The earliest crustacean

Fossils of a new species obtained from 520 million year old Lower Cambrian rocks in Yunnan Province of China represent the earliest known true representatives of the Crustacea, the major group of arthropods that includes shrimps, lobsters, crabs and barnacles. The fossils are exceptionally well preserved, phosphatised in three-dimensions, complete with all their appendages, mouth-parts and even their eyes.

The species is tiny (the fossils are 1-2 millimetres long), but is represented by several growth stages. Crustaceans are present in the fossil record of the last 500 million years (back to the early Ordovician period) and very rare representatives are also known from the late Cambrian; the new find represents the first undoubted true crustacean from the early Cambrian. The limb morphology and other details of the new species are particularly similar to certain living groups of crustaceans such as cephalocarids, branchiopods and copepods. The study by researchers from Kunming, Leicester and Ulm was reported in the scientific journal Nature.

The new species and has been named Yicaris dianensis, eluding to the ethnic minority 'Yi' people present in the ancient kingdom of Dian in southern China where the fossils were found.

Professor David Siveter (University of Leicester) comments: 'This exciting palaeobiological find from a new site yielding exceptionally preserved fossils extends the stratigraphical record of crustaceans by more than 10 million years and has significance for the evolution of a major group of invertebrate animals.'

Its stratigraphical position provides substantial support to the idea that the main evolutionary event that gave rise to the arthropods was before the Cambrian. Small leaf-shaped structures occur on the outer limb base of the new species. Some authors consider that insect wings may have originated from similar structures, and the early Cambrian occurrence of this trait is of potential significance to the debate regarding the emergence of winged forms within the arthropods.