Kingdom Animalia Class Trilobita Suborder Eodiscina Rank Family | Phylum Arthropoda Order Agnostida Superfamily Eodiscoidea | |
Similar Eodiscina, Agnostina, Agnostidae | ||
The Calodiscidae are a family of trilobites belonging to the order Agnostida that lived during the Lower Cambrian (Botomian and Toyonian). They are small or very small, and have a thorax of two or three segments. The Hebediscidae include five genera (see box).
Contents
Taxonomy
The probable ancestors of the Calodiscidae are among the Tsunydiscidae. The Calodiscidae had no descendants.
Description
Like all Agnostida, the Calodiscidae are diminutive and the headshield (or cephalon) and tailshield (or pygidium) are of approximately the same size (or isopygous) and outline. The central raised area of the cephalon (or glabella) 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 not spinose nor expanded. When present, the eye lobes are short and prominent. The thorax is only known in Chelediscus (two segments) and Sinodiscus (three segments). The pygidium has a wide, tapering axis of less than six segments.