The John Day Formation of Oregon is one the richest and best studied assemblages in North America. Including seven members spanning about 20 million years, there are over 150 vertebrate species known from Formation. rodent faunas have not been as well larger mammals, with many families having received little attention last hundred years. Here, twenty rodents described, based on new discoveries previously unpublished specimens material includes four genera species; eutypomyid Allotypomys...

The dermopteran basicranium combines a primitively constructed and oriented auditory bulla formed by ectotympanic, rostral entotympanic, tubal cartilage with derived features of the middle ear transformer internal carotid circulation. Living dermopterans possess primitive eutherian region that has been structurally modified to perceive lower frequency sound spectrum than probably was utilized ancestral Mesozoic therians. Perception low midfrequency range is enhanced in Dermoptera reducing...

Rodents of the Bridgerian (Middle Eocene) Elderberry Canyon Local Fauna

All species of North American marsupials from the Chadronian through Hemingfordian are reviewed. Most didelphids previously referred to Peratherium allocated Herpetotherium. Five Herpetotherium recognized. The donahoei Hough is synonymized with valens (Lambe). Orellan stevensoni Cope resurrected and referred, along titanelix Matthew, a new genus, Copedelphys. Both Copedelphys can be derived known Duchesnean America. Two genera peradectids recognized, Nanodelphys McGrew Didelphidectes Hough....

ABSTRACT A new genus of sciurid, Hesperopetes, contains three species: H. thoringtoni (type species), jamesi, and blacki. is from the early Chadronian (late Eocene) White River Formation central Wyoming represents earliest recognized species sciurid. The other are latest Whitneyan or Arikareean Oligocene) Blue Ash local fauna South Dakota. Hesperopetes closest in dental morphology to Oligopetes Heissig, which known only Oligocene Europe. may also represent occurrence a lineage leading...

ABSTRACT A new genus, Douglassia, is erected for the problematic Chadronian sciurid Sciurus jeffersoni Douglass, 1901. Previously undescribed material adds morphologic information taxon. Douglassia differs from other sciurids in retention of primitive dental and masseteric morphology. Based on postcranial anatomy, genus referred to Tribe Sciurini (tree squirrels), which regarded as sister taxon all Sciurinae. The known fossil Tertiary flying squirrels inadequate determine whether they...

ABSTRACT Excellent material, including two partial skulls, of the geomyoid rodent Heliscomys is basis for a new species (H. ostranderi), and allows recognition family, Heliscomyidae, which includes Cope Apletotomeus Reeder. an early offshoot Geomyoidea, not ancestral to any later geomyoids. Two lineages are recognized, one distinguished by reduction in size specialization premolars, other (which H. ostranderi) enlargement premolars development stylar cusps on upper molars.

ABSTRACT Seven species of aplodontid rodents are recognized from the Orellan, four Whitneyan, and one both horizons Nebraska. Three new genera recognized, Epeiromys Oropyctis Campestrallomys horizons. Orellan (Prosciurus parvus, annectens, spanius), two Whitneyan (Oropyctis pediasius siouxensis), late early magnus) described. An indeterminate is also recognized. Only a few lineages aplodontids can be traced into later times. Campestrallomys, Downsimus, Haplomys derived Prosciurus. may...

Ten species of geomyoid rodents are recognized from the early-early Arikareean Ridgeview local fauna Nebraska: three heliscomyids, four florentiamyids, one heteromyid, and two probable geomyid Tenudomys Rensberger, 1973. Two new genera described, heliscomyid Tylionomys a harrymyine heteromyid Proharrymys. previously described referred to Proharrymys Heliscomys schlaikjeri Black, 1961 Proheteromys fedti Macdonald, 1963 (new combinations). Four named: heliscomyids macdonaldi voorheisi,...

Sixteen rodent species representing five families are recognized from the Barstovian Anceney local fauna of Montana.Of these, seven new: one mylagaulid ( Trilaccogaulus bettae ), sciurid Spermophilus jerae castorid Euroxenomys inconnexus three heteromyids Mookomys thrinax, Peridiomys halis, Perognathus ancenensis and cricetid Copemys lindsayi).The also contains earliest known occurrence Cynomys, otherwise unknown until late Hemphillian times.The heteromyid Cupidinimus madisonensis is shown...

Twenty species of rodents are recognized from the early Whitneyan Cedar Pass Fauna South Dakota. Two new recognized, sciurid Douglassciurus bjorki (including specimens originally referred to Cedromus wilsoni Korth and Emry, 1991, late Blue Ash Fauna) cricetid Paciculus cedrus. Due a more complete record at Pass, florentiamyid Hitonkala martintau Korth, 2008, is allocated genus Kirkomys Wahlert, 1984 as combination, (Korth, 2008). The sample this also allows for description cranium previously...

Additional fossil material from the Valentine Formation in Knox and Brown Counties, Nebraska, has allowed for recognition of three new species rodents, a heteromyid ( Perognathus brevidens ), geomyid Parapliosaccomys annae zapodid Schaubeumys cartomylos ). The specimens referred here to P. were previously identified as furlongi , those S. grangeri recognized Lignimus cf. L. hibbardi . It is evident that Storer should be restricted type montis remainder this genus are Shotwell. earliest...

ABSTRACT The White River Formation at Flagstaff Rim in central Wyoming is a key sequence for understanding the biochronology and chronostratigraphy of Chadronian North American Land Mammal Age. lower part this section represents early time, an interval whose fauna has not been well known. From these levels 15 species rodents are discussed and/or described. Of these, three new species, all belonging to Eomyidae: Namatomys erythrus, Metanoiamys paradoxus, Cristadjidaumo skinneri. These rodent...

ABSTRACT A new genus of eomyid, Metanoiamys, is described from the Uintan southern California. Two species, M. agorus and marinus are also named. All Eocene species previously referred to “Namatomys” included in Metanoiamys. Species Metanoiamys increase crown height lophodonty cheek teeth through time, though no lineages recognizable. represents stem for Namatomyini possibly Eomyinae, but not entire Eomyidae.

A nearly complete skull of Anchitheriomys from the Miocene Nebraska allows description cranial foramina. In characters, most closely resembles Agnotocastor and Neatocastor among castorids; it retains primitive features that shares with eutypomyids (position posterior palatine foramina, smooth palatal surface, parallel tooth rows, retention dP3) combined derived (elongate rostrum, procumbent incisors) are shared only Neatocastor. new subfamily, Agnotocastorinae, is erected for this group beavers.

Upper dentition of Protosciurus mengi Black, from the Orellan Brule Formation, Nebraska, is described for first time. The zygomatic plate tilted anterodorsally, showing beginnings sciuromorphy as in Arikareean species this genus. A new genus sciurid, Oligospermophilus , named originally identified ? douglassi (Korth), based on additional material including a skull and upper dentitions. zygomasseteric structure O. unlike any previously Tertiary sciurid. range extended late Chadronian to...

Two new species, Mojavemys galushai and Phelosaccomys neomexicanus , are described from the Barstovian of New Mexico. Both these species assigned to a subfamily, Mojavemyinae. It is uncertain as whether this subfamily should be referred Heteromyidae or Geomyidae. an retain some heteromyid characteristics while developing advanced traits geomyids. possible that genera represent transitional forms between ancestor geomyines, thus deriving Geomyidae directly sometime in middle Tertiary. also...

ABSTRACT All genera previously referred to the Manitshini are reviewed. Ischyrotomus Matthew is synonymized with Pseudotomus Cope, and tribe restricted this latter genus Chadronian Manitsha. represented by three Bridgerian species, four Uintan one Duchesnean species. Quadratomus Korth removed from included in Paramyini based on morphologic characters of mandible dentitions. The massive postcranial bones interpreted as convergent those manitshines. In addition type two other species...

ABSTRACT Four species of rodents (two heteromyids and two cricetids) one lagomorph are identified from the late Tertiary Sevier River Formation Utah. The include a new genus heteromyine, Metaliomys sevierensis, which is intermediate in morphology between Clarendonian early Hemphillian Diprionomys Kellogg extant genera Liomys Heteromys. A single specimen referred to sp., cf. D. minimus (Kellogg). cricetid Paronychomys lemredfieldi Jacobs known Arizona. second Basirepomys. Peromyscus...