Pakucaris

Extinct genus of bivalved arthropod

Pakucaris is an extinct genus of bivalved arthropod known from a single species, Pakucaris apatis, found in the Marble Canyon locality of the Burgess Shale in British Columbia, Canada. It is thought to be a member of Hymenocarina. Unlike other members of that group, the posterior segments are covered with a separate pygidium shield, covergent on other arthropods like artiopods. Specimens range in length from 11.65 to 26.6 millimetres. The main bivalved carapace covers around 80% of the body, with the pygidium covering the remaining 20%. The head has a forward and downward facing pair of moderately sized eyes on short stalks, along with three pairs of cephalic appendages. The thorax has either 30-35 or 70-80 segments, depending on the specimen, while the pygidium has either 11-13 or 20 segments. The segments of the thorax and pygidium have pairs of thin filamentous limbs divided into 20/21 podomeres, with paddle-like exopods. It was probably nektobenthic, and its ecology was likely that of a selective suspension feeder, using its limbs to scrape and/or suspend food particles from the sea floor, before using its limbs to capture and transfer them to the mouth.

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