714


Journal of Paleontology 92(4):713–733


Notophthalmus is poorly understood (Tihen, 1974; Naylor, 1979; Naylor and Fox, 1993). We identify Oregon’s fossil salamanders and examine


diagnostic skeletal characters for use in future phylogenetic analyses with extinct and extant North American salamandrids. Furthermore, we examine previously described fossil Taricha to determine whether these specimens are truly separate species, morphological variations within a single species, or if they represent a distinct genus from extant Pacific newts. We incor- porate new, previously undescribed specimens from various Oregon localities, along with the previously described speci- mens of T. oligocenica (Van Frank, 1955) and T. lindoei (Naylor, 1979). By pursuing these goals, we aim to answer the following questions: Are previous identifications and descrip- tions of the Oligocene fossil salamanders of Oregon adequate? How do these fossil salamanders relate to each other and to extant taxa? Can we gain any insight on the functional morphology of these newts? Finally, what can the paleoecology and distribution of these salamanders tell us about the distribu- tion and evolution of North American salamandrids?


Geologic setting


flora (34.85–32.8 Ma, 40Ar/39Ar dates), the early Oligocene Willamette flora (>30.64 Ma) is regarded as a critical indicator of climatic and vegetational shift across the Eocene–Oligocene transition (Retallack et al., 2004; Retallack, 2008). Thick lahars separate the dated ash from the lake beds of the Willamette flora, which is found between Spores Point tuff (31.3±0.6 Ma) and a Little Butte Volcanics tuff (30.6 ± 0.5 Ma; Myers et al., 2002; Retallack et al., 2004; McClaughry et al., 2010). The presence of thick andesitic debris-flow deposits suggests that the Willamette Flora (and the salamanders found within it) grew in an unstable environment adjacent to the increasingly active Western Cascades (Myers et al., 2002).


The southern Willamette Valley of Oregon is an alluvial basin bordered to the west by the Coast Range and to the east by the Western Cascades physiographic provinces. The basin is within the seismically active Puget–Willamette Lowland, and is situ- ated along the Cascadia subduction zone, where the Juan de Fuca plate has been subducting obliquely beneath the North American continental plate for much of the Cenozoic (McClaughry et al., 2010). This has resulted in a complicated forearc basin that has locally accumulated >7,000m of sedimentary and volcanic strata since the Paleocene (Retallack et al., 2004; McClaughry et al., 2010). The exposed rocks of the southern Willamette Valley include a diverse series of Paleogene marine sedimentary rocks with submarine lavas, Paleogene and Neogene terrestrial volcanic and sedimentary rocks and intrusions, and Quaternary surficial deposits (Retal- lack et al., 2004; McClaughry et al., 2010). The Mehama Formation of the Little Butte Volcanics, within which the Willamette and Lyons floras and all Western Oregon sala- mander fossils are preserved, is locally fossiliferous and repre- sents generally nondescript volcaniclastic sedimentary rocks that occur between the more distinctive features of the Little Butte Volcanics, such as mapped formations, marker beds, and volcanic centers (McClaughry et al., 2010). Along with the latest Eocene–earliest Oligocene Goshen


The dark gray to whitish-tan shales of the Mehama


Formation produce vertebrate specimens alongside numerous plant fossils. The presence of fossil Taricha agrees with the interpretation of the bedded shales as lake-margin deposits because this genus and the majority of this family feed in a freshwater environment; species of the genus Taricha prefer slow-moving or still water conditions (Wake and Özeti, 1969; Goin et al., 1978; Naylor, 1978a, 1978b, 1979; Retallack et al., 2004; Pollett et al., 2010). The Lyons flora, located in northwestern Oregon (southeast


of the town of Lyons, Oregon in the upper Thomas Creek area), is comprised of at least 24 plant taxa, 12 of which are identifi- able to species, while the other 12 are identifiable to genus. The rocks within which the leaves are preserved are composed of thinly laminated, tuffaceous material that has been silicified (Meyer, 1973). The stratification of the beds, abundance of fossil leaves, and the presence of a water plant (Nymphoides)in the fossil record suggest a shallow, quiet lacustrine environment


(Meyer, 1973). Retallack et al. (2004) have listed the Lyons flora among the forested Oligocene lacustrine floras. The Lyons flora has produced one definite salamander fossil, consisting


of part and counterpart, thus far. The John Day Formation is a complex series of strata with a


unique record of the long-term change (~20 Myr) of climate and biotas for the Pacific Northwest of North America (Fremd, 2010). The John Day Formation occurs within a number of basins in north-central and central Oregon, all within the Blue Mountains physiographic province (Fremd, 2010). The Big Basin Member of the lower John Day Formation


has distinctive red and tan claystones and contains excellent paleobotanical localities, which also produce the vast majority of caudate fossils from eastern Oregon. Radiometric dates indicate that the Big Basin Member preserves ~9Myr of deposition, from ~30–39Ma (Bestland and Retallack, 1994; Retallack et al., 2000). The Bridge Creek Flora type localities, which are near the Eocene-Oligocene boundary, are within the lacustrine shales of the Big Basin Member in the Painted Hills Unit of JohnDay FossilBedsNationalMonument,where fish and amphibian fossils have also been recovered (Meyer and Man- chester, 1997; Retallack et al., 2000; Dillhoff et al., 2009; Fremd, 2010). TheBridgeCreek flora’s age is well dated (Bestland and Retallack, 1994; Retallack et al., 2000) because it is sandwiched between the underlying Biotite Tuff (32.99±0.11Ma) and the overlying Overlook Tuff (32.66±0.03Ma). The fossil salamanders found in the Big Basin Member of


the John Day Formation have been unearthed at the Wheeler County High School exposures in the town of Fossil, Wheeler County, Oregon (Naylor, 1979). Plant, vertebrate, and inver- tebrate fossils preserved in these rocks are consistent with a cooler temperate climate than found in the Willamette flora, with fewer Eocene subtropical holdovers present (Meyer and Manchester, 1997; Retallack, 2008; Dillhoff et al., 2009). Salamander fossil-bearing beds are between 32.66Ma and 32.99Ma, placing these fossils solidly in the Orellan NALMA (Bestland and Retallack, 1994; Retallack et al., 2000; Albright et al., 2008). The smallest fossil salamander, and most recent acquisition


for this study, is from a new locality for vertebrate fossils. The area, near Gray Butte and the town of Prineville in central Oregon, has produced a limited fossil flora in the past. Based on


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