Dikelocephalus

Dikelocephalus is a genus of very large trilobites of up to 50 cm (20 in) long, that lived during the last 3 million years of the Cambrian (Sunwaptan). Their fossils are commonly found as disarticulated sclerites, in the upper Mississippi Valley (northeastern Iowa, southeastern Wisconsin, central to western Wisconsin) and in Canada (Alberta). The exoskeleton is rounded anteriorly, with the thorax and sides of the tailshield (or pygidium) slightly tapering to about ⅔× of the width across the base of the spines at the back of the headshield (or cephalon). At the side corners of the pygidium there may be triangular or hooked spines, pointing backwards, while between the spines the posterior margin is at a 30-75° angle with the lateral margin, gently convex or nearly straight. If pygidial spines are lacking, the margin is gradually rounded. The thorax has 12 segments.