Reproduction in female gundis(Rodentia: Ctenodactylidae)

Five species of the Ctenodactylidae have been studied both in the wild and in captivity. Ctenodactylids have vaginal closure membranes, lateral nipples, relatively long oestrous cycles and relatively long gestation periods for small rodents. In these features they resemble the caviomorph rodents of the New World and some of the hystricomorphs of the Old World. Many of the reproductive features such as well-developed young, small litter size, the position of the nipples and the generally low reproductive rate may equally well be attributed to adaptation to a desert rock habitat.     

A ctenodactylid rodent (Mammalia: Rodentia) from the Middle Miocene of Chios Island (Greece)

Field work carried out in 1991 and 1993 at the Middle Miocene locality of Thymiana (Chios Island, Greece), produced much rodent material including a number of ctenodactylid dental specimens. They represent a single taxon whose upper and lower cheek tooth morphology clearly differs from Prosayimys flynni and all Sayimys species known so far, except for Sayimys intermedius. The ctenodactylid teeth from the Middle Miocene of Chios are identified as pertaining to the latter species, despite minor differences from the Pakistani and Saudi Arabian representatives of S. intermedius.     

A new Oligocene Ctenodactylinae (Rodentia: Mammalia) from Ulantatal (nei Mongol): new insight on the phylogenetic origins of the modern Ctenodactylidae

The four living genera of Ctenodactylidae (Rodentia) are the only survivors of a flourishing Tertiary group. In this paper, we describe a new Oligocene species from Ulantatal (Chinese Mongolia) that highlights the origins of crown ctenodactylids. This species, Helanshania deserta gen. et sp. nov. , is lophodont and displays semi‐hypsodont teeth, a dental pattern that is somewhat transitional between that of primitive Oligocene ctenodactylids and the later hypsodont genera. We perform here a cladistic assessment of the dental evidence for species produced by the successive radiations of the group. In order to get new data, to decipher homologies for the dental pattern of modern ctenodactylids, and to specify their dental replacement, we describe additional dental material of Ctenodactylus, Massoutiera, and Felovia. The phylogenetic analysis (using PAUP) considered 45 characters (mainly dental) and 31 species. The performed heuristic searches yielded 596 equally most parsimonious trees. Protataromys and Karakoromys are stem ctenodactylids and appear as the earliest offshoots of the Ctenodactylidae clade, which represents a well‐supported family rank. Within this family, the Tataromyinae appear paraphyletic, whereas the Ctenodactylinae sensu lato are a clade including the new taxon Helanshania. As such, a revision of the Tataromyinae is envisaged and a new subfamily is erected (Yindirtemyinae). Amongst the Ctenodactylinae, a tribe Ctenodactylini encompassing the crown ctenodactylines is proposed. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 531–550.     

Characterization of microsatellite markers for the North African gundi,Ctenodactylus gundi (Rodentia: Ctenodactylidae)

Eleven highly polymorphic microsatellite loci were isolated from the North African gundi (Ctenodactylus gundi), a gregarious rock‐dwelling rodent found in northern Africa. These loci exhibited high genetic diversity (eight to 19 alleles per locus) and high levels of heterozygosity (62–98%). Collectively, these microsatellite markers are sufficiently variable to estimate levels of relatedness and population genetic structure for C. gundi.     

New Late Miocene murids from China (Mammalia, Rodentia)

New murids of Late Miocene (medial Baodean Chinese Mammal Unit) age from Inner Mongolia, northern China, and from Yunnan Province, southern China, are described. Hansdebruijnia perpusilla nov. sp. represents the earliest known and morphologically most primitive species of the genus, which is known from the latest Miocene of Europe and western Asia. The new species suggests an eastern Palaearctic origin of Hansdebruijnia. “Progonomys” yunnanensisQIU and STORCH, 1990 from Lufeng, Yunnan Province, is referred to Linomys nov. gen. New samples from Leilao, Yuanmou County, Yunnan Province, are included in this species, although this population is somewhat more primitive than that from Lufeng. Leilaomys zhudingi nov. gen. and sp. from Leilao shows a unique combination of apomorphic and plesiomorphic characters, which suggest an early divergence from the murid stem. The new findings indicate that our knowledge of the early radiation of murids in southeast Asia is still in its infancy.     

新疆准噶尔盆地北缘中中新世早期的原圆齿鼠(Promylagaulinae,Mylagaulidae)(英文)

<正>1988年吴文裕描述了产自新疆准噶尔盆地北缘铁尔斯哈巴合地点哈拉玛盖组下部层位的一枚圆齿鼠的P4,定名为Sinomylagaulus halamagaiensis。1997年中国科学院古脊椎动物与古人类研究所新疆考察队又在铁尔斯哈巴合的哈拉玛盖组下部层位中采集到两枚p4。1988年的研究工作仅依据一枚上前臼齿(P4),标本的稀缺决定了当时研究成果的局限性。新材料无疑为认识新疆的圆齿鼠类提供了新的信息     

Neocometes (Rodentia,Platacanthomyinae) from the early Miocene of Echzell,Germany

The dental material described in this paper represents the largest known sample of molar material of the extinct platacanthomyine rodent Neocometes Schaub and Zapfe. It can be attributed to Neocometes similis Fahlbusch, the stratigraphically oldest and most primitive of the two species recognized in the European Miocene. This rich material provides sufficient samples of all molar positions to evaluate and confirm the morphologic and morphometric characters given for N. similis. The evolutionary stage of the Neocometes population from Echzell is only slightly more derived than the one from the type locality Erkertshofen 2, and supports the biostratigraphic setting of Echzell given by earlier authors. N. similis is the first mammal described in detail from the fossiliferous ash layers of Echzell, a locality situated at the southwestern margin of the Vogelsberg volcanic complex in central Germany.     

First Potwarmus from the Miocene of Saudi Arabia and the early phylogeny of murines (Rodentia: Muroidea)

Potwarmus is recorded for the first time in Saudi Arabia. The material comes from the Middle Miocene of the Hofuf Formation at Al‐Jadidah. This species, Potwarmus flynni sp. nov. , is described and compared with all species currently placed in the genera Potwarmus, Dakkamys, Paradakkamys, Vallaris, and some species of ‘Myocricetodon’ (i.e. the so‐called ‘primitive dendromurids’) as well as with two of the most primitive definitive murines (namely Antemus chinjiensis and Progonomys debruijni). Potwarmus flynni sp. nov. differs from the above‐mentioned species in having the anterior part of the m1 strongly reduced. A cladistic analysis provides evidence that this new Arabian taxon is close to Potwarmus primitivus and Potwarmus sp. nov. from Jebel Zelten (Libya), and also that this genus is unlikely to be the sister taxon to Antemus. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 664–679.     

Evolutionary transformation of the subcutaneous muscle in rodents of Ctenohystrica (Rodentia: Diatomyidae,Ctenodactylidae, and Hystricognathi)

The present study examined the subcutaneous muscle (m. cutaneus trunci) in a relict species Laonastes aenigmamus (Diatomyidae) and in two ctenodactylids (Ctenodactylidae: Ctenodactylus gundi and Pectinator spekei), which are closely related to Laonastes according to current phylogenetic hypotheses. The comparative morphological analysis also included four representatives of Hystricognathi: Echimys sp., Proechimys sp., Cercomys cunicularis, and Hystrix indica. Laonastes and ctenodactylids have a number of common ancestral traits in the morphology of m. cutaneus trunci. This suggests that they are probably related to the ancestral forms of Ctenohystrica. However, the structural similarity of the subcutaneous muscle in Diatomyidae and Ctenodactylidae is based not only on plesiomorphic (presence of the medial head of m. cutaneus trunci), but also on an apomorphic (the development of the thoracoabdominal portion) feature which is common to both branches of Ctenohystrica (Ctenodactiloidea and Hystricognathi). The results of the comparative analysis suggest a new scenario for the evolutionary transformations of m. cutaneus trunci within the clade Ctenohystrica. This scenario differs from earlier suggestions and proposes initial differentiation of the subcutaneous muscle and possibly its secondary simplification, but on a new basis. On this new basis a further secondary increase in complexity of subcutaneous muscle appears possible in response to various adaptations in hystricognaths.     

New species of Hispanomys (Rodentia,Cricetodontinae) from the Upper Miocene of Batallones (Madrid,Spain)

Material of Hispanomys (Rodentia, Cricetodontinae) is described from various localities at Batallones (MN10) (Madrid, Spain). All of it belongs to a single species, which differs from the other known species of the genus and a new taxon, Hispanomys moralesi sp. nov. , is created for it. The samples from the various localities show differences interpreted as being the result of slight age disparities amongst the different sites. Although they were previously thought to be coeval, Batallones 10 is probably older than Batallones 1, which is possibly older than Batallones 3. Hispanomys moralesi sp. nov. is characterized by several morphological features such as the lack of cingula and mesolophs, the presence of well‐developed ectolophs, four‐ or five‐rooted M1, short or absent mesolophids, and reduced and simplified M3. Hispanomys moralesi sp. nov. is a relatively derived species, the evolutionary stage of which is comparable to those of other members of the genus from the Upper Vallesian. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 725–747.     

Early Miocene cricetids (Rodentia) from the Junggar basin (Xinjiang, China) and their biochronological implications

Among the 14 small mammal species from the early Miocene locality of the northern area of the Junggar basin (northern Xinjiang, China), four species are cricetids (Rodentia): unnamed species of Cricetodon and Eumyarion, and two new species, Karydomys debruijni nov. sp. and Megacricetodon beijiangensis nov. sp. Some aspects of the morphology of Cricetodon sp. are shared by Eucricetodon from the late Oligocene, suggesting that these specimens could be of intermediate form between Eucricetodon and Cricetodon. One tooth of Eumyarion sp. was found, making its determination uncertain, but its morphology is clearly differentiated from the one of Cricetodon sp. The species K. debruijni nov. sp. is established based on its primitive features compared to the species known in Europe and Anatolia, and its specific association of characters compared to Karydomys dzerzhinskii. M. beijiangensis nov. sp. shows many plesiomorphic features compared to the species already described in the middle Miocene of China. Based on both the whole assemblage of rodents and the species of cricetids, the biochronologic position and the age of the locality are discussed. The locality appears to be biochronologically very close to the fauna from the Chul’adyr Formation in Aktau Mountains, but we propose an age slightly older than the one proposed for this fauna, probably equivalent to the MN3 biozone in Europe.     

Evolutionary and Biological Implications of Dental Mesial Drift in Rodents: The Case of the Ctenodactylidae (Rodentia,Mammalia)

Dental characters are importantly used for reconstructing the evolutionary history of mammals, because teeth represent the most abundant material available for the fossil species. However, the characteristics of dental renewal are presently poorly used, probably because dental formulae are frequently not properly established, whereas they could be of high interest for evolutionary and developmental issues. One of the oldest rodent families, the Ctenodactylidae, is intriguing in having longstanding disputed dental formulae. Here, we investigated 70 skulls among all extant ctenodactylid genera (Ctenodactylus, Felovia, Massoutiera and Pectinator) by using X-ray conventional and synchrotron microtomography in order to solve and discuss these dental issues. Our study clearly indicates that Massoutiera, Felovia and Ctenodactylus differ from Pectinator not only by a more derived dentition, but also by a more derived eruptive sequence. In addition to molars, their dentition only includes the fourth deciduous premolars, and no longer bears permanent premolars, conversely to Pectinator. Moreover, we found that these premolars are lost during adulthood, because of mesial drift of molars. Mesial drift is a striking mechanism involving migration of teeth allowed by both bone remodeling and dental resorption. This dental innovation is to date poorly known in rodents, since it is only the second report described. Interestingly, we noted that dental drift in rodents is always associated with high-crowned teeth favoring molar size enlargement. It can thus represent another adaptation to withstand high wear, inasmuch as these rodents inhabit desert environments where dust is abundant. A more accurate study of mesial drift in rodents would be very promising from evolutionary, biological and orthodontic points of view.     

A new stage in the evolution of the mole rats (Rodentia,Spalacinae) from the Early Miocene of northern Greece

The cheek teeth of Debruijnia kostakii n. sp. from the Early Miocene of Karydia are only slightly smaller than those of the largest extant species of the Spalacinae (Spalax giganteus), but show characteristics that are reminiscent of its Paleogene cricetid ancestor. The peculiar combination of large size and primitive dental morphology of this species bridges the gap between Debruijnia and Pliospalax and thereby supports the hypothesis that these genera form the core of the complex evolutionary history leading to extant Spalax.     

A reassessment of the cranial morphology of Neoepiblema acreensis (Rodentia: Chinchilloidea), a Miocene rodent from South America

The rodent Neoepiblema acreensis (Chinchilloidea: Neoepiblemidae) is member of a lineage that reached gigantic dimensions during the Late Miocene of South America—the Neoepiblemidae. In this paper, the cranial anatomy of this rodent is reviewed. Noninvasive imaging is used to reveal internal structures. Our review is based mainly on an almost complete cranium from the Upper Miocene deposits of the western Amazonia of Brazil. The cranium has an elongated rostrum, large frontal sinuses, a deep temporal fossa, well-developed sagittal, nuchal, medial occipital, and secondary crests, and a tympanic fenestra connected to the external acoustic meatus by a thin ventral cleft. Remarkably, the cranium shows the presence of fossae on the posterior region of the frontal and parietal bones, and a “W-shaped” fronto-parietal suture, which are not present in other analyzed chinchilloids. This study contributes to the knowledge of the morphology of this extinct rodent as well as to the phylogenetic relationships and paleobiology of neoepiblemids.     

A new chinchilloid (Rodentia,Hystricognathi) from the early Miocene of the localities of Bryn Gwyn and Gran Barranca (Patagonia,Argentina)

A new genus and species of chinchilloid rodent is described here. It was found in Colhuehuapian levels (early Miocene) of the localities of Bryn Gwyn and Gran Barranca, Chubut Province, Argentina. The new taxon shows a unique combination of characters (e.g., protohypsodont teeth, upper molars trilophodont, m1 and m2 tri- or tetralophodont with the second crest in position of variable development, and m3 trilophodont, cement absent) that make it different from any other known chinchilloids. We performed a phylogenetic analysis to corroborate the relationships of the new taxon within the Chinchilloidea. Our results indicate that the new taxon is best classified as Chinchilloidea incertae sedis, together with Incamys, Garridomys, and Scotamys. These species form the basal stock that leads to the modern lineage Chinchillidae (chinchillas and viscachas). The presence of the new taxon in these localities increases the diversity of chinchilloids during the early Miocene and reduces the dissimilarity between the faunas found in Bryn Gwyn and Gran Barranca.     

A New Extinct Genus of Cavioidea (Rodentia,Hystricognathi) from the Miocene of Patagonia (Argentina) and the Evolution of Cavioid Mandibular Morphology

The family Caviidae is represented in modern faunas by cavies and maras, whereas the family Hydrochoeridae is represented by capybaras. The evolutionary origin of these families has been related to a diversity of plesiomorphic fossil forms (recorded from the late Oligocene up to the middle Miocene) traditionally grouped in the family “Eocardiidae”. These fossil forms were included, together with Caviidae and Hydrochoeridae, within the Cavioidea s.s. (sensu stricto), because they share high crowned cheek teeth, double-hearted occlusal surface, short lower incisors, and moderate hystricognathy. Within Cavioidea s.s., caviids and hydrochoerids were interpreted as forming its crown group, because they have unique craniomandibular and dental features. In this contribution, a new taxon of Cavioidea s.s. from the middle Miocene of central Patagonia, Argentina, is described, and its phylogenetic position is determined on the basis of a morphological cladistic analysis in which “eocardiids” were included. The study permits the understanding of the sequence of appearance of characters that originated the highly divergent morphology of crown-group cavioids. The analysis of the sequence of appearance of the characters that traditionally diagnosed the crown group indicates that these changes did not occur at the same time. On the contrary, many of these features seem to have appeared at different nodes of the evolutionary history of Cavioidea s.s. The remarkably derived morphology of modern cavioids is the result of a stepwise appearance of a mosaic of evolutionary innovations that originated gradually along the history of Cavioidea during the late-middle Miocene.     

Dental evolution in Neophanomys (Rodentia, Octodontidae) from the late Miocene of central Argentina

The evolutionary pattern of the molar morphology of the small caviomorph (Octodontidae) Neophanomys from the late Miocene Cerro Azul Formation of central Argentina is analyzed. Two new species (chronomorphs) are recognized, which constitute an anagenetically evolving lineage with a gradual and directional pattern of increasing molar hypsodonty. Dental changes related to increasing hypsodonty are comparable to those of the octodontid lineage Chasichimys also recovered from the Cerro Azul Formation. However, Neophanomys shows comparatively less variation in gross morphology and there are no evidences that this lineage achieved euhypsodonty. In contrast, important changes in enamel microstructure (schmelzmuster) are observed among different populations of Neophanomys, supporting the hypothesis that these changes can occur at least partially independently from modifications in dental gross morphology. The patterns of dental evolution detected in the Neophanomys and Chasichimys-Xenodontomys lineages and the unequivocal polarity of the changes involved, related to increasing hypsodonty, reinforce the hypothesis that chronological differences exist among late Miocene outcroppings of Cerro Azul Formation in central Argentina.