Wikipedia
Exigua
Exigua ( synonym: Brassicicephalus) is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from 501 to 497 million years ago during the Dresbachian faunal stage of the late Cambrian Period. Exigua is only known from the central part of the headshield or cranidium, so free cheeks (or librigenae), thorax and pygidium are unknown.