberta Museums Invertebrate Paleontology Collection may be seen on display in the UAlberta Paleontology Museum or in the UAlberta Paleontology Museum Virtual Tour.