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A Triassic Giant Amphipod from Nevada, USA

Journal of Crustacean Biology (Impact Factor: 1.19). 11/2013; 33(5). DOI: 10.1163/1937240X-00002192

ABSTRACT The fossil giant amphipod Rosagammarus minichiellus n. gen., n. sp. occurs in Triassic limestone (Luning Formation, west-central Nevada) in association with giant ichthyosaurs (Shonisaurus sp.) and the deep-water trace fossil Protopaleodictyon ichnosp. Fossil pereion and pereiopod morphology suggest affinities with the Acanthogammaridae, a freshwater amphipod family largely endemic to Lake Baikal. The large size (17 cm) of the Triassic amphipod shows that supergiant, deep marine amphipods comparable to modern Alicella gigantea Chevreux, 1899 were extant during the early Mesozoic. By analogy with Alicella gigantea, Rosagammarus minichiellus n. gen., n. sp. was a necrophagous, benthopelagic scavenger that fed on ichthyosaur and other sea floor carcasses. Rosagammarus minichiellus n. gen., n. sp. appears to be the oldest known fossil amphipod. This discovery extends the known geological range of Amphipoda by at least 170 million years.

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