UNI HARVARD UNIVERSITY Library of the Museum of Comparative Zoology University of Kansas Publications MUSEUM OF NATURAL HISTORY The University of Kansas Publications, Museum of Natural History, beginning with volume 1 in 1946, was discontinued with volume 20 in 1971. Shorter research papers formerly pub- lished in the above series are now published as Occasional Papers, Museum of Natural Histoiy. The Miscellaneous Pub- lications, Museum of Natural History, began with number 1 in 1946. Longer research papers are published in that series. Monographs of the Museum of Natural HUstory were initiated in 1970. All manuscripts are subjected to critical review by intra- and extramural specialists; final acceptance is at the discretion of the publications committee. Institutional libraries interested in exchanging publications may obtain the Occasional Papers and Miscellaneous Publica- tions by addressing the Exchange Librarian, University of Kan- sas Library, Lawrence, Kansas 66045. Individuals may pur- chase separate numbers of all series. Prices may be obtained upon request addressed to Publications Secretary, Museum of Natural History, University of Kansas, Lawrence, Kansas 66045. Editor: Richard F. Johnston PRINTED BY XmiVERSITY OF KANSAS PRINTING SERVICE LAMTIENCE, KANSAS ^ LFBRAo OCCASIONAL PAPERS 200L BRARY DEC 9 1974 of the Harvard MUSEUM OF NATURAL HISTORY f^s/ry The University of Kansas Lawrence, Kansas NUMBER 32, PAGES 1-12 NOVEMBER 19, 1974 NEW RODENTS FROM THE LOWER MIOCENE GERING FORMATION OF WESTERN NERRASKA By Larry D. Martin^ The lower Miocene Gering Formation of northwestern Nebraska was deposited during a time of important modifications in the composition of the North American mammahan fauna. The base of die Gering Formation marks a change from dominantly eohan deposition, typical of arid conditions, to channel and floodplain deposition in broad river valleys, indicating a more mesic climate. A number of characteristically Oligocene mammals make their last known appearance in North America during the time of deposition of the Gering Formation. These include Nanodelphys, Geolahis, Proterix, Eumys, and Hijaenodon (Martin, 1973). Simul- taneously, a number of Eurasian genera, including Amphechinus, Plesiosminthus, and Menoceras, first appear in North America. Only a small fraction of the fauna of the Gering Formation has been noted in print. Reported forms include a canid Sunkahe- tanka geringensis, the scimitar-toothed felid Nimravus, the oreo- donts, and the cricetid rodent Pocicidus (Barbour and Schultz, 1935; Toohey, 1959; Schultz and Falkenbach, 1949, 1954, 1968; Alker, 1969). This paper adds to the rodents from the Gering fauna a new genus and species of phiomyid-like rodent, a new species of sicistine, and a new geomyid. AGKNOWLEDGMENTS I am grateful to C. B. Schultz for permission to describe the Gering fossils in the University of Nebraska State Museum and to ^ Museum of Natural History, and Department of Systematics and Ecology, The University of Kansas. 2 OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY Lloyd Tanner and J. C. Harksen for introducing me to the early Miocene of Nebraska and South Dakota. Craig C. Black has en- couraged and materially assisted me in my work on these fossil rodents. Thanks are also due Elvvyn Simons tor the loan of specimens of Gaudeamus from the Yale Peabody Museum and John Wahlert for his helpful comments on rodent incisor enamel. Marion A. Jenkinson gave editorial assistance. Don Rasmussen prepared the stereophotographs and also critically read the manu- script. FAUNAL AND AGE RELATIONSHIPS The Gering Formation is composed of channel sands and flood- plain silts deposited in an ancient valley system, and is best exposed along Wildcat Ridge and Pine Ridge in western Nebraska, where it has maximum thickness of about 200 feet. In terms of the European Standard, tlie Gering fauna seems to correlate best with part of the fauna from the continental Aquitanian. In North America, tlie Gering fauna correlates almost exactly with that from tlie upper portion of the Sharps formation in South Dakota as reported in detail by Macdonald (1963, 1970). The Gering fauna is also, in part, correlative with the "Lower Harrison" fauna from Wyoming. Portions of the Cabbage Patch beds in Montana and the John Day beds in Oregon are probably very close to Gering time equivalents. In Nebraska, the Gering Formation is the lowest formation in the Arikaree Group and the base of the Gering may lie near the boundary between the Oligocene and Miocene epochs. The age of the lower Gering may be near 28-29 million years B.P. (Obradovich, Izett, and Naeser, 1973). The lower boundary, with the Oligocene Brule Formation, is variable and may be an erosional unconformity or in a few places an ancient soil profile, the Bayard Paleosoil (Schultz and Stout, 1955:46). Both the Sharps Formation and the Gering Formation have a gradational contact with the Monroe Creek Formation. In Nebraska, this boundary is charac- terized by the presence of abundant "pipey concretions" in the Monroe Creek Formation and their absence or rarity in the Gering Fonnation (Schultz, 1941). The collection of small mammal faunas from the early Miocene Sharps Formation of South Dakota and the Gering Formation of Nebraska provides us with critical new information about faunal exchanges and the early radiation of several rodent families in- cluding the aplodontids, cricetids, and geomyids. Known faunal relationships show that the Sharps covers a greater time span than does the Gering (Martin, 1973). The lower Sharps and the upper Sharps are not known to occur together at any single section. Lithologically the lower Sharps resembles the Whitney Member of the Brule Formation, and contains more primitive animals than LOWER MIOCENE GERING FORMATION WESTERN NEBRASKA 3 are found in the lower Gering. This is especially evident in the beavers and lagomorphs. The Sharps also contains a number of typically Oligocene mammals that are not known to occur in the Gering of Nebraska, such as Hyracodon, Leptochoenis, and Scot- timiis. It is possible that the lower Sharps is really late Oligocene (Whitneyan). A small vertebrate fauna from a channel deposit discovered by J. C. Harksen (KU S.D. 16 in Sec. 1 and 2, T. 11 S., R. 9 E., Fall River County, South Dakota) gives us an insight into the lower Sharps fauna. It includes: Trimyhis, Domnina, Proterix, Geolahis, Ictops, Proscalops, Arctoryctes, Sinclairella cf. dakotensis, Palaeolagus hypsodus, Palaeolagus philoi, Prosciurus sp., Pelecomys sp., PAUomys sp., Haplomys sp., PMeniscomys sp., tree squirrel, Protosciunis, Protospermophilus, Miospermophilus, Agnotocastor, Etitypomys, small eomyid, Paradjiaumo, ^^Paciculus" cf. mcgregori, Leidymys cf. blacki, Eiimys hrachyodus, Scottimus cf. kellamorum, Heliscomys, Proheteromys, Tenudomys, Florentiamys, Lepto- choerus, Hypisodus, and Lept ornery x. This fauna (Blue Ash Local Fauna) contains many forms transitional from diose of the Middle Oligocene to those of the Gering. Its main importance is that it may give us a glimpse of a mesic small mammal fauna during Whitneyan times. It is in- teresting that it contains Ictops and eomyids while at the same time lacks the immigrant genera Amphechinus and Ples'iosminthus. SYSTEMATIC ACCOUNTS Class MAMMALIA Linnaeus, 1758 Order RODENTIA Bowdich, 1821 SuPERFAMiLY GEOMYOIDEA Weber, 1904 Family GEOMYIDAE Gill, 1872 Tenudomys Rensberger, 1973 Tenudomys titanus, new species Figure 1 Holotype. — University of Nebraska State Museum 11531, left P'. Tijpe localitii. —UNSM Mo-119, Dumal locality, NW li, SE )i. Sec. 32, T. 20N., R. 52 W., Vz mile soutlrwest of UNSM Mo-110, 6)^ mi. south and 1J4 mi. west of Bayard, Morrill Gounty, Nebraska. Horizon. — Helvas Canyon Member, Gering Formation, Arikaree Group, Miocene. Referred 7naterial. — Left M^ or M", UNSM 11504. From the same locality and horizon as the type. Diagnosis. — Larger and more brachydont than any other Tenudomys or Pleurolictis; protoloph consisting of a single major cusp on P^ P" without cingula. Etymology. — Titanus, Greek Titan, symbolic of large size. Description. — P' very large, brachydont, and cuspate, lacking cingula, protolopli consisting of a single antero-posteriorly compressed cusp, with OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY Fig. 1. — Tenudomijs titanus, occlusal views: A. UNSM 11531 (holotype), left p*; B. UNSM 11504, left M' or M". Plesiosminthiis geringensis: C. UNSM 11708 (holotype), partial right ramus with M1-3, labial and occlusal views; D. UNSM 11519, partial right maxilla with M'-^ All X 10. LOWER MIOCENE GERING FORMATION WESTERN NEBRASKA 5 metacone and hypocone well separated on metaloph, entostyle cuspidate and continuous with metaloph; M^ or M" with a slight posterolabial cingulum ending in a small entostyle, protoloph consisting of small protostyle, protocone, and paracone, metaloph with metacone and hypocone, and medial valley straight. Discussion. — The P^ resembles most closely that of Teniidotiiys clakoteivsis (Macdonald) from the Sharps Formation, but is about 60 per cent larger than the P^ in that species. The P* of Tenudomys titanus can be distinguished from that of Florentiamys by the lack of an anterior cingulum and from Sanctimus by having a single elongated anterior cusp rather than a distinct paracone and proto- cone united only at their bases (Rensberger, 1973:840). Tenudomys titanus can probably be derived from a smaller and more brachy- dont form of Tenudonu/s, which is represented by a number of isolated teeth from the ? Late Oligocene of South Dakota (Blue Ash Local Fauna). Florentiamys also occurs in the Blue Ash Local Fauna indicating that by the late Oligocene the major lineages of fossorial geomyid rodents had already separated from the Heter- omyidae and may have been progressing towards fossorial adaption which finally made them the dominant rodents of the late Ari- karean. SuPERFAMiLY DIPODOIDEA Weber, 1904 Family ZAPODIDAE Coues, 1875 Subfamily SICISTINAE Allen, 1901 Plesiosminthus Viret, 1926 Plesiosminthus geringensis, new species Figure 1 Ttjpe. — UNSM 11708, partial right ramus. Typelocalitii.—VNSM Mo- 119. Horizon. — Helvas Canyon Member, Gering Formation, Arikaree Group, Miocene. Referred material. — UNSM 11519, partial right maxilla with M^'" and alveolus from P*, from the same locality and horizon as type. Diagnosis. — Larger than Plesiosminthus clivosus and smaller than any other described North American sicistine; slightly larger than P. mtjarion or P. schaubi; anterocone absent on M^; cingula indistinct; upper molars rela- tively square. Ettjmoloptj. — Named for the Gering Fonnation. Description. — Posterior border of incisive foramina opposite P*; alveolus for P* indicating posteriorly inclined, single-rooted tooth; upper molars not convex buccally as in P. schatibi, P. mtjarion, or Parasminthus (more similar to Schaiibcumys in this respect); molars (especially M^ ) not elongate as in European species of Plesiosminthus; molars without distinct cingula; molars with paracone and metacone higher than otlier cusps (])ut lower than in other North American species of Plesiosminthus or Schauhcumys); internal embay- ments of the molars U-shaped as in Schatibeumys (Wilson, 1960:84); M^ with anteroloph almost separate from paracone, paracone straight and joining 6 OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY protocone, paracone and protocone joined directly by protoloph, anteiocone absent, endoloph connecting protoloph with hypocone, low mesoloph extending from endoloph to buccal border of tooth and joining a small mesostyle, hypocone witli thin connection (metaloph) with metacone, posteroloph ex- tending from hypocone to buccal margin of tooth; M' with anterior half of tooth wider tlian posterior, anteroloph isolated from paracone and connecting with very small anterocone before joining protocone, protoloph extending from anteroloph to paracone, mesoloph low, short and not connecting with meso- style (although it does have a broad, low connection with the metaloph), metaloph arising from endoloph and connecting with metacone, posteroloph connecting with hypocone and shorter than in M^ ramus small with mental foramen high (about as in Plcsiosminthus clivosus); dorsal and ventral masseteric lines meeting slightly posteroventral to mental foramen with ventral line extending a short distance further anteriorly; small foramen present between Ms and ascending ramus as is found in P. clivosus; lower incisor narrow with smooth enamel; Mi more elongate tlian in P. clivosus with talonid much wider than trigonid, large anteroconid median and double, connected by anterior mure to metaconid, protoconid and metaconid low, about same size and connected by metalophid, ectolophid low and with a large mesoconid leading into a mesolophid ending in mesostylid on lingual border of tooth, mesostylid connected to prominant posterior cingulum; M^ like Mi except with anteroconid small and single and trigonid and talonid nearly same width; Ma much like M2; lingual and buccal cingula not developed on lower molars. Discussion. — Tlesiosminthus geringensis is the oldest and one of the smallest known North American sicistines. It is referred to Plesiosminthus rather than to Schauheumys on the basis of its lack of distinct cingnla (very slight cingula are present on the buccal and lingual anterior margins of the upper molars), low paracone and metacone, and the relative proportions of NL- (anterior end wider than posterior). Because the upper incisors of the new spe- cies are unknown, it is impossible to tell if they were grooved as in Plesiosminthus or ungrooved as in Parasminthus. The cheek tooth pattern of Plesiosminthus geringensis is very similar to that of some specimens of Parasminthus illustrated by Bohlin (1946; plate 1); however, the paracone and metacone seem higher in the illustrations of the Asian genus (possibly an artifact of the stereo- photographs). Plesiosminthus geringensis is smaller than any of the species of Parasminthus described by Bohlin. The earliest known sicistines are from the Upper Oligocene of Europe and Asia. Sicistines are presently unknown from the Oligocene of North America and it seems reasonable to suppose that Plesisminthus geringensis is an immigrant from Eurasia. How- ever, we must not ignore the ecological bias in our collecting. Especially important with sicistines is the almost complete lack of mesic faunas from die Upper Oligocene of the Great Plains. SUPERFAMILY iudct. Zetamys, new genus Type species. — Zetamys nebraskensis, new species. Diagnosis. — Near the size of a rat, Rattus rattus; cheek teeth lophate and LOWER MIOCENE GERING FORMATION WESTERN NEBRASKA 7 moderately liypsodont; pi^ molarifomi; tooth pattern consisting of an anterior trans\'erse crest and a posterior "V" forming a distinct "Z" pattern; lengtli/ width ratio of molars less than in most North American eomyids ( tending to be nearly square); distinct cingula absent. Etymology. — Zeta, Greek, Z; Mys, Greek, mouse. Zetamys nebraskensi.s, new species Figures 2 and 3 Holotype.—UNSM 11514, right P'-M'. Type locality.— \JNSM Mo-104, Roundhouse Rock, SW )i, Sec. 21; W edge, SE M, Sec. 21. T. 19N, R. 51 W, 4M mi. south and 5?^ mi. west of Bridge- port, Morrill County, Nebraska. Horizon. — Helvas Canyon (lower) Member, Gering Formation, Arikaree Group, Miocene. Referred material. — Two partial left rami with M1-2, UNSM 11566 and 11567; three left P.'s, UNSM 11720, 11574, and 11565; one right P, UNSM 11568; one right M\ UNSM 11569; one left M\ UNSM 11718; and a partial right M^ UNSM 11719. All from same locality and horizon as type. Diagnosis. — Cheek teetli moderately hypsodont with a prominent "Z" pattern; p' molarifomi with anteroloph connected to paracone. Etymology. — Named for the State of Nebraska. Description. — P* consisting of an anterior crest composed of "tear-shaped" protocone uniting buccally with anteriorly-arched anteroloph connecting to paracone through small protoconule, two posterior lophs fonning a "V" with the hypocone at its apex ( longest of these lophs rrmning from paracone to hypocone), posterior loph of "V" running from hypocone to metacone and connecting to short posteroloph at about mid-line of tooth, lingual end of anterior crest projecting posteriorly and buccal end of posterior crest projecting anteriorly forming basin-like lingual and buccal \alleys; M'"" essentially like premolar except with anteroloph less arched and protoconule not evident as separate cusp; M' slightly larger than M^; M'' represented by partial tooth (UNSM 11719) missing anteroloph, lophs forming posterior "V" parallel to Fk;. 2.--Zetajniis uchraskensis: A. UNSM 11514 (holotvpe), right P'-M'; B. UNSM 11720, right W; C. UNSM 11719, partial right M. D. Zetamys sp., KU 19001, right P'; E. Gaiideamiis agyptius, YPM 18004, right maxillary with P'-M ■; F. Zetamys sp., KU 19002, right M'. All occlusal views, X5. 8 OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY each other, arched posteriorly and equal in length, two small buccal roots and two larger fused lingual roots on upper cheek teeth; upper and lower teeth have no cingula separate from lophs; P4 submolariform with anterior half narrower than posterior part of tooth, protoconid connected to metaconid by short transverse anterior loph and to entoconid by long diagonal loph which may have short buccal loph near its midpoint, hypoconid fonning buccal margin of posterolophid which is connected to entoconid by narrow enamel band; Mi^- similar to premolar except that they are more rectangular and with anterolophid longer; M.i not recognized in the material studied. Discussion. — The "Z" pattern found in the cheek teeth of rodents has developed independently in a number of different groups, including the Phiomyidae (Gaudeamus), the Caviomorpha (Plagio- dontia), and the Eomyidae (Rhodanomys). The total amount of crested surface has not been increased in these genera and may be reduced from an earlier condition through the loss of transverse crests (mesoloph, posteroloph. etc.). For instance, a lower first molar of Gaudeamus aegijptiiis has only about 57 per cent as much development of crests as on the comparable tooth in Meta- phiomys schaubi (if their teeth are scaled to the same size and the total length of all the crests is measured). This suggests that selec- tion is acting on the arrangement of the transverse crests, rather than for addition or length of crests. The direction of change seems to be towards a diagonal arrangement which is best typified by Plagiodontia. In the terminology of Hershkovitz (1962) the teeth of these rodents, with "Z" tooth patterns, have undergone progres- sive planation, hypsodonty, and involution. Development of these features may indicate that these animals consume abrasive or fibrous foods, although some hypsodonty may be developed to compensate for the loss of crested surfaces. Zetamys seems to provide an example of parallelism. The molar teeth of this genus correspond in almost every detail (they are slightly smaller) to the molar teeth of the early Oligocene phiomyid Gaudeamus from the Fayum basin in Egypt (figures 1 and 3). The cheek teeth of Gaudeamus are more brachydont and the premolars less molariform than in Zetamys. Zetamys might reasonably be considered related to Gaudeamus. However, none of the critical features found in phiomyids, including the size of the infraorbital foramen, the shape of the ramus, or the nature of the incisor enamel, is known for Zetamys. The European eomyid Rhodanomys has a fundamentally similar tooth pattern. In Rhodanomys, the anteroloph may be isolated from the ectoloph, which combines with the protoloph to form a single long transverse crest. To further convert the teeth of Rhodanomys to the pattern found in Zetamys, it would be necessary to move the metaloph posteriorly and reduce the posteroloph to a small crest, arising from the meta- loph at approximately the midline of the tooth. The small buccal loph which sometimes comes oft the long loph between the para- LOWER MIOCENE GERING FORMATION WESTERN NEBRASKA 9 cone and the hypocone may then be a remnant of the mesoloph. On the lower cheek teeth the anterior crest may actually correspond to tlie metalophid in Rhodanomijs as this crest runs from the metaconid to the protoconid. In Wiodanomys, there is a small anteroloph in front of the metalophid. In both Rhodanomys and Zetamys the mesolophid is vestigial or absent and the ectolo- phid combines with the hypolophid to form a loph extending from the protoconid to the entocon.id. The hypoconid is isolated from this long transverse loph and is continuous with the posterolophid forming the posterior border of the tooth. The ancestry of Zetamys seems doubtful. It is not similar enough to Rhodanomys to indicate a close relationship to that genus, but the possibility that it is a Eurasian immigrant should not be discounted. Zetamys shows no close similarity with any known North American eomyid, although Black (1965:40) does compare AuloUthomys from the lower Oligocene of Montana to Rhodamimys. However, the morphological changes necessary to convert AuloUthomys to Zetamys are very great and no real rela- tionship can presently be suggested. The possibility that it is really a phiomyid also cannot be excluded. Zetamys sp. Figure 2 Referred material— Bright P', KU 19001, right M\ KU 19002, and a fragment of a right M^ or M^ KU 19003. Locality.— KU S.D. 16 (Blue Ash Locahty), S. Yi, Sec. 1, T. US., R. 9E., Fall Rixer County, South Dakota. Fig. 3.—Zetamtis nehraskcnsis, occlusal views: A. UNSM 11720, left P'; B. UNSM 11574 and 11566, left P* and Mi-.; Gaiideamus agtjptius, YPM 18036, left Mi-o, occlusal view; D. Zetamys nehraskcnsis, UNSM 11574 and 11566, left Pi and M1-2, lingual view. gUmg^ x\\ x 5. 10 OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY Horizon. — From ant hills, PUpper Oligocene. Diagnosis. — Slightly larger and less hypsodont than Z. i^ehraskcnsis; P' less molariform than in that species and with anten^loph well separated from the paracone. Description. — The unworn P* is nearly square with protocone a lophate cusp, isolated from paracone by a deep groove (valley), crests from paracone and metacone forming "V," with hypocone at its apex, posterloph absent; M^ or M" with a "V" fomied as in premolar except that a small buccal loph occurs near middle of loph between paracone and hypocone; upper molar tooth frag- ment ( KU 19003 ) contributes no additional information. Discussion. — This Zetamys is more primitive than Z. nehrasken- sis, in that it is less hypsodont and the premolar is less molariform. It is also somewhat older. Its presence in the Blue Ash Local Fauna suggests that it might occur in other Oligocene faunas. Table 1. — Measurements of the Teeth of Zetamys, Tenudomys, AND PlesiosmintJnis (in mm.). Length Width Zetam t/s nclnaskcnsis UNSM 11514 (holotype) p. 1.55 1.70 M^ 1.41 1.62 UNSM 11574 p4 1.76 1.59 UNSM 11566 Ml 1.73 1.72 M2 1.86 1.69 UNSM 11720 P. 2.03 1.81 Zetamtis sp. KU 19001 P* 1.54 1.68 KU 19002 M^ 1.71 1.88 Flesiosminihus gcringensis UNSM 11708 (holotype) Ml 1.20 .83 M. 1.21 .97 M. .98 .81 UNSM 11519 M' 1.06 1.01 M- 1.00 1.03 Teniulotntjs titanus UNSM 11531 (holotype) p4 2.43 2.74 UNSM 11504 M^ or M- 1.90 2.22 CONCLUSIONS The development of arid conditions during the late Oligocene may have favored the evolution of the heteromyids, as they have a major radiation at diis time. They must also have given rise to the early gophers during this time, for the Gering and Sharps formations already contain fairly well-differentiated ancestors for the Geomyinae in Sanctimus and the Pleurolicinae in Tenudomys. The sicistines appear to be Eurasian emigrants to North Amer- ica, and Flesiosminihus geringensis is the earliest known North American form. Parris and Green (1969) have reported a sicistine from the lower Sharps but Green (personal communication, 197.3) LOWER MIOCENE GERING FORMATION WESTERN NEBRASKA 11 infonns me that this specimen was misidentified. The Miocene sicistines of North America tend to be cricetid-Uke and had their major radiation during the Hemingtordian age when cricetids were rare. The relationships of Zetamys are unclear. The presence of upper and lower premolars prevent it from being a cricetid. It might be an eomyid, but it is not closely similar to any known form. It is almost identical to the Oligocene phiomyid Gaudeamns from Egypt. Gaudeamns is hystricognathus, hystricomorphus, and has multiserial enamel on its incisors (Wood, 1968). These are features shared by hystricomorphs and caviomorphs. The presence of a form related to Gaudeamns in the late Oligocene and early Miocene of North America might indicate that the caviomorphs have a phiomyid ancestor but this possibility should not be con- sidered seriously without more conclusive evidence. At the present time, Zetamys is best regarded, with some reservation, as an ex- ample of parallelism. SUMMARY A new species of geomyid, Tenudomys titanis, is described and represents one of the earliest occurrences of pleurolicine gophers. A new sicistine, Plesiosminthus geringensis, is also described and is the oldest and most primitive sicistine known from Nortli America. Zetamys is a new genus of rodent from the ? late Oligo- cene and early Miocene of the Central Great Plains. It shows striking similarities to the African Oligocene phiomyid, Gaudeamns, but is probably best not referred to any family. LITERATURE CITED Alker, J. 1969. Pacicuhis ( Cricetinae, incertae sedis) teeth from the Miocene of Nebraska. Jour. Paleontol., 43 ( 1 ): 171-174. Barbour, E. H., Schultz, C. B. 1935. A new Miocene dog, Mesocyon geringen- sis, sp. nov. Bull. Nebr. State Mus., 1:407-418. Black, C. C. 1965. Fossil mammals from Montana: Ft. 2, rodents from the early Oligocene Pipestone Spring local fauna. Ann. Carnegie Mus., .38:1-48. ^ Bohlin, B. 1946. The fossil mammals from the Tertiary deposit of Tabenuluk, western Kansu: Ft. II, Simplicidentata, Carnivora, Artiodactyla, Ferisso- dactyla, and primates. Reports of the scientific expedition to the north- western pro\inces of China, Stockholm, 6(4): 1-259. Hershkovitz, F. 1962. Evolution of neotropical Cricetine rodents (Muridae) with special reference to the phyllotine groups. Chicago Nat. Hist. Mus., Fieldiana: Zoology, 46:1-524. Macdonald, T- R- 1963. The Miocene faunas from the Wounded Knee area of western South Dakota. Bull. Amer. Mus. Nat. Hist., 125:139-238. Macdonald, J. R. 1970. Review of the Miocene Wounded Knee faunas of southwestern South Dakota. Bull. Los Angeles County Mus. Nat. Hist., Sci., 8:1-82. 12 OCCASIONAL PAPERS MUSEUM OF NATURAL HISTORY Martin, L. D. 1973. The mammalian fauna of the lower Miocene Gering Formation and the early evolution of the North American Cricetidae. Ph.D. dissertation. The Uniw of Kansas. Obradovich, J. D., Izett, G. A., Naeser, C. W. 1973. Radiometric ages of volcanic ash and pumice beds in the Gering Sandstone (earliest Miocene) of the Arikaree Group, Southwestern Nebraska. Abstracts witii programs G.S.A. 26th Ann. Meeting, Rocky Mountain Section 5(6):499-500. Parris, D. C., Green, M. 1969. Dinohytis (Mammalia: Entelodontidae ) in the Sharps Formation, South Dakota. Jour. Paleontol., 43(5): 1277-1279. Rensberger, J. M. 1973. Sanctimus (Mammalia, Rodentia) and the phyletic relationships of tlie large Arikareean geomyoids. Jour. Paleontol., 47(5):835-853. Schultz, G. B. 1941. The pipey concretions of the Arikaree. Univ. Nebr. State Mus. Bull., 2(8):69-82. Schultz, G. B., Falkenbach, G. H. 1949. Promerycochoerinae, a new subfamily of oreodonts. Bull. Amer. Mus. Nat. Hist., 93:69-198. Schultz, G. B., Falkenbach, C. H. 1954. Desmatchoerinae, a new subfamily of oreodonts. Bull. Amer. Mus. Nat. Hist., 105:143-256. Schultz, G. B., Falkenbach, G. H. 1968. The phylogeny of the oreodonts. Bull. Amer. Mus. Nat. Hist., 139:1-498. Schultz, G. B., Stout, T. M. 1955. Classification of Oligocene sediments in Nebraska. Bull. Univ. Nebr. State Mus., 4(2): 17-52. Toohey, L. 1959. The species of Nimravus (Camivora, Felidae). Bull. Amer. Mus. Nat. Hist., 118:71-112. Wilson, R. W. 1960. Early Miocene rodents and insectivores from north- eastern Colorado. Univ. Kansas Paleontol. Contr., 7:1-92. Wood, A. E. 1968. Early Genozoic mammalian faunas, Fayum Province, Egypt: Part II. The African Oligocene Rodentia. Peabody Mus. Nat. Hist. Bull., 28:23-105. Date Due APr8-n983- c^, cmc Bookbinding Co., inc. 300 Summer Street Boston, Mass. 02210 2044 093 361 665