A morphological feature of this medium trilobites is the very longished glabella. There are variations of glabellas shape from rectangularly to square (Suborder Leiostegiina), the dilation of the glabella towards anterior cephalon is also to be find, remembering of a pestle at dorsal view.

The CORYNEXOCHIDA are including the Suborders Corynexochina, Illaenina and Leisotegiina.

The image shows a representative of the Family Zacanthoididae, from Suborder Corynexochina.

Zacanthoides typicalis

(Source: Trilobites, Levi-Setti, 1993)

Lower Cambrian to Middle Devonian.

Cephalon

The big cephalon is normally developed semicircular and featuring genal spines (with exception of Suborder Illaenina). Prominent furrows are present as a rule. The sutures run ophistoparian (Gr.- cheek) i. e. the sutures are ending at the posterior cephalons edge. With few exceptions there are big eyes present. The hypostome is developed conterminant. During CORYNEXOCHIDAS  evolution, the hypostome was replaced by the impendent type.

Thorax

The thorax  as a rule consists from 7-8 segments within a spectrum of 2 -12 (at early species sometimes up to 18). Also as a rule the pleures are running out in pleural spines.

Pygidium

The pygidium varying species- specific regarding size and outline. Referring to this the relationship to the cephalon ranges from micropygous to macropygous in every appropriate relationships. Some species have spines.