Cephalon (arthropod head)

In chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace.

In relation with the arthropod head problem, phylogeny studies show that members of the Malacostraca class of crustaceans have five segments in the cephalon, when not fused with the thorax to form a cephalothorax.

In the Late Precambrian or Lower Cambrian Proarticulata species Praecambridium sigillum, that superficially resembles a trilobite, the term is also used to describe the anterior part of the animal.

[2] The size of the glabella and the lateral fringe of the cephalon, together with hypostome variation, have been linked to different lifestyles, diets and specific ecological niches.

[3] The lateral fringe of the cephalon is greatly exaggerated in the Harpetida, in other species a bulge in the pre-glabellar area is preserved that suggests a brood pouch.