FOSSIL DECAPOD CRUSTACEANS FROM THE ASTORIA FORMATION, WASHINGTON AND OREGON, U.S.A.: DEPOSITIONAL ENVIRONMENT IMPLICATIONS

Within the Newport Embayment, north and south of Yaquina Head, Oregon and in southwesternmost Washington state, thirteen new species of fossil decapod crustaceans have been recently described from the early to middle Miocene Astoria Formation. Fossil taxa, that have extant genera, depict an outer shelf, slope to plain depth. This is most evidenced by Paromolopsis piersoni n. sp. for which the only extant species is found in water depths from 295 m to 800 m. The fossil decapod crustaceans are usually well preserved, in many cases preserving the whole individuals, suggesting that there was little to no re-working after death. However, some exhibit post-depositional compression, evidenced by crushing of the dorsal carapace. The Astoria Formation has yielded a vast amount of fossil invertebrates, vertebrates, benthic foraminifera, and paleobotanical studies. This study not only provides further understanding of the evolution and distribution of decapod crustaceans, since the decapod fauna was studied independent of other faunas, it also adds another piece to the puzzle of this important Cenozoic formation, and more importantly, provides a means by which to compare and test patterns derived from molluscan and other faunal data.