How can we know Trilobites existed?

Hint: Trilobites are a gaggle of extinct marine arthropod arthropods that form the category Trilobita. Trilobites form one among the earliest-known groups of arthropods. When danger struck, some trilobites could ball themselves up like underwater pill bugs, with their buttocks flexed under their head.

Complete answer:
Trilobites are extinct marine arthropod arthropods that make up the class Trilobita. Trilobites are one of the earliest known arthropod groups. Trilobites first appeared in the fossil record at the end of the Atdabanian stage of the Early Cambrian period (521 million years ago), and they thrived throughout the lower Paleozoic before going into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out.

The last extant trilobites perished in a mass extinction at the end of the Permian period about 252 million years ago. Trilobites were among the most successful early animals, living in oceans for nearly 300 million years.

Trilobites were already highly diverse and geographically dispersed when they first appeared in the fossil record. Because trilobites had a diverse diversity and an easily fossilized exoskeleton, they left an extensive fossil record.Their fossils have made significant contributions to biostratigraphy, paleontology, evolutionary biology, and plate tectonics. Although several alternative taxonomies are found in the literature.

Trilobites are commonly placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha (equivalent to the Arachnida). They have recently been assigned to the Artiopoda, which includes many organisms that are morphologically similar to trilobites, but are largely unmineralised.

Note: Trilobites had three body lobes, two of which lay on all sides of a longitudinal axial lobe. The trilobite body was segmented and divided into three regions from head to tail: the cephalon, or head region, separated from the thorax, which was followed successively by the pygidium, or tail region.