''Plenocaris plena'' is a

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

arthropod with a bivalved carapace, and is known from the

Burgess shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...

and

Chengjiang Chengjiang (; earlier Tchinkiang) is a city located in Yuxi, Yunnan Province, China, just north of Fuxian Lake. Administrative divisions Chengjiang City has 2 subdistricts and 4 townships. ;2 subdistricts * Fenglu () * Longjie () ;4 towns ...

. Originally described as a species of '' Yohoia'' by Walcott in 1912, it was placed into its own genus in 1974. The head has a pair of simple antennae. The body has 13

tergites A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ...

, with trunk tergites 2 to 4 having pairs of elongate and

uniramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plur ...

appendages, with appendages absent from the other body segments. The body terminates with paired tail flukes. unlike waptiids, but similar to ''

Synophalos ''Synophalos'' is an extinct genus of bivalved arthropod. The genus contains a single species, ''Synophalos xynos'', found in the Cambrian Stage 3-aged Chengjiang biota of Yunnan Yunnan , () is a landlocked Provinces of China, province ...

,'' the tail flukes lack segmentation. 106 specimens of ''Plenocaris'' are known from the Greater

Phyllopod bed The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil '' Lagerstätte''. It was quarried by Charles Walcott from 1911–1917 (and later named Walcott Quarry), and was ...

, where they comprise 0.20% of the community. It has been suggested to be a member of

Hymenocarina Hymenocarina is an order of extinct arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feed ...

, which contains numerous other Cambrian bivalved arthropods.

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of ''Plenocaris'' fossil Burgess Shale fossils Prehistoric arthropod genera Cambrian genus extinctions {{paleo-arthropod-stub Hymenocarina

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Further reading

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