What does trilobite mean?
A trilobite is an extinct marine arthropod belonging to the class Trilobita. Its name reflects its most recognizable feature: the oval, segmented body was divided lengthwise into three longitudinal lobes, usually described as a central lobe flanked by two lateral lobes. Trilobites had armored exoskeletons and appear as common fossils, often as complete specimens, fragmented remains, or impressions in shale and limestone. They were widely distributed across ancient seas, with many species known from the Cambrian and Ordovician periods. The word is primarily used in paleontology, geology, natural-history museums, and the collecting hobby, where it may designate either the original animal or its fossilized remains. Outside specialist contexts, “trilobite” usually refers to a fossil or imprint. Trilobites are also notable for their long evolutionary history: they diversified during the Paleozoic era and disappeared entirely during the end-Permian extinction.
nounA trilobite is an extinct marine arthropod belonging to the class Trilobita, characterized by a broad, segmented body divided lengthwise into three lobes. The term is also commonly used for fossils and imprints of these animals.
- An extinct marine arthropod of the class Trilobita, having a segmented body divided lengthwise into three lobes; by extension, a fossil or imprint of such an arthropod.
"The museum displayed a beautifully preserved trilobite from the Devonian period."
"A large trilobite crawled across the seafloor while other marine animals hunted nearby."
"The fossil hunter discovered a complete trilobite embedded in a slab of shale."
The regular plural takes the suffix -s; the plural form refers to individual animals, fossils, or multiple specimens.
"The rocks contain numerous trilobites preserved in fine detail."
Trilobites ruled ancient seas for more than 250 million years—and vanished completely when the Permian extinction reshaped life on Earth.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does trilobite come from?
“Trilobite” combines the Greek-derived elements tri- meaning “three” and lobe, with the scientific suffix -ite. Its formation reflects the three-part division of the animal's body and follows the naming conventions used for fossils and taxonomic groups. The same roots appear in trilobate, trilobed, and trilobation, which describe forms or structures with three lobes.
Related word forms
How trilobite is actually used
Trilobite is a specialist term used in paleontology, geology, natural history, and collecting. In nontechnical contexts, it usually refers to a preserved fossil, imprint, or reconstruction rather than a living animal.