650
Journal of Paleontology 92(4):648–660
Figure 2. Lithological chart of the Glen Canyon Group in Utah and Arizona, USA, after Lucas et al. (1997), Mathis (2000), and Tanner and Lucas (2007).
Canyon sites was provided by Kirkland et al. (2014). A description of the Olsen Canyon section is provided in Supple- mental Data 1 of the present work.
Materials and methods
Samples collected at field sites (Fig. 4) were prepared at the Center for Integrative Geosciences of UConn, following the methodology of Antonietto et al. (2015, 2016). These samples were disaggregated with 50mL of 30% hydrogen peroxide (H2O2) in a 1 L tall glass beaker for ~ 48 h. After disaggregation, 25–50mL of absolute ethanol was added to each sample/H2O2 solution to interrupt the reaction. The resulting mixtures were individually washed with tap water into 250mL beakers and dried in a Thermo Fisher Isotemp® 630F furnace at 70ºC. Sediments were then separated using a set of 600, 200, 150 and 75 μmTylerTM sieves and the ostracodes were removed under an Olympus S230 stereoscopic microscope. Carapaces and valves of the identified species were pho-
tographed at the Old World Archaeobotany Laboratory of the University of Connecticut (UConn) Anthropology Department, Mansfield, USA. The scanning electron microscope (SEM) used was a JCM-6000PLUS NeoScope Benchtop, at low-vacuum mode and 10kV filament voltage, with no contrast-enhancing coating. Additional images of rock samples preserving ostra- code extinction levels were taken with a Macropod Pro 3D device coupled with Zerene Stacker ‘focus stacking’ software. Specimens were measured with Adobe Acrobat Pro software, by converting photographs into portable document format (PDF)
files and then using the software measuring tool. Abbreviations used in the text include: H=height; L=length,W = width.
Repositories and institutional abbreviations.—The materials photographed for this study (13 specimens of four species from two families) are housed in the collections of the Natural History Museum of Utah (NHMU) in Salt Lake City, USA, under the prefix UMNH (Utah Natural History Museum, former name of the NHMU), combined with the second prefix IP (invertebrate paleospecimens and localities) and numbers 5292 −5304. Samples collected at theSGDS are housed at theSGDS museum (Washington County, Utah), whereas those from Olsen and Potter canyons are currently at the Center for Integrative Geosciences, UConn. Other repositories include The Natural History Museum, London (BMNH).
Systematic paleontology
The classification above family level used herein follows Liebau (2005). The taxonomy of lower ranks is based on Molos- tovskaya (2000), although with reservations that will be further discussed in this paper. Morphological terminology is that used by Moore (1961). Four species recovered from the present samples are listed below. Two were left in open nomenclature, Whipplella? sp. 1 and W.? sp. 2, whereas the other two were identified as Suchonellina globosa (Jones, 1862) and S. stricta (Jones, 1894). These species were previously assigned to the genus Darwinula, but are herein transferred to Suchonellina Spizharsky, 1937. The type species of Suchonellina, S. inornata Molostovskaya, 1980, is properly established.
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