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Background: The paper presents novel findings of little-known species of rodents, the blind tree mice Typhlomys in Son La Province, Vietnam, with the first morphological and genetic characterisation and taxonomical description of the new species, T. taxuansis. The study also summarises all the data available on this genus species distribution, museum collections and notes on its taxonomy, which are important to establish the proper conservation status of the species. An exhaustive map of the findings is provided, along with a refined taxonomic key for all six currently morphologically characterised species of the genus. It is shown that, based on the data available to date, the genus is still far from complete. Most species, apparently, do not need a special conservation measure; their status may be established as Least Concerns and Near Threatened (B1a+2a) and the current population trend is stable (IUCN). New information: The paper introduced innovative findings regarding lesser-known rodents, the blind tree mice Typhlomys in Son La Province, Vietnam, along with the primary morphological and genetic identification and taxonomic explanation of the novel species T. taxuansis. [ABSTRACT FROM AUTHOR]

The diversity of the oryzomyine rat Mindomys (Cricetidae, Sigmodontinae, Oryzomyini), is doubled here with the description of a new species from the remote Cordillera de Kutukú (Ecuador). The novel form can be easily differentiated from Mindomys hammondi -type species of the genus- by a large set of anatomical traits including, among others, larger jugals, parietal "wings" extending to zygomatic roots, larger otic capsules, well-exposed petrosals, narrow zygomatic plates almost without upper free borders, foramen magnum caudally oriented, larger molars, and accessory root of first upper molar present. Until now, the records of Mindomys were restricted to western Andean foothills. The material from Kutukú highlights an Amazonian species and reinforces the valuable biological significance of isolated mountain ranges in eastern Ecuador. Since Mindomys shows some external traits classically related to arboreal life, here we present a brief reappraisal of this poorly explored topic. A partially neglected anatomical system in sigmodontine studies, the fore feet, encloses crucial information reflecting arboreality. [ABSTRACT FROM AUTHOR]

In cursorial mammals, reduction or loss of the clavicle is usually associated with the constitution of the m. brachiocephalicus, a continuous muscle that extends from head and neck regions to the forelimb, protracting it during locomotion. Among caviomorph rodents, the Cavioidea are characterized by many adaptations that improve running performance, such as the presence of a brachiocephalic configuration of the mm. cleidomastoideus, cleido-occipitalis, and deltoideus pars clavicularis, a feature that was interpreted as one of the main modifications for speed in running. However, a comprehensive analysis of this muscular configuration in the Cavioidea is not yet available. In this study, we analyze the morphological diversity, homologies, functions, and evolutionary changes of those shoulder muscles in cavioids that constitute the m. brachiocephalicus in cursorial mammals. We hypothesize that a brachiocephalic muscular arrangement of these muscles has evolved in this group in relation to a swift mode of locomotion. Muscular dissections on seven species of cavioids were performed while myological data on three other species were taken from the literature. Our results indicate that all cavioids have a brachiocephalic arrangement of the mm. cleidomastoideus, cleido-occipitalis, and deltoideus pars clavicularis, whereas a second brachiocephalic arrangement constituted by the mm. omotransversarius and trapezius pars cervicalis is present only in the larger cavioids. Both muscular configurations act in protracting the forelimb during the gait, but we also hypothesize that the particular disposition of the m. omotransversarius around the shoulder joint of larger cavioids could also assist in the stabilization of this joint during fast half-bounding locomotion. [ABSTRACT FROM AUTHOR]

Inquiring into the paleoecology of extinct forms is always a challenge, particularly when the taxa under study correspond to derived ecomorphs of ancient and completely extinct clades. In this contribution, the configuration of the masticatory apparatus and associated features of the Neogene pachyrukhines Paedotherium and Tremacyllus are studied in a detailed, mainly qualitative, comparative analysis of 36 specimens. Tooth morphology and the reconstructed muscular configuration of pachyrukhines indicate an important mediolateral component during chewing, and predominant crushing over grinding, as well as anteroposterior movements for the coupling and action of stronger gnawing incisors. These actions are more compatible with hard and brittle or turgid fruit food consumption than specialized folivorous, and particularly grazing, habits. The infraorbital and palatal foramina morphology and other rostral features indicate increased touch sensibility for object recognition and are congruent with the presence of infoldings of the lips protecting the gingiva during gnawing on hard foods. Additionally, there was a morphological gradient between Tremacyllus and P. bonaerense, from high selection of relatively soft and small food items, to specialized hard item consumption and higher resistance for abrasion and masticatory efforts (e.g., in eventual association with digging habits), respectively. Paedotherium typicum presents intermediate characteristics, with incisors designed for better cropping action or poorer selectivity during feeding. This more profound understanding of the feeding habits of pachyrukhines further allows the suggestion of paleoecological factors that could have contributed to niche segregation between these long-term coexisting rodent-like taxa. [ABSTRACT FROM AUTHOR]

The anthropic effect associated with worldwide European settlements over the last 500 years has caused dramatic environmental changes, modified regional patterns of biodiversity, and often led to local or complete extinctions. The sigmodontine rodents of Bahía Samborombón (Humid Pampas, central-eastern Argentina) constitute a good case study: a late Holocene archaeological site allowed us to compare a pre-European settlement assemblage (12 species) with the extant one (nine species). We used linear morphometrics (16 cranial and ten mandibular measurements) to assess interspecific morphological variations of the masticatory apparatus in relation to dietary habits for each assemblage. Even though sigmodontines have a tendency towards omnivory, groups based on dietary preference only overlapped partially. Size was one of the main variables involved in niche segregation, and shape characteristics such as rostrum elongation or mandible robustness were linked to different diets. We found that a combination of dietary preference and size was associated with extinctions. The main morphospace change between the two assemblages was related to the local extinction of the three greater insectivores and the smallest graminivore, located towards the center of the assemblage's morphospace. An insectivore was incorporated, involving no significant changes in the general morphospace. Graminivores and larvivores were not affected. Our study sheds light on the causes of local extinctions of small mammals at the Humid Pampas, a phenomenon that had never been studied from an ecomorphological approach. [ABSTRACT FROM AUTHOR]

We studied the morphotypic variation of the occlusal pattern of m1 in 13 arvicoline species (genera Microtus and Alexandromys). As a result, 22 m1 morphotypes were identified. In Alexandromys, five morphotypes of m1 were found, while in Microtus only seven. The morphological diversity of m1 morphotypes (H) in voles of the genus Microtus is significantly lower compared to Alexandromys. The largest number of m1 morphotypes and the highest morphological diversity of m1 were revealed in the Mongolian vole (14 morphotypes and H = 2.134), while the lowest values (two morphotypes and H = 0.285) occur in the population of M. levis from Orlov Island. An attempt of ecological and taxonomical interpretation of interspecific differences was made based on the m1 morphotypes. [ABSTRACT FROM AUTHOR]

The extinct clade of caviomorph rodents Neoepiblemidae includes forms that lived in South America from the early Miocene to Pliocene. Among them is Perimys. The exceptional preservation of ear ossicles in this rodent is described and analyzed in a study of the phylogenetic transformations of these structures in caviomorphs including 21 extant and two extinct genera. Caviomorphs exhibit a conserved malleoincudal complex, with synostosis of the malleus and incus, "bullet-shaped" mallear head, and absence of orbicular apophysis. They also show a reduction of the mallear anterior process, in some cases even lacking this structure. The malleoincudal complex of Perimys shows an elongation of the head, but not as marked as in Chinchillinae. The incudal long process of Perimys is slightly more prolonged than the short process, as in chinchillids. In contrast, dinomyids have the incudal long process disproportionally more prolonged than in most caviomorphs. Concerning the disparity of caviomorph middle ear ossicles, Perimys shares the morphospace with chinchillids and other small forms. Within chinchilloids, Perimys is closer to chinchillids than to neoepiblemids. [ABSTRACT FROM AUTHOR]

The main ectoparasites of small rodents at a Mayan community of Yucatán State, southeastern México were determined. Rodents were trapped in peridomestic areas of 20 houses from March to September 2016. Ectoparasites were removed from the rodents and morphologically identified. Total rodents infested were 22.9% (53/231). Prevalence of ectoparasites by rodent species was 65% (13/20) on Sigmodon toltecus Saussure, 50% (4/8) on Peromyscus yucatanicus J.A. Allen & Chapman, 37.5% (3/8) on Heteromys gaumeri J.A. Allen & Chapman, 25% (30/120) on Rattus rattus L., and 4% (3/75) on Mus musculus L. In total, 250 ectoparasites were collected. Mites were identified as Androlaelaps fahrenholzi (Berlese) (n = 115), Echinolaelaps echidninus (Berlese) (n = 89), and Steptolaelaps heteromys Furman (n = 22), and lice were identified as Polyplax spinulosa (Burmeister) (n = 24). Results suggested association among particular ectoparasite and rodent species, i.e., P. spinulosa and E. echidninus with R. rattus. Likewise, S. heteromys was significantly associated with H. gaumeri, and A. fahrenholzi with S. toltecus. The presence of ectoparasites such as E. echidninus and P. spinulosa on peridomestic rodents indicated risk of pathogen transmission to humans in the study area; therefore, focusing on surveillance and control of rodents in household environments is imperative. [ABSTRACT FROM AUTHOR]

Oecomys is a genus of Neotropical arboreal rodents composed of 17 species with diploid number ranging from 2 n = 54 to 86. Despite this high taxonomic and karyotypic diversity, the species-level systematics remains uncertain. We investigated the phylogenetic relationships and species delimitation of Oecomys using multiple approaches based on cytogenetic, molecular (mtDNA and nuDNA sequences) and morphological data sets. Sampling included 73 individuals from 25 localities in Amazonia, Cerrado, Pantanal and the Atlantic Forest, as well as 128 DNA sequences from GenBank. Molecular species boundaries associated with karyotype, morphological characters and geographic distribution led us to recognize 15 distinct lineages in Oecomys. These include five major well-supported clades composed of O. bicolor, O. catherinae, O. cleberi, O. mamorae, O. paricola and O. roberti, which were hypothesized as species complexes with at least eight putative new taxa. Three new karyotypes are also reported for the genus: 2 n = 54 (FN = 54), 2 n = 62 (FN = 62) and 2 n = 70 (FN = 74). Sympatry of up to four species with different diploid numbers recovered in distinct clades illustrates the complex evolutionary history in Oecomys. These data highlight the importance of combining cytogenetic, morphological and geographic information along with molecular coalescent analyses in developing species delimitation scenarios. [ABSTRACT FROM AUTHOR]

Global desert rodent communities were examined for evidence of phylogenetic and morphological community structure. Using geographical distribution data of desert rodents (within 15 assemblages), a composite molecular phylogeny and a geometric morphometric dataset of skulls, the mean pairwise distance and mean nearest taxon distance were calculated for each assemblage and compared with null communities. Community structure metrics detected phylogenetic clumping in two out of the 15 desert assemblages, indicating that co-occurring rodents were more closely related than expected by chance. No other assemblages showed a significant phylogenetic structure. Skull morphology had different structuring patterns, but overall, most examined desert assemblages were not significantly structured in skull morphology. Similar overall lack of community structure patterns was observed at the regional scale in both the phylogenetic and the body mass datasets. We also directly tested the association between phylogenetic and morphological structure and found it to be significant. The association between phylogenetic distance and increased diversity that we observed might indicate that niche partitioning facilities coexistence in diverse assemblages. [ABSTRACT FROM AUTHOR]

Anomaluroidea, commonly known as the “scaly‐tailed squirrels,” are an emblematic group of tropical African mammals that includes gliding forms. The family Anomaluridae was until recently represented by three genera: the flying scaly‐tailed squirrels (Anomalurus), the flying mouse (Idiurus) and the flightless scaly‐tailed squirrels (Zenkerella). Idiurus and Zenkerella have long been grouped into the Zenkerellinae subfamily, and Zenkerella was interpreted as a rare case of evolutionary reversal to non‐gliding lifestyle. Recent studies have demonstrated that Zenkerella is sister to all other modern anomalurids, and represents in fact the monogeneric family Zenkerellidae. The Anomalurus genus was split into Anomalurus and Anomalurops, but no study has ever considered all Anomalurus species together in a phylogeny to test the status of Anomalurops. Here, we used mitogenomic next‐generation sequencing to infer the phylogenetic relationships among all extant anomalurids and to estimate their divergence ages. We found that the arboreal Zenkerella is the sister group of all extant gliding anomalurids (Idiurus and Anomalurus). We confirmed that Anomaluroidea only evolved the gliding adaptation once. A comparison based on morphological traits indicates that Zenkerella harbours several unique morphological features. We propose new morphological characters for the novel classification of modern Anomaluroidea, which includes the families Zenkerellidae and Anomaluridae. Using different calibration schemes, we demonstrated that classical dating methods relying only on mitogenomes provide rather young Miocene estimates between Zenkerellidae and the Anomaluridae. The use of published nuclear genes, internal calibrations and tip dating converged towards an Eocene split between gliding and non‐gliding scaly‐tailed squirrels, which is in agreement with the African fossil record. Finally, we provide the first exhaustive species‐level molecular phylogenetic inference for the genus Anomalurus. We found that Anomalurus beecrofti is the sister group of all other species of Anomalurus and branched off during the Miocene. [ABSTRACT FROM AUTHOR]

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Caviidae is one of the groups of rodents with the greatest ecomorphological disparity, and with currently three known lineages: Caviinae (cuises), Dolichotinae (maras), and Hydrochoerinae (capybaras). Caviinae include small caviids represented by three extant genera (Microcavia, Cavia, and Galea) and three fossils forms (Dolicavia, Palaeocavia, and Neocavia). In Argentina, the fossil record of Caviinae is continuous and abundant since the late Miocene. Neocavia, specifically, is represented by different species recorded in the late Miocene-Pliocene. Here, we describe a new species of Neocavia from the late Miocene-early Pliocene of the Cerro Azul Formation (La Pampa Province, Argentina), and provide a re-description of already known species (Neocavia lozanoi and "Neocavia depressidens"). Also, we perform a more comprehensive review of the genus and include the Neocavia species in a phylogenetic context within Caviinae. We analyze the main patterns of the evolution of the tympanic bullae within Caviidae, and infer about a possible occasional fossorial habit of Neocavia. The morphological and phylogenetic analyses indicate that Neocavia is more closely related to Dolicavia and Microcavia than to the other Caviinae, and confirm the monophyly of the genus, with at least two clearly differentiable species. Since this study cannot confirm the systematic position and validity of "N. depressidens", we suggest not to use this taxon as a biostratigraphic indicator. [ABSTRACT FROM AUTHOR]

Abstract: A new species of Oligoryzomys, a Sigmodontinae rodent of the tribe Oryzomyini, is described from the Patagonian islands of southern Chile. Phylogenetic analyses that included the new form and known species of Oligoryzomys were examined using nucleotide sequence data from the mitochondrial cytochrome b gene. Maximum‐likelihood and Bayesian analyses found the new species to be sister to Oligoryzomys longicaudatus and closely related to a clade composed of O. flavescens, O. spB, and O. andinus. Additionally, we analyzed 223 sequences of the mtDNA Control Region belonging to specimens representing the complete geographic distribution of O. longicaudatus, as well as six sequences of the new form, obtaining signals of budding speciation for the insular specimens. Also, we present analyses of morphometric data and descriptions of external, cranial, and dental morphology, along with the karyotype of the new taxon, allowing us to find a unique combination of characters that support the taxonomic identity of this new form and to disentangle the complex taxonomy for the southern Patagonia Oligoryzomys. This new species is relevant to the insular biogeography of the Patagonia given that, for the first time, we propose the glacial cycles of the Pleistocene as generators of a mammal species in southern Patagonia. [ABSTRACT FROM AUTHOR]

The use of genetic data and tree-based algorithms to delimit evolutionary lineages is becoming an important practice in taxonomic identification, especially in morphologically cryptic groups. The effects of different phylogenetic and/or coalescent models in the analyses of species delimitation, however, are not clear. In this paper, we assess the impact of different evolutionary priors in phylogenetic estimation, species delimitation, and molecular dating of the genus Oligoryzomys (Mammalia: Rodentia), a group with complex taxonomy and morphological cryptic species. Phylogenetic and coalescent analyses included 20 of the 24 recognized species of the genus, comprising of 416 Cytochrome b sequences, 26 Cytochrome c oxidase I sequences, and 27 Beta-Fibrinogen Intron 7 sequences. For species delimitation, we employed the General Mixed Yule Coalescent (GMYC) and Bayesian Poisson tree processes (bPTP) analyses, and contrasted 4 genealogical and phylogenetic models: Pure-birth (Yule), Constant Population Size Coalescent, Multiple Species Coalescent, and a mixed Yule-Coalescent model. GMYC analyses of trees from different genealogical models resulted in similar species delimitation and phylogenetic relationships, with incongruence restricted to areas of poor nodal support. bPTP results, however, significantly differed from GMYC for 5 taxa. Oligoryzomys early diversification was estimated to have occurred in the Early Pleistocene, between 0.7 and 2.6 MYA. The mixed Yule-Coalescent model, however, recovered younger dating estimates for Oligoryzomys diversification, and for the threshold for the speciation-coalescent horizon in GMYC. Eight of the 20 included Oligoryzomys species were identified as having two or more independent evolutionary units, indicating that current taxonomy of Oligoryzomys is still unsettled. [ABSTRACT FROM AUTHOR]

Tuco-tucos (Ctenomys spp.) are subterranean rodents that produce territorial, high intensity long-range vocalizations (LRVs) of broadband and low frequency that are essential for long-distance communication between individuals in different tunnel systems. Despite their importance, the development of LRVs remains poorly understood. In adult Anillaco Tuco-Tucos (Ctenomys sp.) the LRV is composed by two types of syllables (series and individual notes) that are repeated a variable number of times. We studied the development of the LRVs in eight juveniles of the Anillaco Tuco-Tuco ranging from 14-28 to 104-118 days after birth. We (1) tested whether the syllables followed any of three alternative developmental modes (retention of juvenile vocalizations, modification of juvenile precursors or de novo appearance in adults), (2) evaluated the development of structural and acoustic features of syllables, and (3) tested the prediction that juveniles should produce a greater proportion of atypical series in precursors of the LRV than adults, due to lack maturation and/or precise coupling of neuromuscular and anatomical structures. The LRV of the Anillaco Tuco-Tuco exhibited a mixed developmental mode: while series developed from juvenile precursors whose acoustic features gradually approached those of adults, individual notes appeared later in the ontogeny and de novo with acoustic features indistinguishable from those of adults. The number of series per vocalization increased through development and varied from one to 25 in juvenile males and from one to six in juvenile females. The structure of the most common series type (triad) did not exhibit ontogenetic changes and was present as such at the onset of the emission of vocalizations. On the contrary, acoustic features of juvenile triad notes changed with age in both sexes (duration 90% increased through development, while bandwidth 90% and peak frequency decreased). Furthermore, juveniles emitted a higher proportion of atypical series than adults (7.4% vs. 0.3%), as expected in the development of any complex behavior that requires practice to be mastered. The maturation of the LRV occurred well before the sexual maturation, presumably due to the protracted time needed to acquire or build a burrow system long before mating is possible. We propose that protracted vocal development is another component in the slow developmental strategy of Ctenomys and subterranean rodents in general. [ABSTRACT FROM AUTHOR]

Investigation of the incisors of 17 rodent species from 11 genera revealed substantial interspecific and intraspecific variations in the pattern of the daily increment on the incisor surface. The morphology of daily increments is described in detail. Interspecific variations in the pattern are correlated with interspecific variations in the daily activity rhythms in rodents. Intraspecific (up to individual) traits can be attributed to intraspecific (up to individual) differences in daily activity. We can conclude that the daily activity of an individual determines the pattern of its incisor growth rhythm, not being a direct cause of daily increment formation. Thus, the pattern of the increment on the incisor surface can be considered as recording the rhythm of the daily activity of a rodent during the period of incisor renewal. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the pituitary pars intermedia in seasonally captured adult male and immature viscachas by immunohistochemistry and image analysis. The pituitary pars intermedia exhibited a well-developed parenchyma with scarce connective tissue and vascularization. It was formed by a close association of melanotrophs and folliculostellate cells. The folliculostellate cells were stellate in shape with cytoplasmic processes, and they originated follicles with PAS-positive colloid inside. The morphometric parameters of melanotrophs, follicular colloid and folliculostellate cells (S-100-ir and GFAP-ir) varied seasonally and in relation to age. These parameters showed minimal values in the adult males captured in winter and in immature animals, and they were maximal in summer. The percentage of vimentin-positive area of the folliculostellate cells was maximal in immature animals, decreased in relation to age and did not vary seasonally in the adult animals. The greatest development of pars intermedia in the adult animals in relation to the immature ones is probably related to the adults’ adaptation to the semiarid environment. The expression of the tested proteins suggests a probable neuroectodermic origin for the folliculostellate cells of the viscacha pituitary pars intermedia. In addition, the cytoplasmic processes of folliculostellate cells might originate an intercellular communication network inside the pars intermedia. The decrease in the morphometric parameters melanotrophs, follicular colloid and folliculostellate cells in winter suggests a low endocrine activity of this zone. This fact might be due to the effect of the short photoperiod and high melatonin serum levels. [ABSTRACT FROM AUTHOR]

We describe the first new rodent species from Solomon Islands in more than 80 years. This new giant rat is known from a single specimen captured in a commercially felled Dillenia salomonensis tree on Vangunu Island. Morphologically, it closely resembles a fascinating secondary radiation of 3 species of Uromys (Cyromys) that are endemic to Guadalcanal Island. The cranium can be readily distinguished from those of other species of Uromys by its shorter maxillary tooth row, and shorter incisive foramina. The existence of this species has been suspected for over 2 decades. It is rare and cryptic, and conservation status is Critically Endangered due to its small distributional range, apparent low population densities, and rapid progress of commercial logging on Vangunu Island. Further surveys to locate additional animals and support for community led conservation initiatives on Vangunu are urgently needed to safeguard the species. [ABSTRACT FROM AUTHOR]

Mole-rats are known to use their protruding, chisel-like incisors to dig underground networks of tunnels, but it remains unknown how these incisors are used to break and displace the soil. Theoretically, different excavation strategies can be used. Mole-rats could either use their head depressor muscles to power scooping motions of the upper incisors (by nose-down head rotations) or the lower incisors (by nose-up head rotations), or their jaw adductors to grab and break the soil after penetrating both sets of incisors into the ground, or a combination of these mechanisms. To identify how chisel-tooth digging works, a kinematic analysis of this behaviour was performed based on high-speed videos of 19 individuals from the African molerat species Fukomys micklemi placed inside transparent tubes in a laboratory setting. Our analysis showed that the soil is penetrated by both the upper and lower incisors at a relatively high gape angle, generally with the head rotated nose-up. Initially, the upper incisors remain approximately stationary to function as an anchor to allow an upward movement of the lower incisors to grab the soil. Next, a quick, nose-down rotation of the head further detaches the soil and drops the soil below the head. Consequently, both jaw adduction and head depression are jointly used to power tooth-digging in F. micklemi. The same mechanism, but with longer digging cycles, and soil being thrown down at smaller gape sizes, was used when digging in harder soil. [ABSTRACT FROM AUTHOR]

Postural and kinematic aspects of running may have evolved to support high runner (HR)mice to run approximately threefold farther than control mice. Mice from four replicate HR lines selectively bred for high levels of voluntary wheel running show many differences in locomotor behavior and morphology as compared with four nonselected control (C) lines. We hypothesized that HR mice would show stride alterations that have coadapted with locomotor behavior, morphology, and physiology. More specifically, we predicted that HR mice would have stride characteristics that differed from those of Cmice in ways that parallel some of the adaptations seen in highly cursorial animals. For example, we predicted that limbs of HR mice would swing closer to the parasagittal plane, resulting in a twodimensional measurement of narrowed stance width. We also expected that some differences between HR and C mice might be amplified by 6 d of wheel access, as is used to select breeders each generation. We used the DigiGait Imaging System (Mouse Specifics) to capture high-speed videos in ventral view as mice ran on a motorized treadmill across a range of speeds and then to automatically calculate several aspects of strides. Young adults of both sexes were tested both before and after 6 d of wheel access. Stride length, stride frequency, stance width, stance time, brake time, propel time, swing time, duty factor, and paw contact area were analyzed using a nested analysis of covariance, with body mass as a covariate. As expected, body mass and treadmill speed affected nearly every analyzed metric. Six days of wheel access also affected nearly every measure, indicating pervasive training effects, in both HR and C mice. As predicted, stance width was significantly narrower in HR than C mice. Paw contact area and duty factor were significantly greater in minimuscle individuals (subset of HR mice with 50%-reduced hind limb muscle mass) than in normal-muscled HR or C mice. We conclude that stride characteristics of house mice are adaptable in response to both selective breeding and changes in daily locomotor behavior (activity levels) that occur during as few as 6 d. These results have important implications for understanding the evolution and coadaptation of locomotor behavior and performance. [ABSTRACT FROM AUTHOR]

The aim of the present study was to characterize the epididymal sperm of Spix's yellow-toothed cavy ( Galea spixii) through two different recovery methods. Nine sexually mature males were euthanized and the complexes, testes-epididymis, were dissected. For each animal, one epididymis was processed by flotation method and the other was processed by retrograde flushing method, both using a TES-based buffered media. After recovery, we evaluated the sperm for motility, vigour, viability, functional membrane integrity and morphology. Morphometric data from the different sperm regions were evaluated by using an appropriate software. After recovery, both methods provide similar values for all the sperm parameters, aiming the recovery of more than 300 × 106 sperm, presenting >50% motile sperm, with normal morphology and functional membrane. The total sperm length in this sperm was 48.87 ± 0.1, and the sperm head presented 9.4%, on average. A notable characteristic was the prominent acrosome found in the G. spixii sperm. In conclusion, we demonstrate that either flotation or retrograde flushing methods are suitable for the recovery of sperm from cauda epididymis of Spix's yellow-toothed cavies. [ABSTRACT FROM AUTHOR]

Recent palaeontological field campaigns in the westernmost part of the Sahara (Dakhla region, Morocco) have resulted in the discovery of a mammal assemblage including anomaluroid rodents. This new fauna comes from the uppermost part of the Samlat Formation, which contains estuarine deposits dating from the earliest Oligocene. The anomaluroid record from Dakhla (C2) comprises at least five sympatric taxa distributed among four different groups (Anomaluridae, Zenkerellinae, Nonanomaluridae and ?Zegdoumyidae), and includes two new species attributed toParanomalurusLavocat, 1973 (P. riodeoroensisMarivaux sp. nov.; Anomaluridae) andNonanomalurusPickfordet al., 2013 (N. parvusMarivaux sp. nov.; Nonanomaluridae), genera well known from the early Miocene of Sub-Saharan Africa. Three other new anomaluroid taxa – a diminutive anomalurid,Argouburus minutusMarivaux gen. et sp. nov., a zenkerelline-like anomaluroid,Oromys zenkerellinopsisMarivaux gen. et sp. nov., and a ?zegdoumyid,Dakhlamys ultimusMarivaux gen. et sp. nov. – are also documented but remain poorly sampled. The presence in Dakhla (C2) of primitive representatives of two early Miocene anomaluroid genera (ParanomalurusandNonanomalurus) and a possible zenkerelline extends back to the earliest Oligocene the stratigraphical range of these lineages. This exceptional record from Dakhla demonstrates that anomaluroids were diverse near the global cooling event recorded at the Eocene/Oligocene transition, thereby indicating that coastal forests situated in the tropical south-western margin of North Africa were locally less affected by the climatic changes. The occurrence ofParanomalurusandNonanomalurusin the earliest Oligocene reveals the surprisingly long-lived evolutionary pattern of these two genera, which otherwise remained highly conservative through time, especially regarding dental patterns. Considering the palaeontological data so far available and our proposed phylogenetic context including a comprehensive taxonomic sampling for anomaluroids, it appears that the divergences of extant lineages (Anomalurus,IdiurusandZenkerella) were very ancient, and probably can be traced back to the Eocene. Based on our phylogenetic results, some systematic and macroevolutionary implications related to the Anomaluroidea are discussed, with a special emphasis on theZenkerellalineage, which is regarded here as possibly outside the Anomaluridae. http://zoobank.org/urn:lsid:zoobank.org:pub:92621503-34A0-4A61-BB87-2F7D04D66728 [ABSTRACT FROM PUBLISHER]

The "blind mouse" genus, Typhlomys, is an ancient taxon in the family Platacanthomyidae, comprising 2 living species and 4 living subspecies. We sequenced 3 mitochondrial (CytB, COI, and ND2) and 2 nuclear (GHR and IRBP) gene segments to estimate the phylogenetic relationships of the species and subspecies, and to delimit species boundaries. We also evaluated patterns of morphological and morphometric variation of the skull. The molecular results suggest at least 5 species are present, corresponding to the 2 recognized species (Typhlomys cinereus and T. chapensis), 1 species previously considered a subspecies (T. ci. daloushanensis), 1 new species (Typhlomys nanus sp. nov.), and 1 putative new species, for which we lack adequate morphological specimens. We also determined that the subspecies Typhlomys cinereus jingdongensis is conspecific with T. chapensis. Diversification of the genus occurred in the late Miocene and Pliocene. The new species, T. nanus, is distributed in eastern and northeastern Yunnan at middle to high elevations (2,000 m to > 3,000 m above sea level). Interestingly, we detected a frameshift mutation within the IRBP gene, which is the 1st molecular evidence for the degradation of vision. [ABSTRACT FROM AUTHOR]

The importance of the environment in shaping phenotypic evolution lies at the core of evolutionary biology. Chipmunks of the genus Tamias (subgenus Neotamias) are part of a very recent radiation, occupying a wide range of environments with marked niche partitioning among species. One open question is if and how those differences in environments affected phenotypic evolution in this lineage. Herein we examine the relative importance of genetic drift versus natural selection in the origin of cranial diversity exhibited by clade members. We also explore the degree to which variation in potential selective agents (environmental variables) are correlated with the patterns of morphological variation presented. We found that genetic drift cannot explain morphological diversification in the group, thus supporting the potential role of natural selection as the predominant evolutionary force during Neotamias cranial diversification, although the strength of selection varied greatly among species. This morphological diversification, in turn, was correlated with environmental conditions, suggesting a possible causal relationship. These results underscore that extant Neotamias represent a radiation in which aspects of the environment might have acted as the selective force driving species' divergence. [ABSTRACT FROM AUTHOR]

Evolutionary radiations on continents are less well-understood and appreciated than those occurring on islands. The extent of ecological influence on species divergence can be evaluated to determine whether a radiation was ultimately the outcome of divergent natural selection or else arose mainly by nonecological divergence. Here, we used phylogenetic comparative methods to test distinct hypotheses corresponding to adaptive and nonadaptive evolutionary scenarios for the morphological evolution of sigmodontine rodents. Results showed that ecological variables (diet and life-mode) explain little of the shape and size variation of sigmodontine skulls and mandibles. A Brownian model with varying rates for insectivory versus all other diets was the most likely evolutionary model. The insectivorous sigmodontines have a faster rate of morphological evolution than mice feeding on other diets, possibly due to stronger selection for features that aid insectivory. We also demonstrate that rapid early-lineage diversification is not accompanied by high morphological divergence among subclades, contrasting with island results. The geographic size of continents permits spatial segregation to a greater extent than on islands, allowing for allopatric distributions and escape from interspecific competition. We suggest that continental radiations of rodents are likely to produce a pattern of high species diversification coupled with a low degree of phenotypic specialization. [ABSTRACT FROM AUTHOR]

Convergence is widely regarded as compelling evidence for adaptation, often being portrayed as evidence that phenotypic outcomes are predictable from ecology, overriding contingencies of history. However, repeated outcomes may be very rare unless adaptive landscapes are simple, structured by strong ecological and functional constraints. One such constraint may be a limitation on body size because performance often scales with size, allowing species to adapt to challenging functions by modifying only size. When size is constrained, species might adapt by changing shape; convergent shapes may therefore be common when size is limiting and functions are challenging. We examine the roles of size and diet as determinants of jaw shape in Sciuridae. As expected, size and diet have significant interdependent effects on jaw shape and ecomorphological convergence is rare, typically involving demanding diets and limiting sizes. More surprising is morphological without ecological convergence, which is equally common between and within dietary classes. Those cases, like rare ecomorphological convergence, may be consequences of evolving on an adaptive landscape shaped by many-to-many relationships between ecology and function, many-to-one relationships between form and performance, and one-to-many relationships between functionally versatile morphologies and ecology. On complex adaptive landscapes, ecological selection can yield different outcomes. [ABSTRACT FROM AUTHOR]

The functions of the mammalian kidney are closely related to its structure. This suggests that renal function can be completely characterized by accurate knowledge of its quantitative morphological features. The aim of this study was to investigate the histomorphometric features of the kidney using design-based and unbiased stereological methods in the Persian squirrel ( Sciurus anomalus), which is the only representative of the Sciuridae family in the Middle East. The left kidneys of five animals were examined. Total volume of the kidney, cortex, and medulla were determined to be 960.75 ± 87.4, 754.31 ± 77.09 and 206.1 ± 16.89 mm, respectively. The glomerular number was 32844.03 ± 1069.19, and the total glomerular volume was estimated to be 36.7 ± 1.45 mm. The volume and length of the proximal convoluted tubule were estimated at 585.67 ± 60.7 mm and 328.8 ± 14.8 m, respectively, with both values being greater than those reported in the rat kidney. The volume and length of the distal convoluted tubule were calculated at 122.34 ± 7.38 mm and 234.4 ± 17.45 m, respectively, which are also greater than those reported in the rat kidney. Despite the comparable body weight, the total number and mean individual volume of glomeruli in the Persian squirrel kidney were greater than those in the rat kidney. Overall, the stereological variables of the kidneys elucidated in this study are exclusive to the Persian squirrel. Our findings, together with future renal physiological data, will contribute to a better understanding of the renal structure-function relationship in the Persian squirrel. [ABSTRACT FROM AUTHOR]

Understanding both the role of selection in driving phenotypic change and its underlying genetic basis remain major challenges in evolutionary biology. Here, we use modern tools to revisit a classic system of local adaptation in the North American deer mouse, Peromyscus maniculatus, which occupies two main habitat types: prairie and forest. Using historical collections, we find that forest-dwelling mice have longer tails than those from nonforested habitat, even when we account for individual and population relatedness. Using genome-wide SNP data, we show that mice from forested habitats in the eastern and western parts of their range form separate clades, suggesting that increased tail length evolved independently. We find that forest mice in the east and west have both more and longer caudal vertebrae, but not trunk vertebrae, than nearby prairie forms. By intercrossing prairie and forest mice, we show that the number and length of caudal vertebrae are not correlated in this recombinant population, indicating that variation in these traits is controlled by separate genetic loci. Together, these results demonstrate convergent evolution of the long-tailed forest phenotype through two distinct genetic mechanisms, affecting number and length of vertebrae, and suggest that these morphological changes-either independently or together-are adaptive. [ABSTRACT FROM AUTHOR]

The advent of molecular and cytogenetic methodologies has improved our ability to recognize taxonomically distinctive, but morphologically cryptic forms. However, molecular and cytogenetic data are often based on small and geographically restricted samples, often hampering an objective evaluation of alternative hypotheses such as limited and/or uneven sampling leading to character discontinuity. It is important to investigate this alternative possibility, especially when it concerns species distributed parapatrically with confusing geographical limits. In this study, we analyze patterns of qualitative and quantitative variation in cranial morphology in a series of Cerradomys samples from northeastern Brazil. These samples form a north-south transect through this region, where 2 species with parapatric distributions, C. vivoi and C. langguthi, are currently recognized. Our results show that qualitative characters regarded as diagnostic for each species vary gradually along the transect and, despite the overall similarities among samples, cranial morphometric analysis reveals an increase in size and a gradual modification of skull shape from northern to southern samples. These findings indicate that, although the distinction between C. vivoi and C. langguthi is supported by available karyological and molecular variation, these 2 species cannot be confidently distinguished based only on morphology, particularly those samples from intermediate regions of the transect. We propose an intensification of sampling in these regions, and the integrated use of cytogenetic, molecular, and morphological data, in an attempt to refine the resolution of discontinuities among population samples and to access the geographical limits between the recognized species in this genus. [ABSTRACT FROM AUTHOR]

The relationship between the form and function of the skull has been the subject of a great deal of research, much of which has concentrated on the impact of feeding on skull shape. However, there are a number of other behaviours that can influence craniodental morphology. Previous work has shown that subterranean rodents that use their incisors to dig (chisel-tooth digging) have a constrained cranial shape, which is probably driven by a necessity to create high bite forces at wide gapes. Chisel-tooth-digging rodents also have an upper incisor root that is displaced further back into the cranium compared with other rodents. This study quantified cranial shape and upper incisors of a phylogenetically diverse sample of rodents to determine if chisel-tooth-digging rodents differ in craniodental morphology. The study showed that the crania of chisel-tooth-digging rodents shared a similar place in morphospace, but a strong phylogenetic signal within the sample meant that this grouping was nonsignificant. It was also found that the curvature of the upper incisor in chisel-tooth diggers was significantly larger than in other rodents. Interestingly, most subterranean rodents in the sample (both chisel-tooth and scratch diggers) had upper incisors that were better able to resist bending than those of terrestrial rodents, presumably due to their similar diets of tough plant materials. Finally, the incisor variables and cranial shape were not found to covary consistently in this sample, highlighting the complex relationship between a species' evolutionary history and functional morphology. [ABSTRACT FROM AUTHOR]

Aim We describe patterns of skull size and shape variation in an Atlantic forest endemic rodent to test the influence of genetic structure, historical and environmental variables upon intraspecific morphological variability. Location South America, Brazil, Atlantic forest. Methods We analyse subtle differences in skull morphology of Akodon cursor through geometric morphometrics applied to 324 individuals from 12 localities distributed throughout the species range. Using cytochrome- b gene (cyt- b) sequences from 125 individuals (38 localities), we describe underlying patterns of genetic structure and transform them into distance measures that are included in our morphological analyses. We estimate the relative importance of genetic structure, historical variables and environmental variables on skull size and shape through mixed model selection and Akaike's information criterion. Results Geographical patterns in skull size are mainly explained by non-random factors related to primary productivity and precipitation, whereas spatial shifts in shape correlate with mitochondrial divergence. Cytochrome- b data revealed a phylogeographic break around the Jequitinhonha River, yet striking morphological shifts were observed further south. Differences in palaeostability between regions, and the configuration of rivers, appear as secondary sources of explanation for observed patterns. Main conclusions Multiple forces explain morphological variation within A. cursor. Teasing apart the effects of local adaptation and gene flow may be difficult, but is a key to improve our understanding of the drivers of intraspecific morphological variation. Our findings support the view that size is a more labile feature than shape, and that it may more easily break away from constraints imposed by gene flow. The combination of random and non-random factors, together with documented breaks in the distribution of the Atlantic forest over the Late Quaternary, accounts for the majority of morphological differences observed in A. cursor. [ABSTRACT FROM AUTHOR]

We explore diversity of African pouched mice, genus Saccostomus ( Rodentia, Nesomyidae), by sampling molecular and morphological variation across their continental-scale distribution in southern and eastern African savannahs and woodlands. Both mitochondrial (cytochrome b) and nuclear DNA ( IRBP, RAG1) as well as skull morphology confirm the distinction between two recognized species, S. campestris and S. mearnsi, with disjunct distribution in the Zambezian and Somali- Maasai bioregions, respectively. Molecular dating suggests the divergence of these taxa occurred in the Early Pliocene, 3.9 Ma before present, whereas the deepest divergences within each of them are only as old as 2.0 Ma for S. mearnsi and 1.4 Ma for S. campestris. Based on cytochrome b phylogeny, we defined five clades (three within S. campestris, two in S. mearnsi) whose species status was considered in the light of nuclear DNA markers and morphology. We conclude that S. campestris group consists of two subspecies S. campestris campestris ( Peters, 1846; comprising two cytochrome b clades) and S. campestris mashonae (de Winton, 1897) that are moderately differentiated, albeit distinct in IRBP and skull form. They likely hybridize to a limited extent along the Kafue- Zambezi Rivers. Saccostomus mearnsi group consists of two species, S. mearnsi ( Heller, 1910) and S. umbriventer ( Miller, 1910), that are markedly differentiated in both nuclear markers and skull form and may possibly co-occur in south-western Kenya and north-eastern Tanzania. Analysis of historical demography suggests both subspecies of S. campestris experienced population expansion dated to the Last Glacial. In the present range of S. campestris group, the distribution modelling suggests a moderate fragmentation of suitable habitats during the last glacial cycle, whereas in the range of S. mearnsi group it predicts substantial shifts of its occurrence in the same period. [ABSTRACT FROM AUTHOR]

Recent study on Lasiopodomys ( Stenocranius) gregalis has revealed four clear mitochondrial lineages with differences exceeding the species level. The most divergent is the clade from south-eastern Transbaikalia. Multilocus (six nuclear genes), morphological (dental characters of m1 and M3) and behavioural (breeding experiments) analyses were conducted to test the hypothesis that L. gregalis is a complex of two cryptic species. All of the applied methods distinguish the independent status of voles from south-eastern Transbaikalia. This clade occupies a portion of the distribution range of the currently valid subspecies L. g. raddei including its terra typica. According to the results of cyt b analysis, the lectotype of L. g. raddei belongs to the Transbaikal clade. We re-establish the species status for the taxon Lasiopodomys raddei including populations from south-eastern Transbaikalia, as a cryptic species of the narrow-headed vole complex. [ABSTRACT FROM AUTHOR]

We report on intraspecific and interspecific morphological variation in the cranium, mandible and teeth along the ontogenetic trajectories of the two species of the largest living rodent, the capybara. A three dimensional geometric morphometrics approach was used to compare 171 Hydrochoerus hydrochaeris and 44 Hydrochoerus isthmius specimens ranging from newborn to adult. The specimens were assigned to seven different age classes according to cranial suture closure. The species can be differentiated in the morphospace occupation. They differ in the angle between the braincase and rostrum —H. hydrochaeris displays a straight transition whereas the snout of H. isthmius is inclined ventrally. The males in both species are bigger than the females, but no shape differences were detected. The youngest two age classes (up to 0.5 months and 0.5–10 months; before reaching sexual maturity) can be morphologically differentiated from the older age classes. Shape changes during growth are similar in both species: with increasing age, the round neurocranium flattens and the proportionally short snout elongates. Moreover, both species follow similar ontogenetic trajectories. H. hydrochaeris and H. isthmius can be differentiated by size and shape; the shape differences may indicate differences in diet and habitat. This study illustrates the relevance of an ontogenetic perspective to characterize species and examine the bases of disparity in adults. Furthermore, variation recorded in dental features serves to evaluate taxonomic and evolutionary aspects in fossil capybaras. [ABSTRACT FROM AUTHOR]

In Tunisia bothPsammomys obesusandP. vexillarisare found. These taxa have been the subject of taxonomic controversy for some time, due to variability in the classical morphological characters used for taxonomic recognition. In this study we investigated skull size and shape variation in the genusPsammomysby using geometric morphometrics to evaluate the extent of intra- and interspecific shape variation and explicitly tested for the impact of allometric shape variation on species discrimination. Eleven populations of the two species from 10 localities in Tunisia were studied. Statistical analyses of size and shape showed large size variation withinP. obesus, but no shape differences were revealed among populations of this species. Interspecific analysis revealed thatP. vexillarishad the smallest skull. Principal component analysis and Procrustes distances showed good discrimination between the two species after removal of the allometric component of shape variation. The results obtained show that allometric-related shape variation could mask discrimination between the twoPsammomysspecies. This finding might explain the uncertainty in classification of these species in the past. The interspecific allometric-free phenotypic differences observed may be associated with adaptive processes linked to the different environmental and trophic preferences of the two species. [ABSTRACT FROM PUBLISHER]

A human-mediated invasion of a temperate rodent Microtus rossiaemeridionalis on the High Arctic Archipelago of Svalbard in the first half of the 20th century provides an opportunity to explore extent and rate of morphological divergence over decades of isolation. We studied dental size and morphology in 124 voles captured on Svalbard (Spitsbergen) in 1997-2005 and compared the data to mainland conspecific populations across northern Eurasia. Both dental and cranial sizes in the Svalbard population fall within the limits of natural variation of the species. Dental morphology suggests that the population experiences strong effects of isolation as indicated by the significant increase in the frequency of rare dental morphs, possibly caused by inbreeding. No evidence for directional shift towards increased or decreased complexity of the morphotype dental patterns is revealed. Although the population on Svalbard is phenotypically different from the mainland populations (due to increased frequency of rare morphs), those differences are not enough to support the idea of initial rapid evolution related to colonization. The limited spatial extent and environmental homogeneity of suitable habitats on the island allowed the species to initially multiply but not to diversify so that the species exhibits phenotypic conservatism but suffers the consequences of small population size. [ABSTRACT FROM AUTHOR]

In various groups of mammals, the intensity of intermale sperm competition relates to relative testes mass (RTM) with some evidence suggesting that this may also be the case for some aspects of sperm form. In murid rodents, a large RTM generally correlates with a streamlined sperm head, long apical hook and long tail with most data coming from species in the subfamily Murinae. In this study, RTM and sperm form are compared across 15 species of gerbils, seven from the Tribe Taterillini and eight from the Tribe Gerbillini. Marked interspecific differences in RTM and sperm morphology were observed. However, the Gerbilliscus species with the largest RTMdo not have a sperm head with an apical hook nor a longer sperm tail than other species with smaller RTM whereas, by contrast, in the Tribe Gerbillini, species where the sperm head lacks a hook have a relatively small testes mass. We thus suggest that in gerbils, unlike in murine rodents, high levels of postcopulatory sexual selection have not invariably resulted in the evolution of a spermatozoon with a long apical hook and long sperm tail. The possible reasons for this are briefly discussed. [ABSTRACT FROM AUTHOR]

L amottemys okuensis Petter, 1986, is restricted to the Mount Oku montane forest in the central-northern part of the Cameroon Volcanic Line ( CVL; Central West Africa). It is endangered and has a decreasing population trend. The genus is monotypic and little is known about its phylogeny and evolutionary history. Using both molecular and morphological evidence, we tested two competing systematic hypotheses involving L amottemys: whether it is more closely related to D esmomys or to O enomys. We also discuss L amottemys' biogeographical origin. Molecular phylogenies indicated a sister-group relationship with the Ethiopian montane forest endemic genus D esmomys. This reinforces the hypothesis of recurrent connections over time between West and East African mountains, probably facilitated by climate changes that led to expansions and contractions of montane environments. Our molecular dating, consistent with a period of intense volcanic activity in Central East Africa and the CVL, suggests that the geological history of East and Central Africa also contributed to promoting the isolation of L amottemys in the CVL. Moreover, this study provides the most comprehensive phylogenetic analysis for the whole tribe Arvicanthini, sampling 17 of the 18 member genera. In this rodent group, stephanodonty probably appeared independently with grasses expansion. These habitat changes probably promoted the evolution of specialist rodents able to feed on abrasive vegetal matter by a dental adaptation. [ABSTRACT FROM AUTHOR]

DNA barcoding has been proposed as a method for species identification. However, this method has been criticised for its over-reliance on a single mitochondrial gene. In this study, four mitochondrial gene regions and one nuclear gene region were used to investigate their different abilities to identify tissue associated with museum specimens ofAethomys chrysophilus,Aethomys ineptusandMicaelamys namaquensis.Aethomys chrysophilusand the more recently elevatedA. ineptusare indistinguishable on morphological grounds; however, their ranges are largely parapatric with only one syntopic locality currently known. All of the mitochondrial gene regions were able to separateM. namaquensisfromA. chrysophilusandA. ineptus, but they varied in their abilities to resolve differences betweenA. chrysophilusandA. ineptus. The sequence results identified a specimen from KwaZulu-Natal that was misclassified and should have been identified asA. ineptus. Seven specimens that had not been reclassified following the elevation ofA. ineptusto species level were identified asA. ineptus. Individuals ofA. chrysophilusfrom Malawi could not be classified as eitherA. chrysophilusorA. ineptus, and may be a hybrid or a new, distinct species. This study indicates that DNA barcoding may be used to separateM. namaquensisfromA. chrysophilusandA. ineptus, and although it was not able to separateA. chrysophilusandA. ineptus, it did indicate specimens from Malawi may be a new cryptic species. [ABSTRACT FROM PUBLISHER]

African mole-rats are subterranean rodents from the family Bathyergidae. The family consists of six genera, five of which ( Cryptomys, Fukomys, Georychus, Heliophobius and Heterocephalus) are chisel-tooth diggers, meaning they dig underground using procumbent incisors. The remaining genus of mole-rat ( Bathyergus) is a scratch digger, which digs using its forelimbs. Chisel-tooth digging is thought to have evolved to enable exploitation of harder soils. It was hypothesized that to dig successfully using incisors, chisel-tooth digging mole-rats will have a craniomandibular complex that is better able to achieve a large bite force and wide gape compared with scratch digging mole-rats. Linear measurements of morphological characteristics associated with bite force and gape were measured in several chisel-tooth digging and scratch digging mole-rats. Chisel-tooth diggers have increased jaw and condyle lengths relative to their size (characteristics associated with larger gape). They also have relatively wider and taller skulls (characteristics associated with larger bite force). The mechanical advantage of three masticatory muscles of each specimen was also calculated. The mechanical advantage of the temporalis muscle was significantly larger in chisel-tooth digging mole-rats than scratch digging genus. The results demonstrate that chisel-tooth digging bathyergids have a craniomandibular morphology that is better able to facilitate high bite force and wide gape than scratch digging mole-rats. [ABSTRACT FROM AUTHOR]

The phylogenetic position of the Olkhon mountain vole ( Alticola olchonensis Litvinov, 1960) was studied using the sequences of four nuclear ( BRCA, GHR, LCAT, and IRBP) and one mitochondrial ( cyt. b) gene. Until now multiple studies of the systematic position of this vole had been based exclusively on morphological data, while the major taxonomic references contain contradictory information regarding both the subgeneric and species status of this animal. It was established that the molecular data and morphology data allow us to concern the Lake Baikal vole unambiguously as a part of the nominative subgenus Alticola instead of Aschizomys. [ABSTRACT FROM AUTHOR]

The limbs of mammals exhibit a variety of morphologies that reflect the diversity of their habitats and their functional needs, including subtle structural differences in their distal limb integumentary appendages (hooks, claws, adhesive pads). Little is known about structure and function of claws of sigmodontine rodents. Here, we analyze claw shape and forelimb skeleton morphology of 25 species of sigmodontine rodents with different locomotory types (ambulatory, fossorial, natatorial, quadrupedal saltatorial, and scansorial), taking into account their phylogenetic affinities. Qualitative differences in claw shape were examined using digital photographs, and quantitative measurements were made for length, height, and curvature of the claws of all digits, and dimensions of other forelimb skeletal elements. Our results show that both phylogeny and ecological categories explain substantial components of the morphological variation in sigmodontine rodents. Qualitative analysis reveals that non-specialized forms (ambulatory, quadrupedal saltatorial, and scansorial) tend to have high and strongly curved claws, whereas highly specialized forms (fossorial and natatorial) tend to have elongate and smoothly curved claws. However, the quantitative analysis differentiated the fossorial and scansorial by variables related to claw, and natatorial by variables related to bones of the forelimb. No variables that could differentiate ambulatory or quadrupedal saltatorial forms were found, demonstrating that these forms show a generalized morphological pattern. This study indicates that both historical and ecological factors contribute to the evolution of claw length in these groups. [ABSTRACT FROM AUTHOR]

Octodontoidea is the most species-rich clade among hystricomorph rodents. Based on a combined parsimony analysis of morphological and molecular data of extinct and extant species, we analyze the history of South American octodontoids and propose ages of divergence older than interpreted so far. Early Abrocomidae are recognized for the first time, and a new definition of the family is provided. Traditionally accepted fossil-based times of origin for the southern clades are reinterpreted as later stages of differentiation markedly uncoupled from the origin, differentiation implying specializations for open environments as shown in a morphospace of skull variation. Origin of crown groups is also strongly uncoupled from origin of clades as a consequence of extinction of deep lineages. In the resulting diversity pattern of modern southern clades of octodontoids, the combination of greater disparity, less content of evolutionary history, and lower taxonomic diversity, compared to their northern counterparts, appears at first counterintuitive. We propose that primary components of diversity derived from evolutionary transformation or anagenesis, on the one hand, and from cladogenesis and extinction, on the other, should not be considered associated, or at least not necessarily. Certain patterns of relationships between these distinct components could be driven by environmental dynamics. Like environments, octodontoid diversity would have been more stable in northern South America, whereas in the south, both strong adaptive change and extinction would have been triggered by emerging derived environments. [ABSTRACT FROM AUTHOR]

We describe and compare the bacular morphology of the high Andean rodents Thomasomys laniger, T. niveipes, T. princeps, Chilomys instans, Microryzomys minutus and Neomicroxus bogotensis distributed in Chingaza National Natural Park in the Colombian Cordillera Oriental. We also describe the baculum of Thomasomys aureus from two localities from the Cordillera Central. Our analyses used 16 penises from adult specimens, which were cleared and double stained with alizarin and alcian blue. Each of the seven species exhibited a tridigitate complex-penis with clear bacular morphological differences among them. Within the genus Thomasomys, bacula of T. aureus and T. princeps were substantially different, especially in the size and the shape of the base. Likewise, T. laniger showed marked differences in comparison to T. niveipes, contrasting with the latter by an expanded head and digits of the trident of similar size. The baculum of C. instans was similar to those of Thomasomys, with its wide base and distally expanded head. Both M. minutus together with N. bogotensis had the smallest bacula studied. The baculum of M. minutus has a wide and flat base and that of N. bogotensis is slender with a narrow and shallow base; neither set of attributes was seen in the other species analyzed. The differences found within these species led us to conclude that bacular morphology holds great potential to understand both taxonomic boundaries as well as evolutionary trends among sigmodontine rodents. [ABSTRACT FROM AUTHOR]

Predation by nocturnal birds of prey is one of the most frequent modes leading to the concentration of rodents in fossil assemblages. This mode of accumulation leaves characteristic surface alterations on bones and teeth. In order to evaluate and characterize the effects of these pre-diagenesis alterations on rodent fossil samples, we have carried out microstructural and chemical analyses on incisors collected from present day Moroccan wild animals and owl pellets. The microstructure of both dentine and enamel was well preserved, but chemical changes were evident in pellet samples and depended on the particular tissue and the nature of the predator. The comparison of compositional data obtained from electron microprobe chemical analyses and infrared spectrometry has allowed us to assign a possible predator to an incisor extracted from a pellet of an unknown origin. This method has further implications for the understanding of taphonomy and palaeoecology of archaeological and fossil sites. [ABSTRACT FROM AUTHOR]

Phenetic and ecological plasticity in Arvicola has caused a long-standing dispute over the number of species within the genus, which is currently thought to consist of two aquatic ( sapidus, amphibius) and one fossorial species ( scherman). We used mitochondrial cytochrome b (cyt b) gene sequences to reconstruct phylogenetic relationships between the fossorial and the aquatic water voles from the various regions of their European and Asiatic range. These two types differed morphologically and exhibited allopatric ranges. Our study provided 50 new haplotypes, generating a total dataset of 70 different water vole cyt b haplotypes. Phylogenetic reconstructions retrieved two major lineages that were in a sister position to A. sapidus: a fossorial Swiss lineage and a widespread cluster, which contained aquatic and fossorial water voles from Europe and western Siberia. The phylogeographic architecture in water voles is explained by Quaternary climatic dynamics. Our results show that A. scherman in its present scope is not a monophyletic taxon. [ABSTRACT FROM AUTHOR]

Information on circulation of rickettsiae between small mammals and their ectoparasitic mites is scarce. In this study, we investigated infestation rates of rodents with mites in some areas of SW Slovakia and the role of mites as possible vectors of pathogenic rickettsiae. A total of 615 rodents of five species were caught during 2010-2012. All individuals were examined for ectoparasites which resulted in 2821 mites belonging to three species of Laelapidae and six species of Trombiculidae. The most common Laelapidae species was Laelaps agilis (81.25 %), followed by Haemogamasus nidi, and Eulaelaps stabularis. Hirsutiella zachvatkini (16.52 %) was the dominant species of the family Trombiculidae. DNA extracted from rodent blood and ectoparasitic mites was examined for the presence of rickettsiae by PCR. By pooling mites, 345 pool samples were created, of which 112 (32.46 %) were found to be positive for the rickettsial DNA. From 487 examined rodent blood samples, rickettsial DNA was found in 46 (9.44 %). Sequencing DNA from the positive blood samples and mites revealed the identity of Rickettsia helvetica and Rickettsia monacensis. The results of the study suggest that ectoparasitic mites may be reservoirs as well as vectors of some pathogenic rickettsiae. [ABSTRACT FROM AUTHOR]

Newly discovered mandibles and lower dentition of the middle Eocene rodent Thisbemys brevicrista from the Green River Basin, Wyoming, are the basis for a species re-diagnosis. Previously, only the upper dentition and a partial maxilla of T. brevicrista were known from Br3. New specimens from Br2 now include the lower molars, additional upper molars, and maxillary fragments including a partial zygomatic arch that preserves the relationship of the arch to the first upper molar. In addition, the presence of T. brevicrista at Br2 documents the co-existence of T. brevicrista with T. perditus, T. nini, T. plicatus, and T. corrugatus. Formerly, the latter two species were differentiated primarily using stratigraphy. Now, morphology and size can also be used. Thisbemys brevicrista is intermediate in size between T. plicatus and T. corrugatus, and can readily be distinguished from these species based on unique features of the upper and lower molars, which include an additional loph on the two anterior upper molars and a complete metalophid on m1-3. The original type specimen of T. brevicrista appears to be lost, thus a neotype is designated as part of the re-diagnosis. Discovery and description of the lower dentition and mandibles of T. brevicrista clarifies the alpha taxonomy of this species, and increases its utility for studies of phylogenetic relationships and for documenting Eocene mammalian diversity patterns. [ABSTRACT FROM PUBLISHER]

The aim of this investigation was the analysis of the variability within the internal and external ophthalmic artery in the chinchilla (Chinchilla laniger, Molina). The head vasculature of 65 individuals was analysed, with particular emphasis on the internal ophthalmic artery originating from the central and rostral part of the cerebral arterial circle. Head blood vessels were filled with acrylic latex for vascular corrosion casting. The results showed ten variants of blood supply for the orbit, with a predominance of the first variant (66.1%) = bilateral presence of the external ophthalmic artery originating from the maxillary artery. Other variants differed in symmetry and asymmetry, sites of origination and the coexistence of both internal and external arteries. Vascularisation of the brain in chinchillas originates mainly from the vertebra-basilar system. The observed variability seems to confirm the role of the basilar artery in the arterial blood supply of the brain in this species. [ABSTRACT FROM AUTHOR]