Elliptocephala
Elliptocephala is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from the later part of the Tommotian (upper "Schmidtiellus mickwitzi"-zone) to the upper Botomian (early middle "Olenellus"-zone). "Elliptocephala" can easily be confused with "Ellipsocephalus", a trilobite genus of the Ptychopariida order. Etymology. The species "E. walcotti" was named in honor of Charles Doolittle Walcott, a renowned early paleontologist, that described many trilobite species. Taxonomy. Relations within "Elliptocephala". According to Lieberman "E. sequomalus" is an early species, close to the common ancestor of the genus. The rest of the species fall into  two distinct groups. The first consists of the closely related "E. bicensis" and "E. asaphoides", with "E. walcotti" and twin species "E. praenuntius" slightly less close and "E. mediocris" near the basis of this group. The second group consisting of the closely related "E. mirabilis" and "E. lundgreni", with "E. logani" and "E. parvifrons" slightly further removed, followed by "E. paraoculus", and "E. laxocules" near the basis of this second group. Relationship within the Olenelloidea. "Elliptocephala" is the sistergroup of the clade comprising "Wanneria walcottana", the Holmiidae, "Fritzolenellus", "Mummaspis", "Laudonia", the Biceratopsinae and the Bristoliinae. Including "Elliptocephala", this clade is  the sistergroup of the Olenellidae. Description. As with most early trilobites, "Elliptocephala" has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, "Elliptocephala" lacks dorsal sutures. Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon, that is called glabella. The head shield (or cephalon) of "Ellipticephala" carries backwards directed spines at the corner between the halfcircle shaped frontal and side margin and the backmargin that is roughly perpendicular to the  midline. The frontal lobe of the glabella (L4) is roughly 1½× the length of the backward ring-shaped lobe (also called occipital ring or L0) and the most backward set of side lobes (L1) taken together, measured along the midline (or sagittally). L4 is also much wider than L0. Side lobes L2 and L3 do not merge with each other. The line between the backward tip of eye lobe and the junction of the back margin of lobe with glabella with the midline is 10-20°. L3 touches the eye ridge. L0 carries a node at the midline. The  third thorax segment from the front (T3) is not larger than the neighboring segments and does not carry larger spines. Thoracic pleural furrows extend onto spines. Long backward directed spine on the midline of T15, and this spine is broad at its base.