Albright, L. B. III, ed., 2009. Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne. Museum of Northern Arizona Bulletin 65, Flagstaff, Arizona.

BIOSTRATIGRAPHY AND BIOCHRONOLOGY OF THE LATEST WASATCHIAN, BRIDGERIAN, AND UINTAN NORTH AMERICAN LAND MAMMAL “AGES”

GREGG F. GUNNELL1, PAUL C. MURPHEY2, RICHARD K. STUCKY3, K. E. BETH TOWNSEND4, PETER ROBINSON5, JOHN-PAUL ZONNEVELD6, AND WILLIAM S. BARTELS7

1Museum of Paleontology, University of Michigan, Ann Arbor, MI 48109; [email protected] 2Department of Paleontology, San Diego Natural History Museum, 1788 El Prado, Balboa Park San Diego, CA 92101; [email protected] 3Department of Earth Sciences, Denver Museum of Nature and Science, 2001 Colorado Boulevard, Denver, CO 80205; [email protected] 4Department of Anatomy, Arizona College of Osteopathic Medicine, Midwestern University, 19555 N. 59th Avenue, Glendale, AZ 85308; [email protected] 5Section of Paleontology, University of Colorado Museum of Natural History, Boulder, CO 80309; [email protected] 6Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E3; [email protected] 7Department of Geology, Albion College, Albion, MI 49224; [email protected]

ABSTRACT—Biochronological zones for the late Wasatchian, Bridgerian, and Uintan North American Land Mammal Ages are formally defined in this paper. These zones include Wasatchian biochron Wa7, Bridgerian biochrons Br1a, Br1b, Br2, and Br3, and Uintan biochrons Ui1a, Ui2, and Ui3. We argue for the existence of an additional early Uintan biochron between Ui1a and Ui2 and informally recognize Ui1b, although it is not possible to formally define it at this time. For each biochron we designate a stratotype section as well as referred sections where appropriate. In addition we present complete biostratigraphic range information for all known mammalian taxa from stratotype and referred sections and use these ranges to define biochrons based on index taxa and first and last appearance information. Biochron Wa7, all of the Bridgerian biochrons, and Ui1a have stratotype sections in Wyoming, either in the Wind River Basin (biochrons Wa7 and Br1a) or in the Green River Basin. The stratotype sections for Uintan biochrons Ui2 and Ui3 can be found in the Uinta Basin in Utah. Most referred sections can be found in these areas as well although there are isolated referred sections in Colorado (Sand Wash and Huerfano), Texas (basal Devil’s Graveyard Formation), and the Washakie Basin in Wyoming.

INTRODUCTION As now understood, the early and middle Eocene North American Land Mammal “Ages” consist of (from oldest to youngest) the Wasatchian, Bridgerian, Uintan, and Duchesnean as originally codified by Wood et al. (1941). In each case, these NALMAs derived their names from rock units that had been defined earlier (Hayden, 1869, 1878; Comstock, 1875) and each had been subdivided based on either lithostratigraphy (Veatch, 1907; Matthew, 1909; Kay, 1934; Wood, 1934; Van Houten, 1944;) or biostratigraphy (Granger, 1910, 1914; Kay, 1934; Wood, 1934). A detailed history of the development of North American Eocene lithostratigraphy and biostratigraphy can be found in Krishtalka et al. (1987) and Robinson et al. (2004). Most recently, Woodburne (2004) has recognized biochronological zones for all NALMAs. Only the lower and middle biochrons of the early Eocene Wasatchian Land Mammal “Age” have been formally defined with designated stratotype sections and refined biostratigraphic control (see Gingerich, 2001). In the pages that follow we formally define the latest Wasatchian biochron (Wa7), four Bridgerian biochrons (Br1a through Br3) and three of four of the Uintan biochrons (Ui1a, Ui2 and Ui3; for various reasons it is not yet possible to formally define Uintan biochron Ui1b), and offer a discussion of the transition between

279 MUSEUM OF NORTHERN ARIZONA BULLETIN 65 the Bridgerian and Uintan (an interval often referred to as the Shoshonian) which, to date, is not fully understood. It is hoped that a more formal definition of the Duchesnean will soon follow. Procedurally, we follow the general steps laid out in the North American Stratigraphic Code for designation and formalization of chronostratigraphic and geochronologic units (NACSN, 2005). Practically this protocol consists of designating stratotype sections for biostratigraphic units or intervals that are defined by the first and last occurrences of fossil vertebrates contained within the rocks representing those intervals – these units or intervals are essentially equivalent to chronozones as defined in article 75 of the NASC. Units of time, here termed biochrons and designated with a letter and number (e.g., Wa7), are defined based on these biostratigraphically constrained intervals and are essentially equivalent to geochronological units as defined in article 80 of the NACSN. All of the formally recognized biochrons that we discuss are based on biostratigraphic stratotype sections that occur in Wyoming or Utah (Fig. 1), although two referred sections are in northwestern (Sand Wash, see Stucky et al., 1996) and southern Colorado (Huerfano Park, see Robinson, 1966). The informally recognized biochron (Ui1b) is based on faunal assemblages from the Friars and Santiago formations in California, the Washakie Formation in Colorado, and the Adobe Town Member of the Washakie Formation in Wyoming. The stratotype sections that are the basis for Wasatchian biochron Wa7 and Bridgerian biochron Br1a are found near Shoshoni, Wyoming in the Wind River Basin while the stratotype sections for the remaining Bridgerian biochrons (Br1b through Br3) are found in southwestern Wyoming in the southern Green River Basin. These sections are located just north of the Uinta Mountains along the border between Wyoming and Utah. The transitional Bridgerian-Uintan Bridger E section

Figure 1. Map of southern and south-central Wyoming, northeastern Utah, and northwestern Colorado showing the general areas where late Wasatchian, Bridgerian, and Uintan stratotype and referred sections are located.

280 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

(biochron Ui1a) is also found in the southern Green River Basin (West and Hutchison, 1981; Murphey and Evanoff, 2007; Murphey and Walsh, 2007). The stratotype sections of Uintan biochrons Ui2 and Ui3 are found in the Uinta Basin in northeastern Utah, south of the city of Vernal. In addition to stratotype sections, in most cases several referred sections can be designated that represent other areas where biostratigraphically controlled faunal samples have been recovered.

MATERIALS AND METHODS A table of the stratigraphic ranges of all taxa from all sections is included as Appendix I. The summary tables found in each subsection below are based on the ranges listed in Appendix I and in most cases include data not only from the stratotype section but also from referred sections as well. In some cases (in particular those from Uintan biochrons Ui2 and Ui3), lists of faunal assemblages were restricted to the stratotype and referred section in the immediate regional area in the Uinta Basin. In the case of the earliest Uintan (Ui1a and Ui1b), it was necessary to include assemblages from other regions because of the compounding factors of provincial endemism and apparent temporal range differences. Additional and detailed analysis beyond the scope of this paper is required to grasp the intricacies of these continental scale distributions. The sections below were jointly written by all authors, but individual sections were supervised as follows: Wa7 (RKS), Br1a (RKS, GFG), Br1b (GFG, JPZ, WSB), Br2 (GFG, PR), Br3 (GFG, PR, PCM), Ui1a-b (PCM), Ui2-3 (KEBT, PCM).

WASATCHIAN BIOCHRONOLOGICAL ZONE WA7 The latest Wasatchian biochron, Wa7, has long been recognized as the Lostcabinian Land Mammal “Subage” (see Stucky, 1984c), which was defined as the fossiliferous beds in Western North America that include the paleothere, Lambdotherium popoagicum (Sinclair and Granger, 1911). The type area for Wa7 is the same as the type area for the Lost Cabin Member of the Wind River Formation at Buck Spring in the central part of the Wind River Basin (Stucky 1984a; 1984b). Although Osborn (1909) had earlier suggested that two land mammal faunas could be recognized in the upper part of the Wind River Formation, he later suggested that only one zone was present (Osborn, 1929). In 1984, Stucky recognized through stratigraphic studies that Lambdotherium popoagicum came from the lower beds within the Lost Cabin Member and that Eotitanops borealis (=Palaeosyops borealis) came from higher beds within the member and neither taxon overlapped in stratigraphic distribution in measured stratigraphic sequences. Osborn’s (1929) report that they did was in error. Furthermore, it became apparent that other taxa, including Hyrachyus and Trogosus, occurred with Eotitanops and were not found with the late Wasatchian Lambdotherium. As such, the fauna from the Lambdotherium interval zone does not contain any mammals of Bridgerian aspect at the generic level. There are no sites or stratigraphically documented intervals known in North America where Lambdotherium popoagicum and Eotitanops borealis overlap in distribution. Recently reported co- occurrences of these two taxa from the same horizon have now been recognized to be across a stratigraphic interval with occurrences separated by a fault (Gunnell and Yarborough, 2000; Gunnell, personal observation); based on misidentifications (Smith and Holroyd, 2003; Stucky personal observations); or based on samples collected over a broad stratigraphic range in the same area (reports in the Wind River Basin, Guthrie, 1971; Green River Basin, West, 1973). The reported Eotitanops specimen associated with a Wasatchian (or earlier) fauna from Mexico, was actually collected from a different area in Baja California (Novacek et al., 1991; Ferrusquia-Villafranca, personal communication). The two taxa have not been shown to co-occur in the same horizon or overlap in stratigraphic range. The Lambdotherium popoagicum Interval Zone of the Buck Spring section is chosen as the stratotype for the Wa7 biochron (Figs. 2, 3; Table 1) because of the ability to obtain a reasonable sample of the fauna and the prior documentation from this area (Stucky, 1984b). The entire rock unit is the type area as well for the Lost Cabin Member. Osborn (1929; Fig. 3) originally figured this area as typical of the Lost Cabin Member fauna but erred in stating that specimens of Eotitanops had been discovered here. In recent years (since 1975), no specimens of brontotheriids have been recovered from this interval despite their relatively large size and high abundance in upper Wind River Formation sediments elsewhere. Likewise specimens of other Br1a taxa such as Hyrachyus and Trogosus are unknown from 281 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Figure 2. Stratotype Section for Wa7 (Buck Spring) and Br1a (Sullivan Ranch). Numbers to the right are Carnegie Museum Fossil Localities shown in their stratigraphic position within the section (section compiled from Stucky, 1984b). 282 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Figure 3. Type area of the Lost Cabin Member of the Wind River Formation at Buck Spring and Stratotype Section for Wa7 (from Osborn, 1929, Plate VIB). The “Lambdotherium zone” is clearly marked in the photograph and represents a “dark red stratum” often referred to in prior references.

this site or other sites which contain the index taxon Lambdotherium. The fauna is of overall Wasatchian aspect (Table 1) with species of Phenacodus, Artimonius, Cantius, Shoshonius, Paramys, Hyracotherium, and Diacodexis being relatively common. Lambdotherium itself is relatively abundant from most Wa7 localities. Assemblages of Wa7 are found in a number of basins in the Western Interior of North America other than the Wind River Basin. These include the Green River Basin, Wyoming (LaBarge Fauna of the Wasatch Formation, Gazin, 1952, 1962; New Fork Tongue of the Wasatch Formation, Gazin, 1962 and West, 1973; and the Main Body of the Wasatch Formation, Gunnell and Bartels, 2001 and Zonneveld et al., 2000); the Bighorn Basin, Wyoming (Willwood Formation, Schankler, 1980), the Huerfano Basin, Colorado (Robinson, 1966) and the Piceance Creek Basin in Colorado (Debeque Formation, Kihm, 1984). The Red Creek and Deadman Butte sections of the Wind River Formation, Wind River Basin, and the Elk Creek Section of the Willwood Formation, Bighorn Basin, all in Wyoming, are considered as reference sections where detailed stratigraphic studies have been completed and formally published. The Lost Cabin Member of the Wind River Formation and New Fork Tongue of the Wasatch Formation both contain areas and localities where the Eotitanops borealis Interval Zone lies on top of the Lambdotherium interval zone.

BRIDGERIAN BIOCHRONOLOGICAL ZONE BR1A Bridgerian biochron Br1a (= Gardnerbuttean; occasionally informally referred to as Br0 in the past; Br0 is no longer recognized here) contains a true transitional faunal assemblage. Unlike later Bridgerian biochrons, Br1a retains a large number of Wasatchian holdover taxa including 60 species and 52 genera (Table 2). The three largest collections documenting biochron Br1a are those from the stratotype area of Davis Ranch in the Wind River Basin of west-central Wyoming, and the referred sections of the Upper Huerfano from south-central Colorado (Robinson, 1966) and South Pass from the northeastern Green River Basin in southern Wyoming (Gunnell and Bartels, 2001). Some locally endemic taxa exist in each of these assemblages but the majority of Br1a taxa are present in all assemblages. A more detailed analysis of regional biogeography is required to elucidate taxonomic distribution patterns between these three areas but for the purposes of this paper we will treat the Br1a fauna as a whole. Although Osborn (1909, fig. 5) had defined a biostratigraphic zone (his Bathyopsis Zone) within the Wind River Formation that contained Eotitanops borealis above the Lambdotherium zone, he later (1929) suggested that the occurrences of these two genera overlapped. Stucky (1984a,c) found that 283 MUSEUM OF NORTHERN ARIZONA BULLETIN 65 previous authors had considered all variegated sequences of the Wind River Formation as equivalent when, in fact, stratigraphic documentation demonstrated that they contained different faunas from site to site. In several stratigraphic sections (in particular the Red Creek and Deadman Butte sections of Stucky, 1984a-b), faunas containing Eotitanops borealis were mapped stratigraphically above those containing Lambdotherium popoagicum. This resulted in the recognition of the Eotitanops borealis Range Zone of the Lost Cabin Member of the Wind River Formation (Stucky, 1984a). To date, no unambiguous remains of Eotitanops have been found in the same horizon as Lambdotherium. Therefore the Eotitanops borealis Interval Zone of the Davis Ranch section is chosen as the stratotype for the Br1a biochron (Figs. 2, 4; Table 2). Eotitanops borealis is relatively common at those Wind River sites where it occurs and is often associated with Antiacodon, Seleneletes, Hyrachyus and Trogosus that are unknown from any Wa7 locality. Although Eotitanops is a relatively small brontotheriid compared to later occurring Bridgerian through Chadronian taxa in North America, E. borealis is one of the largest herbivores known from Br1a (second only to Trogosus). At the Davis Ranch Br1a stratotype, it is exceeded in size by the oxyaenid creodont Malfelis badwaterensis (Stucky and Hardy, 2007). Besides the Red Creek and Deadman Buttes sections of the Wind River Formation, Eotitanops has been recovered from beds stratigraphically above those containing Lambdotherium at one additional site in the Wind River Formation near Hiland, Wyoming (discovered during the 2007 field season, Hiland-Raptor Heights section). Other sites where Eotitanops is found above Lambdotherium include some in the Huerfano Formation of the Huerfano Basin, Colorado, in the New Fork Tongue of the Wasatch Formation of the Green River Basin, Wyoming, in the Debeque Formation of the Piceance Basin, Colorado, and in the Cathedral Bluffs Tongue of the Wasatch Formation in the northern Great Divide Basin near South Pass, Wyoming (Gunnell and Bartels, 2001; Zonneveld et al., 2000). Additional occurrences of Eotitanops include those from the Eureka Sound Formation on Ellesmere Island (Eberle, 2006), in Baja California, Mexico, and in other parts of the Western Interior (see Gunnell and Yarborough, 2000). Previous reports of Eotitanops from Big Piney, Wyoming (Smith and Holroyd, 2003) and in the Piceance Creek Basin of Colorado are likely misidentifications (see Kihm, 1984). Sites typical of Br1a usually contain holdover Wasatchian taxa such as Shoshonius, Coryphodon, and Didymictis. Importantly, these are among some of the richest localities known during the Paleogene of North America with alpha diversity of up to 80 mammalian species from a single fossil bed (Stucky 1990; Woodburne et al., in press). We here designate the Davis Ranch section (Figs. 2, 4; Table 2) in the Wind River Basin as the stratotype for Biochronological Zone Br1a. Davis Ranch has been selected

Figure 4. Stratotype section for Br1a (Eotitanops Interval Zone) at Davis Ranch, Lost Cabin Member, Wind River Formation. More than 30 specimens of Eotitanops have been found throughout the exposures but have primarily been found in the dark red bed in the middle of the exposures. Six foot human standing in the middle of the red bed at right center for scale. 284 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS predominantly because of the large number of specimens that have been collected there (over 5000 cataloged specimens).

BRIDGERIAN BIOCHRONOLOGICAL ZONE BR1B Matthew (1909) published the first useful subdivision of the Bridger Formation, recognizing five intervals that he designated as Bridger A through Bridger E. Each interval was defined lithologically by persistent, laterally extensive “white-layers” (limestones in most cases) that separate these intervals. The lowest horizon in the Bridger Formation recognized by Matthew was designated as Bridger A (= Lower Blacksforkian) which is now known to consist of 200 m (maximum thickness) of lacustrine and fluvial volcanic and terrigenous clastic sediments that are typified by their drab gray to green color and their relatively high ash content (as is typical of all Bridger Formation sediments). The base of Bridger A is defined by the contact between the Bridger Formation and the underlying Wasatch Formation, while the top is defined by an ostracodal limestone unit now referred to as the Lyman Limestone (Evanoff et al., 1998; also known as Marker Bed G of McGrew and Sullivan, 1970). The faunal assemblage found in sediments included in this section (Gunnell, 1998) is the basis for Bridgerian biochron Br1b (Gunnell and Bartels, 2001). The first and last appearances of Anaptomorphus westi are recorded within this interval therefore it is designated as the Anaptomorphus westi Interval Zone of the RC Bench section and is chosen as the stratotype for the Br1b biochron (Figs. 5, 6; Table 3). Nearly the full extent of the sediments containing the Br1b faunal assemblage can be found in the vicinity of Opal, Wyoming with sections along RC Bench (Fig. 5) and Opal Bench being the best sampled. We here designate the RC Bench section (Fig. 6) as the stratotype, because the section extends to the underlying Wasatch Formation and can be easily extended upward by laterally tracing continuous beds that reach the Lyman Limestone unit beneath Church Butte. Referred sections for Br1b include Opal Bench (McGrew and Sullivan, 1970) and the Big Island-Blue Rim Badlands west of Farson, Wyoming (Gunnell, 1998).

Figure 5. Stratotype section for Br1b (Anaptomorphus westi Interval Zone) at RC Bench, Bridger Formation, Lincoln County, Wyoming (photograph from McGrew and Sullivan, 1970, fig. 4).

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Figure 6. Stratotype section of Br1b indicating the relative stratigraphic positions of University of Michigan fossil localities (BB). Letters A through G represent marker units recognized and mapped by McGrew and Sullivan (1970). Lower 150 meters of section adapted from Zonneveld et al. (2000, 2003).

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Table 3 summarizes the faunal assemblage from biochron Br1b which includes seven index taxa, the most important and abundant being Anaptomorphus westi, Smilodectes mcgrewi, and Sciuravus eucristidens. The first appearances of the omomyid primates Anaptomorphus and Gazinius and the hyaenodontid creodonts Limnocyon and Thinocyon are important records defining Br1b. In terms of specific first appearances, the most wide-spread and important are Bathyopsis middleswarti, Microsyops elegans, Scenopagus curtidens, Thisbemys plicatus, Uintaparamys bridgerensis, and Washakius insignis. Additionally, Br1b faunal assemblages are typified by a high abundance and diversity of metacheiromyid palaeanodonts. The most important taxa making last appearances in Br1b include Notharctus robinsoni and Palaeosyops fontinalis. In general, the Br1b fauna is much more similar to later occurring Bridgerian faunas than it is to the Br1a fauna.

BRIDGERIAN BIOCHRONOLOGICAL ZONE BR2 Matthew’s (1909) Bridger B horizon (= Upper Blacksforkian) was defined as the sediments above his Bridger A beds and below the Sage Creek White Layer, a prominent, thick, and laterally persistent limestone that is easily recognizable across the southern Green River Basin. The entire thickness of Bridger B (maximum) is 235 m but it is difficult to find a single place where the entire section can be traced. We have chosen to designate the lower 110 m of the Bridger B section as the stratotype for two reasons (Fig. 7). First, this part of the section has produced a tremendous number of Br2 mammal specimens (samples of which can be found in nearly every major natural history collection in North America). Secondly, this part of the Bridger B section can easily be traced out in full beginning at the Lyman Limestone below Church Butte and finishing towards the southwest at the top of Grizzly Buttes. Therefore the Church Butte and Grizzly Butte sections combined can be used as the stratotype. Referred sections include the Sage Creek Type area on Sage Creek Mountain (Sinclair, 1906; Murphey, 2001), the Millersville section (Matthew, 1909), the Sugar White Layer section (Gazin, 1976), and the Owl Creek section in the southern Bighorn Basin in northwestern Wyoming (Bown, 1982). The upper part of Bridger B can be traced southward from the top of the section at Grizzly Buttes along the banks of Cottonwood and Sage Creeks to the type locality of the Sage Creek Limestone near the old Sage Creek Stage Station (Sinclair, 1906, plate viii; Fig. 8). The Br2 biochron actually extends above the Sage Creek Limestone, up to and including the Hickey Mountain Limestone (Murphey, 2001) some 70 m above the base of the Sage Creek Limestone (fossil samples are sparse in this part of the section but Br2 mammals do occur throughout). Br2 does not extend as high as the Burnt Fork Limestone (Matthew 1909; Murphey 2001). Characteristic Br2 species from the Hickey Mountain Limestone include Notharctus tenebrosus and N. pugnax. The Notharctus tenebrosus Interval Zone based on the Church Butte-Grizzly Butte combined section is chosen as the stratotype for the Br2 biochron (Figs. 7, 8). Table 4 summarizes the faunal assemblage from Bridgerian biochron Br2 (see also Robinson et al., 2004). In many ways, the fauna of Br2 is ‘the’ Bridgerian fauna that is most familiar to those who study middle Eocene North American vertebrates. There are a large number of index taxa representing Br2 (32) – some of the more abundant and important are Notharctus tenebrosus, Orohippus pumulis, Palaeosyops paludosus, Smilodectes gracilis, and Trogosus hyracoides. Species making their first appearances in Br2 include Antiacodon pygmaeus, Apatemys bellus, Hyopsodus paulus, Hyopsodus minusculus, Microsyops annectens, Pauromys perditus, Taxomys lucaris, and Thisbemys corrugatus. Species appearing for the last time in the record include Reithroparamys huerfanensis, Sciuravus bridgeri, Thisbemys plicatus, and Viverravus sicarius. One of the typical aspects of the Br2 fauna is the large number of range-through taxa that are very abundant in fossil samples. Some of these taxa include Hyrachyus modestus, Metacheiromys dasypus, Microparamys minutus, Microsyops elegans, Omomys carteri (extremely abundant), Paramys delicatior, Paramys delicatus, Scenopagus curtidens (along with two other slightly less abundant species of Scenopagus), Sciuravus nitidus, Sinopa rapax, Sinopa minor, Thinocyon velox, Uintaparamys bridgerensis and Washakius insignis. These taxa are present before and after Br2 but are never found with the same abundance that they are in Br2. Interestingly, uintatheres remain unknown from Br2 although they are present both before (Bathyopsis in Br1a and Br1b) and after (Uintatherium in Br3). 287 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Figure 7. Stratotype section of Br2 indicating the relative stratigraphic positions of University of Michigan fossil localities (BB, BRW). Stratigraphic positions of Sage Creek and Lyman limestones and the Church Butte Tuff taken from Evanoff et al. (1998), date of Church Butte Tuff from Murphey et al. (1999).

288 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Figure 8. Type section of Sage Creek White Layer (arrow points to base of Sage Creek Limestone; see Sinclair, 1906), Bridger Formation, Uinta County, Wyoming. The Sage Creek White Layer separates Matthew’s (1909) Bridger B (below) and Bridger C (above) although the Br2 biochron extends 70 m above the Sage Creek Limestone.

BRIDGERIAN BIOCHRONOLOGICAL ZONE BR3 Murphey and Evanoff (2007) provide a detailed discussion of the sediments and faunas of the Upper Bridger Formation, which includes those levels designated as Bridger C and Bridger D (= Twinbuttean) by Matthew (1909). In Matthew’s original subdivision of the Bridger Formation, the Bridger C beds were separated from those of Bridger B by the Sage Creek White Layer and from those of Bridger D by the Lonetree White Layer. This basic subdivision remains but there are now many finer subdivisions within all three of Matthew’s old Bridger B through D horizons. Matthew (1909) also recognized finer subdivisions within these basic units but often his subdivisions were defined by non- laterally extensive beds so were nearly impossible to trace away from their type section areas (see Murphey and Evanoff, 2007 for a review). The Notharctus robustior Interval Zone of the Twin Buttes Member reference section (Murphey and Evanoff, 2007) is designated as the stratotype for Bridgerian biochron Br3 (Figs. 9, 10; Table 5). This section is 307 m thick and was measured on both sides of the divide between Sage Creek and Hickey Mountains. The lithostratigraphic type section of the Twin Buttes Member of the Bridger Formation is located on Twin Buttes (approximately 30 km east of the stratotype area) but the referred section was

Figure 9. Looking southwest at exposures of the Twin Buttes Member of the Bridger Formation in the vicinity of the Lonetree Divide, Uinta County, Wyoming. Present are strata of middle and upper Bridger C; lower, middle and upper Bridger D; and the lowest redbed of the Turtle Bluff Member (Bridger E) caps Old Hat Mountain (prominent butte in upper right corner of photograph). The area shown includes a portion of the designated stratotype section of biochron Br3 (Twin Buttes Member stratigraphic reference section of Murphey and Evanoff, 2007). 289 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Figure 10. Stratotype Section for Br3. Numbers to the right are University of Colorado Museum (UCM) fossil localities shown in their stratigraphic position within the section (section compiled from Murphey and Evanoff, 2007). 290 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS chosen as the stratotype for Br3 because of the much more paleontologically productive sediments found there. There are 18 Index Taxa (see Table 5) recognized for Br3 including Hyrachyus princeps, Miacis sylvestris, Orohippus agilis, Palaeosyops robustus, Pantolestes natans, Telmatherium validus, and Thisbemys perditus. Eight genera make their first appearance in Br3 with Uintatherium, Telmatherium, and Tillomys being among the most important. Several genera also make their last appearances in Br3 including Anaptomorphus, Helaletes, Mesatirhinus, Metacheiromys, Sinopa, and Thinocyon. Very few species make first appearances in Br3, the exceptions being Notharctus robustior, Tillomys senex, and possibly Pontifactor bestiola (this taxon apparently has been found in Br2 as well although it is extremely rare). In contrast, 37 species make their last appearance in Br3 attesting to the beginning of the faunal turnover that led to Uintan aspect communities. Among the species disappearing by the end of Br3 are Antiacodon pygmaeus, Helaletes nanus, Hemiacodon gracilis (a very abundant Br3 omomyid primate), Hyopsodus minusculus, Hyopsodus paulus, Hyrachyus modestus, Limnocyon verus, all three Br3 species of Metacheiromys, Microsyops elegans, Paramys delicatus, Reithroparamys delicatissimus, Scenopagus curtidens, Sinopa minor, Sinopa rapax, Uintaparamys parvus, and Washakius insignis. Range-through taxa include some ancient holdovers such as the didelphid marsupials Copedelphys innominatum and Herpetotherium knighti, along with the persistent rodents Paramys delicatior and Microparamys minutus as well as a variety of other taxa that form part of the Bridgerian- Uintan transition faunal assemblage documented from Bridger E (Turtle Bluff Member).

BRIDGERIAN-UINTAN TRANSITION – BIOCHRONOLOGICAL ZONES UI1A-B The Uintan NALMA was an important time period that saw the evolution and radiation of selenodont artiodactyls, a family-level diversification of rodents, and a diversification of rhinoceratoid perissodactyls. The Bridgerian-Uintan faunal transition is associated with the decline in diversity of certain archaic mammalian groups including uintatheres, North American primates, hyopsodontid condylarths, and oxyaenid creodonts (Rasmussen et al., 1999; Woodburne, 2004). The faunal characterization, timing and stratigraphic correlation of the Bridgerian-Uintan boundary and the Bridgerian-Uintan transitional interval remains one of the most problematic issues of Eocene biochronology. This is primarily because few continuous fossiliferous sequences across this interval are known, and all are sparsely fossiliferous and/or poorly sampled. Nevertheless, the faunal assemblages from the Turtle Bluff Member of the Bridger Formation (Bridger E) and basal Devil’s Graveyard Formation in Texas (Robinson et al., 2004) clearly indicate that there is a transitional interval between Bridgerian biochron Br3 and early Uintan biochron Ui2, the latter known primarily from strata of Uinta Formation informal unit B in Utah and from well documented Uintan samples from southern California that contain few Bridgerian holdover taxa. In recognition of this fact, Robinson et al. (2004) erected an earliest Uintan biochron designated Ui1. In this section, existing data is evaluated and new faunal evidence is presented in support of this earliest Uintan biochron. Furthermore, additional evidence is presented that supports subdividing biochron Ui1 into Ui1a and Ui1b. A stratotype section for the Ui1a biochron is designated, located in the Turtle Bluff Member of the Bridger Formation.

Stratotype of the Ui1a Biochron The faunal assemblage from the uppermost member of the Bridger Formation, the Turtle Bluff Member (TBM), characterizes biochron Ui1a, and the Turtle Bluff Member lithologic sequence is designated as the stratotype for this biochron. The biostratigraphic designation for this interval is the Hemiacodon engardae Interval Zone, because Hemiacodon engardae (Murphey and Dunn, in press) is restricted to Ui1a (Table 6). Conformably overlying the upper Bridger D subdivision of the Twin Buttes Member of the Bridger Formation, the TBM represents the demonstrably oldest known transitional Uintan interval. Using this stratotype designation, and in light of new evidence presented here, the base of the TBM lithologic section is considered to represent the stratigraphic location of the Bridgerian-Uintan temporal boundary and the beginning of the Bridgerian-Uintan faunal transition in the Bridger Formation. The TBM was selected as stratotype because 1) it represents a (rare) conformable sequence containing a 291 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

NALMA transition zone; and 2) in addition to a large number of Bridgerian holdover taxa, seven Uintan first appearance or previously undescribed taxa reported by Evanoff et al. (1994) and Murphey and Walsh (2007) are known to occur within it. The TBM is stratigraphically equivalent to the Bridger E of Matthew (1909) and the Cedar Mountain Member of West and Hutchison (1981). It was renamed by Evanoff et al. (1998) and described in detail by Murphey (2001) and Murphey and Evanoff (2007). The modern day distribution of the TBM consists of erosional remnants located only in the southern part of Wyoming’s Green River Basin along the northern front of the Uinta Mountains. Specifically, these remnants are located on Hickey Mountain, Sage Creek Mountain, Cedar Mountain, Twin Buttes, and Black Mountain. The type section for the TBM was measured on the southwest flank of Cedar Mountain, Uinta County, Wyoming (Fig. 11). Here, the TBM attains a maximum thickness of 131 m, and consists of predominant variegated red, green and gray claystone and mudstone with lesser amounts of grayish-white tuffaceous sandstone and gray and brown limestone. The unit also contains a high gypsum content (Fig. 12). Matthew (1909) originally defined the base of the Bridger E as being about 75 feet (23 m) above the Upper White Layer at the level of the lowest banded tuff (redbed). This definition most likely refers to outcrops located on the southwest flank of Cedar Mountain where the type section designated by Murphey and Evanoff (2007) was measured, and where the TBM is best exposed. Matthew characterized the Bridger E as being composed of “soft banded tuffs and heavy volcanic ash layers nearly barren of fossils and with large gypsum content” (Matthew, 1909, p. 296). Subsequent to Matthew’s definition, we determined that the thickness of the interval between the Upper White Layer (now renamed the Upper White Limestone) and the base of the TBM, which comprises informal subdivision upper Bridger D is 46 m, and re-defined the base of the TBM using a laterally extensive limestone bed at the approximate level of the lowest TBM redbeds. This unit was named the Basal E Limestone (Murphey, 2001; Murphey and Evanoff, 2007).

Figure 11. Looking east at exposures of the Turtle Bluff Member (Bridger E) of the Bridger Formation exposed in the vicinity of the type section (Murphey and Evanoff, 2007), which was described on the southwest flank of Cedar Mountain, Uinta County, Wyoming. This section is designated as the stratotype section for biochron Ui1a.

Fauna of the Ui1a biochron Historically, the TBM has been variously regarded as Bridgerian or Uintan in age. Matthew was the first to comment on its age, saying that its few mammal fossils prove sufficiently that it “belongs to the Bridger Age” (Matthew, 1909, p. 296). Osborn (1929) correlated the Bridger E with the Washakie B and Uinta B, although he cited no supporting evidence. Simpson (1933), Wood et al. (1941), and Gazin (1976) also regarded the Bridger E as Uintan, although this was apparently not based on fossil evidence. 292 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

On the basis of eight isolated rodent teeth identified as Paramys cf. P. delicatior, a proximal radius identified as belonging to either the common Bridgerian brontothere Palaeosyops or Manteoceras, and the Bridgerian turtles Baptemys wyomingensis and Rhinoclemys terrestris, West and Hutchison (1981) concluded that the TBM was Bridgerian in age. Donna’s Locality (named after Donna Engard who discovered the site) is located approximately two meters above the base of the TBM. Like the basal Devil’s Graveyard assemblage in Texas, Donna’s Locality has yielded a mix of predominantly Bridgerian taxa with some Uintan aspect and range-through taxa. This assemblage was regarded as early Uintan by Evanoff et al. (1994), although only Triplopus was listed as a characteristic Uintan taxon by Robinson et al. (2004). Specifically, the assemblage from Donna’s Locality is characterized by numerous small-bodied Bridgerian aspect taxa, but also includes a derived species of Hemiacodon (H. engardae), the eomyid rodent Metanoiamys, the rhinoceratoid Triplopus cubitalis, and a new genus and species of oromerycid artiodactyl with similarities to Merycobunodon but so far represented by only a single upper molar. Subsequent to the discovery of Donna’s Locality (Evanoff et al., 1994) and the recognition of the Ui1 biochron (Robinson et al., 2004), additional discoveries in the TBM that are relevant to the Bridgerian-Uintan transition problem have been made. In order to further investigate this faunal transition, test the validity of the proposed Shoshonian (earliest Uintan) subage of Flynn (1986), and eventually develop a revised definition of the Bridgerian-Uintan boundary if appropriate, a project was initiated in 2006 to prospect and screen wash all levels of the TBM (Murphey and Walsh, 2007). Preliminary results of this project support the conclusions of Robinson et al. (2004) and provide data sufficient to formally erect an earliest Uintan biochron. Six productive localities have thus far been discovered at five distinct stratigraphic levels, and a total of approximately 2,000 kg of matrix has been screen washed using 30 mesh screens. Among these localities (see Fig. 12), SDSNH L. 5841 (“Sciuravus Surprise”) is one meter above the base of the TBM and has yielded a diverse Bridgerian aspect micromammal assemblage including Microparamys and Mysops, but also including Uintan aspect taxa such as Metanoiamys and a sespedectine insectivore. SDSNH L. 6084 (“Counterparts”) is 36 m above the base of the TBM, and has produced a jaw of the characteristic early Uintan rhinoceratoid Triplopus cubitalis. SDSNH L. 5787 (“Limelight”) is 80 m above the base of the TBM, and has produced an undetermined microchiropteran, as well as Pauromys, and Metanoiamys. SDSNH L. 5843 (“Red Lenses”) and L. 5844 (“Roll the Bones”) are both 105 m above the base of the TBM, which is the stratigraphically highest level in the TBM to yield identifiable mammal fossils. These two localities have thus far yielded approximately 450 mammal teeth. Collectively, the low-diversity assemblage from these two localities is strongly dominated by the small rodents Pauromys and Metanoiamys. However, the characteristic Uintan rodent Pareumys is also present, as is a single deciduous(?) premolar of a small species of Epihippus. Other Bridgerian-aspect and range-through taxa include Herpetotherium, Peradectes, Centetodon, microchiropteran indet., Omomys, Microparamys, Ischyromyoidea, Sciuravus, Hyopsodus (surprisingly rare), Brontotheriidae, and Uintatherium anceps. The Shoshonian is a controversial land mammal “Subage” that was proposed by Flynn (1986) for an earliest Uintan biochron defined as including an assemblage of small-bodied Bridgerian holdover taxa in combination with larger characteristic Uintan mammals including selenodont artiodactyls, the rhinoceros Amynodon and the horse Epihippus. It is important to note that the highly characteristic Uintan taxa that were used in part to define the Shoshonian (Protoreodon, Leptoreodon, Leptotragulus, Protylopus, and Amynodon) are all conspicuously absent from TBM localities thus far discovered. These taxa are all common in Uinta Formation informal unit B lithologies, as well as in the supposed Shoshonian localities of the Friars Formation of San Diego and other locations listed by Robinson et al. (2004). Results presented here indicate that in addition to a large number of Bridgerian holdover and range-through taxa, the base of the Uintan (and the Ui1a biochron) includes the first appearances of seven taxa: Triplopus cubitalis, Pareumys, Metanoiamys, Epihippus, Hemiacodon engardae, a new genus and species of oromerycid artiodactyl, and an undetermined sespedectine insectivore (Table 6 and Appendix 1). On the basis of its large number of Bridgerian holdover taxa (Herpetotherium, Scenopagus, Omomys, Notharctus, Microsyops annectens, Thisbemys, Mysops, Stylinodon, Hyrachyus, and Helohyus), 293 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Figure 12. Stratotype section of Ui1a indicating the relative stratigraphic positions of University of Colorado Museum (UCM) and San Diego Natural History Museum (SDNHM) fossil localities.

in combination with Uintan taxa (Triplopus, Ourayia, Macrotarsius, and Leptoreodon) and range-through taxa (Centetodon, Microparamys, and Uintatherium), the faunal assemblage from the lower part of Devil’s Graveyard Formation of Texas represents a Ui1a reference section. In concurrence with Robinson et al. (2004), the Ui1 (both Ui1a and Ui1b as described herein) is characterized by the presence of Bridgerian holdover taxa including Antiacodon, Hemiacodon, Notharctus, Washakius, and Hyrachyus (see Appendix 1). The TBM and basal Devil’s Graveyard assemblages clearly pre-date early Uintan assemblages in the Uinta Basin with significantly fewer Bridgerian holdover taxa and a diversity of selenodont artiodactyls and Amynodon. However, it should not be assumed that these two truly earliest Uintan (Ui1a) assemblages are strictly isochronous. Robinson et al. (2004) left the question of the validity of the Shoshonian as the earliest Uintan “Subage” (Flynn, 1986) open for further testing. If the apparent absence of undoubted highly selenodont artiodactyls such as Protoreodon and the rhinoceros Amynodon in the TBM should persist in spite of future collecting efforts, then the Shoshonian interval could be redefined as the earliest Uintan biochron that is older than the first appearances of hyper-typical Uintan taxa. Alternatively, and as is proposed here, if the original faunal characterization of the beginning of the Shoshonian is retained, then a truly earliest Uintan biochron, Ui1a, should be recognized for post-Bridgerian, pre-Shoshonian time. It is expected that continued screen washing of matrix from the TBM will continue to increase the taxonomic diversity and biostratigraphic precision of the Ui1a biochron. Additionally, intensive prospecting and systematic screen washing in potentially correlative sections such as Uinta A and B1 in

294 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS the Uinta Formation, the lower part of the Adobe Town Member of the Washakie Formation, and the Sand Wash Basin sequence of the Washakie Formation, will likely add information that will facilitate future correlation and comparisons with Ui1a and Ui1b faunal assemblages.

The Ui1b biochron Because high resolution lithostratigraphic data are presently unavailable for sequences that contain faunal assemblages attributable to biochron Ui1b, no stratotype section for this biochron is designated here. Sequences that are associated with relatively diverse and well-documented mammal assemblages (Table 7 and Appendix 1) and potential biochronological zone stratotypes for Ui1b include the Washakie Formation Sand Wash Basin sequence in northwestern Colorado (West and Dawson, 1975; Stucky, 1992; Stucky et al., 1996); the middle unit of the Adobe Town Member of the Washakie Formation in the Washakie Basin, Wyoming (McCarroll et al., 1996); and the Friars Formation (lower tongue, Conglomerate Tongue, and upper tongue) of San Diego, California (Poway fauna as redefined by Walsh, 1996a; Walsh et al., 1996). Other sequences containing faunal assemblages that are apparently correlative with Ui1b include the lowermost beds of the Tepee Trail Formation, East Fork Basin, Wyoming (McKenna, 1990); the upper part of member B of the Santiago Formation, northwestern San Diego County, California (Walsh, 1996a); the sequence of the Devils Graveyard Formation that produced the Whistler Squat Local Fauna in Texas (Wilson, 1986); and tentatively a portion of the lower sequence of the Uinta Formation in the Uinta Basin, Utah. Rocks of Uinta Formation informal unit A and B1 of Osborn (1929) in the eastern part of the Uinta Basin and the lowest levels of informal unit B in the western part of the Uinta Basin have thus far produced few mammalian fossils. However, these strata are likely to be at least partially temporally synchronous with biochron Ui1b and potentially also with biochron Ui1a.

Fauna of the Ui1b biochron Because no stratotype section is designated for Ui1b, the combined faunal assemblages of the Washakie Formation (West and Dawson, 1975; Stucky, 1992; McCarroll et al., 1996; Stucky et al., 1996), and the Friars Formation (Poway fauna; Walsh, 1996a) are listed for Ui1b (Table 7 and Appendix 1). These assemblages are diverse and well documented, and the sequences from which they were collected represent potential candidates for future designation as a biochronological zone stratotype. Ui1b contains the first appearances of some larger Uintan taxa including the selenodont artiodactyls Protoreodon, Leptoreodon, and Protylopus; the rhinoceratoid Amynodon; and the uintathere Eobasileus. It is apparent that significant regional endemicity exists between the mammalian faunal assemblages of the Pacific coast and the continental interior. As presently defined, the Shoshonian subage of Flynn (1986) correlates most closely to all or part of a potential Ui1b biochron (see discussions in Robinson et al., 2004; Walsh, 2006a, 2006b).

UINTAN BIOCHRONOLOGICAL ZONES UI2-UI3 The mammalian fauna of the Uinta Formation is traditionally considered to be the “type” fauna of the Uintan NALMA and the assemblages (particularly the historic collections) that we designate here as Ui2 and Ui3 have provided the basis for this type fauna (Wood et al., 1941). The Uinta Formation was initially divided into three informal lithostratigraphic units, Uinta A, B, and C (Osborn, 1895, 1929; Prothero, 1996). Faunal assemblages from the Uinta Formation have been defined as characteristic of informal lithostratigraphic units A, B, or C where the fossils were discovered (Osborn, 1929). However, this has proven to be a confusing relationship because many significant faunal changes within the formation do not necessarily correspond to lithostratigraphic boundaries (Prothero, 1996; Walsh, 1996a). Unlike preceding NALMAs, the Uintan has not been assigned land mammal subage names (e.g., Blacksforkian of biochron Br2). Thus, Uintan assemblages from other areas of the continent were assigned regional names, although attempts to correlate them with the known faunal assemblages of Uinta Formation units A, B, and C have been made (Krishtalka et al., 1987; Walsh, 1996a; Robinson et al., 2004). Flynn (1986) assigned the sub-age name Shoshonian to an earliest Uintan faunal assemblage, although subsequent workers have questioned its validity (see discussions in Walsh, 1996b ; Robinson et 295 MUSEUM OF NORTHERN ARIZONA BULLETIN 65 al., 2004). Osborn (1929) assigned biostratigraphic zone names to the lithostratigraphic units of the Uinta Formation. He established four lithostratigraphic units: Uinta A, B1, B2, and C. As defined here, biochronological zone Ui2 corresponds to the Metarhinus zone and the Eobasileus-Dolichorhinus zone of Osborn (1929). Osborn’s perissodactyl-based biostratigraphy was dismissed by later workers. Recently, Uintan faunas were subdivided into three biochronological zones not directly corresponding to the informal lithostratigraphic units of the Uinta Formation: early (Ui1), middle (Ui2) and late (Ui3) (Robinson et al., 2004). Although these biochrons were supposed to be applicable to all Uintan assemblages, some of the index taxa are only found in particular regions (e.g., Rocky Mountain or Southern Californian localities). The definition of these biochrons was considered tentative by Robinson et al. (2004). In some cases, index taxa are in systematic flux, are endemic (e.g., Mytonomeryx), or have incorrectly reported stratigraphic ranges which limits their biochronological utility (e.g., Epitriplopus; Robinson et al., 2004). A major stumbling block to a stable Uintan biochronology has been the lack of stratigraphically controlled fossil mammal collections from the Uinta Formation (Walsh, 1996a; Townsend et al., 2006). Additionally, clarification of taxon ranges locally within the Uinta Formation and from other Uintan assemblages has been hampered by an absence of superimposed stratigraphic sections containing the three biochrons and the reliance on historical collections that have little to no stratigraphic precision (e.g., White River Pocket, Myton Pocket, and Kennedy’s Hole from the Uinta Formation) (Hamblin, 1987; Prothero, 1996; Walsh, 1996b; Rasmussen et al., 1999; Robinson et al., 2004; Townsend et al., 2006). To address this problem, we designate and define stratotypes for biochrons Ui2 and Ui3 based on faunal assemblages collected from Uinta Formation unit C which comprises the Myton Member and the upper part of unit B of the Wagonhound Member. The lithostratigraphic sequence and associated fossil biostratigraphy form the basis for biochrons Ui2 and Ui3 and spans the transition between these biochrons. Data used to define the Ui2 and Ui3 stratotype section were reported by Townsend et al. (2006), and the associated fauna was reported in various publications (Rasmussen and Townsend, 1995; Townsend and Rasmussen, 1995; Rasmussen et al., 1999; Townsend, 2004; Townsend, et al., 2006; Townsend, unpublished data). The stratigraphy and stratigraphically controlled fossil collections made by Washington University (WU) crews for the last 14 years provide the basis for the stratotype fauna. Historical collections were then analyzed and where possible based on existing data, were added to the WU collections in order to obtain a more complete picture of the total Uinta Formation fauna. The Ui2 and Ui3 stratotype faunal assemblages are listed in Tables 8 and 9, respectively.

Uintan Biochronological Zone Ui2 Historical Stratigraphic Associations—As stated above, no stratotype section has been previously defined for the Ui2 biochron. However, the classic Uinta Formation faunal assemblages upon which the Uintan NALMA is based are associated with a number of geographic areas and stratigraphic horizons in the Uinta Formation. Relative stratigraphic positioning in these areas is generally well understood. However most have not been tied into measured sections and correlated regionally. The main area surveyed and collected by early workers was located in the eastern part of the Uinta Basin in outcrops of the Uinta Formation near the Utah/Colorado border to the east of the Green River and north of the White River (Peterson, 1919; Stagner, 1941; Black and Dawson, 1966; Prothero, 1996; Walsh, 1996b; Rasmussen et al., 1999). Uinta B faunas are known from the localities of Willow Creek (Uinta B1 of Osborn , 1929), White River Pocket (Uinta B2 of Osborn, 1929), a region of localities near Chipeta Wells, and some sediments from Kennedy's Hole (see Black and Dawson, 1966; Prothero, 1996). Prothero (1996) notes that specimens designated as Uinta A, particularly from older collections, are actually Uinta B1, using Osborn's (1929) terminology. The lithostratigraphic boundary between the Uinta B and C was originally defined by a stratigraphic marker unit named the Amynodon sandstone (Riggs, 1912). This unit was also used to mark the boundary between the early and late Uintan faunas. According to the work of Cashion (1986) and Townsend et al. (2006), the Amynodon sandstone is not a useful stratigraphic marker because it has a limited aerial distribution. Townsend et al. (2006) place the Uinta B-C boundary in the eastern Uinta Basin on a color and lithology change approximately 73 m above the Amynodon sandstone. The 296 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Amynodon sandstone is mentioned below only as a referential depositional unit. It should be noted that the Utah State Geological Survey has recently mapped the Uinta B-C contact on the Vernal 30’ x 60’ Quadrangle using a laterally persistent green mudstone bed that directly underlies the Amynodon sandstone (Sprinkel, 2007). Recent collecting efforts in the Uinta Formation (beginning in 1993) have produced a number of new micromammal taxa including small primates, marsupials, and insectivores (Rasmussen, 1996; Rasmussen et al., 1999). This project has great importance for understanding Uintan biochronology since the fossil assemblage from the Uinta Formation has been historically depauperate in small mammals (Prothero, 1996; Walsh, 1996a). New Ui2 Stratotype—The Ourayia uintensis – Pareumys milleri Interval Zone of the Deadman Bench section is chosen as the stratotype for the Ui2 biochron (Fig. 13, 14; Table 8). The designated Ui2 stratotype section is a 137 m thick sequence of gray and green fluvial overbank mudstone and claystone beds, interspersed with golden channel and sheet sandstone beds that extends from 65 m below the Amynodon sandstone (the former Uinta B/C lithologic boundary) upwards to the lowest red bed in the Devil’s Playground area above Coyote Basin (Figs. 13, 14; Townsend et al., 2006). Ideally, the Ui2 stratotype would span the entire eastern Uinta Basin Uinta Formation sequence from the top of the Uinta A to the base of Uinta C. However, the rationale for placing the base of the section high in Uinta B and constraining the measured section was that most of the productive fossil localities occur in the upper part of unit B and in unit C. The lower intervals of Uinta B are sparsely fossiliferous (Black and Dawson, 1966; Prothero, 1996; Walsh, 1996b; Rasmussen et al., 1999).

Figure 13. A view of Ui2 stratotype primarily composed of the lower gray beds typical of Uinta B rock as seen in this photograph. The upper red beds are typical of the overlying Duchesne River Formation.

Ui2 Stratotype Fauna—The beginning of Ui2 is defined by 26 index taxa listed in Table 8. In addition to taxa that were previously identified as index taxa for this biochron (e.g., Mesomeryx grangeri), more taxa have been added because of range extensions due to recent collecting efforts. Two other taxa, Bunomeryx and Protoptychus, that were previously identified as index taxa for Ui2 extend into Uinta C and can no longer be considered as unique to Ui2 (Townsend et al., 2006). Mytonolagus is now assigned to Ui2 based on its position in the stratotype section. Previously it was considered to be a late Uintan form. Seventeen genera have their lowest range datum (LRD) in Ui2 including Chipetaia, Bunomeryx, Achaenodon, Mesomeryx, Apataelurus, Mytonolagus, Natrona, Epitriplopus, Diplacodon, Diplobunops, Miocyon, Macrotarsius, Mytonomys, Oxyaenodon, Dolichorhinus, Leptotragulus, and Simidectes. Six genera have their highest range datum (HRD) in Ui2 and include holdovers from the Bridgerian or taxa unique to this biochron: Eobasileus, Eomoropus, Hyrachyus, Mesonyx, Metarhinus, and Uintatherium. Twenty-six species have their LRD in Ui2 and 14 species have their HRD in this biochron, with 13 taxa that range into Ui3 (Table 8). We designate Ui2 as the Ourayia uintensis-Pareumys milleri Interval Zone because it is at this point in the section that both Ourayia uintensis and particularly Pareumys milleri become incredibly abundant. Osborn’s (1929) interval zone names (mainly focusing on larger taxa) are essentially meaningless because: (1) there is no detailed range information within the Uinta Formation for 297 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Figure 14. Stratotype section of Ui2-3 indicating the relative positions of Washington University (WU) fossil localities.

298 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS these taxa (Prothero, 1996); (2) none of these larger taxa are abundant throughout the section; and (3) they cannot be identified to low taxonomic level based on the mostly isolated teeth and fragmentary skeletal elements that are typically preserved. The increased taxonomic diversity in both the index taxa and general fauna of Ui2 is due to the introduction of new taxa and a number of Bridgerian holdover genera that have species specific to biochron Ui2. The combination of recent collections and the redefinition of unit boundaries in the Uinta Formation has led to a series of range extensions (e.g., Bunomeryx, Epihippus uintensis, Epihippus gracilis, Epitriplopus, Mytonolagus, Protoptychus, Simidectes), rendering these taxa useless for biochron definition (Townsend et al., 2006). The stratigraphically correlated localities in the Ui2 stratotype have also resulted in the refinement of taxon ranges which has led to some species becoming useful in defining the Ui2 biochron (e.g., Sciuravus popi, Sciuravus altidens, Pareumys milleri). Also, taxonomic diversity in Ui2 has increased due to collection of new and unique taxa including Chipetaia lamporea, Miocyon vallisrubrae, Reithroparamys sciuroides, Spurimus sp., Trogolemur sp. nov., a new genus and species of lipotyphlan insectivore, and taxa not yet reported for the Uinta Formation (e.g., Pantolestes) (Rasmussen, 1996; Friscia, 1997; Townsend, 2004; Rasmussen, unpublished data). Taxa that have their HRD in Ui2 are unique to this biochron only within the Uinta Formation in the Uinta Basin but their continental ranges may be extended in other regional assemblages. However, basing the Ui2 biochron and stratotype in the Uinta Formation has paleoecological and historical significance. The Uinta Formation has yielded the largest number of fossil mammal specimens of any Uintan-age deposit in North America and includes the highest abundance and species diversity. Historically, the earliest collections defining the Uintan come from the Uinta Formation (Marsh, 1875; Osborn, 1895; Peterson, 1919; Wood et al., 1941). Other areas, particularly southern California and southwestern Texas, also have extensive Uintan collections that are critical for defining the continental biochronology of the middle Eocene, but their contribution is currently hampered by limited stratigraphic data (Walsh, 1996a).

Uintan Biochronological Zone Ui3 Historical Stratigraphic Associations—Strata that have yielded late Uintan faunas, now assigned to biochron Ui3, include Myton Pocket, Kennedy’s Hole, Leota Ranch, Devil’s Playground, Leland Bench Draw, and Antelope Draw. Future stratigraphic correlation between these areas is required to clarify relations (see Prothero, 1996, for magnetostratigraphic correlations). The Ui3 biochron encompasses the Uinta C upward into the Brennan Basin Member of the Duchesne River Formation. The formational contact has been mapped differently by different workers (e.g., Townsend et al., 2006; Sprinkel, 2007). The position of the Uintan-Duchesnean boundary within the sparsely fossiliferous Duchesne River Formation is uncertain, but is thought to occur within the upper part of the Brennan Basin Member or lower part of the Dry Gulch Creek Member based on recent work by Walsh and Murphey (2007). The Brennan Basin Member of Andersen and Picard (1972) is equivalent to the Randlett horizon and the lowermost part of the Halfway Horizon of Kay (1934). New Ui3 Stratotype—The Pentacemylus progressus Interval Zone of the Deadman Bench section is chosen as the stratotype for the Ui3 biochron (Fig. 14, 15; Table 9). The Ui3 stratotype section extends upwards from the 137 meter-level in the Uinta Formation (eastern Uinta Basin) and based on known late Uintan faunas continues into the Brennan Basin Member of the overlying Duchesne River Formation. Therefore, the stratigraphic level where the Ui3 stratotype ceases is currently unknown. The measured portion of the Ui3 stratotype ends at the contact between the Uinta Formation and Duchesne River Formation at the top of Deadman Bench (Figs. 14, 15; Townsend et al., 2006). As the Uinta Formation trends westward, the portion of the Ui3 stratotype section that is composed of Uinta C rock becomes progressively thicker than the eastern exposures (226 m, Townsend et al., 2006). Facies related lithology changes are associated with this thickening. Rocks of the Uinta C in the western portion of the stratotype section are characterized by highly colorful red, orange, purple, and deep gray claystone beds suggestive of paleosols (Bown and Kraus, 1981; Rasmussen et al., 1999; Townsend et al., 2006). There are also numerous high-energy conglomeratic channel sandstone beds in the higher intervals of Ui3 near the contact with the overlying Brennan Basin Member of the Duchesne River Formation. These are 299 MUSEUM OF NORTHERN ARIZONA BULLETIN 65 associated with overbank deposits of mudstone interbedded with claystone. The distinctive golden- colored sheet and channel sandstone beds of the Ui2 stratotype section are restricted to lower levels of the Uinta Formation.

Figure 15. A view north towards Deadman Bench from Antelope Draw. This photograph illustrates a number of the colorful marker beds used to laterally correlate deposits in the Uinta C intervals of the Uinta Formation.

Ui3 Stratotype Fauna—The beginning of Ui3 is defined by 24 index taxa (Table 9), some of which were previously identified as late Uintan (Ui3): Procynodictis vulpiceps, Mytonomeryx scotti, and Janimus rhinophilus. Some taxa, such as Diplobunops, Mytonolagus, Poebrodon, and Epitriplopus, have now had their ranges pushed back into Ui2 and are no longer considered unique to Ui3 or having a LRD in this biochron. Twelve genera have their LRD in Ui3: Auxontodon, Colodon, Duchesneodus, Eosictis, Janimus, Mytonius, Mytonomeryx, Pentacemylus, Procynodictis, Protadjidaumo, Protitanotherium, and Metatelmatherium. Eighteen genera have their HRD in Ui3, eight species have their LRD in Ui3 and 34 species have their HRD in Ui3 (Table 9). It must be emphasized that the stratigraphic range of the Ui3 biochron does not coincide with the Uinta B-C boundary. We place the lower part of the Ui3 biochron boundary at the lowest meter level where an index taxon occurs, which in this case is at 184 m or 120 m above the Amynodon sandstone. A distinguishing feature of Ui3 in contrast to Ui2 is the noticeable dominance of artiodactyls. One of the defining ecological phenomena of the Uintan is the advent of selenodont artiodactyls (Peterson, 1919; Black and Dawson, 1966; Rasmussen et al., 1999). Ten artiodactyl species have LRDs in Ui3 versus five in Ui2. The ten LRD artiodactyls are all selenodont forms, whereas bunoselenodont forms are more common in Ui2 (e.g., Mesomeryx grangeri). It is for this reason that we designate Ui3 as the Pentacemylus progressus Interval Zone, after the most abundant late Uintan selenodont artiodactyl found at Myton Pocket and Leota Ranch (from Leota Quarry; Peterson, 1931). Although the taxonomic composition of the Ui3 fauna is decidedly different from that of Ui2, few genera make a first appearance in this interval. Screen washing efforts in the Brennan Basin Member of the Duchesne River Formation and in the upper intervals of Uinta C have proven quite fruitful. Our current field projects in the Uinta Formation will continue to screen in these areas and in the lower intervals of Uinta B. These efforts should extend a number of local ranges for small-bodied taxa in the Uintan.

SUMMARY Figure 16 summarizes the major trends in mammalian biostratigraphy documented from the end of the early Eocene and through much of the middle Eocene in North America. The earliest Wasatchian

300 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Figure 16. Range chart of mammalian families from Wa7 through Ui3. Note that artiodactyl, perissodactyl, and rodent families are each grouped together at bottom of chart.

was the time of the initial immigration into North America of a large number of new mammals including the earliest representatives of primates, perissodactyls, artiodactyls, and hyaenodontid creodonts. During the remainder of the Wasatchian these new arrivals competed with previous North American residents to eventually establish a relatively stable community dominated by several of the new arrivals by the end of the Wasatchian. The Bridgerian saw the radiation and diversification of two of the new groups (primates and perissodactyls) along with one archaic holdover group (rodents). New families of perissodactyls (Hyracodontidae and Brontotheriidae) dominated the large-bodied end of the mammalian spectrum while a large diversity of primates (especially Omomyidae) and rodents dominated the small body size part of the community. By the Uintan, primates were in decline across North America and many archaic perissodactyls were beginning to be replaced by other perissodactyls such Amynodontidae or by diverse groups of new artiodactyls including Oromerycidae, Camelidae, Agriochoeridae, and Protoceratidae. In addition, new 301 MUSEUM OF NORTHERN ARIZONA BULLETIN 65 and more derived families of rodents were replacing Ischyromyidae, including Cylindrodontidae and Eomyidae. Lagomorphs also first appear during the Uintan and later become more abundant and diverse. Near the end of the Uintan the old tropical and subtropical communities of the early and early middle Eocene had been replaced by the more open-country communities that dominated the later middle Eocene through the Oligocene in the Western Interior of North America. Against this general backdrop of community evolution we have presented specific stratotype sections and mammalian biostratigraphic range information for the latest Wasatchian through Uintan North American Land Mammal “Ages”. We have defined biochronological zones Wa7, Br1a, Br1b, Br2, Br3, Ui1a, Ui2 and Ui3 based on this biostratigraphy in conjunction with the recognition of stratotype and referred sections in order to facilitate the definition of these biochrons and to make direct comparisons more feasible. We have also informally recognized biochron Ui1b which awaits further corroboration and detailed stratigraphic analysis. These zones have been discussed by earlier authors but have never been previously formalized in a rigorous manner. The exceptions are Ui1a and Ui1b, which represent a refinement over previous analyses of what the early Uintan represents. We recognize that endemicity and biogeography are important factors that must be explored further and are cognizant of the fact that taxon ranges are always open to refinement. However, we believe our efforts provide a necessary step forward in the development of a stable biochronology for much of the middle Eocene of North America.

ACKNOWLEDGMENTS All of us wish to thank Barry Albright for the invitation to participate in this volume. We salute Mike Woodburne for his major contributions to geochronology and biochronology as well as Gondwanan evolutionary history and paleobiogeography in addition to a host of other wide-ranging topics. We join with the other authors in this volume in saying thanks to Mike for his many years of service to the vertebrate paleontology community. Peter Robinson acknowledges the many contributions to North American biostratigraphy of M. R. Dawson, M. C. McKenna, L. Gazin, and L. Krishtalka. Beth Townsend thanks A. Friscia, D. T. Rasmussen, K. Muldoon, D. Cope, J. Westgate. We also thank the National Science Foundation, Wenner Gren, Washington University, and Case Western Reserve University for funding that helped make the project possible. Paul Murphey thanks the late Steve Walsh who should have been one of our coauthors. Steve was a great friend and colleague who made tremendous contributions to the discipline of vertebrate paleontology and theoretical stratigraphy during his abbreviated life. He also thanks E. Evanoff, D. Engard, P. Monaco, and all the other participants of the UCM Bridger Basin Project; P. Sena of the Department of Paleontology, San Diego Natural History Museum; M. Imhof of SWCA Environmental Consultants, Vernal, Utah; B. Bohor and J. Dyni of the U.S. Geological Survey, J. Waanders of Waanders Palynological Consulting, Encinitas, California; the Wyoming State Geological Survey, Laramie, Wyoming; D. Hanson, Bureau of Land Management Wyoming State Office, Cheyenne; and Car Quest Auto Parts in Mountain View Wyoming – thanks for the discounted tire chains! Richard Stucky thanks M.R. Dawson, C. Black, T. Hardy and L. Krishtalka for discussions over the years on Eocene Biochronology as well as important discussions with M.O. Woodburne on understanding time in the fossil record. Special thanks to the DMNS volunteers who have collected many of the specimens used for determination of the Wa7 to Br2 collections at DMNS. Financial support for this work over the years has come from the National Science Foundation, National Aeronautics and Space Administration, Carnegie Museum of Natural History, University of Colorado, and the Denver Museum of Natural History. Most recently field support has come from Paul and Harriet Rosen through the Denver Foundation and through a K-T challenge grant (DMNS) from Tim and Kathryn Ryan. Gregg Gunnell, William Bartels and John-Paul Zonneveld thank all of our colleagues, friends, and students who have been involved in field work projects in the Green River Basin over the past 20 years. They are too numerous to mention all but we would especially like to thank W. C. Clyde, J. I. Bloch, G. H. Junne, R. Walker, E. R. Miller, K. M. Muldoon, D. K. Anderson, J. Trapani, C. Childress, E. Strasser, C. Coupar, J. Pope, W. J. Bartels, C. I. Bartels, A. R. Bair, D. L. Robbins, M. D. Uhen, C. M. West, and S. P. Zack. We also thank the National Science Foundation, the National Geographic Society, the Pew Foundation, the National Park Service, the Office of the Vice President for Research at the University of Michigan, the Scott Turner Fund of the Department of Geological Sciences at the University of Michigan, 302 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS and the Museum of Paleontology at the University of Michigan for their generous support of our work. We also would like to thank D. McGinnis, P. Ambrose, V. Santucci, and A. Aase from Fossil Butte National Monument for their support and help. In addition all of us thank the Bureau of Land Management directors and staffs in Wyoming, Utah, and Colorado for their support and hard work – we especially thank D. Hanson and L. Bryant for their long-term support of our work. Finally, we would all like to acknowledge the careful critique of the original manuscript by W. C. Clyde and R. Secord, whose comments and suggestions improved the paper. This paper is dedicated to the memory of the late Steve Walsh – friend and colleague – who knew more about biostratigraphy and biochronology than the rest of us combined. He will be missed.

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Veatch, A. C. 1907. Geography and geology of a portion of southwestern Wyoming. U.S. Geological Survey Professional Paper 56:1-178. Walsh, S. L. 1996a. Middle Eocene mammal faunas of San Diego County, California; pp. 75-119 in D. R. Prothero and R. J. Emry (eds.), The Terrestrial Eocene-Oligocene Transition in North America. Cambridge University Press, Cambridge, U.K. Walsh, S. L. 1996b. Theoretical biochronology, the Bridgerian/Uintan boundary, and the “Shoshonian Subage” of the Uintan; pp. 52-74 in D. R. Prothero and R. J. Emry (eds.). The Terrestrial Eocene-Oligocene Transition in North America. Cambridge University Press, Cambridge, U.K. Walsh, S. L., D.R. Prothero, and D. J. Lundquist. 1996. Stratigraphy and paleomagnetism of the middle Eocene Friars Formation and Poway Group, southwestern San Diego County, California; pp. 120- 154 in D. R. Prothero and R. J. Emry (eds.), The Terrestrial Eocene-Oligocene Transition in North America. Cambridge University Press, Cambridge, U.K. Walsh, S. L., and P. Murphey. 2007. Documenting the Uintan/Duchesnean transition in the Duchesne River Formation, Utah. Journal of Vertebrate Paleontology 27:163A. West, R. M. 1973. Geology and mammalian paleontology of the New Fork-Big Sandy area, Sublette County, Wyoming. Fieldiana Geology 29:1-193. West, R. M., and M.R. Dawson. 1975. Eocene fossil Mammalia from the Sand Wash Basin, northwestern Moffat County, Colorado. Annals of the Carnegie Museum 45:230-253. West, R.M., and J. H. Hutchison. 1981. Geology and paleontology of the Bridger Formation, southern Green River Basin, southwestern Wyoming. Part 6. The fauna and correlation of the Bridger E. Contributions to Biology and Geology, Milwaukee Public Museum 46:1-8. Wilson, J. A. 1986. Stratigraphic occurrence and correlation of early Tertiary vertebrate faunas, Trans- Pecos Texas: Agua Fria-Green Valley areas. Journal of Vertebrate Paleontology 6:350-373. Wood, H. E. 1934. Revision of the Hyrachyidae. Bulletin of the American Museum of Natural History 67:181-295. Wood, H. E., R. W. Chaney, J. Clark, E. H. Colbert, G.L. Jepsen, J.B. Reeside, and C. Stock. 1941. Nomenclature and correlation of the North American continental Tertiary. Geological Society of America Bulletin 52:1-48. Woodburne, M. O. 2004. Global events and the North American mammalian biochronology; pp. 315-343 in M. O. Woodburne (ed.), Late Cretaceous and Cenozoic Mammals of North America. Columbia University Press, New York, New York. Woodburne, M.O., G. F. Gunnell, and R. K. Stucky. 2009. Land mammal faunas of North America rise and fall during the Early Eocene Climatic Optimum. Annals of the Denver Museum of Nature & Science 1:1-80. Zonneveld, J-P., G. F. Gunnell, and W. S. Bartels. 2000. Early Eocene fossil vertebrates from the southwestern Green River Basin, Lincoln and Uinta counties, Wyoming. Journal of Vertebrate Paleontology 20:369-386. Zonneveld, J-P., W. S. Bartels, and W. C. Clyde. 2003. Stratal architecture of an Early Eocene fluvial- lacustrine depositional system, Little Muddy Creek area, southwestern Green River Basin, Wyoming; pp. 253-287 in R. G. Raynolds and R. M. Flores (eds.), Cenozoic Systems of the Rocky Mountain Region. Rocky Mountain Section, SEPM (Society for Sedimentary Geology), Denver, Colorado, p. 253-287.

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TABLES Table 1. Wasatchian Biochronological Zone Wa7. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Buck Spring (Measured Section 13, Stucky 1984b); UTM Coordinates, NAD 27, Grid Zone 13T; Base of Section 298470E, 4795760N; Top of Section 297160E, 4791950N. Reference Sections: Red Creek (Measured Section 1, Stucky 1984a) and Deadman Butte (Measured Section 17, 17a, 18, 19 20 and 21, Stucky 1984b). Biostratigraphic Designation – Lambdotherium popoagicum Interval Zone. Designation Number Taxa Index Species 4 Diacodexis woltonensis Loveina zephyri Honrovits tsuwape Lambdotherium popoagicum Genus LRD 17 Hemiacodon Nyctitherium Huerfanius Patriofelis Lambdotherium Scenopagus Loveina Shoshonius Machaeroides Thisbemys Marsholestes Trogolemur Mattimys Tubulodon Megalesthonyx Uintasorex Notharctus Genus HRD 12 Ageina Icaronycteris Alveojunctus Lambdotherium Anemorhysis Loveina Chlororhysis Macrocranion Gazinocyon Meniscotherium Honrovits Thryptacodon Species HRD 24 Ageina tobeini Lambdotherium popoagicum Anemorhysis sublettensis Loveina zephyri Alveojunctus sp. Macrocranion nitens Anemorhysis cf. A. wortmani Meniscotherium chamense Chlororhysis sp. Microparamys regisylvestris Diacodexis woltonensis Orohippus proteros Gazinocyon vulpeculus Palaeanodon Heptodon posticus Palaeictops multicuspis Hemiacodon casamissus Palaeosinopa didelphoides Huerfanius sp. Paramys excavatus Hyopsodus wortmani Thryptacodon loisi Hyracotherium craspedotum Viverravus cf. V. gracilis Species LRD 24 Artimonius witteri Mattimys kalicola Cantius nunienus Megalesthonyx hopsoni Diacodexis minutes Notharctus venticolus Diacodexis woltonensis Nyctitherium serotinum Didelphodus altidens Palaeosinopa didelphoides Esthonyx acutidens Scenopagus edenensis Hyopsodus cf. H. paulus Shoshonius cooperi Icaronycteris index Thisbemys sp. Knightomys huerfanensis Tubulodon taylori Machaeroides simpsoni Uintasorex sp. nov Marsholestes dasypelix Viverravus minutus Range Through 22 Bunophorus sinclairi Miacis latidens Coryphodon sp. Macrocranion nitens Diacodexis secans Orohippus proteros Gazinocyon vulpeculus Paramys copei Hapalodectes leptognathus Paramys excavates Hexacodus n. sp. Phenacodus primaevus Hyopsodus powellianus Phenacodus vortmani Hyopsodus wortmani Thryptacodon loisi Hyracotherium vasacciense Uintacyon vorax Hyracotherium craspedotum Viverravus cf. V. gracilis Knightomys depressus Vulpavus canavus

308 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Table 2. Bridgerian Biochronological Zone Br1a. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Sullivan Ranch (Stucky, 1984a,b); UTM Coordinates, NAD 27, Grid Zone 13T; Base of Section 312100E, 4790900N; Top of Section 310420E, 4786650N. Reference Sections: South Pass, Huerfano B (Robinson, 1966; Gunnell and Bartels, 2001). Biostratigraphic Designation – Eotitanops borealis Interval Zone. Designation Number Taxa Index Species 29 Anemorhysis natronensis Pauromys schaubi Antiacodon vanvaleni Protopsalis tigrinus Armintodelphys dawsoni Sciuravus wilsoni Armintomys tullbergi Seleneletes scopaeus Artimonius australis Smilodectes sororis Copelemur consortutus Tetrapassalus sp. nov. Didymictis vancleveae Trogolemur fragilis Eotitanops borealis Trogosus grangeri Eotitanops minimus Trogosus hillsi Iridodon datzae Uintasorex sp. nov. Knightomys senior Utahia carina Malfelis badwaterensis Vassacyon sp. nov. Megadelphus lundeliusi Viverravus lutosus Metacheiromys sp. nov. Washakius izetti Microsus sp. nov. Genus LRD 13 Armintomys Palaeosyops Aycrossia Seleneletes Eotitanops Sinopa Hyrachyus Uintanius Iridodon Utahia Megadelphus Washakius Omomys Genus HRD 7 Bunophorus Heptodon Cantius Palaeosinopa Diacodexis Shoshonius Didymictis Species LRD 30 Apatemys bellulus Paramys nini Aycrossia lovei Pseudotomus robustus Brachianodon cf. B. westorum Quadrotomus grandis Herpetotherium knighti Reithroparamys delicatissimus Hyopsodus cf. H. minusculus Reithroparamys huerfanensis Hyrachyus modestus Scenopagus priscus Notharctus robinsoni Sciuravus bridgeri Omomys carteri Sciuravus nitidus Omomys lloydi Sinopa cf. S. rapax Oodectes sp. nov. Thisbemys perditus Palaeictops cf. P. bridgeri Trogosus latidens Palaeosyops fontinalis Uintanius rutherfurdi Pantolestes cf. P. longicaudus Uintaparamys parvus Paramys delicatior Viverravus gracilis Paramys delicatus Viverravus sicarius Species HRD 42 Acritoparamys francesi Hyracotherium vasacciense Antiacodon huerfanensis Knightomys depressus Armintodelphys blacki Knightomys huerfanensis Artimonius nocerai Machaeroides simpsoni Artimonius witteri Mattimys kalicola Bathyopsis sp. Megalesthonyx hopsoni Bunophorus sinclairi Miacis latidens Cantius nunienus Microsyops cf. M. scottianus Coryphodon sp. Microsyops knightensis Diacodexis minutus Notharctus venticolus

309 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Table 2 (continued). Diacodexis secans Palaeosinopa cf. P. lutreola Didelphodus altidens Paramys copei Didymictis altidens Pentapassalus woodi Dipassalus oryctes Phenacolemur cf. P. jepseni Esthonyx acutidens Prolimnocyon antiquus Esthonyx sp. Shoshonius cooperi Hapalodectes leptognathus Thisbemys sp. Heptodon ventorum Trogolemur amplior Hexacodus sp. nov. Tubulodon taylori Hyopsodus powellianus Vulpavus canavus Hyracotherium index Vulpavus cf. V. australis Range-Through 19 Acritoparamys wyomingensis Orohippus cf. O. pumulis Centetodon bembicophagus Patriofelis cf. P. ulta Helaletes nanus Peradectes chesteri Herpetotherium innominatum Phenacodus primaevus Herpetotherium marsupium Scenopagus edenensis Hyopsodus cf. H. paulus Talpavus nitidus Marsholestes dasypelix Tritemnodon agilis Mesonyx obtusidens Uintacyon vorax Microparamys minutus Viverravus minutus Nyctitherium serotinum

Table 3. Bridgerian Biochronological Zone Br1b. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: RC Bench (McGrew and Sullivan, 1970; Gunnell and Bartels, 1994); UTM Coordinates, NAD 27, Grid Zone 12T; Base of Section 551420E, 4606440N; Top of Section 564000E, 4602810N. Reference Sections: Opal Bench, Big Island-Blue Rim (Gunnell, 1998). Biostratigraphic Designation – Anaptomorphus westi Interval Zone. Designation Number Taxa Index Species 7 Anaptomorphus westi Stylinodon inexplicatus Dilophodon destitutus Utahia kayi Sciuravus eucristidens Vulpavus farsonenesis Smilodectes mcgrewi Genus LRD 4 Anaptomorphus Limnocyon Gazinius Thinocyon Genus HRD 1 Armintodelphys Species LRD 21 Bathyopsis middleswarti Scenopagus curtidens Brachianodon westorum Scenopagus priscus Centetodon pulcher Sinopa minor Harpagolestes macrocephalus Stylinodon mirus Metacheiromys dasypus Talpavus nitidus Metacheiromys marshi Tetrapassalus proius Metacheiromys tatusia Thisbemys plicatus Miacis parvivorus Uintaparamys bridgerensis Microsus cuspidatus Uintaparamys caryophilus Microsyops elegans Washakius insignis Patriofelis ulta Species HRD 7 Notharctus robinsoni Trogolemur amplior Omomys lloydi Trogosus latidens Oodectes sp. nov. Uintanius rutherfurdi Palaeosyops fontinalis Range-Through 30 Acritoparamys wyomingensis Paramys nini Apatemys bellulus Peradectes chesteri Centetodon bembicophagus Pseudotomus robustus 310 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Table 3 (continued). Helaletes nanus Quadrotomus grandis Herpetotherium marsupium Reithroparamys delicatissimus Herpetotherium knighti Reithroparamys huerfanensis Herpetotherium innominatum Scenopagus edenensis Hyrachyus modestus Sciuravus nitidus Marsholestes dasypelix Sciuravus bridgeri Microparamys minutus Tritemnodon agilis Nyctitherium serotinum Uintacyon vorax Omomys carteri Uintaparamys parvus Palaeictops sp. Viverravus sicarius Paramys delicatior Viverravus gracilis Paramys delicatus Viverravus minutus

Table 4. Bridgerian Biochronological Zone Br2. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Church Butte and Grizzly Buttes (Evanoff et al., 1998; Alexander and Burger, 2001); UTM Coordinates, NAD 27, Grid Zone 12T; Base of Section 571360E, 4596140N; Top of Section 569060E, 4554340N; Reference Sections: Sage Creek, Millersville, Sugar White Layer, Owl Creek (Evanoff et al., 1998; Robinson et al., 2004); Biostratigraphic Designation – Notharctus tenebrosus Interval Zone Designation Number Taxa Index Species 32 Alveojunctus minutus Pseudotomus hians Aycrossia lovei Pseudotomus horribilis Helohyus plicodon Quadrotomus grossus Herpetotherium comstocki Quadrotomus sundelli Homacodon vagans Sciuravus popi Knightomys cuspidatus Sciuravus rarus Machaeroides eothen Smilodectes gracilis Notharctus tenebrosus Strigorhysis bridgerensis Notharctus pugnax Strigorhysis rugosus Oodectes herpestoides Tillodon fodiens Orohippus pumulis Tillomys parvidens Orohippus major Trogosus gazini Palaeosyops paludosus Trogosus hyracoides Palaeosyops laevidens Uintanius ameghini Pantolestes intermedius Vulpavus palustris Pauromys exallos Wyomomys bridgeri Genus LRD 7 Elwynella Isectolophus Fouchia Mesatirhinus Hapalorestes Wyomomys Hemiacodon Genus HRD 6 Acritoparamys Microsus Brachianodon Phenacodus Marsholestes Quadrotomus Species LRD 16 Anaptomorphus aemulus Nyctitherium velox Antiacodon pygmaeus Orohippus progressus Apatemys bellus Patriofelis ferox Dilophodon minusculus Pauromys perditus Entomolestes grangeri Taxomys lucaris Hyopsodus paulus Thisbemys corrugatus Hyopsodus minusculus Trogolemur myodes Microsyops annectens Uintacyon major Species HRD 11 Gazinius amplus Sciuravus bridgeri Harpagolestes macrocephalus Tetrapassulus proius Miacis parvivorus Thisbemys plicatus 311 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Table 4 (continued). Paramys nini Uintaparamys caryophilus Patriofelis ulta Viverravus sicarius Reithroparamys huerfanensis Range-Through 38 Apatemys bellulus Paramys delicatus Apatemys rodens Peradectes chesteri Centetodon bembicophagus Reithroparamys delicatissimus Centetodon pulcher Scenopagus curtidens Helaletes nanus Scenopagus edenensis Herpetotherium knighti Scenopagus priscus Herpetotherium innominatum Sciuravus nitidus Hyrachyus modestus Sinopa rapax Limnocyon verus Sinopa minor Mesonyx obtusidens Stylinodon mirus Metacheiromys dasypus Talpavus nitidus Metacheiromys marshi Thinocyon velox Metacheiromys tatusia Tritemnodon agilis Microparamys minutus Uintacyon vorax Microsyops elegans Uintaparamys bridgerensis Nyctitherium serotinum Uintaparamys parvus Omomys carteri Viverravus gracilis Pantolestes longicaudus Viverravus minutus Paramys delicatior Washakius insignis

Table 5. Bridgerian Biochronological Zone Br3. LRD = Lowest Range Datum, HRD = Highest Range Datum) Stratotype Section: Reference section of Twin Buttes Member of Bridger Formation (Murphey and Evanoff, 2007). Section measured on northwest flank of Sage Creek Mountain and east flank of Hickey Mountain, Uinta County, Wyoming. Measured thickness of Twin Buttes Member reference section is 307 m. Exposures of Twin Buttes Member and the location of the measured section is shown in Figure 9; it is graphically illustrated in Figure 10. Note: to avoid future nominal confusion, the Twin Buttes Member type section, which was described in the Sage Creek Mountain/Hickey Mountain area and originally designated as the lithologic type section by Murphey (2001), was subsequently re-designated as the Twin Buttes Member reference section by Murphey and Evanoff (2007). Simultaneously, the lithologic type section of the Twin Buttes Member of Murphey (2001) was re-located to Twin Buttes. The reference section of the Twin Buttes Member (Murphey and Evanoff, 2007) was selected as the stratotype for biochron Br3 because it was described in the area of paleontologically rich badlands in the vicinity of the Lonetree divide and north of Sage Creek Mountain (known to early explorers as Big Bone Butte). UTM Coordinates, NAD 27, Grid Zone 12T – Base of Section 568570E, 4558600N; Top of Section 567755E, 4549239N; Reference Sections: Type section of Twin Buttes Member of Bridger Formation; southwest Cedar Mountain section; southeast Sage Creek Mountain section; southeast Cedar Mountain section (Murphey and Evanoff, 2007). Note that these sections span the greatest possible stratigraphic thickness based on exposures and topography. Biostratigraphic Designation – Notharctus robustior Interval Zone Designation Number Taxa Index Species 18 Ageitodendron matthewi Palaeosyops laticeps Centetodon bacchanalis Palaeosyops robustus Desmatotherium intermedius Pantolestes natans Didelphodus incerta Sinopa major Gazinius bowni Sphacorhysis burntforkensis Hyrachyus princeps Synoplotherium vorax Miacis sylvestris Telmatherium validus Neodiacodexis emryi Tetrapassalus mckennai Orohippus agilis Thisbemys perditus Genus LRD 8 Uintatherium Neodiacodexis Telmatherium Desmatotherium Synoplotherium Ageitodendron

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Table 5 (continued). Sphacorhysis Tillomys Genus HRD 9 Anaptomorphus Patriofelis Dilophodon Sinopa Helaletes Thinocyon Mesatirhinus Tritemnodon Metacheiromys Species LRD 3 Notharctus robustior Tillomys senex Pontifactor bestiola Species HRD 37 Anaptomorphus aemulus Nyctitherium velox Antiacodon pygmaeus Orohippus progressus Apatemys bellulus Paramys delicatior Apatemys rodens Paramys delicatus Centetodon pulcher Patriofelis ferox Helaletes nanus Reithroparamys delicatissimus Hemiacodon gracilis Scenopagus curtidens Hyopsodus minusculus Scenopagus edenensis Hyopsodus paulus Sinopa minor Hyrachyus modestus Sinopa rapax Isectolophus latidens Talpavus nitidus Isectolophus radinskyi Thinocyon velox Limnocyon verus Tritemnodon agilis Mesatirhinus megarhinus Trogolemur myodes Metacheiromys dasypus Uintacyon major Metacheiromys marshi Uintaparamys parvus Metacheiromys tatusia Viverravus gracilis Microsyops elegans Washakius insignis Nyctitherium serotinum Range-Through 21 Apatemys bellus Omomys carteri Centetodon bembicophagus Pauromys perditus Copedelphys innominatum Peradectes chesteri Dilophodon minusculus Scenopagus priscus Entomolestes grangeri Sciuravus nitidus Helohyus sp. Taxymys lucaris Herpetotherium marsupium Thisbemys corrugatus Herpetotherium knighti Uintaparamys bridgerensis Mesonyx obtusidens Uintasorex parvulus Microparamys minutus Viverravus gracilis Microsyops annectens

Table 6. Uintan Biochronological Zone Ui1a. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Type Section of Turtle Bluff Member of Bridger Formation (Murphey and Evanoff, 2007). Section measured on Sage Creek Mountain and Hickey Mountain, Uinta County, Wyoming. Measured thickness of Turtle Bluff Member type section is 131 m. Exposures of the Turtle Bluff Member and the location of the measured section is shown in Figure 11; it is graphically illustrated in Figure 12. UTM Coordinates, NAD 27, Grid Zone 12T; Base of Section 575520E, 4548660N; Top of Section 577594E, 4548702N. Reference Sections: Basal Tertiary conglomerate of the Devils Graveyard Formation, Trans-Pecos, Texas; possibly all or part of Uinta Formation informal unit A in the eastern part of the Uinta Basin, and the lower part of informal unit B in the western part of the Uinta Basin, Utah (the latter being equivalent to unit B1 of Osborn [1929] as defined in the eastern part of Uinta Basin). The confident assignment of the lower units of the Uinta Formation in the Uinta Basin to biochron Ui1a is pending the results of additional field work. Biostratigraphic Designation – Hemiacodon engardae Interval Zone. Designation Number Taxa Index Species 2 Hemiacodon engardae Oromerycidae gen. and sp. nov.

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Table 6 (continued). Genus LRD 6 Epihippus Pareumys sp. Oromerycidae gen. & sp. nov. Sespedectinae indet. Metanoiamys Triplopus Genus HRD 7 Entomolestes Paramys Hemiacodon Taxymys Oromerycidae gen. & sp.nov. Uintasorex Mysops Species LRD 3 Epihippus gracilis Triplopus cubitalis Metanoiamys sp. Species HRD 8 Entomolestes grangeri Sciuravus nitidus Paramys delicatior Taxymys lucaris Pauromys perditus Thisbemys corrugatus Pontifactor bestiola Uintasorex parvulus Range-Through 36 Apatemys sp. Nyctitherium sp. Antiacodon sp. Omomys carteri Brontotheriidae spp. Orohippus sylvaticus Centetodon bembicophagus Pantolestes longicaudus Chiroptera indet. Pantolestes natans Copedelphys innominatum Pantolestes sp. Dilophodon minusculus Pauromys sp. Harpagolestes sp. Peradectes chesteri Helohyus sp. Scenopagus priscus Herpetotherium knighti Thisbemys corrugatus Herpetotherium marsupium Tillomys senex Hyopsodus sp. Trogolemur sp. Hyrachyus eximius Uintacyon vorax Isectolophus sp. Uintaparamys bridgerensis Mesonyx obtusidens Uintaparamys caryophilus Microparamys minutus Uintatherium anceps Microsyops annectens Viverravus minutus Notharctus robustior Washakius sp.

Table 7. Uintan Biochronological Zone Ui1b. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: None designated at present due to lack of detailed lithostratigraphic data. Reference Sections: Washakie Formation, Sand Wash Basin sequence, Colorado (Stucky, 1992; Stucky et al., 1996; West and Dawson, 1975); Washakie Formation, middle unit of Adobe Town Member (TWKA2 of McCarroll et al., 1996 [between beds 620 and 675 of Roehler, 1973]), Washakie Basin, Wyoming; lowermost Tepee Trail Formation, East Fork Basin, Wyoming; Friars Formation (lower tongue, Conglomerate Tongue, and upper tongue = Poway fauna as redefined by Walsh, 1996a), San Diego, California; upper part of member B of the Santiago Formation, northwestern San Diego County, California; the Whistler Squat Local Fauna in the Devils Graveyard Formation of Texas (Wilson, 1986); and tentatively all or a portion of Uinta Formation informal units A and B1 in the eastern part of the Uinta Basin, and the lowermost part of unit B in the western part of the Uinta Basin, Utah. Preliminary Biostratigraphic Designation – Achaenodon robustus- Hyrachyus eximius – Amynodon advenus Interval Zone. Note that significant regional endemicity is apparent between the assemblages of the Pacific coast and the continental interior. Taxonomic Summary (data compiled primarily from Stucky et al., 1996; McCarroll et al., 1996; Walsh, 1996a; and unpublished SDSNH paleontological collections data. F = Friars Formation and/or upper part, member B, Santiago Formation, San Diego County, California; SW = Washakie Formation, Sand Wash Basin, Colorado; AT = Washakie Formation Adobe Town Member (interval TWKA2), Washakie Basin, Wyoming). Designation Number Taxa Index Species 24 Achaenodon insolens (AT) Microsyops kratos (F) Achaenodon robustus (F, AT) Patriolestes novaceki (F) Aethomylos simplicidens (F) Protoreodon sp. nov. (F) 314 GUNNELL ET AL.—BIOCHRONOLOGICAL ZONATION OF THE BRIDGERIAN AND UINTAN NALMAS

Table 7 (continued). Amynodon advenus (SW) Protoreodon walshi (F) Antiacodon venustus (F) Sciuravus powayensis (F) Apatemys downsi (F) Stockia powayensis (F) Centetodon aztecus (F) Triplopus cubitalis (AT) Crypholestes vaughni (F) Washakius woodringi (F) Forstercooperia grandis (SW?, AT) Hesperolemur actius (F) Uintaparamys caryophilus (F) Leptoreodon major (F) Uintasorex montezumicus (F) Merycobunodon littoralis (F) Uriscus californicus (F) Microparamys woodi (F) Genus LRD 27 Achaenodon (F, AT) Protoptychus (AT) Aethomylos (F) Protoreodon (F, SW) Amynodon (F, AT) Protylopus (AT) Batodonoides (F) Parahyus (F) Crypholestes (F) Oligoryctes (F) Eobasileus (F, AT) Oromeryx (SW) Eomoropus (AT) Ourayia (F) Forstercooperia (SW?, AT) Sphenocoelus (SW, AT) Hesperolemur (F) Stockia (F) Hylomeryx (SW) Tapocyon (F) Leptoreodon (F) Telmatherium (SW) Metarhinus (F, SW, AT) Triplopus (AT) Patriolestes (F) Uriscus (F) Poebrodon (AT) Genus HRD 21 Antiacodon (F) Patriolestes (F) Batodonoides (F) Pauromys (F) Crypholestes (F) Parahyus (F) Helohyus (F, SW?) Stockia (F) Hesperolemur (F) Tillomys (SW) Merycobunodon (F) Uintacyon (SW) Microsyops (F) Uintasorex (F) Notharctus (SW) Uriscus (F) Omomys (F) Viverravus (SW) Orohippus (SW) Washakius (F) Palaeictops (F) Species LRD 21 Amynodon reedi (F) Ourayia sp. nov. (F) Batodonoides powayensis (F) Parahyus sp. (F) Epihippus gracilis (SW) Pareumys grangeri (F) Eobasileus cornutus (SW, AT) Protoptychus hatcheri (AT) Eomoropus amarorum (AT) Protylopus petersoni (AT) Hyrachyus eximius (F, SW, AT) Isectolophus annectens (SW) Pseudotomus californicus (F) Isectolophus annectens (SW) Pseudotomus littoralis (F) Limnocyon potens (AT) Tapocyon sp. (F) Metarhinus fluviatilis (F) Triplopus implicatus (SW, AT) Metarhinus pater (F) Uintaparamys leptodus (AT) Species HRD 20 Apatemys bellus (F, AT) Parahyus sp. (F) Dilophodon minusculus (SW, AT) Helohyus sp. Peradectes chesteri (F) Hyopsodus markmani (SW) Scenopagus priscus (F) Microparamys minutus (F) Telmatherium acola (SW) Microsyops annectens (F, SW) Thisbemys corrugatus (SW) Notharctus robustior (SW, AT) Tillomys senex (SW) Omomys carteri (F) Uintacyon vorax (SW) Orohippus sylvaticus (SW) Uintaparamys bridgerensis (SW) Palaeictops sp. (F) Viverravus minutus (SW) 315 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Table 7 (continued). Pantolestes longicaudus (AT) Range-Through 19 Brontotheriidae spp. (F, SW) Miacis sp. (F) Centetodon sp. (F, SW) Mesonyx obtusidens (SW) Centetodon bembicophagus (F) Metanoiamys agorus (F) Copedelphys innominatum (F, SW) Epihippus gracilis (SW) Nyctitherium sp. (F) Harpagolestes sp. (F, AT) Oligoryctes sp. (F) Herpetotherium knighti (F, SW) Herpetotherium marsupium (F) Pantolestes natans (SW) Hyopsodus sp. (F, AT) Pantolestes sp. (F) Hyrachyus eximius (SW?, AT) Uintatherium anceps Hyrachyus sp. (F)

Table 8. Uintan Biochronological Zone Ui2. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Coyote Basin, Deadman Bench (Townsend et al., 2006); combined thickness of 366 meters. UTM Coordinates, NAD 27, Grid Zone 12T – Base of Section 657250E, 4442500N; Top of Section 631500E, 4465000N. Reference Sections: White River Pocket, Chipeta Wells, Well No. 2, Willow Creek; all within Uinta Formation (see Prothero, 1996). Biostratigraphic Designation – Ourayia uintensis – Pareumys milleri Interval Zone. Designation Number Taxa Index Species 26 Achaenodon uintensis Ourayia uintensis Apataelurus kayi Oxyaenodon wortmani Apatemys uintensis Pantolestes cf. P. elegans Chipetaia lamporea Pantolestes cf. P. natans Diplobunops vanhouteni Pareumys milleri Dolichorhinus hyognathus Protoreodon medius Harpagolestes uintensis Protoreodon paradoxicus Herpetotherium sp. Sciuravus altidens Hylomeryx annectens Spurimus sp. Mesomeryx grangeri Sthenodectes incisivum Metarhinus abbotti Thisbemys uintensis Microparamys dubius Trogolemur sp. 3 Natrona natronensis Uintamys sp. Genus LRD 17 Achaenodon Macrotarsius Apataelurus Mesomeryx Bunomeryx Miocyon Chipetaia Mytonolagus Diplacodon Mytonomys Diplobunops Natrona Dolichorhinus Oxyaenodon Epitriplopus Simidectes Leptotragulus Genus HRD 6 Eobasileus Mesonyx Eomoropus Metarhinus Hyrachyus Uintatherium Species LRD 26 Bunomeryx montanus Mytonomys robustus Diplacodon elatus Oromeryx plicatus Epihippus parvus/uintensis Oxyaenodon dysodus Epitriplopus uintensis Paramys compressidens Hyopsodus uintensis Poebrodon kayi Leptoreodon marshi Protoreodon minor Leptotragulus proavus Protoreodon parvus Limnocyon douglassi Protylopus sp.

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Table 8 (continued). Macrotarsius jepseni Pseudotomus eugenei Miacis gracilis Pseudotomus petersoni Miocyon scotti Simidectes sp. Miocyon vallisrubrae Tapocyon robustus Mytonolagus petersoni Triplopus obliquidens Species HRD 14 Amynodon reedi Metarhinus fluviatalis Eobasileus cornutus Metarhinus sp. Eomoropus amarorum Ourayia sp. nov. Forstercooperia grandis Pantolestes longicaudus Hyrachyus eximius Pareumys sp. Limnocyon potens Sciuravus popi Mesonyx obtusidens Uintatherium anceps Range-Through 13 Amynodon advenus Pareumys grangeri Copedelphys innominatum Protoptychus hatcheri Epihippus gracilis Protylopus petersoni Herpetotherium comstocki Stylinodon mirus Herpetotherium knighti Triplopus implicatus Herpetotherium marsupium Uintaparamys leptodus Isectolophus annectens

Table 9. Uintan Biochronological Zone Ui3. (LRD = Lowest Range Datum, HRD = Highest Range Datum). Stratotype Section: Coyote Basin, Deadman Bench (Townsend et al., 2006); combined thickness of 366 meters. UTM Coordinates, NAD 27, Grid Zone 13T; Base of Section 298470E, 4795760N; Top of Section 297160E, 4791950N. Reference Sections: Myton Pocket, Kennedy’s Hole (in part), Randlett Horizon, Halfway Hollow, Leota Quarry. Biostratigraphic Designation – Pentacemylus progressus Interval Zone. Designation Number Taxa Index Species 24 Auxontodon pattersoni Mytonomeryx scotti Bunomeryx elegans Mytonomys mytonensis Diplobunops crassus Pentacemylus progressus Diplobunops matthewi Procynodictis vulpiceps Harpagolestes leotensis Protoreodon petersoni Hylomeryx quadricuspis Protylopus annectens Janimus rhinophilus Proviverra longipes Leptotragulus clarki Reithroparamys sciuroides Leptotragulus medius Sciuravus sp. nov. Metatelmatherium ultimum Simidectes magnus Mytonius hopsoni Talpavus duplus Mytonolagus robustus Thisbemys medius Genus LRD 12 Auxontodon Mytonius Colodon Mytonomeryx Duchesneodus Pentacemylus Eosictis Procynodictis Janimus Protadjidaumo Metatelmatherium Protitanotherium Genus HRD 18 Amynodon Limnocyon Diplacodon Miacis Epihippus Mytonolagus Epitriplopus Oromeryx Hyopsodus Oxyaenodon Hylomeryx Poebrodon Isectolophus Protylopus Leptoreodon Stylinodon Leptotragulus Tapocyon 317 MUSEUM OF NORTHERN ARIZONA BULLETIN 65

Table 9 (continued). Species LRD 8 Colodon sp. Pentacemylus progressus Dilophodon leotanus Protadjidaumo typus Duchesneodus uintensis Protoreodon primus Eosictis avinoffi Protoreodon pumilus Species HRD 34 Amynodon advenus Mytonolagus petersoni Bunomeryx montanus Oromeryx plicatus Diplacodon elatus Oxyaenodon dysodus Epihippus gracilis Paramys compressidens Epihippus parvus/uintensis Pareumys grangeri Epitriplopus uintensis Poebrodon kayi Herpetotherium comstocki Protoptychus hatcheri Hyopsodus uintensis Protoreodon minor Isectolophus annectens Protoreodon parvus Leptoreodon marshi Protylopus petersoni Leptotragulus proavus Pseudotomus eugenei Limnocyon douglassi Pseudotomus petersoni Macrotarsius jepseni Stylinodon mirus Miacis gracilis Tapocyon robustus Miacis longipes Triplopus implicatus Miocyon scotti Triplopus obliquidens Miocyon vallisrubrae Uintaparamys leptodus Range-Through 5 Copedelphys innominatum Macrotarsius jepseni Herpetotherium knighti Mytonomys robustus Herpetotherium marsupium

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