Paludicola 8(4):208-251 May 2012 © by the Rochester Institute of Vertebrate Paleontology

NEW RECORDS OF SMALL MAMMALS FROM THE MIDDLE EOCENE DUCHESNE RIVER FORMATION, UTAH, AND THEIR IMPLICATIONS FOR THE UINTAN-DUCHESNEAN NORTH AMERICAN LAND MAMMAL AGE TRANSITION

Thomas S. Kelly1, Paul C. Murphey2, and Stephen L. Walsh†

1Research Associate, Vertebrate Paleontology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd., Los Angeles, California 90007 2Research Associate, Department of Paleontology, San Diego Museum of Natural History, 1788 El Prado, San Diego, California 92101 †Deceased; address correspondence to Thomas A. Deméré, Department of Paleontology, San Diego Natural History Museum, P.O. Box 121390, San Diego, California 92112

ABSTRACT

New records of taxa from the Dry Gulch Creek Member of the Duchesne River Formation are: Copedelphys sp.; Lipotyphla (genera and species indeterminate); Mytonolagus sp.; Pareumys guensburgi; Griphomys sp.; Heliscomys sp.; Passaliscomys sp.; Metanoiamys lacus; Metanoiamys sp., cf. M. korthi; Protadjidaumo typus; Protadjidaumo sp., cf. P. typus; Paradjidaumo sp.; Adjidaumo sp., cf. A. craigi; Simiacritomys sp.; Microeutypomys sp.; Eutypomys sp.; and Poabromylus kayi. The mammalian assemblages from the Dry Gulch Creek and Lapoint members of the Duchesne River Formation are combined as the Halfway/Lapoint Fauna and regarded as the “type fauna” of the Duchesnean North American Land Mammal age. New correlations of the Uintan and Duchesnean faunas from the Sespe Formation of California to the Global Polarity Time Scale (GPTS) are based on taxonomic comparisons of the Sespe faunas to those from the Uinta Basin and radioisotopic data. Based these new correlations, the Uintan-Duchesnean boundary occurs within Chron C19n of the GPTS, or about 41.4 Ma.

INTRODUCTION Formation than to that of the Lapoint horizon (Gazin, 1955, 1956, 1959; Clark et al., 1967). Andersen and The Wood Committee (Wood et al., 1941) Picard (1972) formally subdivided the Duchesne designated the Duchesne River Formation of the River Formation into four members, the Brennan Uinta Basin in Utah as the stratotype for the Basin, Dry Gulch Creek, Lapoint, and Starr Flat Duchesnean North American Land Mammal “Age” members in ascending order. The Brennan Basin (NALMA) with the Pearson Ranch Local Fauna as its Member is equivalent to Kay’s (1934) Randlett correlative. Previously, the validity of the horizon and about the lower quarter of the Halfway Duchesnean NALMA had even been questioned by horizon, the Dry Gulch Creek Member is equivalent some workers due to its sparse fossils and poorly to about the upper three-quarters of the Halfway documented fauna (e.g., Wilson, 1977, 1978, 1986; horizon, and the Lapoint and the Starr Flat members Emry, 1981). A better understanding of the are equivalent to the Lapoint horizon. However, no mammalian fauna and biostratigraphy of the age diagnostic fossils have been recovered from the Duchesne River Formation is key to resolving Starr Flat Member. Lucas (1992) provided a detailed questions related to the biochronology of the history of the biostratigraphic correlations of the Duchesnean NALMA and its correlatives, as well as Duchesne River Formation faunas, wherein he the nature and timing of the Uintan-Duchesnean and considered the Randlett Fauna of the Brennan Basin Duchesnean-Chadronian NALMA transitions. Member to be late Uintan, and tentatively combined Originally, Kay (1934) divided the Duchesne River the meager sample of fossils known from the Dry Formation into three informal “rock-stratigraphic Gulch Creek Member and the better known Lapoint units” that he designated the Randlett, Halfway, and Fauna from the Lapoint Member into the Lapoint “horizons.” The Wood Committee included Halfway/Lapoint Fauna. The combined fauna was all of Kay’s (1934) “horizons” in the Duchesnean. redefined as the “type” fauna of the Duchesnean Subsequently, other investigators regarded the NALMA. Prior to this report, only 16 taxa were Randlett and Halfway horizons as late Uintan in age confidently known from the Halfway/Lapoint Fauna, because the faunas, especially that of the Randlett, many of which are only represented by one or a few were more similar to those from the underlying Uinta specimens (Rasmussen, 1999).

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SDSNH Locality 5939, was 93 kg, and this sample To determine if additional fossils could be yielded three identifiable mammal teeth. From 2007 recovered from the Dry Gulch Creek Member and to 2009, an additional 16 blind matrix samples of other levels of the Duchesne River Formation in various weights were collected from various levels in order to further clarify its age assignment, a field the Brennan Basin and lower Dry Gulch Creek investigation was initiated in 2006. Field methods members in Halfway Hollow, and additional surface include intensive surface prospecting and systematic prospecting efforts and geologic mapping took place blind collection of bulk matrix samples within the over a much larger geographic area. Although most study area (Figure 1). Walsh and Murphey (2007) of these matrix samples contained fossils including reported preliminary results of these efforts, but bone and tooth fragments, snail shells, and silicified subsequently additional specimens were recovered wood, none of the mammalian fossils were and all the fossil specimens have now been more diagnostic. In 2009, 54 kg of matrix was collected intensively studied. The purposes of this report are to from SDSNH Locality 6339, but the only identifiable provide detailed descriptions and identifications of fossil from this locality was collected on the surface the specimens of small mammals recently recovered prior to sampling the matrix at the site. Discovered in from the Duchesne River Formation, and to discuss 2008 during surface reconnaissance, SDSNH their implications for the poorly understood and Locality 6240 is stratigraphically near the base of the controversial Uintan-Duchesnean NALMA transi- Starr Flat Member in the northern portion of Halfway tion. Hollow, and yielded tooth fragments of an indeterminate artiodactyl. Subsequent dry screening METHODS at this locality in 2009 did not result in the recovery of any additional identifiable fossils. It is important to Field work for this project took place note that surface prospecting efforts by the authors in intermittently between 2006 and 2009. Initial efforts all levels of the Duchesne River Formation have included the collection of 24 blind (= no fossils heretofore yielded only one mammalian fossil that is observed on surface) test matrix samples, each identifiable, a fragmentary specimen of Poabromylus weighing approximately 9 kg. Five of these samples kayi from SDSNH Locality 6339. Thus surface were collected from near the base of the Lapoint prospecting has met with far less success than Member in the immediate vicinity of Peterson’s screenwashing of bulk matrix samples. All field (1931) Carnegie Museum “Teleodus Quarry” (= work was conducted under BLM Paleontological Duchesneodus Quarry) at levels stratigraphically Resource Use Permits UT06-014S and UT07-018E. equivalent to and just below the quarry; eleven All matrix samples were sieved through 24 and samples were collected just above and below the base 30 mesh nested screens during screenwashing. The of the Lapoint Member in Halfway Hollow from most effective method for breaking down the various levels in the vicinity of Kay’s (1957) sampled rock matrix proved to be repeated drying microfossil locality; five samples were collected in and washing in water mixed with a ten-percent the lower part of the Lapoint Member from road cuts solution of bleach, making sure that the matrix was to the east of Horseshoe Bend along the Lapoint completely dry and that larger chunks were Highway; and three samples were collected from the mechanically broken prior to each re-washing. approximate middle of the Dry Gulch Creek Member Soaking matrix in soybean oil proved effective in in Halfway Hollow. All test samples were dried, further breaking down some of the samples. The washed and picked during the field session in order to fossiliferous concentrate was further reduced with a permit bulk sampling of the most fossiliferous sample heavy liquid separation and flotation procedure using localities. The washed concentrate from approx- tetrabromoethane, and the reduced concentrate was imately 40% of the 24 test samples contained one or hand-picked under a binocular microscope. more mostly fragmentary small mammal bones and Measurements of teeth were made with an teeth. A bulk sample consisting of 218 kg of a 10 cm optical micrometer to 0.001 mm and then rounded off thick reddish-brown muddy siltstone was collected to the nearest 0.01 mm. Dental terminology for from SDSNH Locality 5939 because the test sample rodent cheek teeth follows Wood and Wilson (1936), yielded the largest initial sample of identifiable Chiment and Korth (1996) and Korth and Branciforte mammal teeth. An additional 227 kg was collected (2007), whereas that for Lagomorpha follows from the locality in December, 2006, and the total Dawson (1958). Upper and lower teeth are sample of 454 kg yielded the fossil sample from designated by uppercase and lowercase letters, SDSNH Locality 5939 described herein. The total respectively. All specimens are curated in the amount of matrix sampled from SDSNH Locality research collections in the Department of 6087, lateral to and approximately 100 m south of 210 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

FIGURE 1. Map showing geographic location of study area (light gray rectangle) within Uinta Basin, Uintah County, Utah, with state index map. Detailed data for localities within study area are on file at the Department of Paleontology, SDNHM. Base map: U.S. Geological Survey Vernal 30 x 60 minute topographic map, 1:100,000 scale. PALUDICOLA, VOL. 8, NO. 4, 2012 211

Paleontology at the San Diego Museum of Natural TABLE 1. Dental measurements (in mm) of specimens from the History. Detailed locality data are available at this Dry Gulch Creek Member (e = estimated). institution. Taxon/Specimen ap tr tra trp_ Older published K-Ar radioisotopic ages Copedelphys sp. presented herein were recalibrated using International dP3, SDSNH 110304 1.10 0.62 ― ― Union of Geological Sciences constants following the m1 trigonid, SDSNH 110302 0.86 0.68 ― ― Lipotyphla, family indet. method of Dalrymple (1979). Older published lower antemolar, 40 39 Ar/ Ar ages were recalibrated relative to the new SDSNH 110305 1.21 0.68 ― ― Fish Canyon Tuff sanidine interlaboratory standard at lower premolar, 28.201 Ma (Kuiper et al., 2008). Age assignments for SDSNH 110250 0.86 0.59 ― ― Mytonolagus sp. Chrons C21n through C16n of the Global Polarity lower cheek tooth, Time Scale (GPTS) follow Gee and Kent (2007), SDSNH 110290 2.05 2.51 1.80 Pälike et al. (2010), and Jovane et al. (2010). Pareumys guensburgi Subzones or subbiozones of the Uintan North partial M1 or 2, SDSNH 110306 1.98 >2.54e ― M3, SDSNH 110307 2.23 2.53 2.41 American Land Mammal age (e.g., Ui1a, Ui2, and Griphomys sp. Ui3) follow Gunnell et al. (2009) and those for the m1 or 2, SDSNH 110325 0.83 0.77 0.75 Arikareean follow Albright et al., 2008. m3, SDSNH 110274 0.65 0.70 0.54 Abbreviations are as follows: ap, greatest m3, SDSNH 110280 0.70 0.68 0.54 Passaliscomys sp. anteroposterior length; L, left; Ma, megannum (one m1 or 2, SDSNH 110324 0.72 0.75 0.70 million years in the radioisotopic time scale); R, Paradjidaumo sp. right; tr, greatest transverse width; tra, anterior M3, SDSNH 110319 1.10 1.18 0.91 transverse width; trp, posterior transverse width. m3, SDSNH 110318 1.32 1.15 0.98 Adjidaumo sp., cf. A. craigi Acronyms are as follows: CM, Carnegie Museum of p4, SDSNH 110321 0.67 0.44 0.64 Natural History; LACM, Natural History Museum of partial M1 or 2, SDSNH 130400 ― ― 0.60 Los Angeles County; LACM(CIT), California Simiacritomys sp. Institute of Technology vertebrate paleontological m1 or 2, SDSNH 110320 1.67 1.35 1.41 Microeutypomys sp. specimens now housed at the LACM; SDNHM, San partial m1 or 2, SDSNH 110251 1.13 ― ― Diego Natural History Museum; SDSNH, San Diego Eutypomys sp. Society of Natural History; TTU-P, Museum, Texas partial m3, SDSNH 110252 1.70 ― ― Tech University . Proabromylus kayi partial m2, SDSNH 9.50 ― ― ______SYSTEMATIC PALEONTOLOGY Cohort Marsupialia Illiger, 1811 metacone. The postprotocrista is well developed and Order Didelphimorpha Gill, 1872 extends from the protocone to an incipient Family Didelphidae Gray, 1921 metaconule positioned near the lingual base of the Genus Copedelphys Korth, 1994 metacone, whereas the preprotocrista is a weakly Copedelphys sp. developed, low loph that extends anterolabially to (Figures 2A-F, Table 1) join the anterior cingulum. A small parastyle is present that extends anteriorly from the anterior base Referred specimens―From SDSNH Loc. of the paracone. Two elongated stylar cusps are 5939, Dry Gulch Creek Member: LdP3, SDSNH present along the metastylar shelf and are separated 110304; Rm1 trigonid, SDSNH 110302. from each other by a distinct notch along the shelf. Description―The dP3 (Figures 2A-B) has a These cusps are identified as C and D (Figures 2A- triangular occlusal outline with a very elongated B), with D being the largest and positioned furthest metastylar wing extending posterolingually from the posteriorly on the stylar shelf. metacone, typical of dP3s of other Eocene didelphids The partial m1 (Figures 2C-F) is missing the (Setoguchi, 1973, 1975, 1977; Lillegraven, 1976; talonid. The trigonid is triangular in occlusal outline Krishtalka and Stucky, 1984; Korth, 1994; Rothecker with the ap dimension greater than the tr dimension. and Storer, 1996). The paracone is smaller and lower The protoconid is well developed and slightly larger in height than the metacone. The postmetacrista is a and taller than the metaconid. The paraconid is the tall, distinct loph that extends to the posterolabial smallest primary cusp and lowest in height. The corner of the tooth. The protocone is slightly paraconid and metaconid are well separated by a elongated anteroposteriorly and is smaller and lower valley resulting in a lingually open and elongated in height than the other primary cusps. The stylar trigonid. The protoconid and metaconid are shelf is only developed along the labial edge of the positioned relatively close to each other and are 212 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

separated from each other by a shallow valley. The = 0.97 – 1.0); and 4) the posterior wall of the trigonid posterior wall of the trigonid is obliquely orientated is obliquely orientated. The m1 trigonid is similar to to the anteroposterior axis of the tooth. those of both Nanodelphys and Copedelphys by being ______expanded anteroposteriorly and open lingually, but with a trigonid tr/trigonid ap ratio of 0.79, like those of those of Nanodelphys, and an obliquely orientated posterior wall of the trigonid, like those of Copedelphys. However, subsequent to Korth (1994), Peratherium innominatum Simpson, 1928, has been reassigned to Copedelphys as C. innominata (Rothecker and Storer, 1996; Korth, 2008). In C. innominata, the m1 trigonid is relatively narrower than those of C. titanelix and C. stevensonii with its trigonid tr/trigonid ap ratio overlapping with that of Nanodelphys and the trigonid from SDSNH Loc. 5939. The holotype of C. innominata is from the Bridger Formation of Wyoming, but it has also been recorded from the Duchesnean of Saskatchewan and at Badwater, Wyoming (Setoguchi, 1975; Krishtalka and Stucky, 1983b; Korth, 2008). The identification of dP3s of a number of Eocene didelphid species have been reported in the literature (e.g., Setoguchi, 1973, 1975, 1977; Krishtalka and Stucky, 1983a, 1983b, 1984; Lillegraven, 1976; Rothecker and Storer, 1996). Setoguchi (1975) referred several dP3s (CM 23851, 23852, and TTU-P 1360) to Nanodelphys cf. N. minutus McGrew, 1937, from Badwater, Wyoming. Subsequently, Kirshtalka and Stucky (1983b)

FIGURE 2. Copedelphys sp. and Lipotyphla (genera referred these dP3s to Peratherium (= Copedelphys) undetermined) from Dry Gulch Creek Member, Duchesne River innominatum. No dP3s have been reported for the Formation. A-F, Copedelphys sp.: A-B, LdP3, SDSNH 110304, other species of Copedelphys (Korth, 1994). occlusal view (A) and oblique labial view (B) showing positions of stylar cusps C and D; C-F, Rm1 trigonid, SDSNH 110302, However, in other Eocene didelphids occlusal view (C), lingual view (D), anterior view (E), and (Herpetotherium and Peradectes) where dP3s have posterior view (F). G-H, Lipotyphla, genus undet., lower antemolar been identified, there appears to be some (?lower canine or p1), SDSNH 110305, occlusal view (G) and consistencies between the stylar cusp patterns of M1 lateral view (H). I, Lipotyphla, genus undet., lower premolar, SDSNH 110250, lateral view. Scale = 1 mm. and dP3 (Lillegraven, 1976; Krishtalka and Stucky, ______1983a, 1983b; Rothecker and Storer, 1996). In all these examples of dP3, even though cusp B is present Discussion―The two didelphid teeth were on M1, it is absent or in one taxon, Herpetotherium provisionally referred to Nanodelphys sp. by Walsh sp., cf. H. marsupium, reduced to a small thin ridge and Murphey (2007), but further study indicates that because a stylar shelf is typically not developed along they represent Copedelphys instead. In Nanodelphys, the lingual margin of the dP3 paracone (Setoguchi, the molar trigonids exhibit the following characters: 1975; Lillegraven, 1976; Kirshtalka and Stucky, 1) expanded anteroposteriorly; 2) relatively narrow, 1983a, 1983b; Rothecker and Storer, 1996). When with the m1 trigonid tr dimension less than the ap cusps C and D are present on M1, these cusps are dimension (ratio of trigonid tr/trigonid ap = 0.78); usually present on the dP3, although their positions and 3) the posterior wall of the trigonid is only may be slightly different because of the elongation of slightly obliquely orientated (McGrew, 1937; Korth, the dP3 metastylar wing. In the M1 of Nanodelphys 1994). In Copedelphys titanelix and C. stevensonii, hunti, cusps C and D are absent or very reduced the trigonids exhibit the following characters (Korth, 1994), so it would be expected that these (Matthew, 1903; Hough, 1961; Korth, 1994): 1) cusps would likely be absent or greatly reduced on its expanded anteriorly and widely open lingually in m1; dP3. The dP3 from SDSNH Loc. 5939 is very similar 2) the paraconid is the smallest cusp; 3) the tr morphologically to those of C. innominata including dimension is equal to or slightly less than the ap the presence of obliquely elongated stylar cusps C dimension (ratio of mean trigonid tr/mean trigonid ap and D, but is slightly smaller in size (Setoguchi, PALUDICOLA, VOL. 8, NO. 4, 2012 213

1973, 1975, 1977; Krishtalka and Stucky, 1983a). document new records of lipotyphlans from the Dry This similarity indicates that the dP3 from SDSNH Gulch Creek Member. Loc. 5939 is most likely referable to Copedelphys instead of Nanodelphys. Furthermore, considering the Order Lagomorpha Brandt, 1855 dP3 and m1 trigonid from SDSNH Loc. 5939 are Family Leporidae Gray, 1921 comparable in size, both specimens probably Genus Mytonolagus Burke, 1934b represent a single species of Copedelphys. Mytonolagus sp. (Figures 3A-C, Table 1) Grandorder Lipotyphla Haeckel, 1866 Lipotyphla, family undetermined Referred specimen―From SDSNH Loc. 5339, (Figures 2G-I, Table 1) Dry Gulch Creek Member: right lower cheek tooth, SDSNH 110290. Referred specimens―From SDSNH Loc. Discussion―The lower cheek tooth (Figures 5939, Dry Gulch Creek Member: lower antemolar, 3A-C) is typical of those of Mytonolagus including SDSNH 110305; lower premolar, SDSNH 110250. the following: 1) relatively low crowned (as Description―Two teeth represent lipotyphlan compared with Oligocene or later leporids); 2) lower antemolars (Figures 2G-I). SDSNH 110305 is simple, persistent internal and external reentrants broken off near the base of the crown. The remainder between the trigonid and talonid (extend to near the of the crown is elongated anteroposteriorly with a base of the crown); and 3) the talonid is well lanceolate occlusal outline. On the occlusal surface developed and relatively large (Burke, 1934b; Wood, are two ridges along the lingual and labial margins 1949; Dawson, 1958, 1970). It is within the size that join anteriorly at about three-quarters of the ranges of p4-m2 of M. ashcrafti from the Renova length of the crown. Two small cuspids are present Formation of Montana and M. wyomingensis from on each ridge. The crown is moderately curved Badwater, and smaller than those of M. petersoni ventrally near the apex. Even though the root is from the Uinta Basin and M. sp. near M. petersoni missing, it is clear that the tooth was procumbent from Badwater (Burke, 1934b; Wood, 1949; Dawson, with the crown directed anteriorly, indicating that it 1970; Fostowicz-Frelik and Tabrum, 2009). probably represents a canine or p1. SDSNH 110250 However, SDSNH 110290 appears more derived than is badly pitted and abraded, so few morphological Uintan M. petersoni by lacking enamel in a details can be determined, but appears to represent a dorsoventrally orientated band centered on the lower premolar. The apex of the crown is positioned anterior wall of the trigonid, similar to that of M. anteriorly with a moderately sloping ridge that wyomingensis (Wood, 1949). extends to the base of the crown. There are two roots that are well fused below the base of the crown. Order Rodentia Bowdich, 1821 Discussion―Previously, only one lipotyphlan Family Cylindrodontidae Miller and Gidley, 1918 had been reported from the Lapoint Fauna. It was Genus Pareumys Peterson, 1919 first described by Peterson (1934) as Protictops Pareumys guensburgi Black, 1970 alticuspidens, but later investigators regarded this (Figures 3D-E, Table 1) taxon as being referable to Centetodon sp. (Tedford, 1970; Van Valen, 1967; Lillegraven et al., 1981; Referred specimens―From SDSNH Loc. Rasmussen et al., 1999). SDSNH 110305 differs 5939, Dry Gulch Creek Member: Partial RM1 or 2, from the canine and anterior premolars of Centetodon SDSNH 110306; RM3, SDSNH 110307. by having two distinct ridges along the margins of the Description―The partial M1 or 2 (Figure 3E) crown and a greater anterior elongation of the crown consists of most of the trigon, talon, and labial and with a ventrally curved apex. It is more similar to anterolabial portions of the tooth. Even in its those of other primitive lipotyphlans with damaged state, the following characters can be overlapping antemolar teeth, such as the lower canine distinguished: 1) a four-lophed occlusal pattern of the soricomorph Eranosorex or the anterior consisting of the anterior cingulum, protoloph, antemolars of certain nyctitheres (Sigé, 1976; Wang metaloph, and posterior cingulum that are tall and all and Li, 1990). SDSNH 110250 is so poorly preserved of about equal height; 2) the anterior cingulum that it provides little information of its familial extends labially from its junction with the protoloph assignment. It does not appear to represent to the anterolabial corner of the tooth where it joins Centetodon because of the fused roots (Lillegraven et the anterior base of the paracone resulting in a deep al., 1981). Even though these two antemolar teeth valley between the anterior cingulum and protoloph; cannot assigned to a family or genus, they do 3) the protoloph is a well developed, complete loph connecting the protocone to an anteroposteriorly 214 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

holotype with p4-m3 and a dentary with m2) from the Lapoint Member of the Duchesne River Formation. Subsequently, Black (1974) described Pareumys cf. P. guensburgi from several specimens, including upper and lower cheek teeth, from the Duchesnean locality 20, Badwater, Wyoming. Black (1974) noted that the p4-m3 specimen of Pareumys from locality 20 is almost identical morphologically to that of the holotype of P. guensburgi from the Lapoint Member. Even though the M1-2s of P. cf. P. guensburgi from locality 20 are well worn, they are very similar to SDSNH 110306 and 110307, including being more unilaterally hypsodont and larger than those of Uintan Pareumys grangeri Burke, 1935, and P. milleri Peterson, 1919. Considering that SDSNH 110306 and 110307 agree morphologically with P. cf. P. guensburgi, are comparable in size with the holotype lower molars of P. guensburgi, and were recovered from the upper part of the same formation as P. guensburgi (although from a stratigraphically lower member), they most likely represent the upper molars of P. guensburgi and are provisionally referred to this species. FIGURE 3. Mytonolagus sp. and Pareumys guensburgi from Dry Gulch Creek Member, Duchesne River Formation. A-C, Mytonolagus sp., right lower cheek tooth, SDSNH 110290, Infraorder Geomorpha Thaler, 1966 occlusal view (A), anterior view (B), and posterior view (C). D-E, Family incertae sedis Pareumys guensburgi: D, RM3, SDSNH 110307, occlusal view; E, Genus Griphomys Wilson, 1940 partial RM1 or 2, SDSNH 110306, occlusal view. Scales = 1 mm. ______Griphomys sp. (Figures 4A-C, Table 1) compressed, but distinct paracone; 4) the metaloph is a well developed loph that extends lingually from the Referred specimens―From SDSNH Loc. metacone and then turns posteriorly to join the 5939, Dry Gulch Creek Member: Rm1 or 2, SDSNH posterior cingulum; 5) a deep, enclosed valley is 110325; Rm3, SDSNH 110274; Lm3, SDSNH present between the protoloph and metaloph; and 6) 110280. the posterior cingulum extends labially from the Discussion―Three lower molars (Figures 4A- protocone in an arc wherein it is joined by the C) are indistinguishable from those of Griphomys metaloph and then continues lingually to join the including the following dental characters: 1) posterior corner of the metacone resulting in a relatively tall, well-developed metalophids and moderately deep, enclosed valley between the hypolophids giving the teeth a strongly bilophodont metaloph and posterior cingulum. The M3 (Figure occlusal pattern; 2) anterior cingulids that extend 3D) is complete and very similar to the partial M1 or across the anterior face of the tooth between 2. Additional characters that can be distinguished in metaconids and protoconids; 3) well-developed the M3 are the apexes of the protocone, paracone, central transverse valleys that are open labially and and metacone, and the lophs are about equal in height lingually; and 4) very small mesoconids or low and a slight indentation is present along the lophids extending from the anterior labial corners of posterolingual wall at a point where the protocone the hypoconids into the central transverse valleys. and posterior cingulum join (incipient hypocone), The m1 or 2 differs from the m3s by having a short which would disappear with further wear. The M3 posterior cingulid present between the entoconid and differs from the partial M1 or 2 by having an hypoconid and its trp is about equal to its tra (not additional, thin loph that extends anterolabially from significantly narrower as in the m3s). the center of the protoloph to anterior cingulum Two species of Griphomys have been resulting in a division of the valley between the previously described from the Uintan and protoloph and the anterior cingulum. Duchesnean of southern California, G. alecer Wood, Discussion―Black (1970) described Pareumys 1940, and G. toltecus Lillegraven, 1977. The guensburgi based on a two partial dentaries (the Griphomys specimens from the Duchesne River Formation differ from those of G. alecer and G. PALUDICOLA, VOL. 8, NO. 4, 2012 215

toltecus primarily in their smaller size. Korth and Fauna of Utah (Korth and Eaton, 2004) and SDSNH Eaton (2004) assigned two partial lower teeth from 110324 is the first record of the genus outside of the the Duchesnean Turtle Basin Local Fauna, Utah, to type locality. Griphomys sp., which are also significantly smaller than the California species. Although the specimens Genus Heliscomys Cope, 1873 from the Duchesne River Formation appear to Heliscomys sp. represent a distinct species, they are referred to (Figures 4E-F, Table 1) Griphomys sp. until a larger sample is available. ______Referred specimens―From SDSNH Loc. 5939, Dry Gulch Creek Member: RP4, SDSNH 110285; Lm1 or 2, SDSNH 110286. Discussion―The P4 and m1 or 2 (Figures 4E- F) are most similar to those of Heliscomys in exhibiting the following dental characters: 1) the P4 has three primary cusps that are arranged in a triangular occlusal pattern with the protocone positioned anteriorly and the metacone and hypocone aligned transversely; 2) an incipient P4 entostyle is present; 3) the m1 or 2 has a moderately developed protostylid and a distinct hypostylid present, which, along with the transversely aligned primary cusps, results in a three-cusped metalophid and hypolophid; and 4) the m1-2 central transverse valley is well developed and open labially and lingually. Only two species of heliscomyids have been previously documented from the Duchesnean, Passaliscomys priscus and Heliscomys walshi Kelly, 2009. SDSNH FIGURE 4. Geomorpha and Heliscomyidae from Dry Gulch Creek 110285 differs from the P4s of P. priscus and H. Member, Duchesne River Formation. A-C, Griphomys sp.: A, walshi by lacking a well-developed paracone. Storer Rm3, SDSNH 110274; B, Rm1 or 2, SDSNH 110325; C, Lm3, SDSNH 110280. D, Passaliscomys sp., Lm1 or 2, SDSNH 110324. (1988) described a single P4 from the Duchesnean E-F, Heliscomys sp.: E, RP4, SDSNH 110285; F, Lm1 or 2, Lac Pelletier Lower Local Fauna of Saskatchewan, SDSNH 110286. All occlusal views. Scale = 1 mm. which he referred to Heliscomys sp. SDSNH 110285 ______differs from the Saskatchewan P4 by having a much less developed entostyle. SDSNH 110286 differs Family Heliscomyidae Korth, Wahlert, and Emry, from m1-2s of P. priscus and SDSNH 110324 1991 (referred above to Passaliscomys sp.) by having a Genus Passaliscomys Korth and Eaton, 2004 distinct protostylid and hypostylid present. SDSNH Passaliscomys sp. 110285 and 110286 appear to represent a small (Figure 4D, Table 1) indeterminate species of Heliscomys and the third record of the genus in the Duchesnean. Referred specimen―From SDSNH Loc. 5939, Dry Gulch Creek Member: Lm1 or 2, SDSNH Family Eomyidae Winge, 1887 110324. Genus Metanoiamys Chiment and Korth, 1996 Discussion―Korth and Eaton (2004) described Metanoiamys lacus Storer, 1987 a new genus and species of heliscomyid, (Figures 5A-L, Table 2) Passaliscomys priscus. SDSNH 110324 agrees well with the m1-2 of P. priscus by having the following: Referred specimens―From SDSNH Loc. 1) four cusps arranged in a bilophate occlusal pattern; 5939, Dry Gulch Creek Member: LP4, SDSNH 2) a continuous cingulid extending from the 110334; LM1 or 2, SDSNH 110256; LM1 or 2, metaconid to the posterior labial corner of the tooth SDSNH 110281; LM1 or 2, SDSNH 110283; partial and lacking stylar cusps along this cingulid; 3) a deep LM1 or 2, SDSNH 110327; LM1 or 2, SDSNH central transverse valley; and 4) a small posterior 110335; RM1 or 2, SDSNH 110255; RM1 or 2, cingulid. It differs from the m1-2 of P. priscus by its SDSNH 110257; RM1 or 2, SDSNH 110258; partial smaller size and from those of Heliscomys by lacking RM1 or 2, SDSNH 110277; RM1 or 2, SDSNH labial stylar cusps. Passaliscomys was previously 110310; Lm1 or 2, SDSNH 110275; Lm1 or 2, known only from the Duchesnean Turtle Basin Local SDSNH 110276; Lm1 or 2, SDSNH 110278; Lm1 or 216 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

2, SDSNH 110279; partial Rm1 or 2, SDSNH of Metanoiamys; 6) the entoloph is complete, 130401. connecting a weakly-developed mesocone with the Discussion―The 16 teeth (Figures 5A-L) from protocone and the hypocone; 7) a small, but distinct the Dry Gulch Creek Member are indistinguishable mesostyle; and 8) a robust posterior cingulum from those of Metanoiamys lacus from the extending from the metacone to the hypocone. Duchesnean of Saskatchewan and Utah (Storer, 1987; The M3s (Figures 6B-D) are characterized by Korth and Eaton, 2004) and are referred to this having the following: 1) a subcircular occlusal species. outline; 2) the paracone is the tallest and largest ______primary cusp with the protocone only slightly smaller; 3) the metacone is a distinct, transversely TABLE 2. Measurements (in mm) of Metanoiamys lacus from the compressed cusp that is lower in height than the Dry Gulch Creek Member, Duchesne River Formation. paracone and protocone; 4) the hypocone is a distinct,

SDSNH anteroposteriorly compressed cusp that is slightly Specimen # Position ap tra trp_ lower in height than the metacone and separated from 110334 P4 0.80 0.82 0.76 the protocone by a distinct notch; 4) the anterior 110255 M1 or 2 0.78 0.80 0.86 cingulum is a tall, well developed loph that extends 110256 M1 or 2 0.79 0.77 0.87 110257 M1 or 2 0.80 0.85 0.81 from the anterior edge of the paracone to the 110258 M1 or 2 0.73 0.74 0.82 anterolingual corner of the tooth with an adlophule 110277 M1 or 2 0.69 ― 0.72 (accessory loph) extending from the cingulum to the 110281 M1 or 2 0.72 0.74 0.71 protocone; 5) the protoloph is relatively tall and 110283 M1 or 2 0.75 0.80 0.77 110310 M1 or 2 0.77 0.82 0.81 complete, connecting the paracone to the protocone; 110327 M1 or 2 0.80 ― ― 6) the metaloph is a well developed, but varies from 110335 M1 or 2 0.71 0.75 0.70 complete (connecting the metacone to the hypocone) 110275 m1 or 2 0.82 0.72 0.80 to incomplete (lacking a connection or weakly 110276 m1 or 2 0.79 0.69 0.75 110278 m1 or 2 0.85 0.78 0.83 connected to the hypocone); 7) the posterior 110279 m1 or 2 0.83 0.78 0.73 cingulum is well developed, extending in an arc from ______the hypocone to the metacone, and is only slightly lower in height than the metacone and hypocone; 8) Metanoiamys sp., cf. M. korthi Kelly and Whistler, the mesoloph is moderately developed and extends 1998 labially from the entoloph into the central transverse (Figures 6A-K, Table 3) valley; and 9) a small, distinct anterocone is present on the anterior cingulum at its connection with the Referred specimens―From SDSNH Loc. adlophule. 5939, Dry Gulch Creek Member: P4, SDSNH The p4s (Figures 6E-F) exhibit the following 110272; LM3, SDSNH 110260; RM3, 110261; characters: 1) the tra is significantly narrower than partial RM3, SDSNH 110311; Ldp4 or p4, SDSNH the trp; 2) the metaconid and protoconid are distinct 110253; partial Rp4, SDSNH 110254; Lm1 or2, and about equal in size and height; 3) the entoconid SDSNH 110 268; Lm1 or 2, SDSNH 110269; Rm1 and hypoconid are the largest primary cusps and or 2, SDSNH 110271; Lm1, SDSNH 110308; Rm3, about equal in height and size; 4) the hypolophid is a SDSNH 110309. tall, well developed, complete lophid that connects Description―Eleven teeth from the Dry Gulch the entoconid to the hypoconid; 5) the posterior Creek Member represent a second species of cingulid is a tall, well developed lophid connecting Metanoiamys that is 26-30% larger (Table 3) than the the hypolophid to the posterior edge of the entoconid; teeth referred above to M. lacus. and 6) the mesoconid is a distinct, short, transversely The P4 (Figure 6A) is slightly worn with some compressed cusp. The ectolophid differs between the areas of the enamel abraded away and is two p4s, wherein on SDSNH 110253 it is a complete characterized by having the following: 1) nearly loph connecting the protoconid and hypoconid and on square occlusal outline; 2) a well-developed anterior SDSNH 11053 it is less complete with shallow cingulid with a distinct indentation along the anterior notches occurring anteriorly and posteriorly between occlusal edge; 3) a complete protoloph and metaloph the protoconid and hypoconid, respectively. SDSNH connecting the paracone to the protocone and the 110253 is possibly deciduous because it is relatively metacone and the hypocone, respectively; 4) the more elongated anteroposteriorly, the tra is relatively protoloph and metaloph are distinctly lower in height narrower, the metaconid and protoconid are than the primary cusps; 5) the primary cusps are tall, positioned closer together, and a well-developed slender cusps resulting in the tooth being relatively anteroconid is present. high crowned, as compared to those of other species PALUDICOLA, VOL. 8, NO. 4, 2012 217

FIGURE 5. Metanoiamys lacus from Dry Gulch Creek Member, Duchesne River Formation. A, LP4, SDSNH 110334. B, LM1 or 2, SDSNH 110335. C, RM1 or 2, SDSNH 110310; D, RM1 or 2, SDSNH 110257; E, LM1 or 2, SDSNH 110256; F, RM1 or 2, SDSNH 110258; G, RM1 or 2, SDSNH 110255; H, partial LM1 or 2, SDSNH 110327; I, LM1 or 2, SDSNH 110283; J, Lm1 or 2, SDSNH 110275; K, Lm1 or 2, SDSNH 110279; L, Lm1 or 2, SDSNH 110278. All occlusal views. Scale = 1 mm.

218 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

FIGURE 6. Metanoiamys sp., cf. M. korthi from Dry Gulch Creek Member, Duchesne River Formation. A, RP4, SDSNH 110272. B, LM3, SDSNH 110260. C, RM3, SDSNH 110261. D, partial RM3, SDSNH 110311. E, Ldp4 or Lp4, SDSNH 110253. F, partial Rp4, SDSNH 110254. G, Lm1 or 2, SDSNH 110269. H, Lm1 or 2, SDSNH 110308. I, Lm1 or 2, SDSNH 110268. J, Rm1 or 2, SDSNH 110271. K, Rm3, SDSNH 110309. All occlusal views. Scale = 1 mm. PALUDICOLA, VOL. 8, NO. 4, 2012 219

Three m1 or 2s (Figures 6H-J) have almost Discussion―The additional accessory lophid identical occlusal morphology and exhibit the follow and robust mesolophid exhibited SDSNH 110269 are characters: 1) a well-developed anterior cingulid that somewhat similar to those of the m1-2s of the extends from the anterior base of the metaconid to the eutypomyid Janimus dawsonae (compare Figure 6G anterolabial corner of the tooth, where it is open with fig. 3h of Storer, 1988). However, SDSNH labially; 2) an adlophulid (accessory lophid) 110269 is lacking certain diagnostic characters of extending between the anterior cingulid and the Janimus, such as basins with rugose enamel or well- protoconid; 3) a small anteroconid at the junction of developed accessory ridges, a distinct metastylid, an the anterior cingulid and adlophulid; 4) the anterior cingulid that does not extend across the metaconid, protoconid, entoconid, and hypoconid are entire anterior face of the tooth, and larger size tall, sharp cusps; 5) the metalophid and hypolophid (Dawson, 1966; Storer, 1984, 1988). Moreover, are well developed, tall, complete lophids, connecting previous investigators have reported a significant the protoconid to the metaconid and the entoconid to amount of variation in the upper and lower molar the hypoconid, respectively; 6) the ectolophid is low, lophs and lophids, respectively, in eomyid species but complete, connecting the protoconid and where large sample sizes were available (e.g., hypoconid; 7) the posterior cingulid is well Anderson, 1984; Storer, 1984; Korth, 1980; Chiment developed and tall, connecting the posterior corner of and Korth, 1996; Kelly, 2010b). Furthermore, in the the entoconid to about the middle of the hypolophid; sample of M. korthi from the Sespe Formation, some 8) the mesolophid is moderately tall and extends lower molar specimens (LACM 153294, 153921, and lingually from about the center of the ectolophid to 153940) exhibit a secondary, low, accessory lophid about half way across the central transverse valley; extending posterolingually from the adlophulid to and 9) a mesoconid that varies from a small swelling near the base of the metaconid (per. observation). to a small, but distinct cusp on the ectolophid. Therefore, the occlusal differences of SDSNH Overall, SDSNH 110269 (Figure 6G) is very similar 110269 are considered to be due to individual to the other three lower molars, but also exhibits variation and it is tentatively referred to the same some distinct differences, including an additional species as the other three m1-2s. Similarly and accessory lophid extending from the adlophulid to the considering the individual variation of the presence base of the metaconid and a slightly more robust or absence of a mesostylid and posterior cingulid on mesolophid. m3 previously reported by Kelly (2010b) for a large The m3 (Figure 6 K) is very similar to the m1- sample of M. korthi, SDSNH 110309 is also 2s, but differs by having the following: 1) a small gap tentatively referred to the same species as the other separates the adlophulid from the anterior cingulid; 2) teeth described above. a mesostylid is present between the metaconid and The eleven teeth from the Dry Gulch Creek entoconid; 3) the hypolophid forms an arc between Member are most similar to those of Metanoiamys the hypoconid and entoconid; and 4) a posterior korthi (Kelly, 1992; Whistler and Kelly, 1998; Kelly, cingulid is lacking. 2010b), but differ primarily by being slightly higher crowned, that is the upper and lower molar ______cusps/cuspids and lophs/lophids, respectively, are relatively taller, and by having more weakly- TABLE 3. Measurements (in mm) of teeth of Metanoiamys sp., cf. developed mesoconids. M. korthi from the Dry Gulch Creek Member, Duchesne River Storer (1987) noted an evolutionary trend Formation. SDSNH wherein the more derived species of Metanoiamys Specimen # Position ap tra trp_ exhibit increased crown height and greater 110272 P4 1.07 1.13 1.10 development of the lophs/lophids, which suggests 110260 M3 0.74 0.87 0.66 that the specimens from the Dry Gulch Creek 110262 M3 0.72 0.82 0.67 110311 M3 0.75 ― ― Member represent a species that is slightly more 110253 dp4 or p4 0.90 0.81 0.70 derived than M. korthi. Although these teeth probably 110254 p4 ― ― 0.73 represent a new species of Metanoiamys, they are 110268 m1 or 2 1.13 1.05 1.13 referred to M. sp., cf. M. korthi until such time that 110269 m1 or 2 1.07 0.99 0.96 110271 m1 or 2 1.16 1.08 1.08 additional specimens are discovered, which will 110308 m1 or 2 1.16 0.98 1.08 allow a better characterization of the species. 110309 m3 1.07 0.91 0.82

220 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

Genus Protadjidaumo Burke, 1934a connection with the protoloph resulting in straighter Protadjidaumo typus Burke, 1934a anterior wall (no indentation); 2) the entolophs are (Figures 7A-L, Table 4) complete lophs in all specimens; and 3) the mesolophs are more distinct in all specimens and Referred specimens―From SDSNH Loc. extend labially to about half way across the central 5939, Dry Gulch Creek Member: Partial RP4, transverse valleys. SDSNH 110314; partial RP4, SDSNH 110315; ______partial LM1 or 2, 110248; partial RM1 or 2, 110316; Rdp4, SDSNH 110287; Rp4, SDSNH 110312; Rm1, TABLE 4. Measurements (in mm) of Protadjidaumo typus from SDSNH 110326; partial Rm2, 110265; Rm2, SDSNH the Dry Gulch Creek Member, Duchesne River Formation. SDSNH 110247; partial Lm2, SDSNH 110313. From SDSNH Specimen # Position ap tra trp_ Loc. 6087, Dry Gulch Creek Member: LM1 or 2, 110314 P4 0.81 0.89 ― SDSNH 130402; partial Lm3, SDSNH 130403. 110315 P4 0.87 0.96 1.00 Description―Protadjidaumo typus was 130402 M1 or 2 0.95 1.11 0.98 110248 M1 or 2 1.02 ― ― previously known only from the holotype, a partial 110316 M1 or 2 1.03 ― ― dentary with p4-m2 (Burke, 1934a; Scott, 1945). 110287 dp4 0.87 0.49 0.64 Except for slight variations in the lengths of the lower 110312 p4 0.89 0.62 0.81 molar mesolophids, the new p4 and m1-2s (Figures 110326 m1 0.93 0.87 0.82 110247 m2 1.02 1.00 0.98 7G-K) do not provide any additional diagnostic 110265 m2 0.98 0.96 0.91 characters for the species. Based on the holotype, m1 110313 m2 1.05 0.84 0.91 can be differentiated from m2 by its lack of a 130403 m3 0.99 0.98 ― connection between the anterior cingulid and the ______protoconid, and by having its width slightly less SDSNH 110287 (Figure 7F) is identified as a relative to the length. dp4 because it is anteroposteriorly elongated and its The partial P4s (Figures 7A-B) lack appression tra is significantly narrower than its trp, facets on their anterior walls and are missing portions characteristics typical of the dp4s of eomyids (Walsh, of the hypocone at their posterolingual corners. They 1997). Additional characters exhibited by SDSNH are characterized by having the following: 1) 110287 include the following: 1) the metaconid is transversely expanded (wider than long); 2) the much larger than the protoconid and they are anterior cingulum is a well developed, short loph positioned very close together with only a very extending from the anterior edge of the paracone to shallow valley or notch separating them; 2) the the labial portion of the protoloph, resulting in a entoconid and hypoconid are distinct, large cusps, slight indentation along the anterior wall of the tooth; about equal in size, that are connected by a 3) the primary cusps are robust and relatively tall; 4) moderately tall hypolophid; 3) the ectolophid is the protoloph and metaloph are complete lophs, complete connecting the protoconid to the connecting the paracone to the protocone and the hypoconid; 4) the mesolophid is a distinct lophid that metacone to the hypocone, respectively, and slightly extends lingually from the center of the ectolophid to lower in height than the primary cusps; 5) the about half way across the central transverse valley; entoloph is complete on SDSNH 110314, connecting and 5) the posterior cingulid extends from the the protocone to the hypocone and incomplete on hypolophid to connect with the posterior edge of the SDSNH 110315, wherein there is a small, shallow entoconid and is about equal in height to the notch present at about the middle of the loph; 6) a hypolophid. short mesoloph is present on SDSNH 110315, but The partial m3 (Figure 7L) is similar to the m1- lacking on SDSNH 110314; 7) a small, but distinct, 2s, but with the following differences: 1) the mesostyle is present on SDSNH 110314, whereas a entoconid is relatively smaller; 2) the hypoconid is mesostyle is lacking on SDSNH 110315; and 8) the more transversely compressed; 3) the hypolophid is posterior cingulum is a robust, tall loph that extends well developed and extends in an arc from the from the posterior edge of the metacone to the hypoconid to the entoconid; and 4) a distinct posterolabial edge of the hypocone. posterior cingulid is lacking. Without intact dentitions, confident Discussion―The p4 and m1-2s agree well in differentiation between M1 from M2 from isolated occlusal morphology with the holotype of teeth cannot be made. The occlusal morphology of Protadjidaumo typus from the Lapoint Member of the M1 or 2s (Figures 7C-E) agree well with that of the Duchesne River Formation and are referred to the P4s, including the heights of the primary cusps this species. Although the upper cheek teeth, dp4 and and lophs, but differ by having the following: 1) the anterior cingulum extends lingually beyond its PALUDICOLA, VOL. 8, NO. 4, 2012 221

FIGURE 7. Protadjidaumo typus from Dry Gulch Creek Member, Duchesne River Formation. A, partial RP4, SDSNH 110315. B, partial RP4, SDSNH 110314. C, LM1 or 2, SDSNH 130402. D, partial RM1 or 2, SDSNH 110316. E, partial LM1 or 2, SDSNH 110248. F, Rdp4, SDSNH 110287. G, Rp4, SDSNH 110312. H, Rm1, SDSNH 110326. I, Rm2, SDSNH 110247. J, Lm2, SDSNH 110313. K, partial Rm1 or 2, SDSNH 110265. L, partial Lm3, SDSNH 130403. All occlusal views. Scale = 1 mm.

222 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

m3 of P. typus were previously unknown, assignment cheek teeth of P. typus, these teeth are referred to of the new specimens to the species is supported Protadjidaumo sp., cf. P. typus. because they are compatible in size to the p4 and m1- ______2s and exhibit occlusal morphologies that are similar to those known for other species of the genus (Storer, TABLE 5. Measurements (in mm) of Protadjidaumo sp., cf. P. 1984, 1987). typus from the Dry Gulch Creek Member, Duchesne River Formation. SDSNH Protadjidaumo sp., cf. P. typus Specimen # Position ap tra trp_ (Figures 8A-F, Table 5) 110266 M1 or 2 1.18 1.42 1.37 110273 M3 0.93 1.03 0.93 110263 p4 1.10 0.85 1.03 Referred specimens―From SDSNH Loc. 110317 p4 1.15 0.80 1.05 5939, Dry Gulch Creek Member: RM1 or 2, SDSNH 110264 m1 or 2 1.13 1.16 1.21 110266; partial LM3, SDSNH 110267; partial Lp4, 110300 m1 or 2 ― 1.24 1.18 SDSNH 110263; Lp4, SDSNH 110317; Rm1 or 2, ______SDSNH 110264; partial Rm1 or 2, SDSNH 110300. Description―Five teeth (Figures 8A and 8C-F) from the Dry Gulch Creek Member are very similar in occlusal morphology to those referred above to Protadjidaumo typus, but differ by being from 15% – 25% larger and by having the following: 1) the M1 or 2 anterior cingulum extends lingually only a short distance past its connection with the protoloph; 2) the p4 protoconid and metaconid are positioned slightly closer together and in SDSNH 110263 are not distinctly separated by a notch or valley; and 3) a transversely elongated mesostylid is present between the p4 metaconid and entoconid that extends labially a short distance into the central transverse valley. The partial M3 (Figure 8B), which is missing a portion of the labial wall, is characterized by having the following: 1) the anterior cingulum is well developed and extends lingually from the anterior edge to the paracone to join with the protoloph and FIGURE 8. Protadjidaumo sp., cf. P. typus from Dry Gulch Creek Member, Duchesne River Formation. A, RM1 or 2, SDSNH then continues a short distance lingually; 2) the 110266. B, partial LM3, SDSNH 110267. C, partial Lp4, SDSNH paracone and protocone are the largest cusps, 110263. D, Lp4, SDSNH 110317. E, partial Rm1 or 2, SDSNH whereas the metacone and hypocone are much 110300. F, Rm1 or 2, SDSNH 110264. reduced; 3) the protoloph is complete, connecting the ______protocone to the paracone; 4) the metaloph is complete connecting the protocone to the metacone; Genus Paradjidaumo Burke, 1934a 5) a short, robust mesoloph extends labially from the Paradjidaumo sp. metaloph into the central transverse valley; and 6) the (Figures 9C-D, Table 1) hypoloph is tall, well developed and forms an arc along the posterior wall of the tooth connecting the Referred specimens―From SDSNH Loc. metacone to the hypocone. 5939: RM3, SDSNH 110319; Rm3, SDSNH 110318. Discussion―The M3 is regarded as conspecific Description―The M3 (Figure 9C) is with the other referred teeth because it is compatible characterized by having the following: 1) the in size and has an occlusal morphology typical of paracone and protocone are robust and the largest those of Protadjidaumo (Storer, 1984; 1987). cusps; 2) the hypocone is a distinct cusp that is Considering the individual variation in size and separated from the protocone by a deep valley; 3) the occlusal morphology seen in other species of metacone is only weakly developed along the Protadjidaumo (Storer, 1984, 1987), referral of these posterolingual corner of the tooth; 4) an anterior six teeth to P. typus might be justified. However, cingulum that connects the paracone to the because of the differences noted above and a lack of anterolabial edge of the protocone; 5) a complete, knowledge regarding the individual variation in the high protoloph connecting the paracone to the anterolingual edge of the protocone; 6) a well- PALUDICOLA, VOL. 8, NO. 4, 2012 223

FIGURE 9. Eomyidae and Eutypomyidae from Dry Gulch Creek Member, Duchesne River Formation. A-B, Adjidaumo sp. cf. A. craigi: A, partial RM1 or 2, SDSNH 130400; B, Rp4, SDSNH 110321. C-D, Paradjidaumo sp., C, RM3, SDSNH 110319; D, Rm3, SDSNH 110318. E, Simiacritomys sp., Lm1 or 2, SDSNH 110320. F, Microeutypomys, partial Lm1 or 2, SDSNH 110251. G, Eutypomys sp., partial Lm3, SDSNH 110252. All occlusal views. Scale = 1 mm.

224 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

developed and complete mesoloph that extends from the anterior cingulum and labial halves of the a high, complete entoloph to the labial margin of the protocone and hypocone. Even with these missing tooth; 7) a complete metaloph connecting the portions, the follow dental characters can be hypocone to the posterolingual edge of the metacone; distinguished: 1) the lophs are well developed and and 8) a high posterior cingulum that extends about equal in height to the primary cusps; 2) the lingually from the hypocone to the metacone. posterior cingulum extends lingually from the The m3 (Figure 9D) is characterized by having posterior corner of the metacone to the posterolabial the following: 1) a high, well-developed anterior corner of the hypocone; 3) the entoloph is thick, tall cingulid that extends from the anterior edge of the and strongly connected to the protocone and metaconid to the anterior edge of the protoconid; 2) a hypocone; and 4) the central valley and the valley relatively high, complete metalophid connecting the between the posterior cingulum and the metaloph are protoconid to the metaconid; 3) a complete relatively deep. ectolophid; 4) a high, well-developed mesolophid The p4 (Figure 9B) exhibits the following that extends from the center of the ectolophid to the dental characters: 1) the tra is considerably narrower lingual margin of the tooth; and 5) a tall, robust than the trp; 2) the metaconid and protoconid are hypolophid that extends from the hypoconid to an positioned closely together with a short, high indistinct entoconid at the posterolingual corner of metalophid extending between them; 3) the the tooth. ectolophid is complete connecting the protoconid and Discussion―SDSNH 110318 and 110319 are hypoconid; 4) the hypolophid is well developed most similar to the M3s/m3s of Paradjidaumo connecting the entoconid and metaconid; 5) the including tall, complete lophs/lophids that form a posterior cingulid is distinct and extends from the four-lophed occlusal pattern, the lower molar anterior anterolingual corner of entoconid to the hypolophid cingulid is connected to the protoconid resulting in an near its connection with the entoconid; and 6) the enclosed valley between it and the metalophid, and mesolophid is tall and extends lingually from the the mesoloph and mesolophid are well developed, center of the ectolophid to about halfway across the extending from the endoloph and ectoloph to the central transverse valley. lingual and labial margins, respectively (Burke, Discussion―The p4 and partial M1 or 2 are 1934a; Wood, 1937, 1980; Russell, 1954, 1972; very similar to those Adjidaumo craigi from the Setoguchi, 1978; Korth, 1980; Kelly, 1992, 2010b) . Duchesnean of Saskatchewan (Storer, 1987) They differ from those referred above to including the following: 1) small size; 2) well- Protadjidaumo by having the following: 1) better developed, complete lophs/lophids that are about development of their lophs/lophids; 2) a different equal in height to the primary cusps; 3) central occlusal pattern in the connections of the lower molar valleys that are centrally positioned; 4) moderately anterior cingulid resulting in an enclosed valley high crowned with the increase in crown height due between it and the metalophid (anterior cingulid not to an increase in the crown base; and 5) the p4 extending to labial margin of the tooth and valley not metaconid and protoconid are positioned closely open labially); 3) a complete mesoloph and together and connected by an equally tall metalophid. mesolophid; and 4) relatively greater crown height. Adjidaumo craigi is primarily distinguished from They further differ from those referred to P. typus other species of the genus by its small size and by and P. sp., cf. P. typus by their larger size and from having lower molar anterior cingulids that are either those of later species of Paradjidaumo from the weakly connected to the protoconid or lack a Chadronian and Orellan by being slightly lower connection to the protoconid (Storer, 1987). crowned. SDSNH 110318 and 110319 document the Unfortunately, no lower molars are present in the occurrence of an undetermined species of sample of teeth from the Dry Gulch Creek Member Paradjidaumo in the Dry Gulch Creek Member. that can be identified as belonging to Adjidaumo. SDSNH 110321 and 130400 differ from those Adjidaumo Hay, 1899 referred above to Metanoiamys by being relatively Adjidaumo sp., cf. A. craigi Storer, 1987 higher crowned and by having much greater (Figures 9A-B, Table 1) development of the lophs/lophids (tall and well- connected to the primary cusps). They differ from Referred specimens―From SDSNH Loc. those referred above to Protadjidaumo and 5939, Dry Gulch Creek Member: Rp4, SDSNH Paradjidaumo by their much smaller size and the 110321; partial RM1 or 2, SDSNH 130400. occlusal morphology of their lophs/lophids. SDSNH Description― The partial M1 or 2 (Figure 9A) 110321 and 130400 represent a small species of is missing the anterior and lingual margins including Adjidaumo, most similar to A. craigi. PALUDICOLA, VOL. 8, NO. 4, 2012 225

resulting in a connection of the central transverse Genus Simiacritomys Kelly, 1992 valley with the valley between the anterior cingulid Simiacritomys sp. and the metalophid; 4) a deep valley between the (Figure 9E, Table 1) anterior cingulid and metalophid that is open labially; and 5) a deep valley between the mesolophid and Referred specimen―From SDSNH Loc. 5939, hypolophid that is open labially. The shared dental Dry Gulch Creek Member: Lm1 or 2, SDSNH characters of SDSNH 110320 and the lower molars 110320. of S. whistleri are so striking that its referral to Description―The lower molar (Figure 9E) has Simiacritomys is warranted. SDSNH 110320 a sub-rectangular occlusal outline with robust, probably represents a new species of the genus, but, rounded primary cusps. The anterior cingulid is tall until a much larger sample of teeth are discovered, it and well developed. It extends from the anterior side is referred to Simiacritomys sp. of the metaconid to the anterolabial corner of the tooth where it is separated from the protoconid by a Family Eutypomyidae Miller and Gidley, 1918 labial extension of the valley between the metalophid Microeutypomys Walton, 1993 and anterior cingulid. A moderately-developed Microeutypomys sp. anteroconid is present at about the middle of the (Figure 9F, Table 1) anterior cingulid. The metalophid is incomplete wherein it is interrupted by a deep notch between the Referred specimen―From SDSNH Loc. 5939, metaconid and the protoconid resulting in a narrow Dry Gulch Creek Member: Partial Lm1 or 2, SDSNH valley that connects the anterior portion of the central 110251. transverse valley with the valley between the Description―The partial m1 or 2 (Figure 9F) is metalophid and anterior cingulid. A tall, transversely missing the labial portion of the tooth and the elongated mesolophid (or mesoconid) extends posterior portion of the talonid is cracked and slightly obliquely from the posterolingual edge of the displaced. SDSNH 110251 exhibits the following protoconid into the central transverse valley and dental characters: 1) a distinct metaconid that is terminates about half way across the valley. A deep larger than the entoconid; 2) the protoconid, valley is present between the mesolophid and the metalophid and mesolophid are obliquely orientated hypolophid that is only slightly interrupted by a very with the mesolophid extending posterolingually to low lophid extending between the mesolophid and join with the anterolabial margin of the entoconid; 3) the hypoconid (incipient ectolophid) and extends to the mesolophid is lower in height than the metalophid the labial margin of the tooth. The hypolophid is a and hypolophid; 4) multiple, small accessory cuspids tall and complete, connecting the entoconid and are present within the central valley; 5) the anterior hypoconid. The posterior cingulid is a tall, well cingulid is well developed and connected to the developed lophid that extends from the anterolingual metaconid by an accessory lophid, resulting in a corner of the hypoconid to the posterolingual corner distinct enclosed valley between the metaconid and of the entoconid. Because the cingulids and lophids anterolingual portion of the anterior cingulid; 6) a are all tall and well developed the tooth has a five- deep, oblique valley is present between the lophed occlusal pattern. protoconid/metalophid and the anterior cingulid; 7) Discussion―Kelly (1992) named a new genus even though the entoconid is slightly displaced, it is and species of eomyid, Simiacritomys whistleri, clear that the lingual wall of the tooth is complete and based on a small sample of isolated teeth from the not distinctly interrupted by the central valley; 8) the Duchesnean Simi Valley Landfill Local Fauna of posterior cingulid is well developed and as tall as the California. Subsequently, additional isolated teeth hypolophid; and 9) small size. were discovered and described (Kelly, 2010b). Even Discussion― Previously, Walsh and Murphey with the small sample size, Kelly (1992, 2010b) (2007) referred SDSNH 110251 to Janimus sp., but it noted a fair amount of individual variation in the differs from the m1-2s of Janimus by having a three- minor connections in the lower molars between the lophed trigonid occlusal pattern, a better developed mesolophid and the protoconid and/or hypoconid, and more obliquely orientated mesolophid, greater and in the length of the mesolophid for S. whistleri. development of accessory cuspids in the central Except for the shorter and more obliquely orientated valley, relatively higher crowned with deeper, more mesolophid, SDSNH 110320 is very similar in size distinct valleys between the lophids, and smaller in (only slightly smaller) and occlusal morphology to size (Dawson, 1966; Storer, 1984, 1988). SDSNH m1-2 of S. whistleri, including the following: 1) tall, 110251 can be confidently referred to well-developed cingulids and lophids; 2) robust, Microeutypomys because it exhibits the following rounded primary cusps; 3) an incomplete metalophid diagnostic dental characters (Storer, 1988; Walton, 226 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

FIGURE 10. Undetermined rodent genera from Dry Gulch Creek Member, Duchesne River Formation. A, Lp4, SDSNH 110472. B, partial RM1 or 2, SDSNH 110322. C, LP4, SDSNH 110284. D, partial LM3, SDSNH 110289. E, Rm1 or 2, SDSNH 110323. F, Rm3, SDSNH 110288. G, Ldp4 or Lp4, SDSNH 110262. H, partial Lm3, SDSNH 130404. I, RM3, SDSNH 110273. All occlusal views. Scale = 1 mm. PALUDICOLA, VOL. 8, NO. 4, 2012 227

1993): 1) smaller in size and relatively lower 1965; Wood, 1974; Storer, 1988). It differs from crowned than the m1-2s of Eutypomys; 2) the those of Microeutypomys (Storer, 1988; Walton, mesolophid is obliquely orientated, lower in height 1993) by having the following: 1) larger size; 2) than the metalophid and hypolophid, and does not better developed lophids and cross-connecting extend to the lingual margin of the tooth; 3) multiple accessory lophids with the mesolophid equal in accessory cuspids are present in the central valley; 4) height to that of the metalophid and hypolophid and the metalophid, mesolophid and hypolophid are extending to the lingual margin of the tooth; and 3) lacking well-developed, transverse connections, relatively higher crowned. SDSNH 110252 which are typical in the lower molars of Eutypomys; documents the occurrence of a second eutypomyid 5) a relatively complete lingual wall; and 6) a three- from the Dry Gulch Creek Member that represents an lophed trigonid occlusal pattern. SDSNH 110251 is undetermined species of Eutypomys. similar in size to the m1-2s of Microeutypomys karenae Walton, 1993, from the Uintan of Texas and Suborder Myomorpha Brandt, 1855 significantly smaller than those of Microeutypomys family and genus undetermined tilliei Storer, 1988, from the Duchesnean of (Figures 10A-I) Saskatchewan. SDSNH 110251 probably represents a new species of Microeutypomys, but, until additional Specimens―From SDSNH Loc. 5939, Dry material is discovered, it is referred to an Gulch Creek Member: LP4, SDSNH 110284; partial undetermined species of the genus. RM1 or 2, SDSNH 110322; LM3, SDSNH 110289; RM3, SDSNH 110273; Ldp4 or p4, SDSNH 110262; Genus Eutypomys Matthew, 1905 Lp4, SDSNH 110472; Rm1 or 2, SDSNH 110323; Eutypomys sp. Rm3, 110288. From SDSNH Loc. 6087, Dry Gulch (Figure 9G, Table 1) Creek Member: Lm3, SDSNH 130404 Discussion―Confident generic assignments of Referred specimen―From SDSNH Loc. 5939, nine isolated teeth (Figure 10) from the Dry Gulch Dry Gulch Creek Member: Partial Lm3, SDSNH Creek Member have not been determined. However, 110252. for completeness, they are documented here. Description―The partial m3 (Figure 9G) is The p4 (Figure 10A) is characterized by having missing a portion of the anterolabial corner of the the following: 1) the tra is distinctly narrower than tooth, including most of the protoconid. Even in its the trp; 2) a well-developed metaconid and incipient broken state, the following dental characters can be protoconid, which are positioned close together distinguished: 1) moderately high crowned 2) the forming a short metalophid; 3) the entoconid and anterior cingulid, metalophid, mesolophid, and hypoconid are distinct, well developed cusps; 4) a hypolophid are tall and of equal height; 3) the well- deep transverse valley that is open lingually and developed anterior cingulid extends labially from the labially; 5) a low lophid is present that extends anterolingual corner of the metaconid and has a anteriorly from the lingual corner of the hypoconid posterolingually orientated accessory lophid that and bifurcates with one spur extending to the extends from it to the labial edge of the metaconid protoconid and one spur extending to the entoconid; forming a distinct valley between the anterior 6) a short hypolophid that extends from the cingulid and the metaconid; 4) the mesolophid posterolabial corner of the entoconid to about the extends to the lingual margin of the tooth and has middle of the posterior cingulid; and 7) an well-developed, tall transverse accessory lophids that incomplete posterior cingulid that extends from the form cross connections with the metalophid and posterior edge of the entoconid to near the hypolophid; 5) the valleys between the lophids are posterolingual edge of the hypoconid, where it is deep; and 6) the lingual wall of the tooth is complete. interrupted by a distinct notch or valley. Walsh and Discussion―Previously, Walsh and Murphey Murphey (2007) questionably referred this tooth to (2007) referred SDSNH 110252 to Janimus sp., but it cf. Pauromys sp., but with further preparation differs from the m3s of Janimus by being relatively (removal of additional matrix) it became apparent higher crowned and having much better developed that it is not assignable to this genus. The overall primary lophids and cross-connecting accessory occlusal morphology is more similar to those of the lophids that form distinct isolated, deep valleys on Eomyidae and is probably referable to an the occlusal surface (Dawson, 1966; Storer, 1984, undetermined genus of the family. 1988). SDSNH 110252 is most similar to the m3s of The partial M1 or 2 (Figure 10B) is Eutypomys (Matthew, 1905; Wood and Konizeski, characterized by having the following: 1) an almost 228 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

square occlusal outline with the trp only slightly The dp4 or p4 (Figure 10G) is characterized by narrower than the tra; 2) four distinct primary cusps; having the following: 1) tra is distinctly narrower 3) an incomplete protoloph between the paracone and than the trp; 2) a small, but distinct anteroconid; 3) protocone; 4) a low, complete metaloph between the the metaconid and protoconid are about equal in size metacone and hypocone; 5) a well-developed anterior and well separated; 4) a very low metalophid that cingulum, which is separated from the protoloph by a extends from the posterolabial base of the metaconid deep valley that is open lingually; 6) a large to the posterolingual base of the protoconid; 5) a very anterocone positioned on the anterior cingulum near low, indistinct ectolophid; 6) a low mesolophid that its lingual terminus; and 7) a tall, well-developed extends lingually from the ectolophid a short distance posterior cingulum that extends from the posterior into the central transverse valley; and 7) the edge of the metacone to join with the posterolabial entoconid and hypoconid are well developed and edge of the hypocone. Its occlusal morphology is connected by a moderately-tall hypolophid. The most similar to those of the Eomyidae and may lower premolar is similar in size and occlusal represent a new genus of the family. In size, it is morphology to the p4s of Metanoiamys sp., cf. M. compatible with the p4 (Figure 10A) described korthi, except that, because it is lacking a posterior above, suggesting that these two teeth may represent cingulid, it does not exhibit the typical, Y-shaped, the same species. eomyid occlusal pattern formed by the hypolophid The P4 (Figure 10C) is well worn and similar in and posterior cingulid. Also, it does not appear to be occlusal morphology to the M1 or 2 described above compatible morphologically or in size with any of the (Figure 10B), but differs by having a much shorter other genera identified from the Dry Gulch Creek anterior cingulum that is not open lingually, a loph Member and is referred to an undetermined that extends posterolabially from the protocone to the myomorph. anterolabial edge of the metacone, and in lacking an The m3 (Figure 10H) is poorly preserved with anterocone. It is most similar to those of the portions of the enamel abraded away. It is Eomyidae and may be referable to this family. characterized by having the following: 1) a well- The M3 (Figure 10D) and m1 or 2 (Figure 10E) developed anterior cingulid than extends labially are well-worn with portions of the occlusal enamel from the anterolingual base of the metaconid to near abraded away. Generic assignments for these two the anterior base of the protoconid; 2) a deep valley teeth are uncertain because of their poor state of between the metalophid and anterior cingulid that is preservation, but they both exhibit similarities to the open labially; 3) the metaconid is the tallest cusp with Eomyidae and may be referable to this family. a tall metastylid spur that extends posteriorly to near The m3 (Figure 10F) is barely worn and is the base of the entoconid; 4) the entoconid is well characterized by having the following: 1) a developed and separated from the posterior cingulid subrectangular occlusal outline; 2) a large, rounded by a distinct notch or valley; 5) the protoconid is metaconid with a projection or spur that extends large and compressed anteroposteriorly; 6) the labially to about half way across the tooth between hypoconid is large and well connected to a tall, thick the protoconid and anterior cingulid; 3) a well- posterior cingulid; and 7) a low mesoconid (or short developed, anteroposteriorly compressed protoconid mesolophid) is present between the protoconid and with a projection or spur that extends lingually to hypoconid, which is connected anteriorly to the near the base of the metaconid; 4) a distinct, well- protoconid and posteriorly to the hypoconid by an developed entoconid; 5) a anteroposteriorly incipient ectolophid. It exhibits some similarity to the compressed hypoconid; 6) a well-developed, tall m3s of Metanoiamys sp. cf. M. korthi, but differs by posterior cingulid that extends from the hypoconid to having an incomplete posterior cingulid that is a moderately distinct hypoconulid; 7) a distinct notch separated from the entoconid by a deep notch and it separates the hypoconulid and entoconid; 8) a very is lacking an adlophulid. It also exhibits some low, poorly-developed ectolophid; 9) a very low, morphological similarities to the m3 of Pauromys, short mesolophid extending lingually from the including comparable connections of the anterior ectolophid into the central transverse valley; and 10) cingulid, a well-developed metastylid spur, and a a well-developed anterior cingulid that extends from large entoconid that is separated from the posterior the anterior edge of the metaconid to near the cingulid by a distinct notch (compare Figure 10H anterolabial corner of the tooth. This tooth is with figs. 39 and 53 of Dawson, 1968). It differs from perplexing because it exhibits dental similarities to the m3 of Pauromys by having a much less both the Eomyidae and Sciuravidae. It probably developed mesoconid. Generic identification of this represents a new genus, but its familial assignment is tooth is withheld, but it may represent either the uncertain. Sciuravidae or Eomyidae. PALUDICOLA, VOL. 8, NO. 4, 2012 229

The M3 (Figure 10I) is moderately-worn and developed m1 or 2 parastylid resulting in relatively exhibits the following characters: 1) the paracone is flat anterior lingual wall; 3) weakly-developed lower tallest and largest cusp; 2) the protocone is well molar cingulids; 4) a weakly-developed ectostylid developed and separated from the much smaller between the m2 protoconid and hypoconid; 5) hypocone by a distinct notch along the posterolingual slightly crenulated enamel; and 6) similar orientation corner of the tooth; 3) the metacone is moderately of the transverse axes of the m2 protoconid and well developed and positioned at the posterolabial hypoconid. All of the preceding characters listed for corner of the tooth; 4) the anterior cingulum extends SDSNH 130406 rule out its referral to Protoreodon. from the anterior edge of the paracone to join the Thus, in size and morphology, SDSNH 130406 anterior edge of the protocone and then continues agrees well with P. kayi and is referred to this lingually for a short distance; 5) the protoloph is species. complete connecting the paracone to the protocone; ______6) the entoloph is complete, connecting the protocone to the hypocone; 7) the metaloph is complete, connecting the hypocone with the labial portion of the hypoloph near its junction with the metacone; 8) the mesoloph extends from the entoloph a short distance into the central transverse valley and then bifurcates into two terminal spurs, one directed posteriorly that joins the metaloph and one directed anterolabially that terminates near the base of the paracone; and 9) a small mesostyle. The overall occlusal pattern is similar to that of eomyids. In size, it is compatible with the teeth referred above to Protadjidaumo sp., cf. P. typus and could represent a M3 variant of this species. However, because of the unusual connections of the bifurcating mesoloph, its generic assignment is uncertain.

Order Artiodactyla Owen, 1848 Family Protoceratidae Marsh, 1891 Poabromylus Peterson, 1931 Poabromylus kayi Peterson, 1931 (Figures 11A-D, Table 1)

Specimen―From SDSNH Loc. 6339, Dry Gulch Creek Member, Duchesne River Formation: two partial left lower molars and associated tooth and dentary fragments, SDSNH 130406. FIGURE 11. Poabromylus kayi from Dry Gulch Creek Member, Discussion―SDSNH 130406 consists of a Duchesne River Formation. A-D, SDSNH 130406. A, anterior lingual wall of m1 or 2 with parastylid (PS) and metaconid (MC), portion of the dentary with the p2 roots, a m1 occlusal view; B, partial Lm1, occlusal view; C-D, partial Lm2, hypoconid with its root, a m1 or 2 partial anterior occlusal view (C) and labial view (D); E, dentary fragment with lingual wall, a partial m2, and associated tooth and roots of p2 and showing diastema (Dia) anterior to p2, lateral view. dentary fragments (Figures 11 A-E). Nine species of Scale = 1 mm. non-suiform artiodactyls have been previously ______recorded from the Duchesne River Formation (Gazin, Artiodactyla, family and genus undetermined 1955; Gunnell et al., 2009). The m2 of SDSNH

130406 is within the size range of those of Specimen― From SDSNH Loc. 6240, Starr Poabromylus kayi (Scott, 1945). It is slightly smaller Flat Member: associated molar and bone fragments, than those of Protoreodon pumilus, much smaller SDSNH 130405. than those of Protoreodon primus and Diplobunops, Discussion―SDSNH 130405 consists of and significantly larger than those of Pentacymelus, numerous, associated enamel and bone fragments Leptotragulus, and Simimeryx. SDSNH 130406 is including some portions of the exterior or interior indistinguishable from P. kayi by having the walls of cheek teeth. The crown heights of the wall following: 1) a two-rooted p2 with a distinct diastema fragments, which represent either portions of an present anterior to the p2; 2) a very weakly- 230 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

upper molar ectoloph or a lower molar lingual wall, Black and Dawson’s (1966) record was incorrect and indicate they represent a relatively selenodont the only prior record of P. typus was from the artiodactyl. SDSNH 130405 is significant because it Lapoint Fauna (Burke, 1934a). It should also be is the first record of a vertebrae fossil from the Starr noted that in a book on the evolution of Tertiary Flat Member of the Duchesne River Formation. Mammals of North America, edited by Janis et al. (2008), Flynn (2008) reported that Protadjidaumo, AGE OF FAUNA Paradjidaumo, and Adjidaumo first appear in the late Bridgerian (Br3). These records are incorrect because The age of the Dry Gulch Creek Member of the the Eomyidae temporal range chart (Flynn, 2008, fig. Duchesne River Formation has been the subject of 25.3) was automatically generated by the editors debate because only one species, Duchesnehippus using an incorrect age for the fauna from the intermedius represented by one specimen, had Kishenehn Formation (Janis et al., 2008, Appendix 1, previously been reported from it with confidence locality NP13), wherein the fauna was regarded as (Peterson, 1931; Rasmussen et al., 1999). Black and Bridgerian or Br2-3 (Larry Flynn, per. Dawson (1966) listed the occurrence of communication, 2011). Emry et al. (1987), Duchesneodus uintensis in the Halfway “horizon” Constenius et al. (1989), and Lucas (1992) had and this record appears to be based on two associated previously provided convincing evidence that the partial dentaries with one molar (CM 11996), which fauna from the Kishenehn Formation described by are listed in the vertebrate paleontology catalog of the Russell (1954, 1964) is Chadronian in age. Flynn CM as coming from the Halfway “horizon” without (2008) lists the next oldest known occurrence for any detailed locality data (Amy Henrici, per. Adjidaumo as Duchesnean (Du) and that of communication, 2011). Because Andersen and Picard Paradjidaumo and Protadjidaumo as late Uintan (1972, fig. 1) correlated Kay’s (1934) Halfway (Ui3). The first appearance datums (FADs) of “horizon” to the uppermost part of the Brennan Basin Protadjidaumo in late Uintan (Ui3) and Adjidaumo in Member and the Dry Gulch Creek Member, which the Duchesnean are rather well documented (e.g., member CM 11996 came from cannot be determined Burke, 1934a; Emry, 1981; Storer, 1984, 1987, with confidence. The stratigraphic position of a third Wilson, 1986; Lucas, 1992; Kelly et al., 1991; Kelly, species, Eosictis avinoffi, has also not been 1992, 2010b; Prothero and Emry, 1996; Walsh, 1996; determined with confidence, but came from either the Robinson et al, 2004; Gunnell et al., 2009). Lapoint Member or the Dry Gulch Creek Member However, the occurrence of Paradjidaumo in the late (Lucas, 1992; Rasmussen et al., 1999). The discovery Uintan (Ui3), which is listed by Flynn (2008) as of additional small mammals from the Dry Gulch occurring at locality CC7B, was based on Walsh's Creek Member reported on herein provides a new (1996) record of cf. Paradjidaumo sp. from the basis for an age determination for the member. Cloud 9 Local Fauna of the Mission Valley Eutypomys first appears in the Duchesnean and Formation and Jeff's Discovery site from Member C continues through the early Arikareean (Flynn and of the Santiago Formation (Larry Flynn, per. Jacobs, 2008). Poabromylus kayi first appears in the communication, 2011). Subsequent to Walsh (1996), Duchesnean and continues through the early two of us (Kelly and Walsh) reexamined the Chadronian (Prothero, 1998; Prothero and Ludtke, specimens that were referred to cf. Paradjidaumo sp. 2007). Heliscomys first appears in the Duchesnean from southern California and agreed that they do not and continues through the early Barstovian (Storer, actually represent Paradjidaumo, but some other 1988; Korth and Eaton, 2004; Kelly, 2009). undetermined eomyid genus. In fact, Walsh (1996, p. Pareumys guensburgi, Passaliscomys, Simiacritomys, 82) stated that Paradjidaumo is only known from Metanoiamys lacus, and Metanoiamys korthi have strata of definite Duchesnean age. Therefore, the been previously recorded only in the Duchesnean FADs for Adjidaumo and Paradjidaumo are (Black, 1970, 1974; Storer, 1987; Kelly, 1992, Duchesnean and that for Protadjidaumo is late 2010b; Kelly and Whistler, 1998; Korth and Eaton, Uintan (Ui3). 2004). Considering the known temporal ranges and Protadjidaumo typus was reported to occur in FADs of the taxa recovered during this study and the late Uintan (Ui3) by Gunnell et al. (2009). those of closely related taxa (Figure 12), the Dry However, this record is incorrect because it was Gulch Creek Member localities can be confidently based on Prothero’s (1996a) record of P. typus in the assigned to the Duchesnean. Lucas (1992) first Randlett Fauna, which was based on Black and proposed combining the taxa from about the upper Dawson’s (1966) record (Rasmussen et al., 1999; three-quarters of the Dry Gulch Creek Member and Beth Townsend, per. communication, 2011). the Lapoint Member as the Halfway/Lapoint Fauna However, Rasmussen et al. (1999) determined that and tentatively redesignated it as the “type fauna” for PALUDICOLA, VOL. 8, NO. 4, 2012 231

FIGURE 12. Recorded North American subbiozone ranges (thick vertical lines) of selected genera and species discussed in text. Abbreviations are: Ar, Arikareean; Ba, Barstovian; Br, Bridgerian; Ch, Chadronian; Cl, Clarendonian; Du, Duchesnean; He, Hemingfordian; Hh, Hemphillian; Ma, megannum in the radioisotopic time scale; Or, Orellan; SBZ, subbiozones of the North American Land Mammal ages; Ui, Uintan; Wh, Whitneyan. Subbiozones Hh-2 and Br-3 extend younger and older, respectively, than shown in SBZ column. ______the Duchesnean. Lucas’s (1992) combination of the species from the member shared with the Lapoint two assemblages, which was followed by Rasmussen Fauna (see above). With the greater correlation of the et al. (1999), is further supported because the Dry taxa from the two assemblages, the assemblage from Gulch Creek Member localities are now confidently the Dry Gulch Creek Member localities is herein also known to share four species (Pareumys guensburgi, combined with the Lapoint Fauna, as the Protadjidaumo typus, Duchesnehippus intermedius, Halfway/Lapoint Fauna (Table 6). An age assignment and Poabromylus kayi) with the Lapoint Fauna. The for the Starr Flat Member of the Duchesne River specimen (CM 11996) of Duchesneodus uintensis Formation cannot be made because the only mammal from the Halfway “horizon” might represent a fifth 232 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

recorded from this member is an indeterminate Member of the Duchesne River Formation. Prothero artiodactyl. (1996a) provided the following correlations of the middle and late Uintan localities of the Uinta THE UINTAN-DUCHESNEAN TRANSITION Formation to the GPTS (Figure 13): 1) the middle Uintan (Ui2) White River Pocket occurs within the Correlations of Faunas from the Duchesne upper part of Chron C20r; 2) the middle Uintan (Ui2) River and Sespe Formations―The Wood Com- Skull Pass Quarry occurs within the lower quarter of mittee (Wood et al., 1941) designated the Pearson Chron C20n; and 3) the late Uintan (Ui3) Myton Ranch Local Fauna from locality LACM(CIT) 150 of Pocket, Leota Quarry, and Thorne Quarry occur the Sespe Formation of California as the principal within the upper half of Chron C20n. In Prothero’s correlative fauna of the “type” Duchesnean fauna (1996a) Willow Creek-Ouray Section, the lower part from the Duchesne River Formation, which then of the Duchesne River Formation spanned the upper included the assemblages from the Randlett, part of Chron C19r through the lower part of C18r. Halfway, and Lapoint “horizons.” As noted above, The majority of the specimens representing the the Randlett Fauna is now regarded by most Randlett Fauna came from the Brennan Basin investigators as latest Uintan because its faunal Member at a level that was just above the base or composition is more similar to other late Uintan near the base of the Duchesne River Formation faunas than to those that can be confidently assigned (Peterson, 1931, 1934; Scott, 1945; Gazin, 1955; to the Duchesnean (Gazin, 1955; Clark et al, 1967; Rasmussen et al., 1999). Based on Prothero’s (1996a) Tedford, 1970; Lucas, 1992; Robinson et al., 2004; magnetostratigraphy, the localities that yielded the Burger, 2011). Randlett Fauna can then be correlated to occur from The middle member of the Sespe Formation about the upper part of Chron C19r to the lower part exposed in the Simi Valley area of southern of C19n (Figure 13). The Lapoint Ash occurs near California has yielded numerous middle Eocene the base of the Lapoint Member of the Duchesne fossil mammals spanning the late Uintan and River Formation and underlies the localities that Duchesnean (e.g., Golz, 1976; Golz and Lillegraven, yielded the Lapoint Fauna and overlies the Dry Gulch 1977; Mason, 1988; Kelly, 1990, 1992, 2009, Creek Member localities (Murphey et al., 2011). 2010a,b; Kelly et al., 1991; Kelly and Whistler, 1994, Prothero and Swisher (1992) provided six 40Ar/39Ar 1998). Five, well-defined superposed local faunas dates based on biotite separates from the Lapoint Ash are now recognized from the middle member of the with a mean age of 39.74 ± 0.07 Ma. Based on the Sespe Formation (Kelly, 1990, 1992, 2009, 2010a, b; new Fish Canyon sanidine recalibration for 40Ar/39Ar Kelly et al., 1991), in ascending stratigraphic order: dates run at the Berkeley Geochronology Laboratory the late Uintan Tapo Canyon Local Fauna; the late before 1994, wherein they used a Fish Canyon Uintan Brea Canyon Local Fauna; the latest Uintan sanidine age of 27.84 Ma (Swisher, 1992), the age of or earliest Duchesnean Strathearn Local Fauna; the 39.74 Ma is recalibrated to 40.26 ± 0.08 Ma. Based Duchesnean Pearson Ranch Local Fauna; and the on the GPTS of Berggren et al. (1995), Prothero and Duchesnean Simi Valley Landfill Local Fauna. Emry (1996) placed the Lapoint Ash within Chron Prothero et al. (1996) documented the C18n. However, the GPTS is being continuously magnetostratigraphy of the Sespe Formation in the updated and refined (e.g., Gradstein et al., 2004; Simi Valley area that included the sections that Luterbacher et al., 2004; Ogg and Smith, 2004; Gee yielded the five superposed faunas, which they and Kent, 2007; Pälike et al., 2010; Jovane et al., correlated to the Global Polarity Time Scale (GPTS) 2010). The calibrated age ranges for Chrons C21n of Berggren et al. (1995) as follows (Figure 13): 1) through C16n provided by Gee and Kent (2007), late Uintan Tapo Canyon and Brea Canyon local Pälike et al. (2010), and Jovane et al. (2010) are in faunas occur within the lower half of Chron C18r; 2) close agreement and are regarded here as currently the late Uintan or early Duchesnean Strathearn Local the most reliable. Using their chron age ranges would Fauna occurs within the upper third of Chron C18r place the Lapoint Ash within the upper part of C18r. through lower third of Chron C18n; 3) the This is problematic because it would place the Duchesnean Pearson Ranch Local Fauna occurs Lapoint Fauna at a level between those to which within the upper two-thirds of Chron C18n (C18n.2n Prothero et al. (1996) correlated the latest Uintan or through C18n.1n); and 4) the Duchesnean Simi early Duchesnean Strathearn and the late Uintan Brea Valley Landfill Local Fauna occurs in Chron C17r. Canyon local faunas (Figure 13). Prothero (1996a) documented the magneto- Tables 7 and 8 provide the generic occurrences stratigraphy of the Uinta Formation in the Uinta and relative percentages of genera, respectively, in Basin, Utah, including two sections that extended selected latest Uintan and Duchesnean faunas and stratigraphically upward into the Brennan Basin PALUDICOLA, VOL. 8, NO. 4, 2012 233

FIGURE 13. Correlation of selected Uintan and Duchesnean faunas from the Sespe Formation of California, the Uinta and Duchesne River formations of Utah, and well-dated faunas from the Chambers Tuff of Texas to the Global Polarity Time Scale (GPTS). Note new proposed correlations of faunas from Sespe Formation as discussed in text. Mean 40Ar/39Ar Ma dates are calibrated to the new Fish Canyon Tuff standard of 28.201 Ma. Abbreviations are: Fm, formation; LF, local fauna; Ma, megannum (one million years in the radioisotopic time scale); NALMA, North American Land Mammal Age. 234 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

their known occurrences in other Uintan (Ui) and River and Uinta formations have significant impacts Chadronian (Chad) faunas of North America. These on some of the previous correlations provided by comparisons indicate that the Porvenir Local Fauna other investigators of Duchesnean faunas from other from the Chambers Tuff of Texas (Wilson, 1986; areas in North America (Table 9). Lucas, 1992) exhibits the most generic similarity to ______Chadronian faunas and is the youngest in age TABLE 6. Revised faunal list for the “type” Duchesnean followed by, in increasing age, the Halfway/Lapoint Halfway/Lapoint Fauna (includes taxa from the Dry Gulch Creek Fauna, the Simi Valley Landfill Local Fauna, the Member1 and Lapoint Member2). Pearson Ranch Local Fauna, the Strathearn Local Fauna, and the Randlett Fauna. The Halfway/Lapoint Didelphimorpha Didelphidae Fauna appears to be closer in age to the Simi Valley Copedelphys sp.1 Landfill Local Fauna than to the other faunas because Lipotyphla of the following: 1) the shared occurrence of genera and spp. undet.1 Simiacritomys; and 2) both record the first Soricomorpha Geolabididae appearances of Paradjidaumo and Heliscomys. Centetodon sp.2 Although, Metanoiamys sp., cf. M. korthi described Cete herein appears to be slightly more derived than M. Mesonychidae 2 korthi of the Simi Valley Landfill Local Fauna (see Hessolestes ultimus Peterson, 1931 Creodonta above), which suggests that the Halfway/Lapoint Hyaenodontidae Fauna is slightly younger than the Simi Valley Hyaenodon sp., cf. H. vetus 2 Stock, 1933 Landfill Local Fauna. Considering the above facts, Carnivora 2 the correlations of the faunas from the Sespe Family indet. Lagomorpha Formation to the GPTS by Prothero et al. (1996) Leporidae appear inconsistent with the relative ages of the Mytonolagus sp. 1 faunas from the Duchesne River Formation because Rodentia the Randlett Fauna would be older than the Tapo Cylindrodontidae Pareumys guensburgi 1, 2 Black, 1970 Canyon and Brea Canyon local faunas and the Geomyoidea Strathearn, Pearson Ranch, and Simi Valley Landfill Griphomys sp. 1 local faunas would all be younger than the Heliscomyidae 1 Halfway/Lapoint Fauna (Figure 13). For all of the Heliscomys sp. Passaliscomys sp. 1 above reasons, we propose that the faunas from the Eomyidae Sespe Formation be correlated to Chrons C19r Protadjidaumo typus 1, 2 Burke, 1934a through C18r (Figure 13). These new correlations 1 would then place the Randlett Fauna and the Protadjidaumo sp., cf. P. typus Burke, 1934a Paradjidaumo sp.1 Strathearn Local Fauna at about the same intervals Adjidaumo sp., cf. A. craigi 1 Storer, 1987 within the GPTS. Based on the faunal composition, Metanoiamys lacus 1 Storer, 1987 Kelly (1990) and Kelly et al. (1991) could not Metanoiamys sp., cf. M. korthi1 Kelly and Whistler, determine if the Strathearn Local Fauna was either 1994 Simiacritomys sp.1 latest Uintan or earliest Duchesnean. As noted above, ? Eomyidae, genera undet.1 we accept a latest Uintan age assignment for the Eutypomyidae Randlett Fauna, which would strongly suggest that Microeutypomys sp.1 1 the Strathearn Local Fauna should also be regarded Eutypomys sp. Myomorpha as latest Uintan. Taking into account our new Myomorpha, genera undet. 1 proposed correlations of the faunas from the Sespe Perissodactyla Formation and relative age assignments of the faunas Tapiroidea 2 from the Uinta Basin, a generalized stratigraphic Colodon sp. Hyracodontidae section of the east-central Uinta Basin with the Hyracodon medius 2 Peterson, 1931 faunas correlated to the magnetostratigraphy is ?Rhinocerotidae presented in Figure 14. These new correlations would rhinocerotid, genus and species indet. 2 indicate that the Uintan-Duchesnean boundary occurs Equidae Duchesnehippus intermedius 1, 2 Peterson, 1931 within the lower half of Chron C19n or at about 41.4 Brontotheriidae Ma. Duchesneodus uintensis 1?, 2 (Peterson, 1931) Correlations of Other Duchesnean Artiodactyla Faunas―Our new correlations of the faunas from Entelodontidae Brachyhyops wyomingensis 2 Colbert, 1938 the Sespe Formation to those from the Duchesne Agriochoeridae PALUDICOLA, VOL. 8, NO. 4, 2012 235

Protoreodon sp., cf. P. pumilus 2 (= ? Eomeryx, see (Figure 13), which would indicate an upper age limit Lander, 2011) for the Duchesnean of at least 37.92 Ma. Agriochoerus maximus 2 Douglass, 1901 Wilson (1977) reported the following strati- Hypertragulidae graphic distribution of the Candelaria Local Fauna Simimeryx minutus 2 Peterson, 1934 within the Colmena Formation (= Colmena Tuff) of the Vieja area: 1) the majority of specimens were Protoceratidae Poabromylus kayi 1, 2 Peterson, 1931 recovered from the lower sedimentary unit or the lower 30 m of the section; 2) one tooth of Amynodon Undetermined Order and family came from the lower 7 m of the Lahar deposits, 1 or 2 Eosictis avinoffi Scott, 1945 which overlie the lower sedimentary unit; and 3) five ______taxa were recovered from the glass facies A number of well characterized Uintan and (“Clabaugh’s” bonebed), which overlie the Lahar Duchesnean faunas have been reported from the deposits at about 115 – 152 m above the base of the Vieja and Agua Fria areas of Trans-Pecos, Texas section. The Candelaria Local Fauna of the Vieja area (Wilson et al., 1968; Wilson 1977, 1980, 1984, has been regarded as either early Duchesnean or 1986). The latest Duchesnean Porvenir Local Fauna latest Uintan in age (e.g., Wilson, 1977; Krishtalka et occurs in the Chambers Tuff, which overlies the al., 1987; Prothero, 1996b; Robinson et al., 2004). Buckshot Ignimbrite in the Vieja area (Wilson, 1986; Prothero (1996b) reevaluated the magnetostrat- Lucas, 1986). Prothero and Swisher (1992) reported igraphy of the Uintan through early Chadronian rocks an 40Ar/39Ar date of 37.8 ± 0.15 Ma for the Buckshot of the Trans-Pecos area and correlated their faunas to Ignimbrite, which corrected to the new Fish Canyon the GPTS of Berggren et al. (1995). The Colmena Tuff standard of 28.201 Ma (Kuiper et al., 2008) Formation that yielded the Candelaria Local Fauna, would recalibrate to 38.29 ± 0.16 Ma. Prothero which included about 152 m of section, exhibited the (1996b) incorrectly cited Henry et al. (1994) as the following magnetostratigraphy, in ascending order reference for an 40Ar/39Ar date of 37.54 ± 0.11 Ma for (Prothero, 1996b): 1) a reversed interval in about the the Buckshot Ignimbrite. Although this date was lower 30.5 m, which included the lower sedimentary never published, it is correct and was obtained by unit and the lowermost part of the lahar deposits; 2) a Michael Kunk, Christopher Henry and others at the normal interval extending from about 30.5 to 106 m U.S. Geological Survey Argon Dating Laboratory, above the base of the section, which included most of Reston, Virginia, using a Fish Canyon age of 27.79 the lahar deposits; and 3) a reversed interval from Ma (Christopher Henry, per. communication, 2011). about 106 to 152 m above the base of the section, Recalibration of this date to the new Fish Canyon which included the glass facies. Based primarily on Tuff standard would change it to 38.10 ± 0.12 Ma. the faunal correlation of the Candelaria Local Fauna Most recently, Christopher Henry, William to the Randlett Fauna provided by Krishtalka et al. McIntosh, and others at the New Mexico (1987) and his magnetostratigraphic correlations of Geochronology Laboratory, Socorro, New Mexico, the lower part of the Duchesne River Formation obtained a third 40Ar/39Ar date for the Buckshot (Prothero, 1996a), Prothero (1996b, p. 196) assigned Ignimbrite of 37.68 ± 0.04 Ma, which was calibrated the normal magnetic interval within the Colmena using the Fish Canyon standard of 28.201 Ma Formation to Chron C19n with parts of Chrons C19r (Christopher Henry, per. communication, 2011). and C18r included in the section that yielded the Prothero (1996b) reevaluated the magneto- Candelaria Local Fauna. However, in figure 6 of stratigraphy of the Chambers Tuff and placed the Prothero (1996b), the normal interval containing part Buckshot Ignimbrite in Chron C17r and the Porvenir of the Candelaria Local Fauna is shown as correlating Local Fauna within early Chron C17n of the GPTS of with Chron C18n. This same correlation of the Berggren et al. (1995). Considering the mean Candelaria Local Fauna with Chron C18n was radioisotopic age of the three 40Ar/39Ar dates (38.02 repeated in the same volume by Prothero and Emry Ma), the ranges for the three dates (37.68, 38.10, and (1996, fig. 2). The correlations of this normal interval 38.29 Ma), and the fact that the Buckshot Ignimbrite to Chron C18n appear to be a lapses because they occurs within a reversed interval, Prothero’s (1996b) would necessitate that the Candelaria Local Fauna to chron assignment for the Porvenir Local Fauna still be younger than the Halfway/Lapoint Fauna and Simi appears valid when recorrelated to the new GPTS Valley Landfill Local Fauna, which is not supported chron age assignments (Gee and Kent, 2007; Pälike by the taxa comprising the majority of the Candelaria et al., 2010; Jovane et al., 2010). This would most Local Fauna (Krishtalka et al, 1987; Robinson et al., likely place the Buckshot Ignimbrite in Chron C17r 2004). Based on his analysis of the rodents of the and the Porvenir Local Fauna within Chron C17n.3n Colmena Formation, Wood (1974) considered some of the rodents of the Candelaria Local Fauna as 236 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

TABLE 7. Records of genera in selected faunas and their known occurrences in other Uintan (Ui) or older faunas and Chadronian (Chad) faunas of North America. Abbreviations are: Stra, Strathearn Local Fauna (LF); Rand, fauna from Randlett “horizon”, primarily from the base or near the base of Brennan Basin Member of Duchesne River Formation (DRF); Pear, Pearson Ranch LF; Simi, Simi Valley Landfill LF; Half, fauna from Halfway “horizon” = Dry Gulch Creek Member and upper quarter of Brennan Basin Member of DRF; Lap, fauna from Lapoint Member of DRF; Por, Porvenir LF. 1Total counts do not include those taxa that are questionably referred to a genus (cf.).

Taxon Ui Rand Stra Pear Simi Half Lap Por Chad Copedelphys X X X Peradectes X X X X Herpetotherium X X X Simidectes X X X Hyaenodon X X X X Ischnognathus X X Hemipsalodon X X X Miacis X X X Daphoenus X X Hessolestes X X Apternodus X X X Leptictis X X Oligoryctes X cf. X X Centetodon X X X X Batodonoides X X X Sespedectes X X X X Proterixoides X X X Uintasorex X cf. Chusmashius X X Dyseolemur X X Rooneyia X Mytonolagus X X X X X Mytonomys X X X Microparamys X X X X Rapamys X X Uintaparamys X X X Quadrotomus X X Ischyrotomus X X Manitsha X X Ischyromys X X Pareumys X X X X X X Pseudocylindrodon X X Ardynomys X X Jaywilsonomys X X Presbymys X Griphomys X X X X Heliscomys X X X Passaliscomys X Metanoiamys X X X Protadjidaumo X X X X Paradjidaumo X X X Adjidaumo X X X Viejadjidaumo X Aulolithomys X X Yoderimys X X Simiacritomys X X Microeutypomys X X Eutypomys X X X PALUDICOLA, VOL. 8, NO. 4, 2012 237

Taxon Ui Rand Stra Pear Simi Half Lap Por Chad Simimys X X X cf. ?Triplopus X X X Colodon X X X X Toxotherium X X Heteraletes X X Epitriplopus X X Hyracodon X X X Trigonias cf. X Subhyracodon cf. X Megalamynodon X X Metamynodon X X X Uintaceras X X Duchesnehippus X X Haplohippus X Mesohippus X X Amynodon X X Amynodontopsis X X Duchesneodus X X X X X X X X Menops X X Protoreodon X X X X X X Diplobunops X X Agriochoerus X X X Aclistomycter X X Brachyops X X X X Archaeotherium X X Leptoreodon X X X Poabromylus X X X X Heteromeryx X X X Pentacymelus X X Protylopus X X X Eotylopus X X X Hendryomeryx X X X Simimeryx X X X X X Leptotragulus X X X Hypertragulus X X Eosictis X? __ 1Number of 13 11 20 12 16 15 41 genera/fauna

______slightly more derived than those from Myton and that yielded the latest Uintan Randlett Fauna and suggested they may be equivalent in age with those Strathearn Local Fauna. Furthermore, if the from the Randlett Fauna or later. We agree that the correlation of the normal interval within the Colmena taxa from the lower 37 m of the Colmena Formation Formation to C19n is correct, then the upper reversed section are Uintan in age because they exhibit more interval within the glass facies, which yielded five taxonomic similarity to Uintan faunas than to taxa at about 91 m higher in the section, would Duchesnean faunas. If the normal interval within the correlate to the lower part of C18r and suggest an Colmena section is Chron C19n, as Prothero early Duchesnean age for these taxa. Another option originally stated (1996b, p. 196), it would place the would be to correlate the normal interval within the majority of specimens of the Candelaria Local Fauna Colmena section to C20n, but that would require within the upper part of Chron C19r through the correlating the lower reversed interval to C20r. lowermost part of Chron C19n. This would correlate However, this correlation would assign a middle the majority of taxa comprising the Candelaria Local Uintan (Ui2) age to the majority of the taxa of the Fauna to about the same interval within the GPTS Candelaria Local Fauna, which does not appear to be 238 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

supported by the faunal composition (Wood, 1974; The Duchesnean faunas from the Skyline and Wilson, 1977; Krishtalka et al., 1987; Robinson et al., Cotter channels in the Devil’s Graveyard Formation 2004). We consider the normal interval within the (Stevens et al., 1984; Wilson, 1986) of the Agua Fria Colmena section as most likely representing Chron area were regarded by Prothero (1996b) and Prothero C19n, which would correlate the majority of taxa of and Emry (1996) as occurring in upper part of Chron the Candelaria Local Fauna from the lower 37 m of C18n and C17r, respectively. Based on faunal the section with the latest Uintan Randlett and comparisons, Wilson (1984, 1986), Wilson and Strathearn Local Faunas. Wilson (1971, 1977) Stevens (1986) and Kelly (1990) argued that the reported the following taxa from the glass facies of Skyline Local Fauna is early Duchesnean and older the Colmena Formation; Manitsha johanniculi, than the Lapoint Fauna, whereas the fauna from the Uintaparamys leptodus, Prolapsus sp., Protoreodon Cotter Channels is late Duchesnean and a correlative petersoni, and Protoreodon pumilus. Uintaparamys of the Porvenir and/or Lapoint Fauna. Lucas (1992) leptodus is a long ranging species (Anderson, 2008; combined the faunas from the Skyline-Cotter Gunnell et al., 2009), previously recognized from the channels and regarded them as older than the early Uintan through latest Uintan (Ui1b – Ui3). Halfway/Lapoint Fauna. Because the Halfway/ Manitsha johanniculi is also known from the Lapoint fauna occurs within Chron C18r of the Duchesnean Porvenir Local Fauna and the GPTS, we propose that the Duchesnean Skyline and Chadronian Little Egypt Local Fauna (Wood, 1974). the Cotter Channels local faunas most likely correlate Wilson (1971, 1977) also recorded Protoreodon with the upper part of Chron C19n and the upper part pumilus and P. petersoni from the lower 37 m of the of Chron C18r, respectively. Colmena section and Rasmussen et al. (1999) ______recorded Protoreodon sp., cf. P. pumilus from the Duchesnean Halfway/Lapoint Fauna. However, TABLE 8. Percentage of genera in selected Uintan (Ui) and Lander (2011) completely revised many of the Duchesnean (Du) faunas that are known only from the Ui or earlier, Ui or earlier and Du, Du, and Du and Chadronian (Ch) or species that were previously referred to Protoreodon later. Abbreviations for faunas are same as for Table 7, except the from the Uinta, Duchesne River, and Colmena taxa from the Dry Gulch Creek Member and Lapoint members are formations, wherein he resurrected the genus combined as the Halfway/Lapoint Fauna (Half/Lap). Eomeryx Marsh, 1894, for many of the species as % of genera/fauna Half/ follows: Protoreodon pumilus (junior synonyms P. known only from Rand Stra Pear Simi Lap Por tardus and P. walshi and probably Protagriochoerus Ui or earlier 46% 18% 30% 8% 8% 0.5% annectens type specimen) = E. pumilus; Protoreodon Ui or earlier & Du 23% 73% 60% 42% 19% 7% pumilus from Myton and Randlett, and Du 0% 0% 0.5% 8% 15% 7% Mesagriochoerus primus from Randlett = E. medius; and Protoreodon petersoni from Myton is an Du & Ch or later 0% 0% 10% 17% 27% 39% oreodontid, which he tentatively regarded as the ______earliest member of genus Bathygenys. Lander (2011) states that E. pumilus first appears in the Uinta B and The age of the Hancock Quarry Local Fauna is followed by E. medius of Myton and Randlett, from Unit E of the Clarno Formation, Oregon, has forming an E. pumilus-E. medius lineage. This been variously assigned by previous investigators to revision would also suggest that the Protoreodon the late Uintan, Duchesnean, or earliest Chadronian specimens indentified by Rasmussen et al. (1999) (Hanson, 1996; Emry et al., 1987; Krishtalka et al., from the Halfway/Lapoint Fauna be referred to 1987; Lucas, 1992; Fremd et al., 1994; Janis et al., Eomeryx. Bathygenys reevesi is known from the 1998; Lucas et al., 2004; Robinson et al., 2004). The Chadronian Little Egypt Local Fauna (Wilson, 1971). age of the Hancock Quarry Local Fauna is bracketed by a K/Ar date of 40.4 ± 1.6 Ma from the underlying Prolapsus has been previously recorded from the 40 39 early to latest Uintan (Wilson, 1977; Walton and Unit D of the Clarno Formation and by Ar/ Ar Porter, 2008). Considering the fauna from the glass dates of 39.22 ± 0.03 and 39.72 ± 0.03(= 39.73 and facies includes taxa that are known from the Uintan, 40.24 Ma recalibrated to the new Fish Canyon Tuff Duchesnean and Chadronian, it is not unreasonable to standard, respectively) from a tuff in the overlying consider the fauna as early Duchesnean in age and Member A of the John Day Formation (Evernden et the reversed Chron that they were recovered from as al., 1964; Bestland et al., 1994; Hanson, 1996; Lucas the lower part of C18r. If this correlation is correct, et al., 2004; Lander and Hanson, 2006). Lander and then the latest Uintan Candelaria Local Fauna should Hanson (2006) correlated the Hancock Quarry Local be revised to include only those taxa that were Fauna with the Randlett Fauna based primarily on the recovered from the lower 37 m of the Colmena Formation. PALUDICOLA, VOL. 8, NO. 4, 2012 239

FIGURE 14. Generalized stratigraphic section of the Uinta and Duchesne River formations in the study area of east-central Uinta Basin, Uintah County, Utah, showing relative stratigraphic positions of localities and faunas discussed in text along with their proposed correlations to the North American Land Mammal Ages (NALMA) and to the magnetostratigraphic section (MS). Mean 40Ar/39Ar Ma date for Lapoint Ash is calibrated to the new Fish Canyon Tuff standard of 28.201 Ma. Obliquely-lined portion of magnetostratigraphic section unsampled in Uinta Basin. See Figure 13 for abbreviations, except for: Mbr, member or informal biostratigraphic zones; Tdr-bb, Brennan Basin Member; Tdr-dgc, Dry Gulch Creek Member; Tdr-l, Lapoint Member; Tdr-sf, Starr Flat Member. ______

occurrence of Agriochoerus matthewi crassus (= of the Skyline Local Fauna because of the co- Diplobunops crassus of other investigators, e.g., occurrence A. matthewi crassus and Duchesneodus Gazin, 1955; Rasmussen et al., 1999) in both faunas. and, following Wood et al. (1941), reassigned the They also regarded the Randlett Fauna a correlative Randlett Fauna to the early Duchesnean. It should be 240 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

noted that Lander (1998) and Lander and Hanson formations, so correlation of these formations to the (2006) regarded D. matthewi from the “Uinta C” and GPTS cannot be made. D. crassus of the Randlett Fauna as successive The Galisteo Formation of New Mexico has subspecies of Agriochoerus (A. matthewi matthewi yielded the Duchesnean Tonque Local Fauna (Lucas and A. matthewi crassus), whereas Ludtke (2007) et al., 1981; Lucas, 1982, 1992; Lucas and regarded these taxa as successive species of Williamson, 1993), which Lucas (1982, 1992) Agriochoerus (A. matthewi and A. crassus). regarded as most similar faunally to the Porvenir However, Ludtke (2008) and Lander (2011) Local Fauna and the Lapoint Fauna. Prothero and resurrected Diplobunops just for these two taxa as D. Lucas (1996) documented the magnetostratigraphy of matthewi and D. crassus or D. matthewi matthewi the Duchesnean part of the Galisteo Formation of and D. matthewi crassus, respectively. Because the New Mexico, wherein the two sections within the K/Ar date from the underlying Unit D of the Clarno formation that yielded the Tonque Local Fauna were Formation has such a large standard deviation, which correlated to Chrons C17n.r1 to C17n.3n (Arroyo del would give the date a range of uncertainty of from Tuerto section) and Chron C17r (Cerrillos section) of 38.8 – 42.0 Ma, it is not very useful for determining a the GPTS of Berggren et al. (1995). The Tonque lower age limit for the Hancock Quarry Local Fauna. Local Fauna includes Duchesneodus uintensis, Based on the more accurate 40Ar/39Ar radioisotopic Hemipsalodon grandis, Amynodon sp., Protoreodon data for the overlying welded tuff in the John Day sp., and Poabromylus minor (Lucas et al., 1981; Formation and the faunal composition, Lucas et al. Lucas, 1982, 1992; Lucas and Schoch, 1989; (2004) regarded the Hancock Quarry Local Fauna as Prothero, 1998; Prothero and Ludtke, 2007). Because late Uintan in age. The co-occurrence of Diplobunops the sample of fossil mammals from the Galisteo crassus (= D. matthewi crassus) in the Randlett Formation is depauperate and the formation lacks Fauna and Hancock Quarry Local Fauna (Lander and radioisotopic dates, it is difficult to correlate it with Hanson, 2006) suggests a similar age for the faunas, other Duchesnean faunas from North America. which would correlate the fauna to the upper part of Hemipsalodon grandis has previously been recorded Chron C19r to the lower part of C19n, making it from the latest Uintan to the early Chadronian latest Uintan in age. Although the 40Ar/39Ar dates of (Mellet, 1969; Kihm, 1987; Storer, 1996; Hanson, 37.73 and 40.24 Ma (mean = 39.99 Ma) for the 1996). Amynodon is a characteristic Uintan taxon and overlying tuff and the most recent recalibrated Chron Protoreodon is known from the Uintan and ages for GPTS (Gee and Kent, 2007; Pälike et al., Duchesnean (Robinson et al., 2004). However, the 2010, Jovane et al., 2010) do not rule out correlation co-occurrence of D. uintensis and P. minor in the of the Hancock Quarry Local Fauna to anywhere Tonque and Porvenir local faunas does suggest a from the lower part of C19n through C18r, which similar age for the two faunas. This would imply that spans part of the latest Uintan and Duchesnean. the normal and reversed magnetic intervals in the two Walsh (1991a,b; 1996, 1997, 2000) provided sections of the Galisteo Formation probably correlate detailed summaries of the early to late Uintan faunas with Chrons C17r and C17n of the GPTS, in support from the San Diego area of southern California and of the original correlations of Prothero and Lucas Walsh et al. (1996) documented the magneto- (1996). stratigraphy of some of the formations that yielded The Baca Formation of New Mexico has these faunas. Walsh (1996) discussed four faunas yielded a fauna that was originally regarded as (Laguna Riveria, Camp San Onofre, Mission del Oro, Chadronian in age (Snyder, 1970, 1971; Schrodt, and Bonita local faunas) that were recovered from 1980; Schiebout and Schrodt, 1981). Subsequently, Member C of the Santiago Formation in coastal other investigators reevaluated the fauna and northern San Diego County, and the “Sweetwater reassigned it to the late Duchesnean (Lucas, 1983, Formation”, south of the city of San Diego. Based on 1992; Lucas and Williamson, 1993; Prothero et al., faunal compositions, Walsh (1996) could not 2004). Prothero et al. (2004) documented that the determine if they were latest Uintan or early stratigraphic section that yielded the fauna is of Duchesnean in age. Mihlbachler and Deméré (2009) reversed magnetic polarity. Based on correlation of reported a Duchesnean assemblage from the “Bone the fauna from the Baca Formation with the Sands” of the upper part of Member C of the Duchesnean fauna from the Galisteo Formation and Santiago Formation at the Ocean Ranch Corporate the Porvenir Local Fauna along with radioisotopic Centre in Oceanside, California. Based on the fauna, dates indicating the Baca Formation is older than 38 which included Amynodontopsis bodei, they regarded Ma, they regarded this reversed interval as Chron this assemblage to be a correlative to the Pearson C17r of the time scale of Berggren et al. (1995). If Ranch Local Fauna. No magnetostratigraphic studies the radioisotopic date of about 38 Ma for the have been done on Santiago and “Sweetwater” overlying Spears Formation is reliable, then the PALUDICOLA, VOL. 8, NO. 4, 2012 241

TABLE 9. Ages of faunas or localities based on faunal comparisons and their proposed correlations to the GPTS as discussed in text. Faunas or localities listed as undetermined for GPTS assignment either lack radioisotopic and/or magnetostratigraphic data.

Fauna or Locality Age GPTS Chron assignments White River Pocket middle Uintan upper part of C20r Skull Pass Quarry middle Uintan lower quarter of C20n Myton Pocket late Uintan upper half of C20n Leota Quarry late Uintan upper half of C20n Thorne Quarry late Uintan upper half of C20n Tapo Canyon late Uintan lower half of C19r Brea Canyon late Uintan lower half of C19r Randlett latest Uintan upper part of C19r – lower part of C19n Strathearn latest Uintan upper third of C19r – lower third of C19n Candelaria (in part) latest Uintan ?lower part of C19n Hancock Quarry ?latest Uintan undetermined Locs. 20, Rodent, and Wood early Duchesnean undetermined Pearson Ranch early Duchesnean upper two-thirds of C19n Skyline early Duchesnean ?upper part of C19n Candelaria (in part) early Duchesnean ?lower part of C18r “Bone Sands”, Santiago Fm. early Duchesnean undetermined Simi Valley Landfill middle Duchesnean about middle of C18r Halfway/Lapoint middle Duchesnean upper half of C18r Cotter Channels middle Duchesnean ?upper part of C18r Lac Pelletier Lower middle Duchesnean undetermined Turtle Basin middle Duchesnean undetermined Slim Buttes ?middle Duchesnean undetermined Baca Fm. localities late Duchesnean C17r Tonque late Duchesnean C17r – C17n.2n Porvenir late Duchesnean C17n.3n Little Egypt early Chadronian C17n.1n ______reversed interval containing the fauna does most of these faunas to the GPTS cannot be made until likely represent Chron C17r of the GPTS. additional data is available. The faunas from Badwater localities 20, Wood, The Duchesnean Lac Pelletier Lower Fauna and Rodent of the Hendry Ranch Member, Wagon from the Cypress Hills Formation, Saskatchewan, is Bed Formation, Wyoming, are regarded by most comprised of a diverse fauna (Krishtalka and Stucky, investigators as Duchesnean in age (e.g., Wood, 1983b; Storer, 1987, 1988, 1995). Although many of 1949; Black, 1969, 1974, 1978, Dawson, 1974, 1980; the rodent species appear endemic to the fauna, Korth Setoguchi, 1975; Krishtalka and Setoguchi, 1977; and Eaton (2004) reported the occurrence of Krishtalka and Stucky, 1983a, b; Maas, 1985; Metanoiamys lacus from the Duchesnean Turtle Krishtalka et al., 1987; Robinson et al., 2004). Black Basin Local Fauna of Utah. The discovery of M. (1969) reported a K/Ar date of 42.3 ± 1.4 Ma lacus in the Dry Gulch Creek Member is the second (corrected) from a tuff stratigraphically overlying record of this species outside of the Lac Pelletier locality 20. However, Prothero and Swisher (1992) Lower Fauna. In addition, the first appearances of provided convincing evidence that this radioisotopic Eutypomys and Adjidaumo are recorded in the date is unreliable and should be disregarded. No Halfway/Lapoint and the Lac Pelletier Lower faunas paleomagnetic studies have been done on the rocks and Passaliscomys, which was previously only exposed in the Badwater area and, as Robinson et al. known from the Duchesnean Turtle Basin Local (2004) noted, the entire Badwater area needs further Fauna (Korth and Eaton, 2004), is now known to sedimentological analysis and comparisons to rock occur also in the Halfway/Lapoint Fauna. exposures in the Beaver Divide area and in the Furthermore, Adjidaumo sp., cf. A. craigi of the northwestern Wind River Basin. Although the faunas Halfway/Lapoint Fauna and A. craigi from the Lac from the Badwater localities, especially locality 20, Pelletier Lower Fauna are very similar may represent some of the earliest Duchesnean morphologically and may even be conspecific. No faunas (Robinson et al., 2004), confident correlation paleomagnetic studies or radioisotopic dates have 242 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

been reported for the Cypress Hills Formation, so define the beginning of the Duchesnean. In the confident correlation of the Lac Pelletier Lower collections of SDSNH and contrary to Walsh (1996), Fauna to the GPTS cannot be made. However, the Amynodontopsis bodei has only been recorded from above faunal records suggest that the Lac Pelletier the Duchesnean “Bone Sands” of the upper part of Lower Fauna may be a correlative of the Turtle Basin Member C of the Santiago Formation (SDSNH Locs. Local Fauna and/or the Halfway/Lapoint Fauna. 3235, 4732, 4821, 5415). Amynodontopsis bodei is Lucas (1992) regarded the fauna from the Slim also known from the Duchesnean Pearson Ranch Buttes Formation of Harding County, South Dakota Local Fauna of the Sespe Formation, the Duchesnean (Bjork, 1967) as possibly early Duchesnean in age Slim Buttes Formation of South Dakota, and because the fauna includes Amynodontopsis, Duchesnean Skyline Channels of Texas (Bjork, 1967; Duchesneodus, Duchesnehippus intermedius, and Wilson, 1986; Wilson and Stevens, 1986; Kelly, Poabromylus. Duchesnehippus intermedius is known 1990). Thus, A. bodei is restricted to the Duchesnean. from the Dry Gulch Creek and Lapoint members of Genera restricted to the Duchesnean include the the Duchesne River Formation (Rasmussen et al., following: Rooneyia, Presbymys, Passaliscomys, 1999), indicating that the fauna from the Slim Buttes Viejadjidaumo, Cristadjidaumo, Simiacritomys, Formation is probably a correlative of the Churcheria, Parvicornus, Duchesnehippus, and Halfway/Lapoint Fauna. However, confident Haplohippus. Additional genera with first correlation of the fauna from the Slim Buttes appearances in the Duchesnean include the Formation to other Duchesnean faunas cannot be following: Sinclairella, Apternodus, Ischyromys, made based on the limited number of taxa in the Ardynomys, Jaywilsonomys, Yoderimys, Aulolith- fauna. omys, Heliscomys, Adjidaumo, Paradjidaumo, Faunal Characterization of the Duches- Eutypomys, Hesperocyon, Daphoenus, Mesohippus, nean―Robinson et al. (2004) listed the following ?Trigonias, Hyracodon, ?Subhyracodon, Menops, first appearances to define the beginning of the Toxotherium, Heptacodon, Agriochoerus, Aclisto- Duchesnean: Hyaenodon, Duchesneodus, mycter, Heteromeryx, Pseudoprotoceras, and Duchesnehippus intermedius, Amynodontopsis, and Trigenicus. Genera with last appearances in the Eotylopus. Lucas (1992) first regarded Duchesneodus Duchesnean include the following: Apatemys, as an index taxon for the Duchesnean. However, Palaeictops, Didelphodus, Nyctitherium, Talpavus, because the type species of Duchesneodus, D. Sespedectes, Proterixoides, Simidectes, Janimus, primitivum, is early Chadronian in age, Lucas et al. Trogolemur, Chusmashius, Omomys, Rapamys, (2004) regarded Duchesneodus uintensis as a Pareumys, Simimys, Mytonomys, Hessolestes, Duchesnean index taxon, instead of the genus. Black Harpagolestes, Uintacyon, Uintasorex, Miocyon, and Dawson (1966) reported Duchesneodus as ?Amynodon, Amynodontopsis, Triplopus, Prot- occurring in the Randlett and Halfway “horizons” of oreodon (= ? Eomeryx, in part, of Lander, 2011), the Duchesne River Formation. As noted above, the Leptoreodon, Leptotragulus, Protylopus, and record from the Halfway “horizon” appears to be Simimeryx. based on CM 11996, which came from either the Species that are restricted to the Duchesnean uppermost part of the Brennan Basin Member or the include the following: Simidectes merriami, Dry Gulch Creek Member. The record from the Hessolestes ultimus, Chusmashius balchi, Randlett “horizon” is based on CM 9174 (Rasmussen Trogolemur leonardi, Rooneyia viejaensis, et al., 1999). The provenance of CM 9174 is listed as Tachylagus gawnaeae, Heliscomys walshi, locality CM 3020, Randlett Point, which would place Passaliscomys priscus, Metanoiamys korthi, it at or near the base of the Brennan Basin Member Metanoiamys lacus, Viejadjidaumo magniscopuli, (Amy Henrici, per. communication, 2011). Cristadjidaumo mckennai, Protadjidaumo pauli, Rasmussen et al. (1999) regard CM 9174 as Protadjidaumo typus, Adjidaumo craigi, Simi- representative of an undescribed species of acritomys whistleri, Simimys landeri, Microparamys Duchesneodus, which, if correct, would still maintain nimius, Churcheria baroni, Presbymys lophatus, D. uintensis as an index taxon for the Duchesnean. Pseudotomus timmys, Microeutypomys tilliei, However, unless the Randlett Fauna is included in the Eutypomys acares, Eutypomys obliquidens, Duchesnean, the first appearance of the genus can no Amynodontopsis bodei, Parvicornus occidentalis, longer be used to define the beginning of the Duchesnehippus intermedius, Haplohippus texanus, Duchesnean. The occurrence of Amynodontopsis sp. Protoreodon pacificus (= Eomeryx pacificus vide in the late Uintan Jeff’s Discovery Local Fauna from Lander, 2011), Protylopus pearsonensis, Simimeryx the lower part of Member C of the Santiago minutus, Hendryomeryx (=“Leptomeryx”) defordi, Formation of California, indicates that the first and Heptacodon pellionis. If Rasmussen et al. (1999) appearance of this genus also cannot be used to are correct that the Duchesneodus specimen of the PALUDICOLA, VOL. 8, NO. 4, 2012 243

Randlett Fauna represents a new undescribed species, Local Fauna is older than the Halfway/Lapoint then Duchesneodus uintensis would also be restricted Fauna; and the Duchesnean Simi Valley Landfill to the Duchesnean. Local Fauna is either slightly older or about equivalent in age to the Halfway/Lapoint Fauna. CONCLUSIONS These correlations would then place the Uintan- Duchesnean boundary within Chron C19n of the Surface collecting and wet screen sieving of GPTS, or at about 41.4 Ma. bulk matrix samples from the Dry Gulch Creek Based on radioisotopic and magnetostrat- Member of the Duchesne River Formation has igraphic data, the latest Duchesnean Porvenir Local resulted in the recovery of a small sample of Fauna of Texas most likely occurs within Chron mammalian fossils, which includes new records of C17n.3n of the GPTS. This implies that the the following taxa: Copedelphys sp.; Lipotyphla, Duchesnean extended up through at least Chron genera and species indeterminate; Mytonolagus sp.; C17n.3n, or to at least 37.92 Ma. Pareumys guensburgi; Griphomys sp.; Heliscomys sp.; Passaliscomys sp.; Metanoiamys lacus; ACKNOWLEDGEMENTS Metanoiamys sp, cf. M. korthi; Protadjidaumo typus; Protadjidaumo sp., cf. P. typus; Paradjidaumo sp.; We gratefully acknowledge the following Adjidaumo sp., cf. A. craigi; Simiacritomys sp.; persons for their assistance during this study: Mark Microeutypomys sp.; Eutypomys sp.; and A. Roeder of the SDNHM; Dave Andersen of San Poabromylus kayi. Based on the taxa in the new Jose State University, California; Scott Foss, Robin sample and the previous record of Duchesnehippus Hanson and John Mayers of the Utah Bureau of Land intermedius, the fauna from Dry Gulch Creek Managnement, Utah; Margaret Madsen, Scott Member can be confidently assigned to the Madsen, Georgia Knauss, Lori Browne, Stephanie Duchesnean North American Land Mammal age. Lukowski, and Wendi Shaver for assistance with Following Lucas (1992) and Rasmussen et al. (1999), field work and matrix processing; Sue Ann Bilbey we combine the assemblages from the Dry Gulch and Evan Hall of the Uinta Paleontological Creek and Lapoint members of the Duchesne River Associates; Heather Finlayson, then of the Utah Field Formation into the Halfway/Lapoint Fauna and House Museum; Alan Tabrum and Amy Henrici of regard it as the “type fauna” for the Duchesnean. We the CM; and Bob Chaudhart, general manager of the document also the first record of a mammal, an Econolodge, Vernal, Utah. We are also indebted to indeterminate artiodactyl, from the Starr Flat Member Thomas A. Deméré and Kesler A. Randall of the of the Duchesne River Formation. Department of Paleontology, SDNHM, for providing The Pearson Ranch Local Fauna from the Sespe access to the fossils described in this paper. We are Formation of California was regarded by the Wood thankful to the following persons for their personal Committee (Wood, et al., 1941) as the principal communications and advice during the preparation of correlative fauna for the Duchesnean. Based on this report: Lawernce J. Flynn of the Peabody taxonomic comparisons of the Uintan and Museum, Harvard University; E. Bruce Lander of Duchesnean faunas from of the Duchesne River, Paleo Environmental Associates, Inc., and the Uinta, and Sespe formations and certain other LACM; Donald R. Prothero of Occidental College; Duchesnean faunas of North America along with a K. E. Beth Townsend of the Arizona College of recalibrated radioisotopic date for the Lapoint Ash of Osteopathic Medicine, Midwestern University; and 40.26 Ma, we propose the following new correlations Michael O. Woodburne of the University of of the faunas from the Sespe Formation to the GPTS California, Riverside. Special thanks are given to (Figure 13) that differ from those of Prothero et al. Christopher Henry of the Nevada Bureau of Mines (1996): the late Uintan Tapo Canyon and Brea and Geology, Reno, for his many constructive Canyon local faunas occur within lower half of comments and for allowing us to cite his unpublished Chron C19r; the latest Uintan Strathearn Local Fauna radioisotopic data for the Buckshot Ignimbrite. We occurs from about the upper third of Chron C19r to are grateful to William W. Korth of the Rochester the lower third of Chron C19n; the Duchesnean Institute of Vertebrate Paleontology, James W. Pearson Ranch Local Fauna occurs within the upper Westgate of the Lamar University and the University two-thirds of Chron C19n; and the Duchesnean Simi of Texas Memorial Museum, and an anonymous Valley Landfill Local Fauna occurs at about the reviewer for their constructive comments on the middle of Chron C18r. This reevaluation indicates original draft of this report. the following faunal correlations: the latest Uintan Randlett Fauna and Strathearn Local Fauna are about equivalent in age; the Duchesnean Pearson Ranch 244 KELLY ET AL.— SMALL MAMMALS FROM DUCHESNE RIVER FORMATION

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