Ovatoryctocara


Ovatoryctocara is a genus of small corynexochid trilobites from the Cambrian, that lived in what now are Siberia, China, Greenland and Canada. Ovatoryctocara can be recognised by the combination of the following characters: the central raised area of the cephalon is approximately cylindrical and has two rows of four triangular or round pits. The thorax only has 5 or 6 segments. The tailshield has an axis of 6 to 12 rings, the pleural furrows are well developed and the border is absent or narrow as a hair.

Etymology

The name of the genus is derived from its type Oryctocara ovata. Ovata refers to its oval overall shape, the Ancient Greek ὀρύκτης means "digger", and the Latin cara is a word for "head" or "face".

Biostratographic significance

The species of the genus Ovatoryctocara occur near the lower limit of the Middle Cambrian in Siberia. The first appearance datum of Ovatoryctocara granulata was proposed as the defining marker for the lower limit of the Wuliuan. O. granulata is moderately widespread.

Distribution

Very small to small trilobite of more or less oval overall shape. The head shield has natural fracture lines that end at the tip of the genal angle or the rear margin. The central area of the cephalon is cylindrical or slightly expanded midlength and/or at the frontal lobe. The furrows that show the segmented origin, are most distinct in the form of four sets of rounded or triangular pits, sometimes with a shallow depression between them at the midline. The glabella is almost touching the front of the cephalon. Narrow eye ridges emerge from the back of the frontal lobe outward and slightly backward. Thorax of 5 or 6 segments. Pygidium approximately the same size or larger than the cephalon, with an axis of 6 to 12 rings, and clear pleural furrows. The border is lacking or hair thin. The surface may be smooth or has granules.