Calodiscidae

The Calodiscidae Kobayashi, 1943 are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian. They are small or very small, and have a thorax of two or three segments. The Calodiscidae includes five genera.

Taxonomy

The probable ancestors of the Calodiscidae are among the Tsunyidiscidae. The Calodiscidae had no descendants.

Description

Like all Agnostida, the Calodiscidae are diminutive and the headshield and tailshield are of approximately the same size and outline. The central raised area of the cephalon has parallel sides or tapers forward, the front being rounded and expanded, and may be divided by transverse glabellar furrows. The occipital ring is defined by a complete transverse furrow and is neither spinose nor expanded. When present, the eye lobes are short and prominent. The thorax is only known in Chelediscus and Sinodiscus. The pygidium has a wide, tapering axis of less than six segments.