The Late Jurassic–Early Cretaceous Slottsmøya Member of the Agardhfjellet Formation in central Sp... more The Late Jurassic–Early Cretaceous Slottsmøya Member of the Agardhfjellet Formation in central Spitsbergen has yielded two new species of asteroids and two species of ophiuroids, one of which is described as new. Polarasterias janusensis Rousseau & Gale gen. et sp. nov. is a forcipulatid neoasteroid with elongated arms, small disc and very broad ambulacral grooves with narrow adambulacrals. Savignaster septemtrionalis Rousseau & Gale sp. nov. is a pterasterid with well-developed interradial chevrons. The Spitsbergen specimens are the fi rst described articulated material of Savignaster and reveal the overall arrangement of the ambulacral groove ossicles. Ophiogaleus sp. is an ophiacanthid with relatively long jaws and lateral arm plates, with a coarsely reticulate outer surface. Here again, we report the fi rst articulated skeletons of this genus, providing unprecedented insights into the disc morphology. Ophioculina hoybergia Rousseau & Thuy gen. et sp. nov. is an ophiopyrgid with a well-developed arm comb and tentacle pores reduced to within-plate perforations starting at median arm segments. These new fi nds are important additions to the asterozoan fossil record with regard to their good degree of articulation and the high latitudinal position of the localities. They signifi cantly add to the set of exhaustively known fossil asterozoan taxa which play a key role in the phylogenetic analysis and reconstruction of evolutionary history.
The Colorado Creek section of Alaska is an important paleontological site first excavated and rep... more The Colorado Creek section of Alaska is an important paleontological site first excavated and reported on in the early 1980s and 1990s. The remains of two individual mammoths (the “Upper” and “Lower”), and elements of horse, bison, and caribou make this a unique faunal assemblage for a region in interior western Alaska, and the western edge of eastern Beringia. The mammoth remains were the only portions of the faunal assemblage radiocarbon dated in the 1980s. The Upper mammoth ages were widespread between 13,000 and 16,200 BP with the older dates being more accepted for the death of the individual. A single age on the Lower mammoth was produced at 22,880 14C yr BP. New accelerator mass spectrometry (AMS) dates generally confirm the accepted ages for the two mammoths and provide more precise ages of 16,200 ± 50 and 22,710 ± 90 14C yr BP for the Upper and Lower mammoths, respectively. AMS dates on caribou and horse are similar to ages on the Upper mammoth and show an overlap in their ecological ranges in interior western Alaska between 16,000 and 17,000 14C yr BP during the Late Glacial, similar to other areas of the state. The sole AMS date on bison produced an infinite 14C age (>43,500 14C yr BP), considerably older than the Upper and Lower mammoths’ remains, and indicates that older deposits are present at the site. A dearth of dated Quaternary paleontological specimens from western Alaska hinders our understanding of this region’s paleoecology. This study enhances our conception of the geographic and chronological spread of late Pleistocene large terrestrial mammals in Alaska and Beringia.
A well-preserved, low-diversity assemblage of fossil echinoderms from the early Middle Volgian in... more A well-preserved, low-diversity assemblage of fossil echinoderms from the early Middle Volgian in the Slottsmøya Member (Agardhfjellet Formation) has been discovered at Janusfjellet, Sassenfjorden area, central Spitsbergen. Five species are recognised: the isocrinid Chariocrinus sp., the pedinoid Hemipedina sp., the forcipulate asteroid Asteriidae sp., the ophiacanthid Ophiacanthidae sp. and the ophiurid Ophiurinae sp. A depositional environment model reconciling autecologic, taphonomic and sedimentary evidence is presented. The Janusfjellet Lagerstätte was formed by a single, rapid burial event during a storm, entombing together autochthonous asteroids and ophiurids, and allochthonous crinoids and echinoidson a dysoxic muddy sea-floor. Comparable echinoderm material from the Boreal Late Jurassic-Early Cretaceous is scarce, outdated and usually poorly described and illustrated. The scarcity of reported occurrences probably results from a collector bias for rare complete specimens and doesnot reflect the true echinoderm composition of Mesozoic high-latitude communities.
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