Burlingiidae

The Burlingiidae constitute a family of trilobites of uncertain affinity, that lived during the Middle to lowest Upper Cambrian (Acadoparadoxides pinus- to Agnostus pisiformis-zone). Burlingiids have a cosmopolitan distribution, can be found in deposits that originate from outside the continental shelves, and may have been planktonic. They are characterized by their oval shape, small size (less than 1 cm), proparian sutures, and non-functional articulations of the thorax. Uniquely the anterior borders of the pleura are raised, and there are between 8 and 15 thorax segments. Burlingiid trilobites have been found in Norway, Sweden, Northern Siberia, Eastern and South-eastern China, Australia (Tasmania), India (Himalayas) and the United Kingdom.

Taxonomy
The relationship of the Burlingiidae with other Cambrian trilobites is uncertain. The only other group this early in trilobite evolution that has proparian sutures are the Eodiscina, but this suborder has many characters that make it very unlikely to be the ancestors of the burlingiids. Early scholars tentatively positioned the burlingiids in the Ptychopariida. The burlingiids have many more characters in common with the Redlichiina however, such as faintly imprinted glabellar furrows.