Knowra Trilobite Trilobite Trilobites were marine arthropods with a segmented exoskeleton divided lengthwise into three lobes. They lived from the Cambrian Period until the end-Permian extinction.
Arthropod : An invertebrate animal with a segmented body, jointed appendages, and an external skeleton. Trilobites belong to this animal phylum and share its segmented, jointed body plan.
Enrollment (trilobite posture) : The curling of a trilobite's body, bringing its head and tail regions together. Some species enrolled to shield their softer underside.
Cambrian explosion : A geological interval of rapid diversification among animal groups, beginning about 539 million years ago. Trilobites appear early in the fossil record during this major expansion of animal diversity.
Biostratigraphy : The dating and correlation of rock layers using their fossil content. Rapidly changing trilobite species help correlate Cambrian and Ordovician strata.
Chelicerata : An arthropod subphylum that includes spiders, scorpions, horseshoe crabs, and extinct relatives. Chelicerates are another major arthropod lineage, distinct from trilobites.
Exoskeleton : A rigid external structure that supports and protects an animal's body. A mineralized exoskeleton preserved most trilobite fossils and recorded growth through molts.
Trilobite feeding strategies : The varied ways trilobites obtained food, including deposit feeding, scavenging, and predation. Mouthparts, trace fossils, and body form suggest diverse diets and feeding modes.
Burgess Shale : A fossil deposit in British Columbia preserving exceptional Cambrian marine animals. Its trilobites and other fossils preserve details rarely captured in ordinary deposits.
Index fossil : A fossil used to identify and correlate rock layers of a particular age. Some trilobite species had limited time ranges and broad geographic distributions.
Eurypterid : An extinct group of aquatic chelicerates commonly called sea scorpions. Eurypterids were marine arthropods that coexisted with trilobites but had a different body plan.
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